UNIVERSITY OF THE DISTRICT OF - UDC Law Review

UNIVERSITY OF THE DISTRICT OF
COLUMBIA LAW REVIEW
2012 Write-On Competition
Instructions
A. HONOR CODE
The Write-On Competition is conducted pursuant to the David A. Clarke School
of Law Honor Code. You may find a copy in the Student Handbook. Violations of
the Honor Code will result in automatic disqualification from the competition and
will be reported.
B. SUBMITTING YOUR WORK
The deadline to submit your work is 6:00 p.m. on Friday, September 7.
Submissions made after this point will not be accepted. Your submission must
be marked with your Exam ID Number ONLY and must not contain your
name or any other identifying information. Any submissions which include
identifying information other than your Exam ID Number will not be accepted.
Your submission should consist only of the provided answer form, with the
filename updated to include your Exam ID Number and your responses entered
into the document. You may download the answer form and upload your
submission at:
http://www.udclawreview.com/write-on-competition-submissions/
C. ADDITIONAL INFORMATION
Write-On Competition submissions will be evaluated anonymously by the law
review editorial board and law review faculty advisors, based on the criteria given
below. Write-On scores are tracked by your Exam ID Number until membership
offers are made. There is no set number of Write-On Competition membership
offers: All submissions will be reviewed and considered on their own merits. Law
Review membership offers will be extended before the beginning of the fall
semester. This competition consists of three sections. More specific instructions
appear at the beginning of each section below.
Thank you for participating, and good luck!
The 2012-2013 UDC Law Review Editorial Board
1

Section 1: Bluebook Literacy
Section 1 Instructions: Below are twenty questions that test your general knowledge
about The Bluebook. These questions are intended both to test your understanding of the
structure of The Bluebook and to require you to apply selected rules. The questions are in
either multiple choice or fill-in-the-blank format. Enter your response to each question
below on the provided answer form.
1. You are a law clerk who has been instructed to
review a draft opinion for technical correctness.
What section of The Bluebook should you refer to
for rules about citations in court documents
2. You are drafting a student note for submission to
your school’s law review. What section of The
Bluebook should you refer to for rules about
citations in law review publications
3. You are a law review associate editor who is
unsure whether the italicized typeface should be
used for a case name that appears in a footnote
citation to an article you are editing. The citation
is a “full” (i.e., not a short form) citation. Which
rule should you refer to
2
Answer Options
A.) Rule 2.1(c)
B.) Table 13
C.) The Whitepages
D.) Rule 4
E.) Rule 2.1(a)
F.) Rule 10.9
G.) Table 6
4. Is the italicized typeface the correct typeface for H.) Rule 10.2.2
this citation
I.) Rule 10.2.1(c)
5. You are a law review associate editor who, while
editing an article that has been submitted to the J.) The Index
law review, is confronted with a footnote citation
to “Louisville & Nashville Railroad Company v. K.) The Bluepages
Mottley, 211 U.S. 149 (1908).” You know that
some words in the case name should be abbreviated, _.) but Rule you 10.9, are not pg. sure
which ones. Which table should you refer to 107
6. Rewrite the citation with the appropriate abbreviations.
7. Later, in the text of the article, you find another reference to “Louisville &
Nashville Railroad Company v. Mottley.” You are not sure whether the
abbreviation rules that apply to case names in law review footnote
citations also apply to article text. Which rule should you refer to
8. Rewrite the case name with the appropriate abbreviations.
9. You are a law review associate editor. While reviewing an article that has
been submitted to the law review, you discover that the author has cited an

article that appeared in the periodical “Texas Journal on Civil Liberties
and Civil Rights.” You are not sure how the words in the periodical title
should be abbreviated in a footnote citation. Which table should you refer
to
10. You are also unsure which typeface should be used for the name of the
periodical in a footnote citation. What rule should you refer to
11. Rewrite the periodical name in the correct typeface and with the correct
abbreviations for a footnote citation.
12. You are a law review associate editor who is reviewing an article that
includes a quotation from the Bible. You are not sure how to cite to the
Bible, and you do not which rule contains this information. Where in The
Bluebook should you begin your search
13. You are preparing a student note for submission to your school’s law
review. You find yourself making a number of successive references to the
same handful of sources. You are concerned that your repetitive full
citations to the same sources are redundant and unnecessary, and would
like general guidance regarding the use of short citation forms. What rule
should you refer to
14. You are a law review associate editor. In citations to an article you are
editing, you come across two case names, “Jordan v. United States
Department of Justice” and “United States v. Morrison.” You know that
sometimes geographic units like “United States” are abbreviated in
citations, but you are not sure when. Naturally, you are concerned that the
edits you submit be in complete conformity with The Bluebook. What rule
should you refer to
15. Rewrite the case names with appropriate abbreviations.
16. You are a respected law professor and sought-after academic who is
preparing an article for publication in a prominent law review. Throughout
your article, you make several references to a case called “Runyon v.
McCrary, 427 U.S. 160 (1976).” Striving, as always, for economy in your
citations, you would like to use a short citation form wherever possible,
but your citations to this case are not all consecutive. What rule can help
you determine where you may use a short citation form for this case
17. In one instance, you cite Runyon in footnote 4, and again in footnote 11.
May you use a short form citation in footnote 11
18. In another instance, you make a full citation to Runyon in footnote 14, use
an “id.” form citation in footnote 15, and cite Runyon again in footnote 20.
May you use a short form in footnote 20
19. Rewrite the citation in the short form, citing specifically to page 170 of the
opinion.
20. May you use a “supra” form for your successive, nonconsecutive
references to Runyon Why or why not
3

Section 2: Editing Exercise
Section 2 Instructions: The excerpt below is from a forthcoming UDC Law Review
article. Several errors have been deliberately inserted: Five grammatical or spelling errors
and ten Bluebook citation errors. Your task is to identify and correct as many of these
errors as possible. This task is a preview of the work performed by an associate editor.
Additionally, you may offer suggestions for substantive improvement where you think
appropriate (i.e., where there is not an error, but sentence phrasing, word choice, or some
other aspect of the writing or argument could be improved).
The Juvenile Justice System and School-to-Prison Pipeline
America is in the midst of a multi-decade explosion of incarceration rates. 1
The number of people in local, state, and federal incarceration facilities has risen,
since 1970, by approximately 1100 percent. 2 Both as a percentage of the
population and in terms of actual numbers, the United States is the mostincarcerated
country in the world, with a rate of incarceration that is four times
the average rates of other countries. 3 The United States’s youth incarceration rate
is the highest, by far, of any developed nation. 4 The over-reliance on incarceration
has been counterproductive not just in terms of dollars wasted, but also, more
significantly, in terms of lives derailed. 5
This unparalleled increase in incarceration is not colorblind. Rather, it is
primarily a function of radical rises in the incarceration rates of black and brown
people, principally low-income African-American males. 6 Although three-fifths
of the youth population of America is white, approximately three-fifths of
incarcerated youth are African-American or Latino. 7 The population of
1 DAVID M. KENNEDY, DON’T SHOOT: ONE MAN, A STREET FELLOWSHIP, AND THE END
OF VIOLENCE IN INNER-CITY AMERICA 146-47 (2011).
2 Id. cf., e.g., Stephen B. Bright, Legal Representation for the Poor: Can Society Afford
this Much Injustice, MISSOURI L. REV. 683 (2010) (calculating increase in the number of
incarcerated persons from approximately 200,000 to 2.3 million as an 800 percent increase).
3 See, e.g., CHRISTOPHER HARTNEY, US RATES OF INCARCERATION: A GLOBAL
PERSPECTIVE 1-3 (2006), available at www.nccdcrc.org/nccd/pubs/2006nov_factsheet_incarceration.pdf
(last visited Feb. 18, 2012).
4 THE ANNIE E. CASEY FOUND., NO PLACE FOR KIDS: THE CASE FOR REDUCING
JUVENILE INCARCERATION 2 (2011), available at
http://www.aecf.org/OurWork/JuvenileJustice/JuvenileJusticeReport.aspx. The juvenile
incarceration rate in the United States in 2002 was 336 per 100,000 persons, nearly five times
higher than the next-highest national rate. Id.
5 Id. at 3.
6 See, Michelle Alexander, The New Jim Crow, 9 Ohio St. J. of Crim. L. 1, 11-15 (2011);
see generally, MICHELLE ALEXANDER, THE NEW JIM CROW: MASS INCARCERATION IN THE AGE OF
COLORBLINDNESS (2010).
7 Annie E. Casey Found., id. note 4, at 2.
4

incarcerated children in the District of Columbia is – and has been for decades –
virtually 100 percent children of color from low-income families. 8
Court-appointed attorney’s ostensibly responsible for defending lowincome
children often have unmanageable caseloads, and, as a result, do not
provide their delinquency clients with adequate representation. 9 Many – perhaps
the vast majority of those children – are children with education-related
disabilities who are not receiving appropriate services in public schools. 10
Exacerbating the problem, state and federal legislatures have promoted “zero
tolerance” discipline policies, and local education officials increasingly have
ceded school disciplinary matters to police officers. Moreover, during the 1990s,
virtually every state amended their delinquency and criminal statutes to push
more children into adult criminal courts and, consequently, into adult jails and
prisons. 11 America’s swelling school-to-prison pipeline is draining inner cities,
sweeping urban children and young adults into mostly rural incarceration
institutions. 12
In 1975, Congress found that students with disabilities were “either totally
excluded from schools or sitting idly in regular classrooms awaiting the time
when they were old enough to drop out.” 13 As a result, Congress passed the
Education for All Handicapped Children Act (EAHCA) 14 – which has since been
amended and renamed the Individuals with Disabilities Education Act (IDEA) 15 –
to address the unmet educational needs of millions of children with disabilities. 16
The IDEA requires public schools to provide such students with a free and
appropriate public education (FAPE). 17
8 Cf., e.g., Arthur L. Burnett, Sr., Race and National Origin as Influential Factors in
Juvenile Detention, 3 D.C. L. REV. 355, 370 (1995) (Table 1 - percentage of detention population
that is minority in D.C. is 100 percent).
9 Cf. generally, Stephen B. Bright, Legal Representation for the Poor: Can Society
Afford this Much Injustice, 75 MO. L. REV. 683 (2010), at 684-85 (across the country, public
defenders for low-income defendants have unmanageable caseloads and were therefore unable to
provide high quality representation).
10 THE ANNIE E. CASEY FOUND., ESSAY: A ROAD MAP FOR JUVENILE JUSTICE REFORM
(2008), available at
http://datacenter.kidscount.org/databook/2008/OnlineBooks/Essay/Essay1.aspx.
11 Id.
12 In July of 2011, the U.S. Attorney General and the U.S. Secretary of Education
announced a joint project, the Supportive School Discipline Initiative, aimed at addressing the
“school-to-prison pipeline” and the disciplinary policies and practices that can push students out of
school and into the justice system. “Ensuring that our educational system is a doorway to
opportunity – and not a point of entry to our criminal justice system – is a critical, and achievable,
goal,” said Attorney General Eric Hollder. Press Release, Department of Justice, Attorney General
Holder, Secretary Duncan Announce Effort to Respond to School-to-Prison Pipeline by
Supporting Good Discipline Practices (July 30, 2011, available at
http://www.justice.gov/opa/pr/2011/July/11-ag-951.html.
13 H.R. Rep. No. 94-332, at 2 (1975).
14 Pub. L. No. 94-142, § 1, 89 Stat. 773 (codified as amended at 20 U.S.C § 1400 et seq.
(1975)).
15 The Individuals with Disabilities Education Act, 20 U.S.C § 1400 et seq.
16 See id. Section 1400(c)(2).
17 “The purposes of this chapter are . . . to ensure that all children with disabilities have
available to them a free, appropriate public education (FAPE) that emphasizes special education
5

One scholar has noted that “[t]he school-to-prison pipeline is the product
of the policies of school districts, law enforcment agencies, and courts that
criminalize in-school behavior or otherwise push disadvantaged, underserved, and
at-risk children from mainstream educational environments into the juvenile
justice system, and all too often [into] the criminal justice system.” 18 In some
circumstances, a child’s acting out in school may indicate that the child has an
education-related disability and should be receiving special education services. 19
School personnel have an affirmative obligation to identify children whom they
suspect have education-related disabilities. 20 A parent has a parallel right to obtain
from the school system, without charge to the parent, evaluations of the child in
any area of suspected disability. 21
Changing what happens in our public schools is critical in that,
absent system reform, children and youths continue to be pushed
into the [juvenile delinquency and criminal] systems. Without
education reform, students caught up in the juvenile system are
much less likely to obtain the services and skills that prevent them
from being funneled into the pipeline again and into the adult
correctional system. 22
and related services designed to meet their unique needs and prepare them for further education,
employment, and independent living.” 20 U.S.C. § 1400 (d)(1)(A) and § 1401(9); see also, id. at §
1400(d)(1)(B)-(C) and (d)(2)-(4).
18 Ronald K. Lospennato, Multifaceted Strategies to Stop the School-to-Prison Pipeline,
42 CLEARINGHOUSE REV. 529; see also ANNIE E. CASEY FOUND., supra note 9 (“A
disproportionate share of public school students referred to the juvenile justice system under zerotolerance
policies are youth with educational disabilities, suggesting that schools are opting to
prosecute rather than educate students with special needs.”)
19 SUE BURELL & LOREN WARBOYS, UNITED STATES DEP’T OF JUSTICE OFFICE OF
JUVENILE AND DELINQUENCY PREVENTION, SPECIAL EDUCATION IN THE JUVENILE JUSTICE
SYSTEM (2000).
20 20 U.S.C. § 1412(a)(3)(A) (2006); see also 34 C.F.R. § 300.111(a)(1) (2006).
21 See generally 20 U.S.C. § 1414(a)-(c) (2006).; 34 C.F.R. §§ 300.300-.311 (2008).; see
also 20 U.S.C. § 1414(b)(3)(B) (2006); 34 C.F.R. § 300.304(c)(4) (2006).
22 Lospennato, supra note 18.
6

Section 3: Writing Exercise
Section 3 Instructions
Scope of your universe: Outside research is prohibited. The contents of your submission
should be based solely upon the materials included in this packet. Failure to adhere to this
requirement will lead to automatic disqualification from the competition. If a source
within this packet refers to a source that is not included within the packet, you may
discuss it in your submission only to the extent that it appears in the provided materials,
but you may not look up the actual source. Citations to sources not included within this
packet, but which are cited by materials that are included in this packet, should comply
with Bluebook citation rules to the greatest extent possible. You may make passing
references to history, current events, or other relevant information. You may rely on your
basic legal knowledge to support your argument. You may also consult dictionaries (legal
or otherwise), thesauri, and style manuals.
Citations: Your citations should comply with The Bluebook rules of citation for
academic publications. You may not use any other form of citation. There is no minimum
or maximum number of footnotes. Citations to page numbers should be based on the page
numbering of the original material, not the numbering of pages in this packet.
Format: Your response to this section should be included within the provided answer
form that you upload, appearing after your responses to sections 1 and 2. Your response
to this section may not exceed five double-spaced pages. Shorter submissions are
acceptable. We will not accept submissions longer than five pages. Your response to this
section should have 1” margins on all sides. Page numbers should be centered at the
bottom of each page and may fall within the bottom margin. Use 12-point Times New
Roman font for your main text, and 10-point Times New Roman font for your footnotes.
Footnotes may be single-spaced. Do not use endnotes.
Approaching your submission: Like any analytical piece of writing, your submission
should include an overarching thesis and contain a well-structured legal argument. Do not
be intimidated by the length of the packet (or these instructions)! This packet contains a
diverse collection of materials so that you can compile and support your argument from a
variety of views. Do not feel compelled to read everything in this packet: We neither
expect nor encourage you incorporate all of the provided materials into your argument.
Many strong submissions will be narrowly focused and concentrated heavily on only a
few sources. There is no significance to the order of the materials included in the packet.
There are no “right” answers: The packet is designed to encourage you to shape a
creative legal argument. Finally, remember to edit your work! Organization, clarity of
thought, grammar, and style are crucial to a successful submission.
Evaluation criteria:
Element
Formatting
Evaluation
This element is weighed heavily. We will be looking to
ensure that you have the ability to accurately follow the
directions provided.
7

Citation
Structure
Reasoning
Writing
This element is also weighed heavily. Knowledge of The
Bluebook is an indispensible asset for law review associate
editors. Spend extra time to ensure that you have properly
formatted your citations.
You will lose points for a poorly structured argument. Your
analysis need not rigidly comply with “IRAC” or “CRAC”
structure, but it should be easy to follow.
We will not judge your opinions, but your arguments should
be well-supported by the provided materials.
Your ability to use proper grammar and sentence structure is
important. Improper spelling or grammatical errors will
reduce your score.
Prompt
The Supreme Court has granted certiorari in the case of Florida v. Jardines to
consider the question of whether the use of a drug-detection dog at a private
residence is a search requiring probable cause within the meaning of the Fourth
Amendment. The Florida Supreme Court ruling in this case (Jardines v. State) is
provided below.
Review the provided packet of materials and formulate a legal argument either for
or against the suppression of evidence obtained with the drug-detection dog. Use
the provided materials to support your opinion. Your opinion may be no longer
than five double-spaced pages formatted in accordance with the instructions
above. The five-page limit includes footnotes.
Provided sources
Jardines v. State, 73 So.3d 34 (Fla. 2011) …………………………………… 9
Katz v. United States, 389 U.S. 347 (1967) ………………………………….. 34
Illinois v. Gates, 462 U.S. 213 (1983) ……………………………………….. 45
Jacobsen v. United States, 466 U.S. 109 (1984) ……………………………... 79
Kyllo v. United States, 533 U.S. 27 (2001) …………………………………… 94
Illinois v. Caballes, 543 U.S. 405 (2005) …………………………………….. 104
United States v. Brock, 417 F.3d 692 (7th Cir. 2005) ………………………... 112
United States v. Jones, 132 S.Ct. 945 (2011) ………………………………… 118
Leslie Lunney, Has the Fourth Amendment Gone to the Dogs
Unreasonable Expansion of Canine Sniff Doctrine to
Include Sniffs of the Home, 88 OR. L. REV. 829, 835 (2009) ………………… 131
1 WAYNE R. LAFAVE, SEARCH AND SEIZURE: A TREATISE
ON THE FOURTH AMENDMENT § 2.3 (4th ed. 2004) …………………………... 181
8

Opinion
PERRY, J.
73 So.3d 34
Supreme Court of Florida.
Joelis JARDINES, Petitioner,
v.
STATE of Florida, Respondent.
No. SC08–2101. | April 14, 2011.
We have for review State v. Jardines, 9 So.3d 1 (Fla. 3d
DCA 2008), in which the district court certified conflict
with State v. Rabb, 920 So.2d 1175 (Fla. 4th DCA 2006).
We have jurisdiction. See art. V, § 3(b)(4), Fla. Const. We
quash the decision in Jardines and approve the result in
Rabb.
Police conducted a warrantless “sniff test” by a drug
detection dog at Jardines’ home and discovered live
marijuana plants inside. The trial court granted Jardines’
motion to suppress the evidence, and the State appealed.
The district court reversed, and Jardines sought review in
this Court. Jardines claims that the warrantless “sniff test”
violated his right against unreasonable searches under the
Fourth Amendment. The issue presented here is *36
twofold: (i) whether a “sniff test” by a drug detection dog
conducted at the front door of a private residence is a
“search” under the Fourth Amendment and, if so, (ii)
whether the evidentiary showing of wrongdoing that the
government must make prior to conducting such a search
is probable cause or reasonable suspicion.
The Fourth Amendment provides that “[t]he right of the
people to be secure in their persons, houses, papers, and
effects, against unreasonable searches and seizures, shall
not be violated, and no warrants shall issue, but upon
probable cause.” U.S. Const. amend. IV. The United
States Supreme Court has held that “ ‘[a]t the very core’
of the Fourth Amendment ‘stands the right of a man to
retreat into his own home and there be free from
unreasonable governmental intrusion.’ ” Kyllo v. United
States, 533 U.S. 27, 31, 121 S.Ct. 2038, 150 L.Ed.2d 94
(2001) (quoting Silverman v. United States, 365 U.S. 505,
511, 81 S.Ct. 679, 5 L.Ed.2d 734 (1961)). Or, more
succinctly, “[w]ith few exceptions, the question whether a
warrantless search of a home is reasonable and hence
constitutional must be answered no.” Kyllo, 533 U.S. at
31, 121 S.Ct. 2038.
9
First, the dog “sniff test” that was conducted in the
present case was an intrusive procedure. As explained
more fully below, the “sniff test” was a sophisticated
undertaking that was the end result of a sustained and
coordinated effort by various law enforcement agencies.
On the scene, the procedure involved multiple police
vehicles, multiple law enforcement personnel, including
narcotics detectives and other officers, and an experienced
dog handler and trained drug detection dog engaged in a
vigorous search effort on the front porch of the residence.
Tactical law enforcement personnel from various
government agencies, both state and federal, were on the
scene for surveillance and backup purposes. The entire
on-the-scene government activity—i.e., the preparation
for the “sniff test,” the test itself, and the aftermath, which
culminated in the full-blown search of Jardines’ home—
lasted for hours. The “sniff test” apparently took place in
plain view of the general public. There was no anonymity
for the resident.
Such a public spectacle unfolding in a residential
neighborhood will invariably entail a degree of public
opprobrium, humiliation and embarrassment for the
resident, for such dramatic government activity in the
eyes of many—neighbors, passers-by, and the public at
large—will be viewed as an official accusation of crime.
Further, if government agents can conduct a dog “sniff
test” at a private residence without any prior evidentiary
showing of wrongdoing, there is nothing to prevent the
agents from applying the procedure in an arbitrary or
discriminatory manner, or based on whim and fancy, at
the home of any citizen. Such an open-ended policy
invites overbearing and harassing conduct. Accordingly,
we conclude that a “sniff test,” such as the test that was
conducted in the present case, is a substantial government
intrusion into the sanctity of the home and constitutes a
“search” within the meaning of the Fourth Amendment.
As such, it must be preceded by an evidentiary showing
of wrongdoing.
And second, we note that the parties in the present case
have failed to point to a single case in which the United
States Supreme Court has indicated that a search for
evidence for use in a criminal prosecution, absent special
needs beyond the normal need of law enforcement, may
be based on anything other than probable cause. We
assume that this is because, as explained more fully
below, all that Court’s precedent in this area indicates just
the opposite. And that precedent, we recognize, *37
applies with extra force where the sanctity of the home is
concerned. Accordingly, we conclude that probable cause,
not reasonable suspicion, is the proper evidentiary
showing of wrongdoing that the government must make

prior to conducting a dog “sniff test” at a private
residence.
I. BACKGROUND
On November 3, 2006, Detective Pedraja of the Miami–
Dade Police Department received an unverified “crime
stoppers” tip that the home of Joelis Jardines was being
used to grow marijuana. One month later, on December 6,
2006, Detective Pedraja and Detective Bartlet and his
drug detection dog, Franky, approached the residence.
The underlying facts, which are discussed more fully
below, are summarized briefly in the separate opinion of a
district court judge in Jardines:
The Miami–Dade County Police Department received a
Crime Stoppers tip that marijuana was being grown at the
home of defendant-appellee Joelis Jardines. One month
later the detective went to the home at 7 a.m. He watched
the home for fifteen minutes. There were no vehicles in
the driveway, the blinds were closed, and there was no
observable activity.
After fifteen minutes, the dog handler arrived with the
drug detection dog. The handler placed the dog on a leash
and accompanied the dog up to the front door of the
home. The dog alerted to the scent of contraband.
The handler told the detective that the dog had a positive
alert for the odor of narcotics. The detective went up to
the front door for the first time, and smelled marijuana.
The detective also observed that the air conditioning unit
had been running constantly for fifteen minutes or so,
without ever switching off. [N. 8. According to the
detective, in a hydroponics lab for growing marijuana,
high intensity light bulbs are used which create heat. This
causes the air conditioning unit to run continuously
without cycling off.]
The detective prepared an affidavit1 and applied for a
search warrant, which *38 was issued. A search was
conducted, which confirmed that marijuana was being
grown inside the home. The defendant was arrested.
The defendant moved to suppress the evidence seized at
his home. The trial court conducted an evidentiary
hearing at which the detective and the dog handler
testified. The trial court suppressed the evidence on
authority of State v. Rabb.
Jardines, 9 So.3d at 10–11 (Cope, J., concurring in part
and dissenting in part) (footnote omitted).
The State appealed the suppression ruling, and the district
10
court reversed based on the following reasoning:
In sum, we reverse the order suppressing the
evidence at issue. We conclude that no illegal
search occurred. The officer had the right to go up
to defendant’s front door. Contrary to the holding
in Rabb, a warrant was not necessary for the drug
dog sniff, and the officer’s sniff at the exterior
door of defendant’s home should not have been
viewed as “fruit of the poisonous tree.” The trial
judge should have concluded substantial evidence
supported the magistrate’s determination that
probable cause existed. Moreover, the evidence at
issue should not have been suppressed because its
discovery was inevitable. To the extent our
analysis conflicts with Rabb, we certify direct
conflict.
Jardines, 9 So.3d at 10 (footnote omitted). Jardines
sought review in this Court based on certified conflict
with State v. Rabb, 920 So.2d 1175 (Fla. 4th DCA 2006),2
which we *39 granted.3
II. THE APPLICABLE LAW
[1] The Fourth Amendment to the United States
Constitution contains both the Search and Seizure Clause
and the Warrant Clause and provides as follows in full:
The right of the people to be secure in their
persons, houses, papers, and effects, against
unreasonable searches and seizures, shall not be
violated, and no warrants shall issue, but upon
probable cause, supported by oath or affirmation,
and particularly describing the place to be
searched, and the persons or things to be seized.
U.S. Const. amend. IV.4 With respect to the meaning of
the amendment, the courts have come to accept the
formulation set forth by Justice Harlan in Katz5:
As the Court’s opinion states, “the Fourth Amendment
protects people, not places.” The question, however, is
what protection it affords to those people. Generally, as
here, the answer to that question requires reference to a
“place.” My understanding of the rule that has emerged
from prior decisions is that there is a twofold
requirement, first that a person have exhibited an actual
(subjective) expectation of privacy and, second, that the
expectation be one that society is prepared to recognize
as “reasonable.” Thus a man’s home is, for most
purposes, a place where he expects privacy, but objects,

activities, or statements that he exposes to the “plain
view” of outsiders are not “protected” because no
intention to keep them to himself has been exhibited. On
the other hand, conversations in the open would not be
protected against being overheard, for the expectation of
privacy under the circumstances would be unreasonable.
Katz, 389 U.S. at 361, 88 S.Ct. 507 (emphasis added)
(Harlan, J., concurring); see California v. Ciraolo, 476
U.S. 207, 211, 106 S.Ct. 1809, 90 L.Ed.2d 210 (1986)
*40 (“Katz posits a two-part inquiry: first, has the
individual manifested a subjective expectation of privacy
in the object of the challenged search Second, is society
willing to recognize that expectation as reasonable”). In
sum, “wherever an individual may harbor a ‘reasonable
expectation of privacy’ he is entitled to be free from
unreasonable governmental intrusion.” Terry v. Ohio, 392
U.S. 1, 9, 88 S.Ct. 1868, 20 L.Ed.2d 889 (1968) (quoting
Katz, 389 U.S. at 361, 88 S.Ct. 507 (Harlan, J.,
concurring)).
A. Federal “Dog Sniff” Cases
The United States Supreme Court has addressed the issue
of “sniff tests” by drug detection dogs in three cases.
First, in United States v. Place, 462 U.S. 696, 103 S.Ct.
2637, 77 L.Ed.2d 110 (1983), that Court addressed the
issue of whether police, based on reasonable suspicion,
could temporarily seize a piece of luggage at an airport
and then subject the luggage to a “sniff test” by a drug
detection dog. After Place’s behavior at an airport aroused
suspicion, police seized his luggage and subjected it to a
“sniff test” by a drug detection dog at another airport and
ultimately discovered cocaine inside. The federal district
court denied Place’s motion to suppress, and the court of
appeals reversed. The United States Supreme Court
affirmed, concluding that the seizure, which lasted ninety
minutes, was an impermissibly long Terry6 stop, but the
Court ruled as follows with respect to the dog “sniff test”:
The Fourth Amendment “protects people from
unreasonable government intrusions into their legitimate
expectations of privacy.” We have affirmed that a person
possesses a privacy interest in the contents of personal
luggage that is protected by the Fourth Amendment. A
“canine sniff” by a well-trained narcotics detection dog,
however, does not require opening the luggage. It does
not expose noncontraband items that otherwise would
remain hidden from public view, as does, for example, an
officer’s rummaging through the contents of the luggage.
Thus, the manner in which information is obtained
through this investigative technique is much less intrusive
than a typical search. Moreover, the sniff discloses only
the presence or absence of narcotics, a contraband item.
Thus, despite the fact that the sniff tells the authorities
something about the contents of the luggage, the
information obtained is limited. This limited disclosure
also ensures that the owner of the property is not
subjected to the embarrassment and inconvenience
entailed in less discriminate and more intrusive
investigative methods.
In these respects, the canine sniff is sui generis. We are
aware of no other investigative procedure that is so
limited both in the manner in which the information is
obtained and in the content of the information revealed by
the procedure. Therefore, we conclude that the particular
course of investigation that the agents intended to pursue
here—exposure of respondent’s luggage, which was
located in a public place, to a trained canine—did not
constitute a “search” within the meaning of the Fourth
Amendment.
Place, 462 U.S. at 706–07, 103 S.Ct. 2637 (quoting
United States v. Chadwick, 433 U.S. 1, 7, 97 S.Ct. 2476,
53 L.Ed.2d 538 (1977)).
*41 Second, in City of Indianapolis v. Edmond, 531 U.S.
32, 121 S.Ct. 447, 148 L.Ed.2d 333 (2000), the United
States Supreme Court addressed the issue of whether
police could stop a vehicle at a drug interdiction
checkpoint and subject the exterior of the vehicle to a
“sniff test” by a drug detection dog. Police stopped
Edmond and other motorists at a dragnet-style drug
interdiction checkpoint, and a drug detection dog was
walked around the exterior of each vehicle. Later,
Edmond filed a class action lawsuit against the city,
claiming that the checkpoints violated his Fourth
Amendment rights, and he sought a preliminary
injunction barring the practice. The federal district court
denied the injunction, and the court of appeals reversed.
The United States Supreme Court affirmed, explaining
that “[w]e have never approved a checkpoint program
whose primary purpose was to detect evidence of ordinary
criminal wrongdoing.” Edmond, 531 U.S. at 41, 121 S.Ct.
447. With respect to the dog “sniff test,” the Court stated
as follows:
It is well established that a vehicle stop at a highway
checkpoint effectuates a seizure within the meaning of the
Fourth Amendment. The fact that officers walk a
narcotics-detection dog around the exterior of each car at
the Indianapolis checkpoints does not transform the
seizure into a search. See United States v. Place, 462 U.S.
696 [103 S.Ct. 2637, 77 L.Ed.2d 110] (1983). Just as in
Place, an exterior sniff of an automobile does not require
11

entry into the car and is not designed to disclose any
information other than the presence or absence of
narcotics. See ibid. Like the dog sniff in Place, a sniff by
a dog that simply walks around a car is “much less
intrusive than a typical search.” Ibid.
Edmond, 531 U.S. at 40, 121 S.Ct. 447 (citation omitted)
(quoting Place, 462 U.S. at 707, 103 S.Ct. 2637).
And third, in Illinois v. Caballes, 543 U.S. 405, 125 S.Ct.
834, 160 L.Ed.2d 842 (2005), the United States Supreme
Court addressed the issue of whether police, during the
course of a lawful traffic stop, could subject the exterior
of a vehicle to a “sniff test” by a drug detection dog. After
Caballes was stopped for speeding and while the officer
was writing the citation, a second officer arrived at the
scene and subjected the exterior of the vehicle to a dog
“sniff test.” The dog alerted at the trunk and the officers
searched the trunk and found marijuana. The state trial
court denied Caballes’ motion to suppress, and the Illinois
Supreme Court reversed. The United States Supreme
Court reversed, ruling as follows:
Official conduct that does not “compromise any
legitimate interest in privacy” is not a search subject to
the Fourth Amendment. Jacobsen, 466 U.S., at 123 [104
S.Ct. 1652]. We have held that any interest in possessing
contraband cannot be deemed “legitimate,” and thus,
governmental conduct that only reveals the possession of
contraband “compromises no legitimate privacy interest.”
Ibid. This is because the expectation “that certain facts
will not come to the attention of the authorities” is not the
same as an interest in “privacy that society is prepared to
consider reasonable.” Id., at 122 [104 S.Ct. 1652]
(punctuation omitted). In United States v. Place, 462 U.S.
696 [103 S.Ct. 2637, 77 L.Ed.2d 110] (1983), we treated a
canine sniff by a well-trained narcotics-detection dog as
“sui generis ” because it “discloses only the presence or
absence of narcotics, a contraband item.” Id., at 707 [103
S.Ct. 2637]; see also Indianapolis v. Edmond, 531 U.S.
32, 40 [121 S.Ct. 447, 148 L.Ed.2d 333] (2000).
Respondent likewise *42 concedes that “drug sniffs are
designed, and if properly conducted are generally likely,
to reveal only the presence of contraband.” Although
respondent argues that the error rates, particularly the
existence of false positives, call into question the premise
that drug-detection dogs alert only to contraband, the
record contains no evidence or findings that support his
argument. Moreover, respondent does not suggest that an
erroneous alert, in and of itself, reveals any legitimate
private information, and, in this case, the trial judge found
that the dog sniff was sufficiently reliable to establish
probable cause to conduct a full-blown search of the
trunk.
12
Accordingly, the use of a well-trained narcotics-detection
dog-one that “does not expose noncontraband items that
otherwise would remain hidden from public view,” Place,
462 U.S., at 707 [103 S.Ct. 2637]–during a lawful traffic
stop generally does not implicate legitimate privacy
interests. In this case, the dog sniff was performed on the
exterior of respondent’s car while he was lawfully seized
for a traffic violation. Any intrusion on respondent’s
privacy expectations does not rise to the level of a
constitutionally cognizable infringement.
Caballes, 543 U.S. at 408–09, 125 S.Ct. 834 (citation
omitted).
Further, the Court in Caballes distinguished its ruling in
Kyllo v. United States, 533 U.S. 27, 121 S.Ct. 2038, 150
L.Ed.2d 94 (2001), as follows:
This conclusion is entirely consistent with our recent
decision that the use of a thermal-imaging device to detect
the growth of marijuana in a home constituted an
unlawful search. Kyllo v. United States, 533 U.S. 27 [121
S.Ct. 2038, 150 L.Ed.2d 94] (2001). Critical to that
decision was the fact that the device was capable of
detecting lawful activity—in that case, intimate details in
a home, such as “at what hour each night the lady of the
house takes her daily sauna and bath.” Id., at 38 [121
S.Ct. 2038]. The legitimate expectation that information
about perfectly lawful activity will remain private is
categorically distinguishable from respondent’s hopes or
expectations concerning the nondetection of contraband in
the trunk of his car. A dog sniff conducted during a
concededly lawful traffic stop that reveals no information
other than the location of a substance that no individual
has any right to possess does not violate the Fourth
Amendment.
Caballes, 543 U.S. at 409–10, 125 S.Ct. 834.
B. Two Additional Federal Cases
In two additional cases, the United States Supreme Court
has addressed Fourth Amendment issues that are relevant
here. First, in United States v. Jacobsen, 466 U.S. 109,
104 S.Ct. 1652, 80 L.Ed.2d 85 (1984), the Court
addressed the issue of whether police, without a showing
of probable cause, could temporarily seize and inspect a
small portion of the contents of a package, which had
been damaged in transit and was being held by a private
shipping company, and then subject the contents to a field
test for cocaine. After employees of a private freight
carrier discovered a suspicious white powder in a

damaged package and notified federal agents, the agents
conducted a field chemical test on the powder and
determined that it was cocaine. The federal district court
denied Jacobsen’s motion to suppress, and the court of
appeals reversed. The United States Supreme Court
reversed, reasoning as follows:
A chemical test that merely discloses whether or not a
particular substance is cocaine does not compromise any
legitimate interest in privacy. This conclusion *43 is not
dependent on the result of any particular test. It is
probably safe to assume that virtually all of the tests
conducted under circumstances comparable to those
disclosed by this record would result in a positive finding;
in such cases, no legitimate interest has been
compromised. But even if the results are negative—
merely disclosing that the substance is something other
than cocaine—such a result reveals nothing of special
interest. Congress has decided—and there is no question
about its power to do so—to treat the interest in
“privately” possessing cocaine as illegitimate; thus
governmental conduct that can reveal whether a substance
is cocaine, and no other arguably “private” fact,
compromises no legitimate privacy interest.
This conclusion is dictated by United States v. Place, 462
U.S. 696 [103 S.Ct. 2637, 77 L.Ed.2d 110] (1983), in
which the Court held that subjecting luggage to a “sniff
test” by a trained narcotics detection dog was not a
“search” within the meaning of the Fourth Amendment....
Here, as in Place, the likelihood that official conduct of
the kind disclosed by the record will actually compromise
any legitimate interest in privacy seems much too remote
to characterize the testing as a search subject to the Fourth
Amendment.
Jacobsen, 466 U.S. at 123–24 [104 S.Ct. 1652] (footnote
omitted).
And second, in Kyllo v. United States, 533 U.S. 27, 121
S.Ct. 2038, 150 L.Ed.2d 94 (2001), the United States
Supreme Court addressed the issue of whether police,
without a warrant, could use a thermal-imaging device to
scan a private home to determine if the amount of heat
generated by the home was consistent with the use of
high-intensity lamps used in growing marijuana. After
federal agents became suspicious that Kyllo was growing
marijuana in his home, agents scanned the outside of the
triplex with a thermal-imaging device, which showed that
the garage roof and side of the residence were
inordinately warm. The agents obtained a warrant and
searched the residence and found live marijuana plants
inside. The federal district court denied Kyllo’s motion to
13
suppress, and the circuit court affirmed. The United States
Supreme Court reversed, reasoning as follows:
The Katz test—whether the individual has an expectation
of privacy that society is prepared to recognize as
reasonable—has often been criticized as circular, and
hence subjective and unpredictable. While it may be
difficult to refine Katz when the search of areas such as
telephone booths, automobiles, or even the curtilage and
uncovered portions of residences is at issue, in the case of
the search of the interior of homes—the prototypical and
hence most commonly litigated area of protected
privacy—there is a ready criterion, with roots deep in the
common law, of the minimal expectation of privacy that
exists, and that is acknowledged to be reasonable. To
withdraw protection of this minimum expectation would
be to permit police technology to erode the privacy
guaranteed by the Fourth Amendment. We think that
obtaining by sense-enhancing technology any information
regarding the interior of the home that could not
otherwise have been obtained without physical “intrusion
into a constitutionally protected area” constitutes a
search—at least where (as here) the technology in
question is not in general public use. This assures
preservation of that degree of privacy against government
that existed when the Fourth Amendment was adopted.
On the basis of this criterion, *44 the information
obtained by the thermal imager in this case was the
product of a search.
....
We have said that the Fourth Amendment draws “a firm
line at the entrance to the house.” That line, we think,
must be not only firm but also bright—which requires
clear specification of those methods of surveillance that
require a warrant. While it is certainly possible to
conclude from the videotape of the thermal imaging that
occurred in this case that no “significant” compromise of
the homeowner’s privacy has occurred, we must take the
long view, from the original meaning of the Fourth
Amendment forward.
“The Fourth Amendment is to be construed in the light of
what was deemed an unreasonable search and seizure
when it was adopted, and in a manner which will
conserve public interests as well as the interests and rights
of individual citizens.” Carroll v. United States, 267 U.S.
132, 149 [45 S.Ct. 280, 69 L.Ed. 543] (1925).
Where, as here, the Government uses a device that is not
in general public use, to explore details of the home that
would previously have been unknowable without physical
intrusion, the surveillance is a “search” and is

presumptively unreasonable without a warrant.
Kyllo, 533 U.S. at 34–40, 121 S.Ct. 2038 (citations
omitted) (quoting Silverman, 365 U.S. at 512, 81 S.Ct.
679; Payton v. New York, 445 U.S. 573, 590, 100 S.Ct.
1371, 63 L.Ed.2d 639 (1980)).
III. ANALYSIS
As noted above, the issue raised in the present case is
twofold: (i) whether a “sniff test” by a drug detection dog
conducted at the front door of a private residence is a
“search” under the Fourth Amendment and, if so, (ii)
whether the evidentiary showing of wrongdoing that the
government must make prior to conducting such a search
is probable cause or reasonable suspicion.
A. The Federal “Dog Sniff” Cases Are Inapplicable to
the Home
For reasons explained below, we conclude that the
analysis used in the above federal “dog sniff” cases is
inapplicable to a “sniff test” conducted at a private home.
First, we recognize that the United States Supreme Court
has ruled that because a “sniff test” conducted by a drug
detection dog is “sui generis,” or unique, in the sense that
it is minimally intrusive and is designed to detect only
illicit drugs and nothing more, Place, 462 U.S. at 707,
103 S.Ct. 2637, a dog “sniff test” does not implicate
Fourth Amendment rights when employed in the
following settings: (i) when conducted on luggage that
has been seized at an airport based on reasonable
suspicion of unlawful activity, where the luggage has
been separated from its owner and the “sniff test” is
conducted in a public place, see Place, 462 U.S. 696, 103
S.Ct. 2637; (ii) when conducted on the exterior of a
vehicle that has been stopped in a dragnet-style stop at a
drug interdiction checkpoint, see Edmond, 531 U.S. 32,
121 S.Ct. 447; and (iii) when conducted on the exterior of
a vehicle that has been subjected to a lawful traffic stop.
See Caballes, 543 U.S. 405, 125 S.Ct. 834. Further, the
United States Supreme Court has applied a similar
analysis to a chemical “field test” for drugs when
conducted on the contents of a package that has been
damaged in transit and is being held by a private shipping
company. See Jacobsen, 466 U.S. 109, 104 S.Ct. 1652.
We note, however, that in each of the above cases, the
United States Supreme Court was careful to tie its ruling
to the particular facts of the case. See *45 Place, 462
14
U.S. at 707, 103 S.Ct. 2637 (“[W]e conclude that the
particular course of investigation that the agents intended
to pursue here—exposure of respondent’s luggage, which
was located in a public place, to a trained canine—did not
constitute a ‘search’ within the meaning of the Fourth
Amendment.”); Edmond, 531 U.S. at 40, 121 S.Ct. 447
(“The fact that officers walk a narcotics-detection dog
around the exterior of each car at the Indianapolis
checkpoints does not transform the seizure into a
search.”); Caballes, 543 U.S. at 409, 125 S.Ct. 834 (“In
this case, the dog sniff was performed on the exterior of
respondent’s car while he was lawfully seized for a traffic
violation. Any intrusion on respondent’s privacy
expectations does not rise to the level of a constitutionally
cognizable infringement.”); Jacobsen, 466 U.S. at 123,
104 S.Ct. 1652 (“It is probably safe to assume that
virtually all of the tests conducted under circumstances
comparable to those disclosed by this record would result
in a positive finding; in such cases, no legitimate interest
has been compromised.”). Nothing in the above cases
indicates that the same analysis would apply to a dog
“sniff test” conducted at a private residence.
Significantly, all the sniff and field tests in the above
cases were conducted in a minimally intrusive manner
upon objects—luggage at an airport in Place, vehicles on
the roadside in Edmond and Caballes, and a package in
transit in Jacobsen—that warrant no special protection
under the Fourth Amendment. All the tests were
conducted in an impersonal manner that subjected the
defendants to no untoward level of public opprobrium,
humiliation or embarrassment. There was no public link
between the defendants and the luggage as it was being
tested in Place or the package as it was being tested in
Jacobsen, and the defendants retained a degree of
anonymity during the roadside testing of their vehicles in
Edmond and Caballes. Further, and more important,
under the particular circumstances of each of the above
cases, the tests were not susceptible to being employed in
a discriminatory or arbitrary manner—the luggage in
Place had been seized based on reasonable suspicion; the
vehicle in Edmond had been seized in a dragnet-style
stop; the vehicle in Caballes had been seized pursuant to a
lawful traffic stop; and the contents of the package in
Jacobsen had been seized after the package had been
damaged in transit by a private carrier. All these objects
were seized and tested in an objective and
nondiscriminatory manner, and there was no evidence of
overbearing or harassing government conduct. There was
no need for Fourth Amendment protection. As explained
below, however, such is not the case with respect to a dog
“sniff test” conducted at a private residence.

B. “Sniff Test” at a Private Home
As noted above, the United States Supreme Court has
held that “wherever an individual may harbor a
reasonable ‘expectation of privacy,’ he is entitled to be
free from unreasonable government intrusion.” Terry, 392
U.S. at 9, 88 S.Ct. 1868 (quoting Katz, 389 U.S. at 351,
88 S.Ct. 507 (Harlan, J., concurring)). Nowhere is this
right more resolute than in the private home: “ ‘At the
very core’ of the Fourth Amendment ‘stands the right of a
man to retreat into his own home and there be free from
unreasonable governmental intrusion.’ ” Kyllo, 533 U.S.
at 31, 121 S.Ct. 2038 (quoting Silverman v. United States,
365 U.S. 505, 511, 81 S.Ct. 679, 5 L.Ed.2d 734 (1961)).
The sanctity of the citizen’s home is a basic tenet of
Anglo–American jurisprudence:
In 1604, an English court made the now-famous
observation that “the house of every one is to him as his
castle and fortress, as well for his defence against *46
injury and violence, as for his repose.” Semayne’s Case, 5
Co. Rep. 91a, 91b, 77 Eng. Rep. 194, 195 (K.B.). In his
Commentaries on the Laws of England, William
Blackstone noted that
“the law of England has so particular and tender a regard
to the immunity of a man’s house, that it stiles it his
castle, and will never suffer it to be violated with
impunity: agreeing herein with the sentiments of ancient
Rome.... For this reason no doors can in general be broken
open to execute any civil process; though, in criminal
causes, the public safety supersedes the private.” 4
Commentaries 223 (1765–1769).
The Fourth Amendment embodies this centuries-old
principle of respect for the privacy of the home....
Wilson v. Layne, 526 U.S. 603, 609–10, 119 S.Ct. 1692,
143 L.Ed.2d 818 (1999); see also United States v. United
States Dist. Court for Eastern Dist. of Mich., 407 U.S.
297, 313, 92 S.Ct. 2125, 32 L.Ed.2d 752 (1972) (
“[P]hysical entry of the home is the chief evil against
which the wording of the Fourth Amendment is
directed....”).
[2] Although police generally may initiate a “knock and
talk” encounter at the front door of a private residence
without any prior showing of wrongdoing, see State v.
Morsman, 394 So.2d 408, 409 (Fla.1981) (“Under Florida
law it is clear that one does not harbor an expectation of
privacy on a front porch where salesmen or visitors may
appear at any time.”), a dog “sniff test” is a qualitatively
different matter. Contrary to popular belief, a “sniff test”
conducted at a private residence is not necessarily a
15
casual affair in which a canine officer and dog approach
the front door and the dog then performs a subtle “sniff
test” and signals an “alert” if drugs are detected. Quite the
contrary. In the present case, for instance, on the morning
of December 5, 2006, members of the Miami–Dade
Police Department, Narcotics Bureau, and agents of the
Drug Enforcement Administration (DEA), United States
Department of Justice, conducted a surveillance of
Jardines’ home. As Detectives Pedraja and Bartlet and the
drug detection dog, Franky, approached the residence,
Sergeant Ramirez and Detective Donnelly of the Miami–
Dade Police Department established perimeter positions
around the residence and federal DEA agents assumed
stand-by positions as backup units.
The “sniff test” conducted by the dog handler and his dog
was a vigorous and intensive procedure. Detective Bartlet
testified as follows on direct examination at the
suppression hearing:
Q. After you stepped onto the property, what did you do
A. I, basically, approached with my canine partner. The
way my canine partner works, he is very strongly driven,
so he is actually out in front of me. He is one of the dogs
that will actually pull me around very dramatically.
So he pulled directly up the porch as he is trained to do,
and immediately upon crossing the threshold of the
archway which you see here, upon entering the alcove of
the porch, he began tracking an airborne odor.
Q. Let me stop you there, Officer.
A. Sure.
Q. At this time in time, how far into this home did you get
or into the entranceway of the home did you get I want
you to point to the Court.
A. You see there’s a walker there That’s about the area
that it was I was in.
Q. There is also an archway there. Did you ever cross in
through that archway
*47 A. Not that I recall, no.
Q. So, where exactly was your dog when he alerted to an
alert of contraband
A. The alert for the dog, basically, is the minute I
observed out of normal behavior for him.
In this particular case, the abnormal behavior would have

een the head high, tracking the airborne odor. He began
tracking that airborne odor by bracketing and tracking
back and forth.
Q. What exactly is bracketing
A. Bracketing is a technique that the dog uses once he
comes to an odor—which is basically you can think of it
as a cloud of odor.
Once he gets into that cloud of odor, he is trained to go to
the strongest point. We call that source.
So, he is bracketing back and forth, back and forth, within
the cone of odor to determine the strongest source. In this
particular residence source for him was the base of the
door.
Q. And is Detective Pedraja observing this as well You
can’t speak for him
A. Yeah, I—to be honest with you, all I’m doing is
concentrating on the dog, watching the dog’s head
movements, his body postures, whence he is indicating
towards me.
Q. Detective, your dog is on a leash at that point
A. Oh, absolutely.
Q. How long is that leash
A. It’s approximately six feet. And then you have the
length of my arm, so you can assume from there.
Q. Okay. Once the dog began—what is it the dog did that
told you he had an alert
A. Okay. He immediately told me he had an alert when he
began tracking that odor. Now I know he is in odor and he
needs to find source.
So, what I do is I get back as far as I can. I let him have
the full six feet of the leash plus whatever safe distance I
can give him without running off in order for him to
determine where source is.
For example, if I don’t do that, source could be the
motorcycle, it could be somewhere else other than the
front door.
So, in order for me to fully observe his alert and where
the source is, I need to be creating as much distance as I
can.
16
Often handlers will drop the leash and walk away
completely. I don’t do that with him because he is a little
bit wild, so I maintain control of the leash and observe
him from a distance so that I can indicate where source is
going to be.
Q. Okay. So, once he detects a source and he is bracketing
and he is doing this behavior, what is the next thing that
you observe this dog do
A. The final culmination of his abnormal behavior is a
sitting position, and he did that immediately following the
sniff at the base of the door, which indicates source to me.
Q. And once Franky, your dog, did that, what did you
then do
A. I then pulled him off of the sit and returned to my
vehicle.
Q. Did you at any point in time communicate what the
dog did to anybody
A. Yeah, I indicated to the lead detective that there was a
positive alert for the odor of narcotics.
Q. And where exactly, in what direction around you, was
the detective at that point
A. He would have been behind me, so I passed him up in
the driveway.
*48 Q. Once you pulled the dog away from the door,
where did you then go
A. To my vehicle.
With respect to the location of Detective Pedraja in
relation to Detective Bartlet and Franky during the “sniff
test,” Bartlet testified as follows on redirect examination
at the suppression hearing:
Q. Would Detective Pedraja be in front of you as you are
conducting canine—I don’t even know what you would
call it.
....
[A.] Would he be in front of—while Franky is sniffing the
door Definitely not.
Q. Why not
A. Because he would be obstructing his ability to
perform. He would be blocking him. He would be—if he

was standing in front of the door, Franky may not be able
to get to source. So he needs to be out of the way.
Q. Was Detective Pedraja standing next to you
A. No.
Q. Why not
A. Because he probably would get knocked over by
Franky when Franky is spinning around trying to find
source.
[THE PROSECUTOR]: No further questions.
After the “sniff test” was completed, Detective Bartlet
and Franky left the scene to assist in another case.
Detective Pedraja, after waiting at the residence for
fifteen or twenty minutes, also left the scene to prepare a
search warrant and to submit it to a magistrate. Federal
DEA agents, however, remained behind to maintain
surveillance of Jardines’ home. Pedraja obtained a search
warrant later that day and returned to the scene. About an
hour later, members of the Miami–Dade Police
Department, Narcotics Bureau, and DEA agents executed
the warrant by gaining entry to Jardines’ home through
the front door. As agents entered the front door, Jardines
exited through a sliding glass door at the rear of the
house. He was apprehended by Special Agent Wilson of
the DEA and was turned over to the Miami–Dade Police
Department. He was charged with trafficking in marijuana
and theft of electricity.
Based on the foregoing, we conclude that the dog “sniff
test” that was conducted here was an intrusive procedure.
The “sniff test” was a sophisticated undertaking that was
the end result of a sustained and coordinated effort by
various law enforcement departments. On the scene, the
procedure involved multiple police vehicles, multiple law
enforcement personnel, including narcotics detectives and
other officers, and an experienced dog handler and trained
drug detection dog engaged in a vigorous search effort on
the front porch of the residence. Tactical law enforcement
personnel from various government agencies, both state
and federal, were on the scene for surveillance and
backup purposes. The entire on-the-scene government
activity—i.e., the preparation for the “sniff test,” the test
itself, and the aftermath, which culminated in the fullblown
search of Jardines’ home—lasted for hours. The
“sniff test” apparently took place in plain view of the
general public. There was no anonymity for the resident.
Such a public spectacle unfolding in a residential
neighborhood will invariably entail a degree of public
17
opprobrium, humiliation and embarrassment for the
resident, whether or not he or she is present at the time of
the search, for such dramatic government activity in the
eyes of many-neighbors, passers-by, and the public at
large-will be viewed as an official accusation of crime.
Cf. Place, 462 U.S. at 707, 103 S.Ct. 2637 (explaining
that the dog *49 “sniff test” in that case was not a
“search” within the meaning of the Fourth Amendment
because it was limited in scope and was anonymous and
did not subject the individual to “embarrassment and
inconvenience”). And if the resident happens to be
present at the time of the “sniff test,” such an intrusion
into the sanctity of his or her home will generally be a
frightening and harrowing experience that could prompt a
reflexive or unpredictable response.
Further, all the underlying circumstances that were
present in the above federal “dog sniff” and “field test”
cases that guaranteed objective, uniform application of
those tests—i.e., the temporary seizure of luggage based
on reasonable suspicion of criminal activity in Place; the
temporary seizure of a vehicle in a dragnet-style stop at a
drug interdiction checkpoint in Edmond; the temporary
seizure of a vehicle based on a lawful traffic stop in
Caballes; and the temporary seizure of a portion of the
contents of a package that had been damaged in transit in
Jacobsen—are absent from a warrantless “sniff test”
conducted at a private residence. Unlike the objects in
those cases, a private residence is not susceptible to being
seized beforehand based on objective criteria. Thus, if
government agents can conduct a dog “sniff test” at a
private residence without any prior evidentiary showing
of wrongdoing, there is simply nothing to prevent the
agents from applying the procedure in an arbitrary or
discriminatory manner, or based on whim and fancy, at
the home of any citizen. Cf. Camara v. Mun. Court of
City & Cnty. of S. F., 387 U.S. 523, 528, 87 S.Ct. 1727,
18 L.Ed.2d 930 (1967) (“The basic purpose of [the
Fourth] Amendment, as recognized in countless decisions
of this Court, is to safeguard the privacy and security of
individuals against arbitrary invasions by governmental
officials.”). Such an open-ended policy invites
overbearing and harassing conduct.7
[3] In sum, a “sniff test” by a drug detection dog
conducted at a private residence does not only reveal the
presence of contraband, as was the case in the federal “sui
generis” dog sniff cases discussed above, but it also
constitutes an intrusive procedure that may expose the
resident to public opprobrium, humiliation and
embarrassment, and it raises the specter of arbitrary and
discriminatory application. Given the special status
accorded a citizen’s home under the Fourth Amendment,
we conclude that a “sniff test,” such as the test that was

conducted in the present case, is a substantial government
intrusion into the sanctity of the home and constitutes a
“search” within the meaning of the Fourth Amendment.
As such, it warrants the safeguards that inhere in that
amendment—specifically, the search must be preceded by
an evidentiary showing of wrongdoing. We note that the
rulings of other state8 and federal9 courts with respect *50
to a dog “sniff test” conducted at a private residence are
generally mixed, as are the rulings of other state10 and
federal11 courts with respect a dog “sniff test” conducted
at an apartment or other temporary dwelling.
C. The Requirement of Probable Cause
As noted above, the Warrant Clause of the Fourth
Amendment provides that “no warrants shall issue, but
upon probable cause, supported by oath or affirmation,
and particularly describing the place to be searched, and
the persons or things to be seized.” U.S. Const. amend.
IV. The United States Supreme Court has noted the key
protective role that this clause plays with respect to
private property:
Though there has been general agreement as to the
fundamental purpose of the Fourth Amendment,
translation of the abstract prohibition against
“unreasonable searches and seizures” into
workable guidelines for the decision of particular
cases is a difficult task which has for many years
divided the members of this Court. Nevertheless,
one governing principle, justified by history and
by current experience, has consistently been
followed: except in certain carefully defined
classes of cases, a search of private property
without proper consent is “unreasonable” unless it
has been authorized by a valid search warrant.
Camara, 387 U.S. at 528–29, 87 S.Ct. 1727. Specifically,
with respect to the home, that Court has noted as follows:
*51 The right of officers to thrust themselves into
a home is also a grave concern, not only to the
individual but to a society which chooses to dwell
in reasonable security and freedom from
surveillance. When the right of privacy must
reasonably yield to the right of search is, as a rule,
to be decided by a judicial officer, not by a
policeman or government enforcement agent.
Johnson v. United States, 333 U.S. 10, 14, 68 S.Ct. 367,
92 L.Ed. 436 (1948); see also Welsh v. Wisconsin, 466
U.S. 740, 748, 104 S.Ct. 2091, 80 L.Ed.2d 732 (1984)
(“[A] principal protection against unnecessary intrusions
into private dwellings is the warrant requirement imposed
by the Fourth Amendment on agents of the government
who seek to enter the home for purposes of search or
arrest.”). Or, more succinctly: “With few exceptions, the
question whether a warrantless search of a home is
reasonable and hence constitutional must be answered
no.” Kyllo, 533 U.S. at 31, 121 S.Ct. 2038; see also
Payton v. New York, 445 U.S. 573, 586, 100 S.Ct. 1371,
63 L.Ed.2d 639 (1980) (“It is a basic principle of Fourth
Amendment law that searches and seizures inside a home
without a warrant are presumptively unreasonable.”)
(internal quotation marks omitted).
The Court of Appeals for the District of Columbia in
United States v. Colyer, 878 F.2d 469 (D.C.Cir.1989),
was confronted with the following question: if a dog
“sniff test” is a “search” under the Fourth Amendment
and must be preceded by an evidentiary showing of
wrongdoing, must that showing be probable cause, or
reasonable suspicion That court addressed the question
at length:
In his concurring opinion in Place, Justice Blackmun
suggested that “a dog sniff may be a search, but a
minimally intrusive one that could be justified in this
situation under Terry upon a mere reasonable suspicion.”
462 U.S. at 723 [103 S.Ct. 2637] (Blackmun, J.,
concurring in judgment). We find ourselves hard pressed
for authority from the Supreme Court to support Justice
Blackmun’s underlying premise—that there is a category
of “minimally intrusive” searches that are supportable
under Terry on less than probable cause.
It is certainly true that the Supreme Court has upheld a
wide variety of searches on less than probable cause as
traditionally understood, but in no case was a lawenforcement
search denominated “minimally intrusive.”
Indeed, the Supreme Court’s opinion in Arizona v. Hicks,
[480 U.S. 321, 107 S.Ct. 1149, 94 L.Ed.2d 347 (1987) ]
may indicate that the contrary is the case, i.e., that the
Fourth Amendment knows no search but a “full-blown
search.” Hicks, 480 U.S. at 328 [107 S.Ct. 1149] (“A
search is a search, even if it happens to disclose nothing
but the bottom of a turntable.”). Compare id. with id. at
333 [107 S.Ct. 1149] (O’Connor, J., dissenting)
(“distin[guishing] between searches based on their
relative intrusiveness ... is entirely consistent with our
Fourth Amendment jurisprudence”).
Rather than interpreting Terry as broad authority for the
proposition that minimally intrusive searches may be
18

justified on the basis of reasonable suspicion, the
Supreme Court has on several occasions limited Terry to
its precise underpinnings, i.e., protective searches for
weapons. See Dunaway v. New York, 442 U.S. 200, 210
[99 S.Ct. 2248, 60 L.Ed.2d 824] (1979) (Terry is directed
to “limited, on-the-street frisk[s] for weapons.”). Indeed,
the Court has gone so far as to say that Terry provides no
support for “any search whatever for anything but
weapons.” Ybarra v. Illinois, 444 U.S. 85, 93–94 [100
S.Ct. 338, 62 L.Ed.2d 238] (1979). See also Pennsylvania
*52 v. Mimms, 434 U.S. 106, 110 [98 S.Ct. 330, 54
L.Ed.2d 331] (1977) (per curiam); Sibron v. New York,
392 U.S. 40, 64–65 [88 S.Ct. 1889, 20 L.Ed.2d 917]
(1968) (“The search was not reasonably limited in scope
to the accomplishment of the only goal which might
conceivably have justified its inception-the protection of
the officer by disarming a potentially dangerous man.”).
Thus, Professor LaFave seems correct in concluding that
“there is no search-for-evidence counterpart to the Terry
weapons search, permissible on only a reasonable
suspicion that such evidence would be found.” [3 Wayne
R. LaFave, Search and Seizure: A Treatise on the Fourth
Amendment, § 9.4(g), at 539 (2d ed. 1987) ].
However, Terry does represent one of a lengthy line of
cases in which the Supreme Court has upheld a search or
seizure “[w]here a careful balancing of governmental and
private interests suggests that the public interest is best
served by a Fourth Amendment standard of
reasonableness that stops short of probable cause.” New
Jersey v. T.L.O., 469 U.S. 325, 341 [105 S.Ct. 733, 83
L.Ed.2d 720] (1985). Yet a careful reading of the
Supreme Court’s teachings leaves us doubtful that
“reasonableness balancing” is appropriate in the context
of the present case. Five times in as many years the Court
has indicated that balancing is only appropriate when
warranted by “special needs, beyond the normal need for
law enforcement.” See Skinner v. Railway Labor
Executives’ Assoc., 489 U.S. 602 [109 S.Ct. 1402, 103
L.Ed.2d 639] (1989); National Treasury Employees
Union v. Von Raab, 489 U.S. 656 [109 S.Ct. 1384, 103
L.Ed.2d 685] (1989); Griffin v. Wisconsin, 483 U.S. 868,
107 S.Ct. 3164, 97 L.Ed.2d 709 (1987); O’Connor v.
Ortega, [480 U.S. 709, 107 S.Ct. 1492, 94 L.Ed.2d 714
(1987) ]; New Jersey v. T.L.O., 469 U.S. at 351 [105 S.Ct.
733] (Blackmun, J., concurring in judgment).
This interpretation explains the various cases in which the
Supreme Court has held searches to be lawful despite the
absence of probable cause as traditionally understood. See
T.L.O., 469 U.S. 325 [105 S.Ct. 733] (search by school
official of student’s purse); O’Connor, 480 U.S. 709 [107
S.Ct. 1492] (work-related search by governmental
19
employer); Griffin, 483 U.S. [at] 873–74 [107 S.Ct. 3164]
(search of probationer’s home); Camara v. Municipal
Court, 387 U.S. 523 [87 S.Ct. 1727, 18 L.Ed.2d 930]
(1967) (housing inspections); New York v. Burger, [482
U.S. 691, 107 S.Ct. 2636, 96 L.Ed.2d 601 (1987) ]
(inspections of highly regulated business premises);
Donovan v. Dewey, 452 U.S. 594 [101 S.Ct. 2534, 69
L.Ed.2d 262] (1981) (inspections of underground mines);
Bell v. Wolfish, 441 U.S. 520, 558–60 [99 S.Ct. 1861, 60
L.Ed.2d 447] (1979) (body cavity searches of prison
inmates); United States v. Brignoni–Ponce, 422 U.S. 873,
880–81 [95 S.Ct. 2574, 45 L.Ed.2d 607] (1975) (border
patrols); United States v. Biswell, 406 U.S. 311, 316 [92
S.Ct. 1593, 32 L.Ed.2d 87] (1972) (inspections of
“pervasively regulated business” for compliance with Gun
Control Act); Terry, 392 U.S. 1 [88 S.Ct. 1868] (search
for weapons, to protect officer and public). In no case has
the Supreme Court indicated that a search for evidence
qua evidence might qualify as a “special need” that would
warrant reasonableness balancing. Common sense
suggests that it is not.
To be sure, the Supreme Court has upheld on reasonable
suspicion a variety of “minimally intrusive” seizures in
contexts different from the “stop and frisk” originally
approved in Terry. In such *53 cases, the “ ‘seizures’
[were] so substantially less intrusive than arrests that the
general rule requiring probable cause to make Fourth
Amendment ‘seizures’ reasonable could be replaced by a
balancing test.” Dunaway v. New York, 442 U.S. at 210
[99 S.Ct. 2248]. See, e.g., United States v. Sharpe, 470
U.S. 675, 685 [105 S.Ct. 1568, 84 L.Ed.2d 605] (1985)
(investigative stop of vehicle); Delaware v. Prouse, 440
U.S. 648 [99 S.Ct. 1391, 59 L.Ed.2d 660] (1979) (random
checks for drivers’ licenses and vehicle registration);
United States v. Brignoni–Ponce, 422 U.S. at 880–81 [95
S.Ct. 2574] (brief investigative stop of motorists near
border for questioning; analogizing situation to encounter
addressed in Terry ); see also United States v.
Villamonte–Marquez, 462 U.S. 579, 592 [103 S.Ct. 2573,
77 L.Ed.2d 22] (1983) (random seizure of vessel in order
to examine manifest); United States v. Martinez–Fuerte,
428 U.S. [543, 560, 96 S.Ct. 3074, 49 L.Ed.2d 1116
(1976) ] (brief random checkpoint questioning for aliens).
Although there may be no compelling reason to
differentiate between seizures on the basis of their
intrusiveness and failing to likewise differentiate between
types of searches, the fact remains that we are unable to
point to a single Supreme Court case that has upheld a
search on reasonable suspicion merely because it was
minimally intrusive. See, e.g., Michigan v. Long, 463 U.S.
1032 [103 S.Ct. 3469, 77 L.Ed.2d 1201] (1983);
Pennsylvania v. Mimms, 434 U.S. 106 [98 S.Ct. 330, 54

L.Ed.2d 331] (1977) (per curiam); Adams v. Williams,
407 U.S. 143 [92 S.Ct. 1921, 32 L.Ed.2d 612] (1972); cf.
Martinez–Fuerte, 428 U.S. at 561 [96 S.Ct. 3074]
(upholding as reasonable a random seizure and noting that
it was not dealing with a search).
Colyer, 878 F.2d at 477–79 (citations omitted).
Professor LaFave has reached the same conclusion with
respect to the issue of probable cause versus reasonable
suspicion:
Assuming now that some uses of these dogs constitutes a
search, it does not inevitably follow that they should be
encumbered by the restrictions ordinarily applicable to
other types of searches which are clearly more intrusive in
character. While it has sometimes been asserted that if the
use of trained dogs is a search then such surveillance is
unconstitutional if conducted in absence of a warrant
supported by probable cause, it may be argued that the
Fourth Amendment does not demand such a result. In
Terry v. Ohio, the Court upheld a limited warrantless
search made upon less than full probable cause “by
balancing the need to search ... against the invasion which
the search ... entails,” and thus a similar approach might
be taken as to the kind of search here under discussion.
Although there are sound reasons for not employing too
generously a graduated model of the fourth amendment,
the notion that searches by use of dogs trained to detect
narcotics ... is a lesser intrusion subject to lesser Fourth
Amendment restrictions is an appealing one. This is
because this particular investigative technique is a distinct
police practice which quite obviously is much less
intrusive than other searches. It seems rather unlikely,
however, that the Supreme Court would now reach such a
conclusion. The Court has declared that the Fourth
Amendment knows no search but a “full-blown search,”
asserted that Terry provides no support for “any search
whatever for anything but weapons,” and cautioned that
the balancing process is appropriate only when warranted
by “special needs *54 beyond the normal need of law
enforcement.”
1 Wayne R. LaFave, Search and Seizure: A Treatise on
the Fourth Amendment § 2.2(g), at 540–41 (4th ed. 2004)
(quotation marks and footnotes omitted).
[4] We agree with the above analyses and note that the
parties in the present case have failed to point to a single
case in which the United States Supreme Court has
indicated that a search for evidence for use in a criminal
prosecution, absent special needs beyond the normal need
of law enforcement, may be based on anything other than
probable cause. We assume that this is because, as noted
20
in the commentary above, all that Court’s precedent in
this area indicates just the opposite. And that precedent,
we recognize, applies with extra force where the sanctity
of the home is concerned. Accordingly, we conclude that
probable cause, not reasonable suspicion, is the proper
evidentiary showing of wrongdoing that the government
must make under the Fourth Amendment prior to
conducting a dog “sniff test” at a private residence.
IV. THE SUPPRESSION RULING
[5] [6] [7] A magistrate’s determination that probable
cause exists for issuance of a search warrant is entitled to
great deference when a trial court is considering a motion
to suppress. Illinois v. Gates, 462 U.S. 213, 238–39, 103
S.Ct. 2317, 76 L.Ed.2d 527 (1983) (“[T]he duty of a
reviewing court is simply to ensure that the magistrate
had a ‘substantial basis for ... conclud [ing] that’ probable
cause existed.”). And a trial court’s ruling on a motion to
suppress in such a case is subject to the following
standard of review: the reviewing court must defer to the
trial court’s factual findings if supported by competent,
substantial evidence but must review the trial court’s
ultimate ruling independently, or de novo. State v.
Glatzmayer, 789 So.2d 297, 301 n. 7 (Fla.2001); see also
Connor v. State, 803 So.2d 598 (Fla.2001).
In the present case, the trial court granted Jardines’
motion to suppress, ruling as follows:
This cause having come before this Court on Defendant,
Joelis Alex Jardines’, motion to suppress evidence seized
from his house and this Court having reviewed the
motion, the arguments of counsel, the court file and the
records in this case, and being otherwise fully advised in
the premises therein:
A drug detector dog was used to support probable cause
for the issuance of a search warrant of the Defendant’s
house. The Defendant moved to suppress the evidence of
drugs recovered from his house as a result of the search
warrant. Pursuant to State v. Rabb, 920 So.2d 1175 (Fla.
4th DCA 2006), this Court concludes that law
enforcement’s use of a drug detector dog at the
Defendant’s house door constituted an unreasonable and
illegal search.
However, the Court must also consider, absent the dog
sniff information, whether any independent and lawfully
obtained evidence establishes a substantial basis for
concluding that probable cause existed to support the
issuance of a search warrant for the Defendant’s house.

The probable cause affidavit listed the information
provided from a crime stoppers tip that marijuana was
being grown at the residence as a basis to support
probable cause for the issuance of a search warrant.
However, the crime stoppers tip was unverified and came
from an unknown individual rather than a qualified
confidential informant. Additionally, there was no
evidence to suggest *55 the crime stoppers tip was
corroborated by any evidence resulting from surveillance
of the house. The only other evidence contained in the
affidavit was that the window blinds were closed and the
air conditioner unit was constantly running without
recycling. This information, considered in its totality,
simply does not suggest a fair probability of any broader
criminal activity, such as the growing of marijuana in the
Defendant’s house. Therefore, this Court concludes that
no independent and lawfully obtained evidence
establishes the probable cause necessary to support the
issuance of a search warrant for the Defendant’s house.
Ordered and adjudged that even with great deference
afforded to the search warrant for the Defendant’s house
in this case, the probable cause affidavit did not provide a
substantial basis for concluding that probable cause
existed. Therefore, the motion to suppress evidence seized
from the Defendant’s house is granted.
With respect to the fact that Detective Pedraja testified
that he smelled the odor of live marijuana plants as he
stood outside the front door of Jardines’ house, the trial
court stated as follows in a footnote: “There was evidence
that after the drug detection dog had alerted to the odor of
a controlled substance, the officer also detected a smell of
marijuana plants emanating from the front door.
However, this information was only confirming what the
detection dog had already revealed.”
As explained above, a warrantless “sniff test” by a drug
detection dog conducted at the front door of a private
residence is impermissible under the Fourth Amendment.
Thus, the trial court properly excluded the results of the
“sniff test” from its review of the magistrate’s probable
cause determination. The remaining evidence consisted of
the following: the unverified “crime stoppers” tip, the
closed window blinds, and the constantly running air
conditioner. As for Detective Pedraja’s statement that he
detected the odor of live marijuana plants as he stood
outside the front door, we note that the trial court had the
opportunity to observe Detective Pedraja’s testimony
first-hand at the suppression hearing. Further, the district
court in Rabb addressed an identical situation and
concluded as follows:
[B]ecause the chronology of the probable cause
affidavit suggests that the dog alert to marijuana
occurred prior to law enforcement’s detection of
its odor, we cannot assume that law enforcement
detected the odor of marijuana before the dog
alerted.... As such, this is not a case in which a law
enforcement officer used his senses to detect
something within his plain smell; rather, a law
enforcement officer used enhanced, animal senses
to detect something inside a home that he might
not otherwise have detected.
Rabb, 920 So.2d at 1191. Based on our review of the
present record, we conclude that the trial court’s factual
findings are supported by competent, substantial evidence
and the trial court’s ultimate ruling is supported in the
law. The district court erred in reversing the suppression
ruling.
V. CONCLUSION
“We have said that the Fourth Amendment draws ‘a firm
line at the entrance to the house.’ That line, we think,
must be not only firm but also bright—which requires
clear specification of those methods of surveillance that
require a warrant.” Kyllo, 533 U.S. at 40, 121 S.Ct. 2038
(citation omitted) (quoting Payton, 445 U.S. at 590, 100
S.Ct. 1371). Given the special status accorded a citizen’s
home in Anglo–American jurisprudence, we hold that the
warrantless “sniff test” that was conducted *56 at the
front door of the residence in the present case was an
unreasonable government intrusion into the sanctity of the
home and violated the Fourth Amendment.
We quash the decision in Jardines and approve the result
in Rabb.
It is so ordered.
PARIENTE, LEWIS, QUINCE, and LABARGA, JJ.,
concur.
LEWIS, J., specially concurs with an opinion, in which
PARIENTE and LABARGA, JJ., concur.
POLSTON, J., dissents with an opinion, in which
CANADY, C.J., concurs.
LEWIS, J., specially concurring.
21

The importance of freedom and liberty upon which this
nation was founded is expressed in the Fourth
Amendment and its protection of our homes from the
government. This precious amendment reflects who we
are as a people and reflects our values that protect every
citizen from unreasonable intrusions by the government. “
‘At the very core’ of the Fourth Amendment ‘stands the
right of a man to retreat into his own home and there be
free from unreasonable government intrusion.’ ” Kyllo v.
United States, 533 U.S. 27, 31, 121 S.Ct. 2038, 150
L.Ed.2d 94 (2001) (quoting Silverman v. United States,
365 U.S. 505, 511, 81 S.Ct. 679, 5 L.Ed.2d 734 (1961)).
“Of all the places that can be searched by the police, one’s
home is the most sacrosanct, and receives the greatest
Fourth Amendment protection.” United States v.
McGough, 412 F.3d 1232, 1236 (11th Cir.2005) (citing
Payton v. New York, 445 U.S. 573, 585, 100 S.Ct. 1371,
63 L.Ed.2d 639 (1980)). In light of the elevated
protections afforded to the privacy of one’s home, the
United States Supreme Court has held that “[w]ith few
exceptions, the question whether a warrantless search of a
home is reasonable and hence constitutional must be
answered no.” Kyllo, 533 U.S. at 31, 121 S.Ct. 2038
(citing Illinois v. Rodriguez, 497 U.S. 177, 110 S.Ct.
2793, 111 L.Ed.2d 148 (1990)). This Court has also
expressed its reluctance to intrude on the privacy of one’s
home:
The Fourth Amendment establishes “[t]he right of the
people to be secure in their persons, houses, papers, and
effects, against unreasonable searches and seizures....”
U.S. Const. amend. IV (emphasis added). Indeed,
“physical entry of the home is the chief evil against which
the wording of the Fourth Amendment is directed,”
United States v. United States District Court, 407 U.S.
297, 313, 92 S.Ct. 2125, 32 L.Ed.2d 752 (1972), and “[a]t
the very core [of the Fourth Amendment] stands the right
of a man to retreat into his own home and there be free
from unreasonable governmental intrusion.” Silverman v.
United States, 365 U.S. 505, 511, 81 S.Ct. 679, 5 L.Ed.2d
734 (1961).
State v. Titus, 707 So.2d 706, 708 (Fla.1998). In my view
the primary emphasis in this case must fall on this concept
of “home” and its sacred place under Fourth Amendment
law.
First, the underlying basis for the search in question here,
i.e., the anonymous tip, was insufficient to justify a search
that would otherwise be in violation of the Fourth
Amendment. In J.L. v. State, 727 So.2d 204 (Fla.1998),
aff’d, 529 U.S. 266, 120 S.Ct. 1375, 146 L.Ed.2d 254
(2000), this Court held that an anonymous tip cannot be a
stand alone basis for reasonable suspicion. This Court
22
made clear that when presented with an anonymous tip,
“police must observe additional suspicious circumstances
as a result of ... independent investigation” before the
police can act on that tip. Id. at 207 (citing *57 Alabama
v. White, 496 U.S. 325, 329, 110 S.Ct. 2412, 110 L.Ed.2d
301 (1990)). In unanimously upholding this Court’s
decision in J.L., the United States Supreme Court also
held that an uncorroborated anonymous tip is not a
reliable justification for a Fourth Amendment search
because, “[u]nlike a tip from a known informant whose
reputation can be assessed and who can be held
responsible if her allegations turn out to be fabricated ...
‘an anonymous tip alone seldom demonstrates the
informant’s basis of knowledge or veracity.’ ” Florida v.
J.L., 529 U.S. 266, 270, 120 S.Ct. 1375, 146 L.Ed.2d 254
(2000) (citing Adams v. Williams, 407 U.S. 143, 146–47,
92 S.Ct. 1921, 32 L.Ed.2d 612 (1972)) (quoting White,
496 U.S. at 329, 110 S.Ct. 2412).
Here, the “sniff test” was conducted based on nothing
more than an unverifiable anonymous tip. See State v.
Jardines, 9 So.3d 1, 2 (Fla. 3rd DCA 2008). Prior to
entering the private porch of Jardines, the only purported
“additional suspicious circumstance” referenced by the
investigating officer was that he observed the air
conditioning unit running continuously for fifteen minutes
without interruption. See id. If a continuously running air
conditioner is indicative of marijuana cultivation, then
most Florida citizens and certainly all of my neighbors
would be suspected drug dealers subject to intrusive
searches by law enforcement. The elevation of such a
ridiculous observation in the heat of Florida cannot serve
as a basis for intrusion on the heightened expectation of
privacy that one enjoys in one’s home. Further, there was
no evidence of any impending emergency or concern with
regard to destruction of evidence. In light of the complete
lack of any legitimate, articulable grounds for searching
Jardines’ home, the police officer, and his accompanying
dog, should not have been on Jardines’ porch “sniffing”
under the front door in the first place.
Second, it is my view that the dog action here constituted
a search of a home, in and of itself, and falls within the
concept of a search under the Fourth Amendment. A
reasonable expectation of privacy, a value of this society
that has developed over many decades, applies not only to
the physical, tangible items within a home, but also to the
air and odors that may be within and may unintentionally
escape from within. The scent of items cooking on a
stove, the whiff of an air freshener, or even the foul smell
associated with a ruptured sewage line are all intimate
details of a home that are expected to remain private and
unavailable to the public. We as Americans have an

unwavering expectation that there will not be someone, or
something, sniffing into every crack, crevice, window, or
chimney of our homes. We especially do not expect
strangers to bring dogs onto or into our private front
porches to sniff under our front doors or any of the cracks
or crevices of our homes. This protected interest of the
expectation of privacy will be obliterated if a single
individual, manipulating an animal, is permitted to make
the final determination as to whether the government
should enter into a private residence based upon an
unverified, uncorroborated, anonymous tip. To sanction
and approve turning the “dogs loose” on the homes of
Florida citizens is the antithesis of freedom of private
property and the expectation of privacy as we have known
it and contrary to who we are as a free people.
The private residence is completely unlike the operation
of a motor vehicle on highways, the transport of suitcases
in public places, or the transport of packages in public
transport. See City of Indianapolis v. Edmond, 531 U.S.
32, 121 S.Ct. 447, 148 L.Ed.2d 333 (2000); United States
v. *58 Place, 462 U.S. 696, 103 S.Ct. 2637, 77 L.Ed.2d
110 (1983). The sanctity of the private residence, above
all other expectations of privacy, has been a hallmark of
this nation. A private residence is the most sacred of
places under the Fourth Amendment, and an intrusion into
that sacrosanct privacy commands the highest level of
judicial scrutiny. As articulated by the Fourth District
Court of Appeal, “An airport and a highway are
unquestionably public places with little or no privacy, as
much as a home is undoubtedly a private place
characterized by its very privacy.” State v. Rabb, 920
So.2d 1175, 1186 (Fla. 4th DCA 2006). Further, luggage
located in a public airport, the interior of a vehicle driving
on a public highway, and the contents of a package in
public transport are “quite different from a house, not
only in physical attributes, but also in the historical
protection granted by law.” Id. at 1184. A private home,
on the other hand, is just that, a private, individual home.
While the expectation of privacy inherent within the
private residence may not exist in or extend to common
walkways, roadways, or other locations that are not within
a private dwelling, that which is within the private
residence is most assuredly protected. A hallway outside a
college dormitory, for example, may not contain the same
expectation of privacy as the front door and living room
of a private home. We may discuss and debate the
concept and extent of curtilage and the nexus with a
private residence necessary to be considered part of a
protected area. However, it is inescapable that the air and
the content of the air within the private home is
inextricably interwoven as part of the protected zone of
23
privacy to which the expectation of privacy attaches. This
air is inextricably interwoven in the constitutional context
as part of the sanctity of a Florida private home and the
private lives of our citizens protected therein. The home
and the air within the home are expected and intended to
remain within the sanctity of the home with no intent,
design, or expectation that they become public or exposed
beyond the walls of the home. While one of great wealth
with a newly constructed air-tight private home surely has
an expectation of privacy of the home and of the air
constituted therein, his less wealthy Florida neighbor
should not be denied the same fundamental protection
simply because his less substantially constructed private
home may have a crack or crevice through which air or
odors may unintentionally and unexpectedly escape to its
curtilage. Allowing a dog to sniff the air and odors that
escape from within a home under a door is tantamount to
physical entry into that home. Under the view articulated
by the dissent, a dog entering a home through the front
door, a window, or any other large crack or crevice would
not amount to an unconstitutional search. Surely we
cannot permit the sanctity of the privacy of our homes to
be measured by the size of the cracks or crevices from
which air may escape.
My esteemed colleague in dissent incorrectly asserts that
a recognition of the right of Floridians to be free from
unauthorized dog sniffs in their homes is a violation of
United States Supreme Court precedent. Specifically, my
colleague relies on four inapplicable United States
Supreme Court decisions that approve the validity of dog
sniffs in limited situations outside the home, each of
which is so clearly distinguishable from the facts
presently before the Court. In United States v. Place, 462
U.S. 696, 697–98, 103 S.Ct. 2637, 77 L.Ed.2d 110
(1983), the narrow question before the United States
Supreme Court was whether the Fourth Amendment
prohibits law enforcement authorities from temporarily
detaining personal luggage *59 outside the home in a
public place for exposure to a trained narcotics detection
dog on the basis of reasonable suspicion that the luggage
contains narcotics. In United States v. Jacobsen, 466 U.S.
109, 111, 104 S.Ct. 1652, 80 L.Ed.2d 85 (1984), the
Supreme Court simply determined whether police needed
to obtain a warrant before searching a damaged package
in a public location, visibly leaking a white powdery
substance, while in the possession of a private freight
carrier. In City of Indianapolis v. Edmond, 531 U.S. 32,
34, 121 S.Ct. 447, 148 L.Ed.2d 333 (2000), the United
Supreme Court considered in a public place the
“constitutionality of a highway checkpoint program
whose primary purpose is the discovery and interdiction
of illegal narcotics.” (Emphasis supplied.) Finally, in

Illinois v. Caballes, 543 U.S. 405, 407, 125 S.Ct. 834, 160
L.Ed.2d 842 (2005), the question before the Court was in
a public place or roadway “[w]hether the Fourth
Amendment requires reasonable, articulable suspicion to
justify using a drug-detection dog to sniff a vehicle during
a legitimate traffic stop.” (Emphasis supplied.) None of
these decisions, or any other decision of the United States
Supreme Court, has ever addressed whether the Fourth
Amendment requires reasonable, articulable suspicion to
justify a dog sniff under the front door of a single family
private residence. Accordingly, contrary to the assertion
of the dissent, there is no “binding United States Supreme
Court precedent” to violate. Dissenting op. at 61.
The core of the dissent’s opinion fails to accommodate
and is built upon a lack of appreciation for the elevated
status that a protected private home has in both this Court
and the United States Supreme Court. The dissent asserts
that “[b]ecause the dog sniff is only capable of detecting
contraband, it is only capable of detecting that which is
not protected by the Fourth Amendment.” Dissenting op.
at 70. Perhaps this statement holds true for luggage in a
public airport, a package in a public transport and
distribution facility, or in a vehicle on a public roadway,
but as discussed above, there are many intimate details
associated with the content and odors that may flow from
the cracks and crevices of a home. Each of the
aforementioned items carries an expectation of privacy
that is in no way as great as the expectation of privacy
that exists in an individual’s home. The dissent fails to
accommodate and recognize the increased expectation of
privacy that exists in one’s home, an expectation that all
courts have recognized as greater than any other. To
dismiss the critical difference between this case, involving
a dog sniff of an individual’s home, and the four other
cases relied on by the dissent dangerously undermines the
most sacrosanct place that is vulnerable to intrusion by
the government, our homes.
Further, the complete absence of any United States
Supreme Court precedent on dog sniffs of the cracks and
crevices of a private home does not in any way preclude
this Court from declaring such a search unconstitutional;
rather, it empowers this Court to do so. Although it is true
that article 1, section 12 of the Florida Constitution
requires this Court to “follow the interpretations of the
United States Supreme Court with respect to the Fourth
Amendment and provide to Florida citizens no greater
protection than those interpretations,” Soca v. State, 673
So.2d 24, 27 (Fla.1996), it is also true that in the absence
of a controlling United States Supreme Court decision,
Florida courts are still not prohibited from providing our
citizens with a higher standard of protection from
24
governmental intrusion than that afforded by the Federal
Constitution. See id. at 26–27 (citing State v. Lavazzoli,
434 So.2d 321, 323 (Fla.1983)).
*60 Third, the lack of a uniform system of training and
certification for drug detection canines makes it
unconstitutionally difficult for a defendant to challenge a
dog sniff after circumstances such as these have occurred.
As articulated by the Second District Court of Appeal in
Matheson v. State, 870 So.2d 8, 14 (Fla. 2d DCA 2003):
[C]onditioning and certification programs vary widely in
their methods, elements, and tolerances of failure.
Consider, for example, the United States Customs Service
regime:
The Customs Service puts its dog and handler teams
through a rigorous twelve-week training course, where
only half of the canines complete the training. Customs
Service dogs are trained to disregard potential distractions
such as food, harmless drugs, and residual scents. Agents
present distractions during training, and reward the dogs
when those diversions are ignored. The teams must
complete a certification exam in which the dog and
handler must detect marijuana, hashish, heroin, and
cocaine in a variety of environments. This exam and the
following annual recertifications must be completed
perfectly, with no false alerts and no missed drugs. If a
dog and handler team erroneously alerts, the team must
undergo remedial training. If the team fails again, the
team is disbanded, and the dog is permanently relieved
from duty.
[Robert C. Bird, An Examination of the Training and
Reliability of the Narcotics Detection Dog, 85 Ky. L.J.
405, 410–11 (1997) ]. In contrast, the testimony below
disclosed that Razor and his handler had undergone just
one initial thirty-day training course and one week-long
annual recertification course. In neither course was Razor
conditioned to refrain from alerting to residual odors.
Whereas the Customs Service will certify only dogs who
achieve and maintain a perfect record, Razor’s
certification program accepted a seventy percent
proficiency. These disparities demonstrate that simply
characterizing a dog as “trained” and “certified”
imparts scant information about what the dog has been
conditioned to do or not to do, or how successfully.
Finally, dogs themselves vary in their abilities to accept,
retain, or abide by their conditioning in widely varying
environments and circumstances. “[E]ach dog’s
performance is affected differently by working conditions
and its respective attention span. There is also the
possibility that the handler may unintentionally or

otherwise prompt his dog to alert.” [Max A. Hansen,
United States v. Solis: Have the Government’s
Supersniffers Come Down With a Case of Constitutional
Nasal Congestion, 13 San Diego L.Rev. 410, 416 (1976)
]. The Customs Service monitors its dogs’ performance in
the field. Recognizing that a dog’s ability can change over
time, it maintains records for only thirty to sixty days,
then discards them because older records are not
probative of the dog’s skills. Bird, 85 Ky. L.J. at 415. The
Hillsborough County Sheriff’s Office maintained no
records of Razor’s performance, and his handler had not
kept track.
(Emphasis supplied.) Due to the clear lack of uniformity
in certification for drug detection dogs, the Second
District in Matheson held that the fact that a dog is trained
and certified, standing alone, is insufficient to establish
probable cause to search a home based exclusively on the
dog’s alert. See id. I agree with the sound reasoning
articulated in Matheson. The complete lack of a uniform
or standardized *61 system of certifying drug detection
canines renders it unduly burdensome for a defendant to
challenge the validity of an intrusive dog sniff into a
private home that results in an arrest. Forcing finders of
fact to rely exclusively on the assertions of police officers
that their own dogs are properly trained is inconsistent
with our time honored understanding of due process.
Here, the probable cause affidavit simply notes that the
drug detection dog received “weekly maintenance
training,” but does not at all indicate what that training
entails or how extensive that training may be. See
Jardines, 9 So.3d at 2. This statement, void of any
specificity or substance, cannot serve as an irrefutable
declaration that establishes a dog’s ability to detect drugs.
Finally, the dissent asserts that “distinguishing this case
from the United States Supreme Court’s dog sniff cases
based upon the level of embarrassment the majority
presumes to be present here is improper.” Dissenting op.
at 69–70. This case involves an unconstitutional search of
a private residence by dogs without any verifiable
training, the underlying premise of which does not pass
constitutional muster. The level of embarrassment
suffered by the party that has been searched is not a
significant part of the constitutional analysis and does not
in any way negate the constitutional invalidity of the
search.
We cannot permit the protections of the Fourth
Amendment, fragile as they may be, to be decimated
piece by piece and little by little until they become mere
vestiges of our past. All courts recognize that the home
and curtilage of a home are protected and the protection is
25
determined by factors with regard to whether an
individual reasonably may expect that the area in question
should receive the same status as the home itself. The
cracks and crevices around our front doors or windows
that may permit air to unintentionally escape are surely in
a reasonably free society areas protected by our most
cherished document.
PARIENTE and LABARGA, JJ., concur.
POLSTON, J., dissenting.
Because the majority’s decision violates binding United
States Supreme Court precedent, I respectfully dissent.
Despite the majority’s focus upon multiple officers and
the supposed time involved in surveillance and in
execution of the search warrant,12 it is undisputed that
one dog and two officers were lawfully and briefly
present near the front door of Jardines’ residence when
the dog sniff at issue in this case took place. And despite
statements about privacy interests in items and odors
within and escaping from a home,13 the United States
Supreme Court has ruled that there are no legitimate
privacy interests in contraband under the Fourth
Amendment. See Illinois v. Caballes, 543 U.S. 405, 408,
125 S.Ct. 834, 160 L.Ed.2d 842 (2005) (“Official conduct
that does not ‘compromise any legitimate interest in
privacy’ is not a search subject to the Fourth Amendment.
We have held that any interest in possessing contraband
cannot be deemed ‘legitimate.’ ”) (quoting United States
v. Jacobsen, 466 U.S. 109, 123, 104 S.Ct. 1652, 80
L.Ed.2d 85 (1984)).
Contrary to the majority’s position, the United States
Supreme Court has ruled that a dog sniff is not a search
within the meaning of the Fourth Amendment because a
dog sniff only reveals contraband in which there is no
legitimate privacy *62 interest. See id. (holding that dog
sniff of vehicle was not a search within meaning of Fourth
Amendment and explaining that “governmental conduct
that only reveals the possession of contraband
‘compromises no legitimate privacy interest.’ ”) (quoting
Jacobsen, 466 U.S. at 123, 104 S.Ct. 1652); City of
Indianapolis v. Edmond, 531 U.S. 32, 40, 121 S.Ct. 447,
148 L.Ed.2d 333 (2000) (“Just as in United States v.
Place, 462 U.S. 696, 103 S.Ct. 2637, 77 L.Ed.2d 110
(1983), an exterior sniff of an automobile does not require
entry into the car and is not designed to disclose any
information other than the presence or absence of

narcotics.”); Jacobsen, 466 U.S. at 124 n. 24, 104 S.Ct.
1652 (“[T]he reason [the dog sniff in Place] did not
intrude upon any legitimate privacy interest was that the
governmental conduct could reveal nothing about
noncontraband items.”); Place, 462 U.S. at 707, 103 S.Ct.
2637 (“[T]he sniff discloses only the presence or absence
of narcotics, a contraband item. Thus, despite the fact that
the sniff tells the authorities something about the contents
of the luggage, the information obtained is limited.”).
Accordingly, the dog sniff involved in this case, which
occurred while law enforcement was lawfully present at
the front door, cannot be considered a search in violation
of the Fourth Amendment.
I. BACKGROUND
On November 3, 2006, law enforcement received an
anonymous tip identifying Jardines’ home as a place used
to grow marijuana. On December 5, 2006, law
enforcement set up surveillance of Jardines’ residence.
After Detective Pedraja of the Miami–Dade Police
Department had conducted surveillance for fifteen
minutes, Detective Bartlet of the Miami–Dade Police
Department arrived with a drug-detection dog, Franky.
Detective Bartlet and Franky, who was on a six-foot
leash, approached the front porch of the residence with
Detective Pedraja behind them. Franky began tracking an
odor and traced it to the front door, where Franky
assumed a sitting position after sniffing at the base of the
door, thereby alerting to the scent of marijuana. Detective
Bartlet and Franky immediately returned to Detective
Bartlet’s vehicle. Thereafter, Detective Pedraja smelled
the scent of live marijuana at the front door. Detective
Pedraja then knocked on the front door, received no
response, and noticed that Jardines’ air conditioner was
running excessively.14
Based upon this information, a search warrant was
obtained, and Jardines’ residence was searched. The
search resulted in the seizure of live marijuana plants and
equipment used to grow those plants. Jardines was
charged with trafficking in cannabis and grand theft.
Jardines moved to suppress the seized evidence, arguing
that Franky’s sniff was an unconstitutional search and that
Officer Pedraja’s smell of marijuana was tainted by
Franky’s prior sniff. The trial court granted Jardines’
motion. On appeal, *63 however, the Third District
reversed, reasoning as follows:
[F]irst, a canine sniff is not a Fourth Amendment
26
search; second, the officer and the dog were
lawfully present at the defendant’s front door; and
third, the evidence seized would inevitably have
been discovered.
State v. Jardines, 9 So.3d 1, 4 (Fla. 3d DCA 2008). In
holding that a dog sniff does not constitute a search under
the Fourth Amendment, the Third District certified
conflict with the Fourth District’s decision in State v.
Rabb, 920 So.2d 1175 (Fla. 4th DCA 2006).
II. ANALYSIS
The Fourth Amendment to the United States Constitution
provides that “[t]he right of the people to be secure in
their persons, houses, papers, and effects, against
unreasonable searches and seizures, shall not be violated.”
The similar right contained in the Florida Constitution is
“construed in conformity with the 4th Amendment to the
United States Constitution, as interpreted by the United
States Supreme Court.” Art. I, § 12, Fla. Const. Therefore,
this Court’s jurisprudence in this area must conform to the
United States Supreme Court’s precedent interpreting the
Fourth Amendment.
In this case, it is undisputed that law enforcement was
lawfully present at Jardines’ front door. While the Fourth
Amendment certainly protects “the right of a man to
retreat into his own home and there be free from
unreasonable governmental intrusion,” Silverman v.
United States, 365 U.S. 505, 511, 81 S.Ct. 679, 5 L.Ed.2d
734 (1961), the publicly accessible area around the front
door of the home is not accorded the same degree of
Fourth Amendment protection. See, e.g., United States v.
French, 291 F.3d 945, 953 (7th Cir.2002) (“The route
which any visitor or delivery man would use is not private
in the Fourth Amendment sense....”) (quoting United
States v. Evans, 27 F.3d 1219, 1229 (7th Cir.1994));
United States v. Hersh, 464 F.2d 228, 230 (9th Cir.1972)
(“Absent express orders from the person in possession
against any possible trespass, there is no rule of private or
public conduct which makes it illegal per se, or a
condemned invasion of the person’s right of privacy, for
anyone openly and peaceably, at high noon, to walk up
the steps and knock on the front door of any man’s
‘castle’ with the honest intent of asking questions of the
occupant thereof—whether the questioner be a pollster, a
salesman, or an officer of the law.”) (quoting Davis v.
United States, 327 F.2d 301, 303 (9th Cir.1964)). In fact,
the majority acknowledges that “one does not harbor an
expectation of privacy on a front porch where salesmen or
visitors may appear at any time.” Majority op. at 46

(quoting State v. Morsman, 394 So.2d 408, 409
(Fla.1981)).
Furthermore, there are no allegations here that an officer’s
detection of the scent of marijuana while lawfully present
at Jardines’ front door would have violated the Fourth
Amendment. There are no such allegations because “the
police may see what may be seen ‘from a public vantage
point where [they have] a right to be.’ ” Florida v. Riley,
488 U.S. 445, 449, 109 S.Ct. 693, 102 L.Ed.2d 835
(1989) (quoting California v. Ciraolo, 476 U.S. 207, 213,
106 S.Ct. 1809, 90 L.Ed.2d 210 (1986)) (reversing a
decision of this Court that had factually distinguished a
United States Supreme Court decision to hold that a
helicopter’s flight at 400 feet over property near a home
violated the Fourth Amendment); see also United States
v. Ventresca, 380 U.S. 102, 85 S.Ct. 741, 13 L.Ed.2d 684
(1965) (search warrant properly based in part upon
investigators’ smell of odor when they walked in front of
home). Or, as the Ninth Circuit plainly put it with *64
regard to the sense of smell, one does not have “a
reasonable expectation of privacy from drug agents with
inquisitive nostrils.” United States v. Johnston, 497 F.2d
397, 398 (9th Cir.1974); see also 1 Wayne R. LaFave,
Search and Seizure: A Treatise on the Fourth Amendment
§ 2.3(c), at 575–77 (4th ed. 2004) (“[I]f police utilize
‘normal means of access to and egress from the house’ for
some legitimate purpose, such as to make inquiries of the
occupant, to serve a subpoena, or to introduce an
undercover agent into the activities occurring there, it is
not a Fourth Amendment search for the police to see or
hear or smell from that vantage point what is happening
inside the dwelling.”) (footnotes omitted) (quoting
Lorenzana v. Superior Court, 9 Cal.3d 626, 108 Cal.Rptr.
585, 511 P.2d 33, 37 (1973)); United States v. Angelos,
433 F.3d 738, 747 (10th Cir.2006) (applying the “plain
smell” doctrine).
Accordingly, the only remaining question at issue in this
case is whether a law enforcement officer, who is lawfully
present at the front door of a private residence, may
employ a dog sniff at that front door. Based upon binding
United States Supreme Court precedent, the answer is
quite clearly yes.
The United States Supreme Court has explained that “a
Fourth Amendment search does not occur—even when
the explicitly protected location of a house is concerned—
unless ‘the individual manifested a subjective expectation
of privacy in the object of the challenged search,’ and
‘society [is] willing to recognize that expectation as
reasonable.’ ” Kyllo v. United States, 533 U.S. 27, 33, 121
S.Ct. 2038, 150 L.Ed.2d 94 (2001) (quoting Ciraolo, 476
U.S. at 211, 106 S.Ct. 1809) (alteration in original).
Additionally, and of great importance here, the United
States Supreme Court has held that a dog sniff does not
constitute a search within the meaning of the Fourth
Amendment because it only reveals contraband and there
is no legitimate privacy interest in contraband that society
is willing to recognize as reasonable. See Caballes, 543
U.S. 405, 125 S.Ct. 834; Edmond, 531 U.S. 32, 121 S.Ct.
447; Place, 462 U.S. 696, 103 S.Ct. 2637; see also
Jacobsen, 466 U.S. 109, 104 S.Ct. 1652.
First, in Place, 462 U.S. at 707, 103 S.Ct. 2637, the
United States Supreme Court stated the following
regarding the unique and very limited nature of a dog
sniff when holding that a dog sniff of a passenger’s
luggage in an airport was not a search under the Fourth
Amendment:
We have affirmed that a person possesses a privacy
interest in the contents of personal luggage that is
protected by the Fourth Amendment. Id., at 13 [97 S.Ct.
2476]. A “canine sniff” by a well-trained narcotics
detection dog, however, does not require opening the
luggage. It does not expose noncontraband items that
otherwise would remain hidden from public view, as
does, for example, an officer’s rummaging through the
contents of the luggage. Thus, the manner in which
information is obtained through this investigative
technique is much less intrusive than a typical search.
Moreover, the sniff discloses only the presence or absence
of narcotics, a contraband item. Thus, despite the fact that
the sniff tells the authorities something about the contents
of the luggage, the information obtained is limited. This
limited disclosure also ensures that the owner of the
property is not subjected to the embarrassment and
inconvenience entailed in less discriminate and more
intrusive investigative methods.
In these respects, the canine sniff is sui generis. We are
aware of no other investigative procedure that is so
limited *65 both in the manner in which the information
is obtained and in the content of the information revealed
by the procedure. Therefore, we conclude that the
particular course of investigation that the agents intended
to pursue here—exposure of respondent’s luggage, which
was located in a public place, to a trained canine—did not
constitute a “search” within the meaning of the Fourth
Amendment.
Then, the United States Supreme Court further explained
its decision in Place when holding in Jacobsen, 466 U.S.
at 123, 104 S.Ct. 1652, that a chemical test of a package
did not constitute a search because “governmental
27

conduct that can reveal whether a substance is cocaine,
and no other arguably ‘private’ fact, compromises no
legitimate privacy interest.” The Court stated that this
holding was “dictated” by Place because, “as in Place,
the likelihood that official conduct of the kind disclosed
by the record will actually compromise any legitimate
interest in privacy seems much too remote to characterize
the testing as a search subject to the Fourth Amendment.”
Jacobsen, 466 U.S. at 124, 104 S.Ct. 1652. The Court
explained that “the reason [the dog sniff in Place] did not
intrude upon any legitimate privacy interest was that the
governmental conduct could reveal nothing about
noncontraband items.” Id. at 124 n. 24, 103 S.Ct. 2637.
Thereafter, in Edmond, 531 U.S. at 40, 121 S.Ct. 447, the
United States Supreme Court reaffirmed Place when
briefly discussing why a dog sniff of the exterior of a car
stopped at a checkpoint did not constitute a search:
It is well established that a vehicle stop at a highway
checkpoint effectuates a seizure within the meaning of the
Fourth Amendment. See, e.g., Sitz, [496 U.S.] at 450 [110
S.Ct. 2481]. The fact that officers walk a narcoticsdetection
dog around the exterior of each car at the
Indianapolis checkpoints does not transform the seizure
into a search. See United States v. Place, 462 U.S. 696,
707 [103 S.Ct. 2637, 77 L.Ed.2d 110] (1983). Just as in
Place, an exterior sniff of an automobile does not require
entry into the car and is not designed to disclose any
information other than the presence or absence of
narcotics. See ibid. Like the dog sniff in Place, a sniff by
a dog that simply walks around a car is “much less
intrusive than a typical search.” Ibid. Cf. United States v.
Turpin, 920 F.2d 1377, 1385 (C.A.8 1990).
Finally, in Caballes, 543 U.S. at 408–09, 125 S.Ct. 834,
the United States Supreme Court again reaffirmed Place
as well as Jacobsen when holding that a dog sniff of the
exterior of a vehicle during a lawful traffic stop was not a
search because the sniff only revealed contraband in
which there is no legitimate privacy interest:
[C]onducting a dog sniff would not change the character
of a traffic stop that is lawful at its inception and
otherwise executed in a reasonable manner, unless the
dog sniff itself infringed respondent’s constitutionally
protected interest in privacy. Our cases hold that it did
not.
Official conduct that does not “compromise any
legitimate interest in privacy” is not a search subject to
the Fourth Amendment. Jacobsen, 466 U.S., at 123 [104
S.Ct. 1652]. We have held that any interest in possessing
contraband cannot be deemed “legitimate,” and thus,
28
governmental conduct that only reveals the possession of
contraband “compromises no legitimate privacy interest.”
Ibid. This is because the expectation “that certain facts
will not come to the attention of the authorities” is not the
same as an interest in “privacy that society is prepared to
consider reasonable.” *66 Id., at 122 [104 S.Ct. 1652]
(punctuation omitted). In United States v. Place, 462 U.S.
696 [103 S.Ct. 2637, 77 L.Ed.2d 110] (1983), we treated a
canine sniff by a well-trained narcotics-detection dog as
“sui generis ” because it “discloses only the presence or
absence of narcotics, a contraband item.” Id., at 707 [103
S.Ct. 2637] see also Indianapolis v. Edmond, 531 U.S. 32,
40 [121 S.Ct. 447, 148 L.Ed.2d 333] (2000)....
Accordingly, the use of a well-trained narcotics-detection
dog—one that “does not expose noncontraband items that
otherwise would remain hidden from public view,” Place,
462 U.S., at 707 [103 S.Ct. 2637]—during a lawful traffic
stop, generally does not implicate legitimate privacy
interests. In this case, the dog sniff was performed on the
exterior of respondent’s car while he was lawfully seized
for a traffic violation. Any intrusion on respondent’s
privacy expectations does not rise to the level of a
constitutionally cognizable infringement.
In Caballes, the Court also explained why its dog sniff
decisions are consistent with its thermal-imaging
decision, namely because—unlike a thermal imaging
device—a dog sniff only reveals contraband:
This conclusion is entirely consistent with our recent
decision that the use of a thermal-imaging device to detect
the growth of marijuana in a home constituted an
unlawful search. Kyllo v. United States, 533 U.S. 27 [121
S.Ct. 2038, 150 L.Ed.2d 94] (2001). Critical to that
decision was the fact that the device was capable of
detecting lawful activity—in that case, intimate details in
a home, such as “at what hour each night the lady of the
house takes her daily sauna and bath.” Id., at 38 [121
S.Ct. 2038]. The legitimate expectation that information
about perfectly lawful activity will remain private is
categorically distinguishable from respondent’s hopes or
expectations concerning the nondetection of contraband in
the trunk of his car. A dog sniff conducted during a
concededly lawful traffic stop that reveals no information
other than the location of a substance that no individual
has any right to possess does not violate the Fourth
Amendment.
To summarize, in Place, Jacobsen, Edmond, and
Caballes, the United States Supreme Court held that dog
sniffs are not searches within the meaning of the Fourth
Amendment because they only detect contraband and
there is no legitimate privacy interest in contraband that

society recognizes as reasonable. A vast majority of
federal15 and state16 courts have interpreted *68 the
United States Supreme Court’s decisions as holding that
dog sniffs are not searches under the Fourth Amendment,
even in the context of private residences.17
In this case, Franky the dog was lawfully present at
Jardines’ front door when he alerted to the presence of
marijuana. And because, under the binding United States
Supreme Court precedent described above, a dog sniff
only reveals contraband in which there is no legitimate
privacy interest, Franky’s sniff cannot be considered a
search violating the Fourth Amendment.
The majority concludes that the United States Supreme
Court’s precedent regarding dog sniffs does not apply
here because those dog sniff cases did not involve dog
sniffs of a home. See majority op. at 44. However, the
United States Supreme Court did not limit its reasoning
regarding dogs sniffs to locations or objects unrelated to
the home. There is no language in Place, Jacobsen,
Edmond, or Caballes that indicates the reasoning that dog
sniffs are not searches (because they only reveal
contraband in which there is no legitimate expectation of
privacy) would change if the cases involved private
residences. And, most importantly, the United States
Supreme Court issued Caballes after its ruling *69 in
Kyllo, a case involving a home. Caballes specifically
distinguishes Kyllo, not based upon the object sniffed, but
by explaining that, unlike the thermal imaging device
involved in Kyllo, a dog sniff only reveals contraband.
See Caballes, 543 U.S. at 409–10, 125 S.Ct. 834.
Therefore, the very limited and unique type of intrusion
involved in a dog sniff is the dispositive distinction under
United States Supreme Court precedent, not whether the
object sniffed is luggage, an automobile, or a home.
Accordingly, the majority’s holding based upon the object
sniffed is contrary to the United States Supreme Court’s
precedent.18 Kyllo is the precedent that is inapplicable to
this dog sniff case, not the United States Supreme Court’s
cases that actually involve dog sniffs.
In addition, the majority distinguishes the binding
precedent regarding dog sniffs based upon what it terms
“public opprobrium, humiliation and embarrassment.”
Majority op. at 36, 45, 48, 49–50. By focusing upon the
multiple officers and the supposed time involved in
surveillance and the execution of the search warrant, the
majority concludes that the sniff here was more intensive
and involved a higher level of embarrassment than the
sniffs involved in Place, Edmond, and Caballes. See
majority op. at 46–47, 48–49. However, Place, Edmond,
and Caballes all involved law enforcement activity by
29
multiple officers. See Place, 462 U.S. at 698–99, 103
S.Ct. 2637 (describing law enforcement activity by
multiple officers in Miami and two DEA agents in New
York); Edmond, 531 U.S. at 34–36, 121 S.Ct. 447
(describing law enforcement activity by approximately
thirty officers of the Indianapolis Police Department);
Caballes, 543 U.S. at 406, 125 S.Ct. 834 (describing law
enforcement activity by two officers). And although the
majority states that the law enforcement activity in this
case “lasted for hours,” majority op. at 36, 48, there is no
evidence in the record to support that supposition. To the
contrary, when asked during the suppression hearing how
long he and the dog “remain[ed] on the scene that day,”
Detective Bartlet responded, “That was a day we were
doing multiple operations and I had probably two other
people waiting for the dog. So I couldn’t have been there
much more than five or ten minutes, just enough to grab
the information on the flash drive, hand it over and
leave.” The other specific testimony regarding time in the
record is Detective Pedraja’s testimony during the
suppression hearing explaining that he conducted
surveillance for fifteen minutes before approaching the
residence with Detective Bartlet and the dog and that it
was “approximately 15 to 20 minutes from the time that
[he] went to the front door, was standing at the threshold,
went to the front door and then came back.” Furthermore,
as explained above, there are no allegations here that the
multiple officers near Jardines’ residence violated the
Fourth Amendment, regardless of the level of “public
opprobrium, humiliation, and embarrassment” that the
presence of these officers may have caused Jardines.
Therefore, distinguishing this case from the United States
Supreme Court’s dog sniff cases based upon the level of
embarrassment *70 the majority presumes to be present
here is improper.
Finally, it is critical to note that the majority’s (and the
special concurrence’s) assumption that Jardines had a
reasonable expectation that the smell of marijuana coming
from his residence would remain private is contrary to the
explicit pronouncements in Jacobsen and Caballes that
the possessor of contraband has no legitimate expectation
of privacy in that contraband. See United States v. Colyer,
878 F.2d 469, 475 (D.C.Cir.1989) ( “[T]he Supreme
Court’s analyses in Place and Jacobsen indicate that a
possessor of contraband can maintain no legitimate
expectation that its presence will not be revealed.”).
Indeed, the fact that one has no reasonable expectation of
privacy in contraband is precisely why a dog sniff is not a
search under the United States Supreme Court’s precedent
interpreting the Fourth Amendment. Because the dog sniff
is only capable of detecting contraband, it is only capable
of detecting that which is not protected by the Fourth
Amendment. See Caballes, 543 U.S. at 408, 125 S.Ct. 834

(“We have held that any interest in possessing contraband
cannot be deemed ‘legitimate,’ and thus, governmental
conduct that only reveals the possession of contraband
‘compromises no legitimate privacy interest.’ ”) (quoting
Jacobsen, 466 U.S. at 123, 104 S.Ct. 1652).
under the Fourth Amendment. Therefore, I would approve
the Third District’s decision in Jardines and disapprove
the Fourth District’s contrary decision in Rabb.
Accordingly, I respectfully dissent.
III. CONCLUSION
As held by United States Supreme Court, a dog sniff is
not a search within the meaning of the Fourth
Amendment because it only reveals contraband and there
is no legitimate expectation of privacy in contraband that
society is willing to recognize as reasonable. Given this
binding precedent, Franky’s sniff, while lawfully present
at Jardines’ front door, cannot be considered a search
CANADY, C.J., concurs.
Parallel Citations
36 Fla. L. Weekly S147
Footnotes
1 The affidavit that Detective Pedraja submitted to the magistrate provided as follows, in relevant part:
“Your Affiant’s” reasons for the belief that “The Premises” is being used as [a marijuana hydroponics grow lab] and that “The
Property [consisting of marijuana and the equipment to grow it]” listed above is being concealed and stored at “The Premises” is as
follows:
On November 3, 2006, “Your Affiant” detective William Pedraja, # 1268, received information from a crime stoppers tip that
marijuana was being grown at the described residence.
On December 5, 2006, “Your Affiant” conducted surveillance at the residence and observed no vehicles in the driveway. “Your
Affiant” also observed windows with the blinds closed. “Your Affiant” and Detective Doug Bartelt with K–9 drug detection dog
“FRANKY” approached “The Premises” in an attempt to obtain a consent to search. While at front door [sic], “Your Affiant”
detected the smell of live marijuana plants emanating from the front door of “The Premises.” The scent of live marijuana is a
unique and distinctive odor unlike any other odor. Additionally, K–9 drug detection dog “FRANKY” did alert to the odor of one of
the controlled substances he is trained to detect. “Your Affiant,” in an attempt to obtain a written consent to search, knocked on the
front door of “The Premises” without response. “Your Affiant” also heard an air conditioning unit on the west side of the residence
continuously running without recycling. The combination of these factors is indicative of marijuana cultivation.
Based upon the positive alert by narcotics detector dog “FRANKY” to the odor of one or more of the controlled substances that she
is trained to detect and “FRANKY” [sic] substantial training, certification, and past reliability in the field in detecting those
controlled substances, it is reasonable to believe that one or more of those controlled substances are present within the area alerted
to by “FRANKY.” Narcotics Canine handler, Detective Bartelt, Badge number 4444, has been a police officer with the Miami–
Dade Police Department for nine years. He has been assigned to the Narcotics Bureau for six years and has been a canine handler
since May 2004. In the period of time he has been with the Department, he has participated in over six hundred controlled
substances searches. He has attended the following training and received certification as a canine handler....
Since becoming a team, Detective Bartelt and narcotics detector canine “FRANKY” have received weekly maintenance training....
Narcotics detector canine “FRANKY” is trained to detect the odor of narcotics emanating from the following controlled substances
to wit: marijuana.... To date, narcotics detector canine “FRANKY” has worked approximately 656 narcotics detection tasks in the
field. He has positively alerted to the odor of narcotics approximately 399 times. “FRANKY’S” positive alerts have resulted in the
detection and seizure of approximately 13,008 grams of cocaine, 2,638 grams of heroin, 180 grams of methamphetamine, 936,614
grams of marijuana, both processed ready for sale and/or live growing marijuana.
WHEREFORE, Affiant prays that a Search Warrant be issued ... to search “The Premises” above-described....
2 The Fourth District Court of Appeal in State v. Rabb, 920 So.2d 1175 (Fla. 4th DCA 2006), affirmed the trial court’s suppression
of illicit drugs (marijuana found growing in Rabb’s house) following a warrantless “sniff test” by a drug detection dog at the front
door of Rabb’s home. The district court based its ruling on Kyllo v. United States, 533 U.S. 27, 121 S.Ct. 2038, 150 L.Ed.2d 94
(2001), reasoning as follows:
[Our logic here] is no different than that expressed in Kyllo, one of the recent pronouncements by the United States Supreme Court
on law enforcement searches of houses. The use of the dog, like the use of a thermal imager, allowed law enforcement to use
sense-enhancing technology to intrude into the constitutionally-protected area of Rabb’s house, which is reasonably considered a
search violative of Rabb’s expectation of privacy in his retreat. Likewise, it is of no importance that a dog sniff provides limited
information regarding only the presence or absence of contraband, because as in Kyllo, the quality or quantity of information
30

obtained through the search is not the feared injury. Rather, it is the fact that law enforcement endeavored to obtain the information
from inside the house at all, or in this case, the fact that a dog’s sense of smell crossed the “firm line” of Fourth Amendment
protection at the door of Rabb’s house. Because the smell of marijuana had its source in Rabb’s house, it was an “intimate detail”
of that house, no less so than the ambient temperature inside Kyllo’s house. Until the United States Supreme Court indicates
otherwise, therefore, we are bound to conclude that the use of a dog sniff to detect contraband inside a house does not pass
constitutional muster. The dog sniff at the house in this case constitutes an illegal search.
Rabb, 920 So.2d at 1184.
3 We note that the First District Court of Appeal in Stabler v. State, 990 So.2d 1258 (Fla. 1st DCA 2008), also certified conflict with
Rabb. In Stabler, the district court held that a dog “sniff test” conducted at an apartment door that opens onto a common area
accessible to the general public does not constitute a “search” for Fourth Amendment purposes. As noted herein, Stabler is
distinguishable from Rabb in that Stabler involved a “sniff test” conducted at an apartment or other temporary dwelling, not a
“sniff test” conducted at a private residence. See infra note 10.
4 The comparable provision of the Florida Constitution is contained in article I, section 12, which further provides: “This right shall
be construed in conformity with the 4th Amendment to the United States Constitution, as interpreted by the United States Supreme
Court.” Art. I, § 12, Fla. Const.
5 Katz v. United States, 389 U.S. 347, 88 S.Ct. 507, 19 L.Ed.2d 576 (1967) (addressing the issue of whether police, without a
warrant, can listen to and record one end of a telephone conversation in a public phone booth via an electronic listening and
recording device attached to the outside surface of the booth).
6 Terry v. Ohio, 392 U.S. 1, 88 S.Ct. 1868, 20 L.Ed.2d 889 (1968) (addressing the issue of whether police, based on an evidentiary
showing of less than probable cause, can temporarily seize and search a person).
7 There is little doubt, however, that a dragnet-style sweep of an entire residential neighborhood or of a multi-unit residential
dwelling, conducted without any individualized suspicion of wrongdoing, would be impermissible. Cf. City of Indianapolis v.
Edmond, 531 U.S. at 41, 121 S.Ct. 447 (“We have never approved a checkpoint program whose primary purpose was to detect
evidence of ordinary criminal wrongdoing. Rather, our checkpoint cases have recognized only limited exceptions to the general
rule that a seizure must be accompanied by some measure of individualized suspicion.”).
8 Compare State v. Rabb, 920 So.2d 1175 (Fla. 4th DCA 2006) (holding that a dog “sniff test” outside a private residence is a
“search” within the meaning of the Fourth Amendment); with People v. Jones, 279 Mich.App. 86, 755 N.W.2d 224 (2008)
(holding that a dog “sniff test” outside a private residence is not a “search” within the meaning of the Fourth Amendment); and
Porter v. State, 93 S.W.3d 342 (Tex.App.2002) (holding that a dog “sniff test” outside a private residence is not a “search” within
the meaning of the Fourth Amendment); and Rodriguez v. State, 106 S.W.3d 224 (Tex.App.2003) (holding that a dog “sniff test”
outside a private residence is not a “search” within the meaning of the Fourth Amendment).
9 See United States v. Tarazon–Silva, 960 F.Supp. 1152 (W.D.Tex.1997) (holding that a dog “sniff test” outside a private residence
is not a “search” within the meaning of the Fourth Amendment).
10 Compare State v. Ortiz, 257 Neb. 784, 600 N.W.2d 805 (1999) (holding that a dog “sniff test” outside an apartment is a “search”
within the meaning of the Fourth Amendment); with Fitzgerald v. State, 384 Md. 484, 864 A.2d 1006 (2004) (holding that a dog
“sniff test” outside an apartment is not a “search” within the meaning of the Fourth Amendment); and Stabler v. State, 990 So.2d
1258 (Fla. 1st DCA 2008) (holding that a dog “sniff test” outside an apartment is not a “search” within the meaning of the Fourth
Amendment); and Nelson v. State, 867 So.2d 534 (Fla. 5th DCA 2004) (indicating that a dog “sniff test” outside a hotel room is
not a “search” within the meaning of the Fourth Amendment); and People v. Dunn, 77 N.Y.2d 19, 563 N.Y.S.2d 388, 564 N.E.2d
1054 (1990) (holding that a dog “sniff test” outside an apartment is not a “search” within the meaning of the Fourth Amendment,
but is a search within the meaning of the state constitution).
11 Compare United States v. Whitehead, 849 F.2d 849 (4th Cir.1988) (holding that a dog “sniff test” outside a railway sleeper
compartment is a “search” within the meaning of the Fourth Amendment); and United States v. Thomas, 757 F.2d 1359 (2d
Cir.1985) (holding that a dog “sniff test” outside an apartment is a “search” within the meaning of the Fourth Amendment); with
United States v. Brock, 417 F.3d 692 (7th Cir.2005) (holding that a dog “sniff test” outside a locked bedroom is not a “search”
within the meaning of the Fourth Amendment); and United States v. Roby, 122 F.3d 1120 (8th Cir.1997) (indicating that a dog
“sniff test” outside a hotel room is not a “search” within the meaning of the Fourth Amendment); and United States v. Colyer, 878
F.2d 469 (D.C.Cir.1989) (holding that a dog “sniff test” outside a railway sleeper compartment is not a “search” within the
meaning of the Fourth Amendment); and United States v. Broadway, 580 F.Supp.2d at 1179 (D.Colo.2008) (holding that a dog
“sniff test” outside an apartment is not a “search” within the meaning of the Fourth Amendment).
31

12 See majority op. at 35–36, 46, 47–49.
13 See special concurrence at 57.
14 According to testimony presented at the suppression hearing, Detective Pedraja remained behind Franky and Detective Bartlet
while the dog sniff occurred. And based upon the facts described in the State’s response to Jardines’ motion to suppress, Sergeant
Ramirez and Detective Donnelly established perimeter positions during the dog sniff with agents of the Drug Enforcement
Administration (DEA) as a support unit. The State’s response also explains that DEA continued surveillance after the sniff while
Detective Pedraja obtained a search warrant. Detective Pedraja testified at the suppression hearing that he got in his vehicle and
“drove to a location close by” to prepare the warrant. Furthermore, Jardines’ motion to suppress states that DEA agents and
members of the Miami–Dade Police Department executed the search warrant “[a]bout an hour later.”
15 See United States v. Scott, 610 F.3d 1009, 1016 (8th Cir.2010) (holding that dog sniff of apartment’s front door from common
hallway was not a search under the Fourth Amendment and rejecting argument that Kyllo should be extended to dog sniffs,
explaining that “the Supreme Court rejected such an interpretation of Kyllo in Caballes ”); United States v. Brock, 417 F.3d 692,
696 (7th Cir.2005) (“[W]e hold that the dog sniff inside Brock’s residence [specifically at the locked door of bedroom rented by
Brock] was not a Fourth Amendment search because it detected only the presence of contraband and did not provide any
information about lawful activity over which Brock had a legitimate expectation of privacy.”); United States v. Reed, 141 F.3d 644,
649–50 (6th Cir.1998) (holding that dog sniff of flat was not a search when dog was lawfully present in the flat and rejecting
argument that Place only applies to “public sniffs”); United States v. Broadway, 580 F.Supp.2d 1179, 1193 (D.Colo.2008)
(rejecting the applicability of Kyllo, holding a dog sniff of apartment from hallway and from walkway outside window was not a
search under the Fourth Amendment, and explaining that “as long as a canine unit is lawfully present when a drug sniff occurs, the
sniff is not a search”); United States v. Cota–Lopez, 358 F.Supp.2d 579, 592 (W.D.Tex.2002) (rejecting argument that the
heightened privacy interest makes dog sniff of front door at private residence intrusive, explaining “Place and Jacobsen compel the
conclusion that a canine sniff capable of detecting only the presence or absence of contraband is not a search within the meaning of
the Fourth Amendment”), aff’d, 104 Fed.Appx. 931 (5th Cir.2004); United States v. Meindl, 83 F.Supp.2d 1207, 1216–17
(D.Kan.1999) (rejecting argument that plain view/smell exception was inapplicable because the dog sniff occurred in a home rather
than a public place); United States v. Tarazon–Silva, 960 F.Supp. 1152, 1162–63 (W.D.Tex.1997) (holding dog sniff of the outside
of a residence and alert at a dryer vent was not a search when dog and officer had the right to be positioned alongside residence),
aff’d, 166 F.3d 341 (5th Cir.1998); see also United States v. Roby, 122 F.3d 1120, 1124–25 (8th Cir.1997) (holding that a dog sniff
in hallway outside hotel room was not a search); United States v. Lingenfelter, 997 F.2d 632, 638 (9th Cir.1993) (holding that dog
sniff of warehouse was not a search because defendant “could have no legitimate expectation that a narcotics canine would not
detect the odor of the marijuana stored in the warehouse”); United States v. Seals, 987 F.2d 1102, 1106 (5th Cir.1993) (“A dog
‘sniff’ is not a search.”); United States v. Vasquez, 909 F.2d 235, 238 (7th Cir.1990) (concluding that sniff of garage from public
alley was not a search); United States v. Colyer, 878 F.2d 469, 477 (D.C.Cir.1989) (holding that dog sniff of train sleeper
compartment was not a search); United States v. Burns, 624 F.2d 95, 101 (10th Cir.1980) (stating that “olfactory activities of a
trained police dog legitimately on the premises do not constitute a search” and holding that dog sniff of briefcase in motel room did
not violate constitution); United States v. Marlar, 828 F.Supp. 415, 419 (N.D.Miss.1993) (holding that dog sniff of motel room
door was not a search); but see United States v. Thomas, 757 F.2d 1359, 1367 (2d Cir.1985) (holding that dog sniff at front door of
apartment was a search under the Fourth Amendment requiring warrant based on probable cause); but cf. United States v.
Whitehead, 849 F.2d 849, 853 (4th Cir.1988) (“[T]he brief exposure of the interior of a train compartment to narcotics detection
dogs is constitutionally permissible when based on a reasonable, articulable suspicion that luggage within the compartment
contains contraband.”).
Somewhat confusingly, while the Second Circuit in Thomas, 757 F.2d 1359, held that a dog sniff at a front door of an apartment
was a search, the Second Circuit more recently held that a dog sniff in the front yard of a home was not a search because the
defendant “had no legitimate expectation of privacy in the front yard of his home insofar as the presence of the scent of narcotics in
the air was capable of being sniffed by the police canine.” United States v. Hayes, 551 F.3d 138, 145 (2d Cir.2008) (citing
Caballes, 543 U.S. at 409–10, 125 S.Ct. 834).
16 See State v. Guillen, 222 Ariz. 81, 213 P.3d 230, 234 (App.2009) (“[W]e join the majority of jurisdictions in concluding that ... a
dog sniff reaching into a home does not rise to the level of a ‘cognizable infringement’ under the Fourth Amendment to the United
States Constitution.”), vacated on other grounds, 223 Ariz. 314, 223 P.3d 658 (2010); Stabler v. State, 990 So.2d 1258, 1263 (Fla.
1st DCA 2008) (holding that dog sniff at front door of apartment was not a search within the meaning of the Fourth Amendment
because “it did not violate a legitimate privacy interest”); People v. Guenther, 225 Ill.App.3d 574, 167 Ill.Dec. 705, 588 N.E.2d
346, 350 (1992) (applying Place and Jacobsen to conclude that “[s]ince a canine sniff does not constitute a search, and the police
had probable cause to believe there was marijuana in the living room, the police could have brought in the dog”); Hoop v. State,
909 N.E.2d 463, 468 (Ind.Ct.App.2009) (holding that dog sniff at front door of residence was not a search under the Fourth
Amendment, explaining that “[a]s long as an officer is lawfully on the premises, the officer may have a dog sniff the residence
32

without implicating the Fourth Amendment”); Fitzgerald v. State, 384 Md. 484, 864 A.2d 1006, 1017 (2004) (“[A] dog sniff of the
exterior of a residence is not a search under the Fourth Amendment. To be sure, the dog and police must lawfully be present at the
site of the sniff.”); People v. Jones, 279 Mich.App. 86, 755 N.W.2d 224, 228 (2008) (holding that dog sniff outside front door of
home was not a search under the Fourth Amendment and explaining that “a canine sniff is not a search within the meaning of the
Fourth Amendment as long as the sniffing canine is legally present at its vantage point when its sense is aroused”); People v. Dunn,
77 N.Y.2d 19, 563 N.Y.S.2d 388, 564 N.E.2d 1054, 1056 (1990) (holding dog sniff at door of apartment from common hallway
was not a search within the meaning of the Fourth Amendment “[s]ince the ‘canine sniff’ conducted outside his apartment could
reveal only the presence or absence of illicit drugs”); Romo v. State, 315 S.W.3d 565, 573 (Tex.App.2010) (“[The dog’s] sniffs of
the garage door and the backyard fence [which were accessible from public alley] were not searches under the Fourth Amendment
... because he sniffed areas that were not protected from observation by passersby and because Romo had no reasonable
expectation of privacy in the odor of marihuana coming from his backyard.”); Smith v. State, No. 01–02–00503–CR, 2004 WL
213395, at *4 (Tex.App.2004) (concluding that dog sniff of house’s garage door was not a search under the Fourth Amendment
and explaining that “[u]nlike the surveillance device used in Kyllo, a drug-dog sniff does not explore the details of a house”
because it “can do no more than reveal the presence or absence of contraband”); Rodriguez v. State, 106 S.W.3d 224, 229
(Tex.App.2003) (holding that dog sniff of front door of private residence was not a search, reasoning that “a government
investigative technique, such as a drug-dog sniff, that discloses only the presence or absence of narcotics, and does not expose
noncontraband items, activity, or information that would otherwise remain hidden from public view, does not intrude on a
legitimate expectation of privacy and is thus not a ‘search’ for Fourth Amendment purposes”); Porter v. State, 93 S.W.3d 342,
346–47 (Tex.App.2002) (distinguishing Kyllo and holding that dog sniff of front door of home was not a search); see also Nelson
v. State, 867 So.2d 534, 536–37 (Fla. 5th DCA 2004) (holding that dog sniff of hotel room door was not a search); but see State v.
Ortiz, 257 Neb. 784, 600 N.W.2d 805, 816–17, 819 (1999) (holding that a dog sniff of a private residence implicates the Fourth
Amendment by relying primarily on other state courts’ decisions interpreting state constitutions); State v. Woljevach, 160 Ohio
App.3d 757, 828 N.E.2d 1015, 1018 (2005) (“The information obtained from the drug-detecting dog is not available to support the
warrant, because the use of the dog on appellant’s property was a search that, unlike using a drug-detecting dog to sniff around a
vehicle on a highway or around luggage in a public place, must itself have been premised on probable cause.”).
17 Even the dissenting justices in Caballes acknowledged that the United States Supreme Court has held that dog sniffs are not
searches because they only reveal contraband in which there is no legitimate expectation of privacy protected by the Fourth
Amendment. See Caballes, 543 U.S. at 411, 125 S.Ct. 834 (Souter, J., dissenting) (“At the heart both of Place and the Court’s
opinion today is the proposition that sniffs by a trained dog are sui generis because a reaction by the dog in going alert is a
response to nothing but the presence of contraband. Hence, the argument goes, because the sniff can only reveal the presence of
items devoid of any legal use, the sniff ‘does not implicate legitimate privacy interests’ and is not to be treated as a search.”
(citations and footnote omitted)); Caballes, 543 U.S. at 421, 125 S.Ct. 834 (Ginsburg, J., dissenting) (“Dog sniffs that detect only
the possession of contraband may be employed without offense to the Fourth Amendment, the Court reasons, because they reveal
no lawful activity and hence disturb no legitimate expectation of privacy.”).
18 As the highest court in Maryland explained, “The Supreme Court precedent [makes] clear that the status of a dog sniff does not
depend on the object sniffed.” Fitzgerald, 864 A.2d at 1016. This is so because, as the highest court in New York explained,
“[w]hether or not there exists a heightened expectation of privacy, the fact remains that a ‘canine sniff’ reveals only evidence of
criminality.” Dunn, 563 N.Y.S.2d 388, 564 N.E.2d at 1057 (citations omitted).
End of Document
© 2012 Thomson Reuters. No claim to original U.S. Government Works.
33

88 S.Ct. 507
Supreme Court of the United States
Charles KATZ, Petitioner,
v.
UNITED STATES.
No. 35. | Argued Oct. 17, 1967. | Decided Dec. 18,
1967.
Opinion
MR. JUSTICE STEWART delivered the opinion of the
Court.
[1] [2] The petitioner was convicted in the District Court
for the Southern District of California under an eightcount
indictment charging him with transmitting wagering
information by telephone from Los Angeles to Miami and
Boston in violation of a federal statute.1 At trial the
Government was permitted, over the petitioner’s
objection, to introduce evidence of the petitioner’s end of
telephone coversations, overheard by FBI agents who had
attached an electronic listening and recording device to
the outside of the public telephone booth from which he
had placed his calls. In affirming his conviction, the Court
of Appeals rejected the contention that the recordings had
been obtained in violation of the Fourth Amendment,
*349 because ‘(t)here was no physical entrance into the
area occupied by, (the petitioner).’2 **510 We granted
certiorari in order to consider the constitutional questions
thus presented.3
The petitioner had phrased those questions as follows:
‘A. Whether a public telephone booth is a constitutionally
protected area so that evidence obtained by attaching an
electronic listening recording device to the top of such a
booth is obtained in violation of the right to privacy of the
user of the booth.
*350 ‘B. Whether physical penetration of a
constitutionally protected area is necessary before a
search and seizure can be said to be violative of the
Fourth Amendment to the United States Constitution.’
[3] [4] [5] [6] [7] [8] We decline to adopt this formulation
of the issues. In the first place the correct solution of
Fourth Amendment problems is not necessarily promoted
by incantation of the phrase ‘constitutionally protected
area.’ Secondly, the Fourth Amendment cannot be
34
translated into a general constitutional ‘right to privacy.’
That Amendment protects individual privacy against
certain kinds of governmental intrusion, but its
protections go further, and often have nothing to do with
privacy at all.4 Other provisions of the Constitution
protect personal privacy from other forms of
governmental invasion.5 But the protection of a **511
person’s general right to privacy-his right to be let alone
by other people6-is, like the *351 protection of his
property and of his very life, left largely to the law of the
individual States.7
[9] [10] [11] [12] Because of the misleading way the
issues have been formulated, the parties have attached
great significance to the characterization of the telephone
booth from which the petitioner placed his calls. The
petitioner has strenuously argued that the booth was a
‘constitutionally protected area.’ The Government has
maintained with equal vigor that it was not.8 But this
effort to decide whether or not a given ‘area,’ viewed in
the abstract, is ‘constitutionally protected’ deflects
attention from the problem presented by this case.9 For
the Fourth Amendment protects people, not places. What
a person knowingly exposes to the public, even in his own
home or office, is not a subject of Fourth Amendment
protection. See Lewis v. United States, 385 U.S. 206, 210,
87 S.Ct. 424, 427, 17 L.Ed.2d 312; United States v. Lee,
274 U.S. 559, 563, 47 S.Ct. 746, 748, 71 L.Ed. 1202. But
what he seeks to preserve as private, even in an area
accessible to the public, may be constitutionally
protected. *352 See Rios v. United States, 364 U.S. 253,
80 S.Ct. 1431, 4 L.Ed.2d 1688; Ex parte Jackson, 96 U.S.
727, 733, 24 L.Ed. 877.
[13] The Government stresses the fact that the telephone
booth from which the petitioner made his calls was
constructed partly of glass, so that he was as visible after
he entered it as he would have been if he had remained
outside. But what he sought to exclude when he entered
the booth was not the intruding eye-it was the uninvited
ear. He did not shed his right to do so simply because he
made his calls from a place where he might be seen. No
less than an individual in a business office,10 in a friend’s
apartment,11 or in a taxicab,12 a person in a telephone
booth may rely upon the protection of the Fourth
Amendment. One who occupies it, shuts the door behind
him, and pays the toll that permits **512 him to place a
call is surely entitled to assume that the words he utters
into the mouthpiece will not be broadcast to the world. To
read the Constitution more narrowly is to ignore the vital
role that the public telephone has come to play in private
communication.

[14] The Government contends, however, tha the
activities of its agents in this case should not be tested by
Fourth Amendment requirements, for the surveillance
technique they employed involved no physical penetration
of the telephone booth from which the petitioner placed
his calls. It is true that the absence of such penetration
was at one time thought to foreclose further Fourth
Amendment inquiry, Olmstead v. United States, 277 U.S.
438, 457, 464, 466, 48 S.Ct. 564, 565, 567, 568, 72 L.Ed.
944; Goldman v. United States, 316 U.S. 129, 134-136,
62 S.Ct. 993, 995-997, 86 L.Ed. 1322, for that
Amendment was thought to limit only searches and
seizures of tangible *353 property.13 But ‘(t)he premise
that property interests control the right of the Government
to search and seize has been discredited.’ Warden, Md.
Penitentiary v. Hayden, 387 U.S. 294, 304, 87 S.Ct. 1642,
1648, 18 L.Ed.2d 782. Thus, although a closely divided
Court supposed in Olmstead that surveillance without any
trespass and without the seizure of any material object fell
outside the ambit of the Constitution, we have since
departed from the narrow view on which that decision
rested. Indeed, we have expressly held that the Fourth
Amendment governs not only the seizure of tangible
items, but extends as well to the recording of oral
statements overheard without any ‘technical trespass
under * * * local property law.’ Silverman v. United
States, 365 U.S. 505, 511, 81 S.Ct. 679, 682, 5 L.Ed.2d
734. Once this much is acknowledged, and once it is
recognized that the Fourth Amendment protects peopleand
not simply ‘areas’-against unreasonable searches and
seizures it becomes clear that the reach of that
Amendment cannot turn upon the presence or absence of
a physical intrusion into any given enclosure.
[15] We conclude that the underpinnings of Olmstead and
Goldman have been so eroded by our subsequent
decisions that the ‘trespass’ doctrine there enunciated can
no longer be regarded as controlling. The Government’s
activities in electronically listening to and recording the
petitioner’s words violated the privacy upon which he
justifiably relied while using the telephone booth and thus
constituted a ‘search and seizure’ within the meaning of
the Fourth Amendment. The fact that the electronic
device employed to achieve that end did not happen to
penetrate the wall of the booth can have no constitutional
significance.
*354 The question remaining for decision, then, is
whether the search and seizure conducted in this case
complied with constitutional standards. In that regard, the
Government’s position is that its agents acted in an
entirely defensible manner: They did not begin their
electronic surveillance until investigation of the
petitioner’s activities had established a strong probability
35
that he was using the telephone in question to transmit
gambling information to persons in other States, in
violation of federal law. Moreover, the surveillance was
limited, both in scope and in duration, to the specific
purpose of establishing the contents of the petitioner’s
unlawful telephonic communications. The agents
confined their surveillance to the brief periods during
which he used the telephone booth,14 and **513 they took
great care to overhear only the conversations of the
petitioner himself.15
[16] [17] Accepting this account of the Government’s
actions as acccurate, it is clear that this surveillance was
so narrowly circumscribed that a duly authorized
magistrate, properly notified of the need for such
investigation, specifically informed of the basis on which
it was to proceed, and clearly apprised of the precise
intrusion it would entail, could constitutionally have
authorized, with appropriate safeguards, the very limited
search and seizure that the Government asserts in fact
took place. Only last Term we sustained the validity of
*355 such an authorization, holding that, under
sufficiently ‘precise and discriminate circumstances,’ a
federal court may empower government agents to employ
a concealed electronic device ‘for the narrow and
particularized purpose of ascertaining the truth of the * *
* allegations’ of a ‘detailed factual affidavit alleging the
commission of a specific criminal offense.’ Osborn v.
United States, 385 U.S. 323, 329-330, 87 S.Ct. 429, 433,
17 L.Ed.2d 394. Discussing that holding, the Court in
Berger v. State of New York, 388 U.S. 41, 87 S.Ct. 1873,
18 L.Ed.2d 1040, said that ‘the order authorizing the use
of the electronic device’ in Osborn ‘afforded similar
protections to those * * * of conventional warrants
authorizing the seizure of tangible evidence.’ Through
those protections, ‘no greater invasion of privacy was
permitted than was necessary under the circumstances.’
Id., at 57, 87 S.Ct. at 1882.16 Here, too, **514 a similar
*356 judicial order could have accommodated ‘the
legitimate needs of law enforcement’17 by authorizing the
carefully limited use of electronic surveillance.
[18] [19] The Government urges that, because its agents
relied upon the decisions in Olmstead and Goldman, and
because they did no more here than they might properly
have done with prior judicial sanction, we should
retroactively validate their conduct. That we cannot do. It
is apparent that the agents in this case acted with restraint.
Yet the inescapable fact is that this restraint was imposed
by the agents themselves, not by a judicial officer. They
were not required, before commencing the search, to
present their estimate of probable cause for detached
scrutiny by a neutral magistrate. They were not
compelled, during the conduct of the search itself, to

observe precise limits established in advance by a specific
court order. Nor were they directed, after the search had
been completed, to notify the authorizing magistrate in
detail of all that had been seized. In the absence of such
safeguards, this Court has never sustained a search upon
the sole ground that officers reasonably expected to find
evidence of a particular crime and voluntarily confined
their activities to the least intrusive *357 means consistent
with that end. Searches conducted without warrants have
been held unlawful ‘notwithstanding facts unquestionably
showing probable cause,’ Agnello v. United States, 269
U.S. 20, 33, 46 S.Ct. 4, 6, 70 L.Ed. 145, for the
Constitution requires ‘that the deliberate, impartial
judgment of a judicial officer * * * be interposed between
the citizen and the police * * *.’ Wong Sun v. United
States, 371 U.S. 471, 481-482, 83 S.Ct. 407, 414, 9
L.Ed.2d 441. ‘Over and again this Court has emphasized
that the mandate of the (Fourth) Amendment requires
adherence to judicial processes,’ United States v. Jeffers,
342 U.S. 48, 51, 72 S.Ct. 93, 95, 96 L.Ed. 59, and that
searches conducted outside the judicial process, without
prior approval by judge or magistrate, are per se
unreasonable under the Fourth Amendment18 -subject
only to a few specifically established and well-delineated
exceptions.19
[20] [21] [22] It is difficult to imagine how any of those
exceptions could ever apply to the sort of search and
seizure involved in this case. Even electronic surveillance
substantially contemporaneous with an individual’s arrest
could hardly be deemed an ‘incident’ of that arrest.20
**515 *358 Nor could the use of electronic surveillance
without prior autorization be justified on grounds of ‘hot
pursuit.’21 And, of course, the very nature of electronic
surveillance precludes its use pursuant to the suspect’s
consent.22
The Government does not question these basic principles.
Rather, it urges the creation of a new exception to cover
this case.23 It argues that surveillance of a telephone
booth should be exempted from the usual requirement of
advance authorization by a magistrate upon a showing of
probable cause. We cannot agree. Omission of such
authorization
‘bypasses the safeguards provided by an objective
predetermination of probable cause, and substitutes
instead the far less reliable procedure of an after-the-event
justification for the * * * search, too likely to be subtly
influenced by the familiar shortcomings of hindsight
judgment.’ Beck v. State of Ohio, 379 U.S. 89, 96,
85S.Ct. 223, 228, 13 L.Ed.2d 142.
And bypassing a neutral predetermination of the scope of
a search leaves individuals secure from Fourth
36
Amendment *359 violations ‘only in the discretion of the
police.’ Id., at 97, 85 S.Ct. at 229.
[23] [24] These considerations do not vanish when the
search in question is transferred from the setting of a
home, an office, or a hotel room to that of a telephone
booth. Wherever a man may be, he is entitled to know
that he will remain free from unreasonable searches and
seizures. The government agents here ignored ‘the
procedure of antecedent justification * * * that is central
to the Fourth Amendment,’24 a procedure that we hold to
be a constitutional precondition of the kind of electronic
surveillance involved in this case. Because the
surveillance here failed to meet that condition, and
because it led to the petitioner’s conviction, the judgment
must be reversed.
It is so ordered.
Judgment reversed.
Mr. Justice MARSHALL took no part in the
consideration or decision of this case.
Mr. Justice DOUGLAS, with whom Mr. Justice
BRENNAN joins, concurring.
While I join the opinion of the Court, I feel compelled to
reply to the separate concurring opinion of my Brother
**516 WHITE, which I view as a wholly unwarranted
green light for the Executive Branch to resort to electronic
eavesdropping without a warrant in cases which the
Executive Branch itself labels ‘national security’ matters.
Neither the President nor the Attorney General is a
magistrate. In matters where they believe national security
may be involved they are not detached, disinterested, and
neutral as a court or magistrate must be. Under the
separation of powers created by the Constitution, the
Executive Branch is not supposed to be neutral and
disinterested. Rather it should vigorously investigate *360
and prevent breaches of national security and prosecute
those who violate the pertinent federal laws. The
President and Attorney General are properly interested
parties, cast in the role of adversary, in national security
cases. They may even be the intended victims of
subversive action. Since spies and saboteurs are as
entitled to the protection of the Fourth Amendment as
suspected gamblers like petitioner, I cannot agree that
where spies and saboteurs are involved adequate
protection of Fourth Amendment rights is assured when

the President and Attorney General assume both the
position of adversary-and-prosecutor and disinterested,
neutral magistrate.
There is, so far as I understand constitutional history, no
distinction under the Fourth Amendment between types of
crimes. Article III, s 3, gives ‘treason’ a very narrow
definition and puts restrictions on its proof. But the Fourth
Amendment draws no lines between various substantive
offenses. The arrests on cases of ‘hot pursuit’ and the
arrests on visible or other evidence of probable cause cut
across the board and are not peculiar to any kind of crime.
I would respect the present lines of distinction and not
improvise because a particular crime seems particularly
heinous. When the Framers took that step, as they did
with treason, the worst crime of all, they made their
purpose manifest.
Mr. Justice HARLAN, concurring.
I join the opinion of the Court, which I read to hold only
(a) that an enclosed telephone booth is an area where, like
a home, Weeks v. United States, 232 U.S. 383, 34 S.Ct.
341, 58 L.Ed. 652, and unlike a field, Hester v. United
States, 265 U.S. 57, 44 S.Ct. 445, 68 L.Ed. 898, a person
has a constitutionally protected reasonable expectation of
privacy; (b) that electronic as well as physical intrusion
into a place that is in this sense private may constitute a
violation of the Fourth Amendment; *361 and (c) that the
invasion of a constitutionally protected area by federal
authorities is, as the Court has long held, presumptively
unreasonable in the absence of a search warrant.
As the Court’s opinion states, ‘the Fourth Amendment
protects people, not places.’ The question, however, is
what protection it affords to those people. Generally, as
here, the answer to that question requires reference to a
‘place.’ My understanding of the rule that has emerged
from prior decisions is that there is a twofold requirement,
first that a person have exhibited an actual (subjective)
expectation of privacy and, second, that the expectation
be one that society is prepared to recognize as
‘reasonable.’ Thus a man’s home is, for most purposes, a
place where he expects privacy, but objects, activities, or
statements that he exposes to the ‘plain view’ of outsiders
are not ‘protected’ because no intention to keep them to
himself has been exhibited. On the other hand,
conversations in the open would not be protected against
being overheard, for the expectation of privacy under the
circumstances would be unreasonable. Cf. Hester v.
United States, supra.
The critical fact in this case is that ‘(o)ne who occupies it,
(a telephone **517 booth) shuts the door behind him, and
pays the toll that permits him to place a call is surely
entitled to assume’ that his conversation is not being
intercepted. Ante, at 511. The point is not that the booth is
‘accessible to the public’ at other times, ante, at 511, but
that it is a temporarily private place whose momentary
occupants’ expectations of freedom from intrusion are
recognized as reasonable. Cf. Rios v. United States, 364
U.S. 253, 80 S.Ct. 1431, 4 L.Ed.2d 1688.
In Silverman v. United States, 365 U.S. 505, 81 S.Ct. 679,
5 L.Ed.2d 734, we held that eavesdropping accomplished
by means of an electronic device that penetrated the
premises occupied by petitioner was a violation of the
Fourth Amendment. *362 That case established that
interception of conversations reasonably intended to be
private could constitute a ‘search and seizure,’ and that
the examination or taking of physical property was not
required. This view of the Fourth Amendment was
followed in Wong Sun v.United States, 371 U.S. 471, at
485, 83 S.Ct. 407, at 416, 9 L.Ed.2d 441, and Berger v.
State of New York, 388 U.S. 41, at 51, 87 S.Ct. 1873, at
1879, 18 L.Ed.2d 1040. Also compare Osborne v. United
States, 385 U.S. 323, at 327, 87 S.Ct. 429, at 431, 17
L.Ed.2d 394. In Silverman we found it unnecessary to reexamine
Goldman v. United States, 316 U.S. 129, 62
S.Ct. 993, 86 L.Ed. 1322, which had held that electronic
surveillance accomplished without the physical
penetration of petitioner’s premises by a tangible object
did not violate the Fourth Amendment. This case requires
us to reconsider Goldman, and I agree that it should now
be overruled.* Its limitation on Fourth Amendment
protection is, in the present day, bad physics as well as
bad law, for reasonable expectations of privacy may be
defeated by electronic as well as physical invasion.
Finally, I do not read the Court’s opinion to declare that
no interception of a conversation one-half of which occurs
in a public telephone booth can be reasonable in the
absence of a warrant. As elsewhere under the Fourth
Amendment, warrants are the general rule, to which the
legitimate needs of law enforcement may demand specific
exceptios. It will be time enough to consider any such
exceptions when an appropriate occasion presents itself,
and I agree with the Court that this is not one.
Mr. Justice WHITE, concurring.
I agree that the official surveillance of petitioner’s
telephone conversations in a public booth must be
subjected *363 to the test of reasonableness under the
Fourth Amendment and that on the record now before us
37

the particular surveillance undertaken was unreasonable
absent a warrant properly authorizing it. This application
of the Fourth Amendment need not interfere with
legitimate needs of law enforcement.**
**518 In joining the Court’s opinion, I note the Court’s
asknowledgment that there are circumstance in which it is
reasonable to search without a warrant. In this connection,
in footnote 23 the Court points out that today’s decision
does not reach national security cases. Wiretapping to
protect the security of the Nation has been authorized by
successive Presidents. The present Administration would
apparently save national security cases from restrictions
against wiretapping. See Berger v. State of New York,
388 U.S. 41, 112-118, 87 S.Ct. 1873, 1911-1914, 18
L.Ed.2d 1040 (1967) (White, J., *364 dissenting). We
should not require the warrant procedure and the
magistrate’s judgment if the President of the United States
or his chief legal officer, the Attorney General, has
considered the requirements of national security and
authorized electronic surveillance as reasonable.
Mr. Justice BLACK, dissenting.
If I could agree with the Court that eavesdropping carried
on by electronic means (equivalent to wiretapping)
constitutes a ‘search’ or ‘seizure,’ I would be happy to
join the Court’s opinion. For on that premise my Brother
STEWART sets out methods in accord with the Fourth
Amendment to guide States in the enactment and
enforcement of laws passed to regulate wiretapping by
government. In this respect today’s opinion differs
sharply from Berger v.State of New York, 388 U.S. 41,
87 S.Ct. 1873, 18 L.Ed.2d 1040, decided last Term, which
held void on its face a New York statute authorizing
wiretapping on warrants issued by magistrates on
showings of probable cause. The Berger case also set up
what appeared to be insuperable obstacles to the valid
passage of such wiretapping laws by States. The Court’s
opinion in this case, however, removes the doubts about
state power in this field and abates to a large extent the
confusion and near-paralyzing effect of the Berger
holding. Notwithstanding these good efforts of the Court,
I am still unable to agree with its interpretation of the
Fourth Amendment.
My basic objection is twofold: (1) I do not believe that the
words of the Amendment will bear the meaning given
them by today’s decision, and (2) I do not believe that it is
the proper role of this Court to rewrite the Amendment in
order ‘to bring it into harmony with the times’ and thus
reach a result that many people believe to be desirable.
38
*365 While I realize that an argument based on the
meaning of words lacks the scope, and no doubt the
appeal, of broad policy discussions and philosophical
discourses on such nebulous subjects as privacy, for me
the language of the Amendment is the crucial place to
look in construing a written document such as our
Constitution. The Fourth Amendment says that
‘The right of the people to be secure in their
persons, houses, papers, and effects, against
unreasonable searches and seizures, shall not be
violated, and no Warrants shall issue, but upon
probable cause, supported by Oath or affirmation,
and particularly describing the place to be
searched, and the persons or things to be seized.’
The first clause protects ‘persons, houses, papers, and
effects, against unreasonable searches and seizures * * *.’
**519 These words connote the idea of tangible things
with size, form, and weight, things capable of being
searched, seized, or both. The second clause of the
Amendment still further establishes its Framers’ purpose
to limit its protection to tangible things by providing that
no warrants shall issue but those ‘particularly describing
the place to be searched, and the persons or things to be
seized.’ A conversation overheard by eavesdropping,
whether by plain snooping or wiretapping, is not tangible
and, under the normally accepted meanings of the words,
can neither be searched nor seized. In addition the
language of the second clause indicates that the
Amendment refers not only to something tangible so it
can be seized but to something already in existence so it
can be described. Yet the Court’s interpretation would
have the Amendment apply to overhearing future
conversations which by their very nature are nonexistent
until they take place. How can one ‘describe’ a future
conversation, and, if one cannot, how can a magistrate
issue a warrant to eavesdrop one in the future It is argued
that information showing what *366 is expected to be said
is sufficient to limit the boundaries of what later can be
admitted into evidence; but does such general information
really meet the specific language of the Amendment
which says ‘particularly describing’ Rather than using
language in a completely artificial way, I must conclude
that the Fourth Amendment simply does not apply to
eavesdropping.
Tapping telephone wires, of course, was an unknown
possibility at the time the Fourth Amendment was
adopted. But eavesdropping (and wiretapping is nothing
more than eavesdropping by telephone) was, as even the
majority opinion in Berger, supra, recognized, ‘an ancient
practice which at common law was condemned as a

nuisance. IV Blackstone, Commentaries s 168. In those
days the eavesdropper listened by naked ear under the
eaves of houses or their windows, or beyond their walls
seeking out private discourse.’ 388 U.S., at 45, 87 S.Ct.,
at 1876. There can be no doubt that the Framers were
aware of this practice, and if they had desired to outlaw or
restrict the use of evidence obtained by eavesdropping, I
believe that they would have used the appropriate
language to do so in the Fourth Amendment. They
certainly would not have left such a task to the ingenuity
of language-stretching judges. No one, it seems to me, can
read the debates on the Bill of Rights without reaching the
conclusion that its Framers and critics well knew the
meaning of the words they used, what they would be
understood to mean by others, their scope and their
limitations. Under these circumstances it strikes me as a
charge against their scholarship, their common sense and
their candor to give to the Fourth Amendment’s language
the eavesdropping meaning the Court imputes to it today.
I do not deny that common sense requires and that this
Court often has said that the Bill of Rights’ safeguards
should be given a liberal construction. This *367
principle, however, does not justify construing the search
and seizure amendment as applying to eavesdropping or
the ‘seizure’ of conversations. The Fourth Amendment
was aimed directly at the abhorred practice of breaking in,
ransacking and searching homes and other buildings and
seizing people’s personal belongings without warrants
issued by magistrates. The Amendment deserves, and this
Court has given it, a liberal construction in order to
protect against warrantless searches of buildings and
seizures of tangible personal effects. But until today this
Court has refused to say that eavesdropping comes within
the ambit of Fourth Amendment restrictions. See, e.g.,
Olmstead v. United States, 277 U.S. 438, 48 S.Ct. 564, 72
L.Ed. 944 (1928), and Goldman v. United States, 316
U.S. 129, 62 S.Ct. 993, 86 L.Ed. 1322 (1942).
**520 So far I have attempted to state why I think the
words of the Fourth Amendment prevent its application to
eavesdropping. It is important now to show that this has
been the traditional view of the Amendment’s scope since
its adoption and that the Court’s decision in this case,
along with its amorphous holding in Berger last Term,
marks the first real departure from that view.
The first case to reach this Court which actually involved
a clear-cut test of the Fourth Amendment’s applicability
to eavesdropping through a wiretap was, of course,
Olmstead, supra. In holding tha the interception of private
telephone conversations by means of wiretapping was not
a violation of the Fourth Amendment, this Court,
speaking through Mr. Chief Justice Taft, examined the
language of the Amendment and found, just as I do now,
that the words could not be stretched to encompass
overheard conversations:
‘The amendment itself shows that the search is to be of
material things-the person, the house, his papers, or his
effects. The description of the warrant necessary to make
the proceeding lawful is *368 that it must specify the
place to be searched and the person or things to be seized.
* * *
‘Justice Bradley in the Boyd case (Boyd v. United States,
116 U.S. 616, 6 S.Ct. 524, 29 L.Ed. 746), and Justice
Clarke in the Gouled case (Gouled v. United States, 255
U.S. 298, 41 S.Ct. 261, 65 L.Ed. 647), said that the Fifth
Amendment and the Fourth Amendment were to be
liberally construed to effect the purpose of the framers of
the Constitution in the interest of liberty. But that can not
justify enlargement of the language employed beyond the
possible practical meaning of houses, persons, papers, and
effects, or so to apply the words search and seizure as to
forbid hearing or sight.’ 277 U.S., at 464-465, 48 S.Ct., at
568.
Goldman v. United States, 316 U.S. 129, 62 S.Ct. 993, 86
L.Ed. 1322, is an even clearer example of this Court’s
traditional refusal to consider eavesdropping as being
covered by the Fourth Amendment. There federal agents
used a detectaphone, which was placed on the wall of an
adjoining room, to listen to the conversation of a
defendant carried on in his private office and intended to
be confined within the four walls of the room. This Court,
referring to Olmstead, found no Fourth Amendment
violation.
It should be noted that the Court in Olmstead based its
decision squarely on the fact that wiretapping or
eavesdropping does not violate the Fourth Amendment.
As shown, supra, in the cited quotation from the case,
theCourt went to great pains to examine the actual
language of the Amendment and found that the words
used simply could not be stretched to cover
eavesdropping. That there was no trespass was not the
determinative factor, and indeed the Court in citing Hester
v. United States, 265 U.S. 57, 44 S.Ct. 445, 68 L.Ed. 898,
indicated that even where there was a trespass the Fourth
Amendment does not automatically apply to evidence
obtained by ‘hearing or *369 sight.’ The Olmstead
majority characterized Hester as holding ‘that the
testimony of two officers of the law who trespassed on the
defendant’s land, concealed themselves 100 yards away
from his house, and saw him come out and hand a bottle
39

of whiskey to another, was not inadmissible. While there
was a trespass, there was no search of person, house,
papers, or effects.’ 277 U.S., at 465, 48 S.Ct., at 568.
Thus the clear holding of the Olmstead and Goldman
cases, undiluted by any question of trespass, is that
eavesdropping, in both its original and modern forms, is
not violative of the Fourth Amendment.
While my reading of the Olmstead and Goldman cases
convinces me that they were decided on the basis of the
inapplicability **521 of the wording of the Fourth
Amendment to eavesdropping, and not on any trespass
basis, this is not to say that unauthorized intrusion has not
played an important role in search and seizure cases. This
Court has adopted an exclusionary rule to bar evidence
obtained by means of such intrusions. As I made clear in
my dissenting opinion in Berger v. State of New York,
388 U.S. 41, 76, 87 S.Ct. 1873, 1892, 18 L.Ed.2d 1040, I
continue to believe that this exclusionary rule formulated
in Weeks v. United States, 232 U.S. 383, 34 S.Ct. 341, 58
L.Ed. 652, rests on the ‘supervisory power’ of this Court
over other federal courts and is not rooted in the Fourth
Amendment. See Wolf v. People of State of Colorado,
concurring opinion, 338 U.S. 25, 39, at 40, 69 S.Ct. 1359,
1367, at 1368, 93 L.Ed. 1782. See also Mapp v. Ohio,
concurring opinion, 367 U.S. 643, 661-666, 81 S.Ct.
1684, 1694-1698, 6 L.Ed.2d 1081. This rule has caused
the Court to refuse to accept evidence where there has
been such an intrusion regardless of whether there has
been a search or seizure in violation of the Fourth
Amendment. As this Court said in Lopez v. United States,
373 U.S. 427, 438-439, 83 S.Ct. 1381, 1387, 10 L.Ed.2d
462, ‘The Court has in the past sustained instances of
‘electronic eavesdropping’ against constitutional
challenge, when devices have been used to enable
government agents to overhear conversations which
would have been beyond the reach of the human ear
(citing *370 Olmstead and Goldman). It has been insisted
only that the electronic device not be planted by an
unlawful physical invasion of a constitutionally protected
area. Silverman v. United States.’
To support its new interpretation of the Fourth
Amendment, which in effect amounts to a rewriting of the
language, the Court’s opinion concludes that ‘the
underpinnings of Olmstead and Goldman have been * * *
eroded by our subsequent decisions * * *.’ But the only
cases cited as accomplishing this ‘eroding’ are Silverman
v. United States, 365 U.S. 505, 81 S.Ct. 679, 5 L.Ed.2d
734, and Warden, Md. Penitentiary v. Hayden, 387 U.S.
294, 87 S.Ct. 1642, 18 L.Ed.2d 782. Neither of these
cases ‘eroded’ Olmstead or Goldman. Silverman is an
interestng choice since there the Court expressly refused
40
to re-examine the rationale of Olmstead or Goldman
although such a re-examination was strenuously urged
upon the Court by the petitioners’ counsel. Also it is
significant that in Silverman, as the Court described it,
‘the eavesdropping was accomplished by means on an
unauthorized physical penetration into the premises
occupied by the petitioners,’ 365 U.S., at 509, 81 S.Ct., at
681, thus calling into play the supervisory exclusionary
rule of evidence. As I have pointed out above, where there
is an unauthorized intrusion, this Court has rejected
admission of evidence obtained regardless of whether
there has been an unconstitutional search and seizure. The
majority’s decision here relies heavily on the statement in
the opinion that the Court ‘need not pause to consider
whether or not there was a technical trespass under the
local property law relating to party walls.’ (At 511, 81
S.Ct., at 682.) Yet this statement should not becloud the
fact that time and again the opinion emphasizes that there
has been an unauthorized intrusion: ‘For a fair reading of
the record in this case shows that the eavesdropping was
accomplished by means of an unauthorized physical
penetration into the premises occupied by the petitioners.’
(365 U.S., at 509, 81 S.Ct., at 682 emphasis added.)
‘Eavesdropping *371 accomplished by means of such a
physical intrusion is beyond the pale of even those
decisions * * *.’ (At 509, 81 S.Ct., at 682, emphasis
added.) ‘Here * * * the officers overheard the petitioners’
conversations only by usurping part of the petitioners’
house or office * * *.’ (At 511, 81 S.Ct., at 682, emphasis
added.) ‘(D)ecision here * * * is based upon the reality of
an actual intrusion * * *.’ (At 512, 81 S.Ct., at 683,
emphasis added.) ‘We find no occasion to re-examine
Goldman **522 here, but we decline to go beyond it, by
even a fraction of an inch.’ (At 512, 81 S.Ct., at 683,
emphasis added.) As if this were not enough, Justices
Clark and Whittaker concurred with the following
statement: ‘In view of the determination by the majority
that the unauthorized physical penetration into petitioners’
premises constituted sufficient trespass to remove this
case from the coverage of earlier decisions, we feel
obliged to join in the Court’s opinion.’ (At 513, 81 S.Ct.,
at 684, emphasis added.) As I made clear in my dissent in
Berger, the Court in Silverman held the evidence should
be excluded by virtue of the exclusionary rule and ‘I
would not have agreed with the Court’s opinion in
Silverman * * * had I thought that the result depended on
finding a violation of the Fourth Amendment * * *.’ 388
U.S., at 79-80, 87 S.Ct., at 1894. In light of this and the
fact that the Court expressly refused to re-examine
Olmstead and Goldman, I cannot read Silverman as
overturning the interpretation stated very plainly in
Olmstead and followed in Goldman that eavesdropping is
not covered by the Fourth Amendment.

The other ‘eroding’ case cited in the Court’s opinion is
Warden, Md. Penitentiary v. Hayden, 387 U.S. 294, 87
S.Ct. 1642, 18 L.Ed.2d 782. It appears that this case is
cited for the proposition that the Fourth Amendment
applies to ‘intangibles,’ such as conversation, and the
following ambiguous statement is quoted from the
opinion: ‘The premise that property interests control the
right of the Government to search and seize has been
discredited.’ 387 U.S., at 304, 87 S.Ct., at 1648. But far
from being concerned *372 with eavesdropping, Warden,
Md. Penitentiary v. Hayden upholds the seizure of
clothes, certainly tangibles by any definition. The
discussion of property interests was involved only with
the common-law rule that the right to seize property
depended upon proof of a superior property interest.
Thus, I think that although the Court attempts to convey
the impression that for some reason today Olmstead and
Goldman are no longer good law, it must face up to the
fact that these cases have never been overruled or even
‘eroded.’ It is the Court’s opinions in this case and Berger
which for the first time since 1791, when the Fourth
Amendment was adopted, have declared that
eavesdropping is subject to Fourth Amendment
restrictions and that conversation can be ‘seized.’* I must
align myself with all those judges who up to this year
have never been able to impute such a meaning to the
words of the Amendment.
*373 Since I see no way in which the words of the Fourth
Amendment can be construed to apply to eavesdropping,
that closes the matter for me. In interpreting the Bill of
Rights, I willingly go as far **523 as a liberal
construction of the language takes me, but I simply cannot
in good conscience give a meaning to words which they
have never before been thought to have and which they
certainly do not have in common ordinary usage. I will
not distort the words of the Amendment in order to ‘keep
the Constitution up to date’ or ‘to bring it into harmony
with the times.’ It was never meant that this Court have
such power, which in effect would make us a
continuously functioning constitutional convention.
With this decision the Court has completed, I hope, its
rewriting of the Fourth Amendment, which started only
recently when the Court began referring incessantly to the
Fourth Amendment not so much as a law against
unreasonable searches and seizures as one to protect an
individual’s privacy. By clever word juggling the Court
finds it plausible to argue that language aimed specifically
at searches and seizures of things that can be searched and
seized may, to protect privacy, be applied to
eavesdropped evidence of conversations that can neither
be searched nor seized. Few things happen to an
individual that do not affect his privacy in one way or
another. Thus, by arbitrarily substituting the Court’s
language, designed to protect privacy, for the
Constitution’s language, designed to protect against
unreasonable searches and seizures, the Court has made
the Fourth Amendment its vehicle for holding all laws
violative of the Constitution which offend the Court’s
broadest concept of privacy. As I said in Griswold v. State
of Connecticut, 381 U.S. 479, 85 S.Ct. 1678, 14 L.Ed.2d
510, ‘The Court talks about a constitutional ‘right of
privacy’ as though there is some constitutional provision
or provisions forbidding any law ever to be passed which
might abridge the ‘privacy’ *374 of individuals. But there
is not.’ (Dissenting opinion, at 508, 85 S.Ct. at 1695.) I
made clear in that dissent my fear of the dangers involved
when this Court uses the ‘broad, abstract and ambiguous
concept’ of ‘privacy’ as a ‘comprehensive substitute for
the Fourth Amendment’s guarantee against ‘unreasonable
searches and seizures.“ (See generally dissenting opinion,
at 507-527, 85 S.Ct., at 1694-1705.)
The Fourth Amendment protects privacy only to the
extent that it prohibits unreasonable searches and seizures
of ‘persons, houses, papers, and effects.’ No general right
is created by the Amendment so as to give this Court the
unlimited power to hold unconstitutional everything
which affects privacy. Certainly the Framers, well
acquainted as they were with the excesses of
governmental power, did not intend to grant this Court
such omnipotent lawmaking authority as that. The history
of governments proves that it is dangerous to freedom to
repose such powers in courts.
For these reasons I respectfully dissent.
Parallel Citations
88 S.Ct. 507, 19 L.Ed.2d 576
Footnotes
1 18 U.S.C. s 1084. That statute provides in pertinent part:
‘(a) Whoever being engaged in the business of betting or wagering knowingly uses a wire communication facility for the
transmission in interstate or foreign commerce of bets or wagers or information assisting in the placing of bets or wagers on any
41

sporting event or contest, or for the transmission of a wire communication which entitles the recipient to receive money or credit as
a result of bets or wagers, or for information assisting in the placing of bets or wagers, shall be fined no more than $10,000 or
inprisoned not more than two years, or both.
‘(b) Nothing in this section shall be construed to prevent the transmission in interstate or foreign commerce of information for use
in news reporting of sporting events or contests, or for the transmission of information assisting in the placing of bets or wagers on
a sporting event or contest from a State where betting on that sporting event or contest is legal into a State in which such betting is
legal.’
2 9 Cir., 369 F.2d 130, 134.
3 386 U.S. 954, 87 S.Ct. 1021, 18 L.Ed.2d 102. The petition for certiorari also challenged the validity of a warrant authorizing the
search of the petitioner’s premises. In light of our disposition of this case, we do nto reach that issue.
We find no merit in the petitioner’s further suggestion that his indictment must be dismissed. After his conviction was affirmed by
the Court of Appeals, he testified before a federal grand jury concerning the charges involved here. Because he was compelled to
testify pursuant to a grant of immunity, 48 Stat. 1096, as amended, 47 U.S.C. s 409(l), it is clear that the fruit of his testimony
cannot be used against him in any future trial. But the petitioner asks for more. He contends that his conviction must be vacated
and the charges against him dismissed lest he be ‘subjected to (a) penalty * * * on account of (a) * * * matter * * * concerning
which he (was) compelled * * * to testify * * *.’ 47 U.S.C. s 409(l). Frank v. United States, 120 U.S.App.D.C. 392, 347 F.2d 486.
We disagree. In relevant part, s 409(l) substantially repeats the language of the Compulsory Testimony Act of 1893, 27 Stat. 443,
49 U.S.C. s 46, which was Congress’ response to this Court’s statement that an immunity statute can supplant the Fifth
Amendment privilege against self-incrimination only if it affords adequate protection from future prosecution or conviction.
Counselman v. Hitchcock, 142 U.S. 547, 585-586, 12 S.Ct. 195, 206-207, 35 L.Ed. 1110. The statutory provision here involved
was designed to provide such protection, see Brown v. United States, 359 U.S. 41, 45-46, 79 S.Ct. 539, 543-544, 3 L.Ed.2d 609,
not to confer immunity from punishment pursuant to a prior prosecution and adjudication of guilt. Cf. Reina v. United States, 364
U.S. 507, 513-514, 81 S.Ct. 260, 264-265, 5 L.Ed.2d 249.
4 ‘The average man would very likely not have his feelings soothed any more by having his property seized openly than by having it
seized privately and by stealth. * * * And a person can be just as much, if not more, irritated, annoyed and injured by an
unceremonious public arrest by a policeman as he is by a seizure in the privacy of his office or home.’ Griswold v. State of
Connecticut, 381 U.S. 479, 509, 85 S.Ct. 1678, 1695, 14 L.Ed.2d 510 (dissenting opinion of MR. JUSTICE BLACK).
5 The First Amendment, for example, imposes limitations upon govermental abridgment of ‘freedom to associate and privacy in
one’s associations.’ NAACP v. State of Alabama, 357 U.S. 449, 462, 78 S.Ct. 1163, 1172, 2 L.Ed.2d 1488. The Third
Amendment’s prohibition against the unconsented peacetime quartering of soldiers protects another aspect of privacy from
governmental intrusion. To some extent, the Fifth Amendment too ‘reflects the Constitution’s concern for * * * ’* * * the right of
each individual ‘to a private enclave where he may lead a private life. “’ Tehan v. United States ex rel. Shott, 382 U.S. 406, 416, 86
S.Ct. 459, 465, 15 L.Ed.2d 453. Virtually every governmental action interferes with personal privacy to some degree. The question
in each case is whether that interference violates a command of the United States Constitution.
6 See Warren & Brandeis, The Right to Privacy, 4 Harv.L.Rev. 193 (1890).
7 See, e.g., Time, Inc. v. Hill, 385 U.S. 374, 87 S.Ct. 534, 17 L.Ed.2d 456. Cf. Breard v. City of Alexandria, 341 U.S. 622, 71 S.Ct.
920, 95 L.Ed. 1233; Kovacs v. Cooper, 336 U.S. 77, 69 S.Ct. 448, 93 L.Ed. 513.
8 In support of their respective claims, the parties have compiled competing lists of ‘protected areas’ for our consideration. It appears
to be common ground that a private home is such an area, Weeks v. United States, 232 U.S. 383, 34 S.Ct. 341, 58 L.Ed. 652, but
that an open field is not. Hester v. United States, 265 U.S. 57, 44 S.Ct. 445, 68 L.Ed. 898. Defending the inclusion of a telephone
booth in his list the petitioner cites United States v. Stone, D.C., 232 F.Supp. 396, and United States v. Madison, 32 L.W. 2243
(D.C.Ct.Gen.Sess.). Urging that the telephone booth should be excluded, the Government finds support in United States v.
Borgese, D.C., 235 F.Supp. 286.
9 It is true that this Court has occasionally described its conclusions in terms of ‘constitutionally protected areas,’ see, e.g.,
Silverman v. United States, 365 U.S. 505, 510, 512, 81 S.Ct. 679, 682, 683, 5 L.Ed.2d 734; Lopez v. United States, 373 U.S. 427,
438-439, 83 S.Ct. 1381, 1387-1388, 10 L.Ed.2d 462; Berger v. State of New York, 388 U.S. 41, 57, 59, 87 S.Ct. 1873, 1882, 1883,
18 L.Ed.2d 1040, but we have never suggested that this concept can serve as a talismanic solution to every Fourth Amendment
problem.
10 Silverthorne Lumber Co. v. United States, 251 U.S. 385, 40 S.Ct. 182, 64 L.Ed. 319.
42

11 Jones v. United States, 362 U.S. 257, 80 S.Ct. 725, 4 L.Ed.2d 697.
12 Rios v. United States, 364 U.S. 253, 80 S.Ct. 1431, 4 L.Ed.2d 1688.
13 See Olmstead v. United States, 277 U.S. 438, 464-466, 48 S.Ct. 564, 567-569, 72 L.Ed. 944. We do not deal in this case with the
law of detention r arrest under the Fourth Amendment.
14 Based upon their previous visual observations of the petitioner, the agents correctly predicted that he would use the telephone
booth for several minutes at approximately the same time each morning. The petitioner was subjected to electronic surveillance
only during this predetermined period. Six recordings, averaging some three minutes each, were obtained and admitted in
evidence. They preserved the petitioner’s end of conversations converning the placing of bets and the receipt of wagering
information.
15 On the single occasion when the statements of another person were inadvertently intercepted, the agents refrained from listening to
them.
16 Although the protections afforded the petitioner in Osborn were ‘similar * * * to those * * * of conventional warrants,’ they were
not identical. A conventional warrant ordinarily serves to notify the suspect of an intended search. But if Osborn had been told in
advance that federal officers intended to record his conversations, the point of making such recordings would obviously have been
lost; the evidence in question could not have been obtained. In omitting any requirement of advance notice, the federal court that
authorized electronic surveillance in Osborn simply recognized, as has this Court, that officers need not announce their purpose
before conducting an otherwise authorized search if such an announcement would provoke the escape of the suspect or the
destruction of critical evidence. See, Ker v. State of California, 374 U.S. 23, 37-41, 83 S.Ct. 1623, 1631-1634, 10 L.Ed.2d 726.
Although some have thought that this ‘exception to the notice requirement where exigent circumstances are present,’ id., at 39, 83
S.Ct. at 1633, should be deemed inapplicable where police enter a home before its occupants are aware that officers are present,
id., at 55-58, 83 S.Ct. at 1640-1642 (opinion of MR. JUSTICE BRENNAN), the reasons for such a limitation have no bearing here.
However true it may be that ‘(i)nnocent citizens should not suffer the shock, fright or embarrassment attendant upon an
unannounced police intrusion,’ id., at 57, 83 S.Ct. at 1642, and that ‘the requirement of awareness * * * serves to minimize the
hazards of the officers’ dangerous calling,’ id., at 57-58, 83 S.Ct. at 1642, these considerations are not relevant to the problems
presented by judicially authorized electronic surveillance.
Nor do the Federal Rules of Criminal Procedure impose an inflexible requirement of prior notice. Rule 41(d) does require federal
officers to serve upon the person searched a copy of the warrant and a receipt describing the material obtained, but it does not
invariably require that this be done before the search takes place. Nordelli v. United States, 9 Cir., 24 F.2d 665, 666-667.
Thus the fact that the petitioner in Osborn was unaware that his words were being electronically transcribed did not prevent this
Court from sustaining his conviction, and did not prevent the Court in Berger from reaching the conclusion that the use of the
recording device sanctioned in Osborn was entirely lawful. 388 U.S. 41, 57, 87 S.Ct. 1873, 1882.
17 Lopez v. United States, 373 U.S. 427, 464, 83 S.Ct. 1381, 1401, 10 L.Ed.2d 462 (dissenting opinion of MR. JUSTICE
BRENNAN).
18 See, e.g., Jones v. United States, 357 U.S. 493, 497-499, 78 S.Ct. 1253, 1256-1257, 2 L.Ed.2d 1514; Rios v. United States, 364
U.S. 253, 261, 80 S.Ct. 1431, 1436, 4 L.Ed.2d 1688; Chapman v. United States, 365 U.S. 610, 613-615, 81 S.Ct. 776, 778, 779, 5
L.Ed.2d 828; Stoner v. State of California, 376 U.S. 483, 486-487, 84 S.Ct. 889, 891-892, 11 L.Ed.2d 856.
19 See, e.g., Carroll v. United States, 267 U.S. 132, 153, 156, 45 S.Ct. 280, 285, 286, 69 L.Ed. 543; McDonald v. United States, 335
U.S. 451, 454-456, 69 S.Ct. 191, 192-194, 93 L.Ed. 153; Brinegar v. United States, 338 U.S. 160, 174-177, 69 S.Ct. 1302, 1310-
1312, 93 L.Ed. 1879; Cooper v. State of California, 386 U.S. 58, 87 S.Ct. 788, 17 L.Ed.2d 730; Warden Md. Penitentiary v.
Hayden, 387 U.S. 294, 298-300, 87 S.Ct. 1642, 1645-1647, 18 L.Ed.2d 782.
20 In Agnello v. United States, 269 U.S. 20, 30, 46 S.Ct. 4, 5, 70 L.Ed. 145, the Court stated:
‘The right without a search warrant contemporaneously to search persons lawfully arrested while committing crime and to search
the place where the arrest is made in order to find and seize things connected with the crime as its fruits ar as the means by which it
was committed, as well as weapons and other things to effect an escape from custody is not to be doubted.’
Whatever one’s view of ‘the long-standing practice of searching for other proofs of guilt within the control of the accused found
upon arrest,’ United States v. Rabinowitz, 339 U.S. 56, 61, 70 S.Ct. 430, 433, 94 L.Ed. 653; cf. id., at 71-79, 70 S.Ct. at 437-441
(dissenting opinion of Mr. Justice Frankfurter), the concept of an ‘incidental’ search cannot readily be extended to include
surreptitious surveillance of an individual either immediately before, or immediately after, his arrest.
21 Although ‘(t)he Fourth Amendment does not require police officers to delay in the course of an investigation if to do so would
43

gravely endanger their lives or the lives of others,’ Warden Md. Penitentiary v. Hayden, 387 U.S. 294, 298-299, 87 S.Ct. 1642,
1646, 18 L.Ed.2d 782, there seems little likelihood that electronic surveillance would be a realistic possibility in a situation so
fraught with urgency.
22 A search to which an individual consents meets Fourth Amendment requirements, Zap v. United States, 328 U.S. 624, 66 S.Ct.
1277, 90 L.Ed. 1477, but of course ‘the usefulness of electronic surveillance depends on lack of notice to the suspect.’ Lopez v.
United States, 373 U.S. 427, 463, 83 S.Ct. 1381, 1401, 10 L.Ed.2d 462 (dissenting opinion of MR. JUSTICE BRENNAN).
23 Whether safeguards other than prior authorization by a magistrate would satisfy the Fourth Amendment in a situation involving the
national security is a question not presented by this case.
24 See Osborn v. United States, 385 U.S. 323, 330, 87 S.Ct. 429, 433, 17 L.Ed.2d 394.
* I also think that the course of development evinced by Silverman, supra, Wong Sun, supra, Berger, supra, and today’s decision
must be recognized as overruling Olmstead v. United States, 277 U.S. 438, 48 S.Ct. 564, 72 L.Ed. 944, which essentially rested on
the ground that coversations were not subject to the protection of the Fourth Amendment.
** In previous cases, which are undisturbed by today’s decision, the Court has upheld, as reasonable under the Fourth Amendment,
admission at trial of evidence obtained (1) by an undercover police agent to whom a defendant speaks without knowledge that he is
in the employ of the police, Hoffa v. United States, 385 U.S. 293, 87 S.Ct. 408, 17 L.Ed.2d 374 (1966); (2) by a recording device
hidden on the person of such an informant, Lopez v. United States, 373 U.S. 427, 83 S.Ct. 1381, 10 L.Ed.2d 462 (1963); Osborn v.
United States, 385 U.S. 323, 87 S.Ct. 429, 17 L.Ed.2d 394 (1966); and (3) by a policeman listening to the secret micro-wave
transmissions of an agent coversing with the defendant in another location, On Lee v. United States, 343 U.S. 747, 72 S.Ct. 967, 96
L.Ed. 1270 (1952). When one man speaks to another he takes all the risks ordinarily inherent in so doing, including the risk that the
man to whom he speaks will make public what he has heard. The Fourth Amendment does not protect against unreliable (or lawabiding)
associates. Hoffa v. United States, supra. It is but a logical and reasonable extension of this principle that a man take the
risk that his hearer, free to memorize what he hears for later verbatim repetitions, is instead recording it or transmitting it to
another. The present case deals with an entirely different situation, for as the Court emphasizes the petitioner ‘sought to exclude *
* * the uninvited ear,’ and spoke under circumstances in which a reasonable person would assume that uninvited ears were not
listening.
* The first paragraph of my Brother HARLAN’s concurring opinion is susceptible of the interpretation, although probably not
intended, that this Court ‘has long held’ eavesdropping to be a violation of the Fourth Amendment and therefore ‘presumptively
unreasonable in the absence of a search warrant.’ There is no reference to any long line of cases, but simply a citation to Silverman,
and several cases following it, to establish this historical proposition. In the first place, as I have indicated in this opinion, I do not
read Silverman as holding any such thing; and in the second place, Silverman was decided in 1961. Thus, whatever it held, it
cannot be said it ‘has (been) long held.’ I think by Brother HARLAN recognizes this later in his opinion when he admits that the
Court must now overrule Olmstead and Goldman. In having to overrule these cases in order to establish the holding the Court
adopts today, it becomes clear that the Court is promulgating new doctrine instead of merely following what it ‘has long held.’
This is emphasized by my Brother HARLAN’s claim that it is ‘bad physics’ to adhere to Goldman. Such an assertion simply
illustrates the propensity of some members of the Court to rely on their limited understanding of modern scientific subjects in order
to fit the Constitution to the times and give its language a meaning that it will not tolerate.
End of Document
© 2012 Thomson Reuters. No claim to original U.S. Government Works.
44

103 S.Ct. 2317
Supreme Court of the United States
ILLINOIS, Petitioner
v.
Lance GATES et ux.
No. 81-430. | Argued Oct. 13, 1982. | Reargued
March 1, 1983. | Decided June 8, 1983.
Opinion
*216 Justice REHNQUIST delivered the opinion of the
Court.
Respondents Lance and Susan Gates were indicted for
violation of state drug laws after police officers, executing
a search warrant, discovered marijuana and other
contraband in their automobile and home. Prior to trial the
Gates’ moved to suppress evidence seized during this
**2321 search. The Illinois Supreme Court, 85 Ill.2d 376,
53 Ill.Dec. 218, 423 N.E.2d 887 (1981) affirmed the
decisions of lower state courts, 82 Ill.App.3d 749, 38
Ill.Dec. 62, 403 N.E.2d 77 (1980) granting the motion. It
held that the affidavit submitted in support of the State’s
application for a warrant to search the Gates’ property
*217 was inadequate under this Court’s decisions in
Aguilar v. Texas, 378 U.S. 108, 84 S.Ct. 1509, 12 L.Ed.2d
723 (1964) and Spinelli v. United States, 393 U.S. 410, 89
S.Ct. 584, 21 L.Ed.2d 637 (1969).
We granted certiorari to consider the application of the
Fourth Amendment to a magistrate’s issuance of a search
warrant on the basis of a partially corroborated
anonymous informant’s tip. After receiving briefs and
hearing oral argument on this question, however, we
requested the parties to address an additional question:
“Whether the rule requiring the exclusion at a
criminal trial of evidence obtained in violation of
the Fourth Amendment, Mapp v. Ohio, 367 U.S.
643, 81 S.Ct. 1684, 6 L.Ed.2d 1081 (1961); Weeks
v. United States, 232 U.S. 383, 34 S.Ct. 341, 58
L.Ed. 652 (1914), should to any extent be
modified, so as, for example, not to require the
exclusion of evidence obtained in the reasonable
belief that the search and seizure at issue was
consistent with the Fourth Amendment.”
45
We decide today, with apologies to all, that the issue we
framed for the parties was not presented to the Illinois
courts and, accordingly, do not address it. Rather, we
consider the question originally presented in the petition
for certiorari, and conclude that the Illinois Supreme
Court read the requirements of our Fourth Amendment
decisions too restrictively. Initially, however, we set forth
our reasons for not addressing the question regarding
modification of the exclusionary rule framed in our order
of November 29, 1982, --- U.S. ----, 103 S.Ct. 436, 74
L.Ed.2d 595.
I
[1] Our certiorari jurisdiction over decisions from state
courts derives from 28 U.S.C. § 1257, which provides that
“Final judgments or decrees rendered by the highest court
of a State in which a decision could be had, may be
reviewed by the Supreme Court as follows: ... (3) By writ
of certiorari, ... where any title, right, privilege or
immunity is specially set up or claimed under the
Constitution, treaties or statutes *218 of ... the United
States.” The provision derives, albeit with important
alterations, see, e.g., Act of December 23, 1914, c. 2, 38
Stat. 790; Act of June 25, 1948, c. 646, 62 Stat. 929, from
the Judiciary Act of 1789, c. 20, § 25, 1 Stat. 85.
Although we have spoken frequently on the meaning of §
1257 and its predecessors, our decisions are in some
respects not entirely clear. We held early on that § 25 of
the Judiciary Act of 1789 furnished us with no
jurisdiction unless a federal question had been both raised
and decided in the state court below. As Justice Story
wrote in Crowell v. Randell, 10 Pet. 368, 391, 9 L.Ed. 458
(1836), “If both of these requirements do not appear on
the record, the appellate jurisdiction fails.” See also
Owings v. Norwood’s Lessee, 5 Cranch. 344, 3 L.Ed. 120
(1809).1
More recently, in McGoldrick v. Compagnie Generale,
309 U.S. 430, 435-436, 60 S.Ct. 670, 673, 84 L.Ed. 849
(1940), the Court observed:
**2322 But it is also the settled practice of this
Court, in the exercise of its appellate jurisdiction,
that it is only in exceptional cases, and then only
in cases coming from the federal courts, that it
considers questions urged by a petitioner or
appellant not pressed or passed upon in the courts
below.... In cases coming here from state courts in

which a state statute is assailed as
unconstitutional, there are reasons of peculiar
force which should lead us to refrain from
deciding questions not presented or decided in the
highest court of the state whose judicial action we
are called upon to review. Apart from the *219
reluctance with which every court should proceed
to set aside legislation as unconstitutional on
grounds not properly presented, due regard for the
appropriate relationship of this Court to state
courts requires us to decline to consider and
decide questions affecting the validity of state
statutes not urged or considered there. It is for
these reasons that this Court, where the
constitutionality of a statute has been upheld in the
state court, consistently refuses to consider any
grounds of attack not raised or decided in that
court.
Finally, the Court seemed to reaffirm the jurisdictional
character of the rule against our deciding claims “not
pressed nor passed upon” in state court in State Farm
Mutual Automobile Insurance Co. v. Duel, 324 U.S. 154,
160, 65 S.Ct. 573, 576, 89 L.Ed. 812 (1945), where we
explained that “Since the [state] Supreme Court did not
pass on the question, we may not do so.” See also Hill v.
California, 401 U.S. 797, 805-806, 91 S.Ct. 1106, 1111,
1112, 28 L.Ed.2d 484 (1971).
Notwithstanding these decisions, however, several of our
more recent cases have treated the so-called “not pressed
or passed upon below” rule as merely a prudential
restriction. In Terminiello v. Chicago, 337 U.S. 1, 69
S.Ct. 894, 93 L.Ed. 1131 (1949), the Court reversed a
state criminal conviction on a ground not urged in state
court, nor even in this Court. Likewise, in Vachon v. New
Hampshire, 414 U.S. 478, 94 S.Ct. 664, 38 L.Ed.2d 666
(1974), the Court summarily reversed a state criminal
conviction on the ground, not raised in state court, or
here, that it had been obtained in violation of the Due
Process Clause of the Fourteenth Amendment. The Court
indicated in a footnote, id., at 479, n. 3, 94 S.Ct., at 665,
n. 3, that it possessed discretion to ignore the failure to
raise in state court the question on which it decided the
case.
In addition to this lack of clarity as to the character of the
“not pressed or passed upon below” rule, we have
recognized that it often may be unclear whether the
particular federal question presented in this Court was
raised or passed upon below. In Dewey v. Des Moines,
173 U.S. 193, 197-198, 19 S.Ct. 379, 380-381, 43 L.Ed.
665 (1899), the fullest treatment of the subject, the Court
said *220 that “if the question were only an enlargement
of the one mentioned in the assignment of errors, or if it
were so connected with it in substance as to form but
another ground or reason for alleging the invalidity of the
[lower court’s] judgment, we should have no hesitation in
holding the assignment sufficient to permit the question to
be now raised and argued. Parties are not confined here to
the same arguments which were advanced in the courts
below upon a Federal question there discussed.”2 We
have not attempted, and **2323 likely would not have
been able, to draw a clear-cut line between cases
involving only an “enlargement” of questions presented
below and those involving entirely new questions.
The application of these principles in the instant case is
not entirely straightforward. It is clear in this case that
respondents expressly raised, at every level of the Illinois
judicial system, the claim that the Fourth Amendment had
been violated by the actions of the Illinois police and that
the evidence seized by the officers should be excluded
from their trial. It also is clear that the State challenged, at
every level of the Illinois court system, respondents’
claim that the substantive requirements of the Fourth
Amendment had been violated. The State never, however,
raised or addressed the question whether the federal
exclusionary rule should be modified in any respect, and
none of the opinions of the *221 Illinois courts give any
indication that the question was considered.
[2] The case, of course, is before us on the State’s petition
for a writ of certiorari. Since the Act of December 23,
1914, c. 2, 38 Stat. 790, jurisdiction has been vested in
this Court to review state court decisions even when a
claimed federal right has been upheld. Our prior decisions
interpreting the “not pressed or passed on below” rule
have not, however, involved a State’s failure to raise a
defense to a federal right or remedy asserted below. As
explained below, however, we can see no reason to treat
the State’s failure to have challenged an asserted federal
claim differently from the failure of the proponent of a
federal claim to have raised that claim.
We have identified several purposes underlying the “not
pressed or passed upon” rule: for the most part, these are
as applicable to the State’s failure to have opposed the
assertion of a particular federal right, as to a party’s
failure to have asserted the claim. First, “questions not
raised below are those on which the record is very likely
to be inadequate since it certainly was not compiled with
those questions in mind.” Cardinale v. Louisiana, 394
U.S. 437, 439, 89 S.Ct. 1161, 1163, 22 L.Ed.2d 398
(1969). Exactly the same difficulty exists when the state
urges modification of an existing constitutional right or
46

accompanying remedy. Here, for example, the record
contains little, if anything, regarding the subjective good
faith of the police officers that searched the Gates’
property-which might well be an important consideration
in determining whether to fashion a good faith exception
to the exclusionary rule. Our consideration of whether to
modify the exclusionary rule plainly would benefit from a
record containing such facts.
[3] [4] Likewise, “due regard for the appropriate
relationship of this Court to state courts,” McGoldrick v.
Compagnie Generale, 309 U.S. 430, 435-436, 60 S.Ct.
670, 673, 84 L.Ed. 849 (1940), demands that those courts
be given an opportunity to consider the constitutionality
of the actions of state officials, and, equally important,
proposed changes in existing remedies for
unconstitutional *222 actions. Finally, by requiring that
the State first argue to the state courts that the federal
exclusionary rule should be modified, we permit a state
court, even if it agrees with the State as a matter of federal
law, to rest its decision on an adequate and independent
state ground. See Cardinale, supra, 394 U.S., at 439, 89
S.Ct., at 1163. Illinois, for example, adopted an
exclusionary rule as early as 1923, see People v.
Brocamp, 307 Ill. 448, 138 N.E. 728 (1923), and might
adhere to its view even if it thought we would conclude
that the federal rule should be modified. In short, the
reasons supporting our refusal to hear federal claims not
raised in state court apply with equal force to the State’s
failure to challenge the availability of a well-settled
federal remedy. Whether the “not pressed or passed upon
below” rule is jurisdictional, as our earlier decisions
indicate, see 2320, supra, or prudential, as several of our
later decisions assume, nor whether its character might be
different in cases like **2324 this from its character
elsewhere, we need not decide. Whatever the character of
the rule may be, consideration of the question presented in
our order of November 29, 1982, would be contrary to the
sound justifications for the “not pressed or passed upon
below” rule, and we thus decide not to pass on the issue.
[5] The fact that the Illinois courts affirmatively applied
the federal exclusionary rule-suppressing evidence against
respondents-does not affect our conclusion. In Morrison
v. Watson, 154 U.S. 111, 14 S.Ct. 995, 138 L.Ed. 927
(1894), the Court was asked to consider whether a state
statute impaired the appellant’s contract with the appellee.
It declined to hear the case because the question presented
here had not been pressed or passed on below. The Court
acknowledged that the lower court’s opinion had restated
the conclusion, set forth in an earlier decision of that
court, that the state statute did not impermissibly impair
contractual obligations. Nonetheless, it held that there was
47
no showing that “there was any real contest at any stage
of this case upon the point,” id., at 115, 14 S.Ct., at 997,
and that without such a contest, the routine restatement
*223 and application of settled law by an appellate court
did not satisfy the “not pressed or passed upon below”
rule. Similarly, in the present case, although the Illinois
courts applied the federal exclusionary rule, there was
never “any real contest” upon the point. The application
of the exclusionary rule was merely a routine act, once a
violation of the Fourth Amendment had been found, and
not the considered judgment of the Illinois courts on the
question whether application of a modified rule would be
warranted on the facts of this case. In such circumstances,
absent the adversarial dispute necessary to apprise the
state court of the arguments for not applying the
exclusionary rule, we will not consider the question
whether the exclusionary rule should be modified.
[6] Likewise, we do not believe that the State’s repeated
opposition to respondent’s substantive Fourth
Amendment claims suffices to have raised the question
whether the exclusionary rule should be modified. The
exclusionary rule is “a judicially created remedy designed
to safeguard Fourth Amendment rights generally” and not
“a personal constitutional right of the party aggrieved.”
United States v. Calandra, 414 U.S. 338, 348, 94 S.Ct.
613, 620, 38 L.Ed.2d 561 (1974). The question whether
the exclusionary rule’s remedy is appropriate in a
particular context has long been regarded as an issue
separate from the question whether the Fourth
Amendment rights of the party seeking to invoke the rule
were violated by police conduct. See, e.g., United States
v. Havens, 446 U.S. 620, 100 S.Ct. 1912, 64 L.Ed.2d 559
(1980); United States v. Ceccolini, 435 U.S. 268, 98 S.Ct.
1054, 55 L.Ed.2d 268 (1978); United States v. Calandra,
supra; Stone v. Powell, 428 U.S. 465, 96 S.Ct. 3037, 49
L.Ed.2d 1067 (1976). Because of this distinction, we
cannot say that modification or abolition of the
exclusionary rule is “so connected with [the substantive
Fourth Amendment right at issue] as to form but another
ground or reason for alleging the invalidity” of the
judgment. Dewey v. Des Moines, supra, 173 U.S., at 197-
198, 19 S.Ct., at 380-381. Rather, the rule’s modification
was, for purposes of the “not pressed or passed upon
below” rule, a separate claim that had to be specifically
presented to the State courts.
[7] *224 Finally, weighty prudential considerations
militate against our considering the question presented in
our order of November 29, 1982. The extent of the
continued validity of the rules that have developed from
our decisions in Weeks v. United States, 232 U.S. 383, 34
S.Ct. 341, 58 L.Ed. 652 (1961), and Mapp v. Ohio, 367

U.S. 643, 81 S.Ct. 1684, 6 L.Ed.2d 1081 (1961), is an
issue of unusual significance. Sufficient evidence of this
lies just in the comments on the issue that members of this
Court recently have made, e.g., **2325 Bivens v. Six
Unknown Named Agents, 403 U.S. 388, 415, 91 S.Ct.
1999, 2014, 29 L.Ed.2d 619 (1971) (BURGER, C.J.,
dissenting); Coolidge v. New Hampshire, 403 U.S. 443,
490, 91 S.Ct. 2022, 2050, 29 L.Ed.2d 564 (1971) (Harlan,
J., concurring); id., at 502, 91 S.Ct., at 2056 (Black, J.,
dissenting); Stone v. Powell, 428 U.S. 465, 537-539, 96
S.Ct. 3037, 3072-3073, 49 L.Ed.2d 1067 (1976) (WHITE,
J., dissenting); Brewer v. Williams, 430 U.S. 387, 413-
414, 97 S.Ct. 1232, ----, 51 L.Ed.2d 424 (1977)
(POWELL, J., concurring); Robbins v. California, 453
U.S. 420, 437, 443-444, 101 S.Ct. 2841, 2851, 2854-
2855, 69 L.Ed.2d 744 (1981) (REHNQUIST, J.,
dissenting). Where difficult issues of great public
importance are involved, there are strong reasons to
adhere scrupulously to the customary limitations on our
discretion. By doing so we “promote respect ... for the
Court’s adjudicatory process [and] the stability of [our]
decisions.” Mapp v. Ohio, supra, 367 U.S., at 677, 81
S.Ct., at 1703 (Harlan, J., dissenting). Moreover, fidelity
to the rule guarantees that a factual record will be
available to us, thereby discouraging the framing of broad
rules, seemingly sensible on one set of facts, which may
prove ill-considered in other circumstances. In Justice
Harlan’s words, adherence to the rule lessens the threat of
“untoward practical ramifications,” id., at 676, 81 S.Ct., at
1703 (Harlan, J., dissenting), not foreseen at the time of
decision. The public importance of our decisions in Weeks
and Mapp and the emotions engendered by the debate
surrounding these decisions counsel that we meticulously
observe our customary procedural rules. By following this
course, we promote respect for the procedures by which
our decisions are rendered, as well as confidence in the
stability of prior decisions. A wise exercise of the powers
confided in this Court dictates that we reserve for another
day the question whether the exclusionary rule should be
modified.
*225 II
[8] We now turn to the question presented in the State’s
original petition for certiorari, which requires us to decide
whether respondents’ rights under the Fourth and
Fourteenth Amendments were violated by the search of
their car and house. A chronological statement of events
usefully introduces the issues at stake. Bloomingdale, Ill.,
is a suburb of Chicago located in DuPage County. On
May 3, 1978, the Bloomingdale Police Department
48
received by mail an anonymous handwritten letter which
read as follows:
“This letter is to inform you that you have a couple in
your town who strictly make their living on selling drugs.
They are Sue and Lance Gates, they live on Greenway,
off Bloomingdale Rd. in the condominiums. Most of their
buys are done in Florida. Sue his wife drives their car to
Florida, where she leaves it to be loaded up with drugs,
then Lance flys down and drives it back. Sue flys back
after she drops the car off in Florida. May 3 she is driving
down there again and Lance will be flying down in a few
days to drive it back. At the time Lance drives the car
back he has the trunk loaded with over $100,000.00 in
drugs. Presently they have over $100,000.00 worth of
drugs in their basement.
They brag about the fact they never have to work, and
make their entire living on pushers.
I guarantee if you watch them carefully you will make a
big catch. They are friends with some big drugs dealers,
who visit their house often.
Lance & Susan Gates
Greenway
in Condominiums”
The letter was referred by the Chief of Police of the
Bloomingdale Police Department to Detective Mader,
who decided to pursue the tip. Mader learned, from the
office of the Illinois Secretary of State, that an Illinois
driver’s license had *226 been issued to one Lance Gates,
residing at a stated address in Bloomingdale. He
contacted a confidential informant, whose examination of
certain financial records revealed a more recent address
for the Gates, and he also learned from a police officer
assigned to O’Hare Airport that “L. Gates” **2326 had
made a reservation on Eastern Airlines flight 245 to West
Palm Beach, Fla., scheduled to depart from Chicago on
May 5 at 4:15 p.m.
Mader then made arrangements with an agent of the Drug
Enforcement Administration for surveillance of the May 5
Eastern Airlines flight. The agent later reported to Mader
that Gates had boarded the flight, and that federal agents
in Florida had observed him arrive in West Palm Beach
and take a taxi to the nearby Holiday Inn. They also
reported that Gates went to a room registered to one
Susan Gates and that, at 7:00 a.m. the next morning,
Gates and an unidentified woman left the motel in a
Mercury bearing Illinois license plates and drove

northbound on an interstate frequently used by travelers to
the Chicago area. In addition, the DEA agent informed
Mader that the license plate number on the Mercury
registered to a Hornet station wagon owned by Gates. The
agent also advised Mader that the driving time between
West Palm Beach and Bloomingdale was approximately
22 to 24 hours.
Mader signed an affidavit setting forth the foregoing
facts, and submitted it to a judge of the Circuit Court of
DuPage County, together with a copy of the anonymous
letter. The judge of that court thereupon issued a search
warrant for the Gates’ residence and for their automobile.
The judge, in deciding to issue the warrant, could have
determined that the modus operandi of the Gates had been
substantially corroborated. As the anonymous letter
predicted, Lance Gates had flown from Chicago to West
Palm Beach late in the afternoon of May 5th, had checked
into a hotel room registered in the name of his wife, and,
at 7:00 a.m. the following morning, had headed north,
accompanied by an unidentified woman, *227 out of
West Palm Beach on an interstate highway used by
travelers from South Florida to Chicago in an automobile
bearing a license plate issued to him.
At 5:15 a.m. on March 7th, only 36 hours after he had
flown out of Chicago, Lance Gates, and his wife, returned
to their home in Bloomingdale, driving the car in which
they had left West Palm Beach some 22 hours earlier. The
Bloomingdale police were awaiting them, searched the
trunk of the Mercury, and uncovered approximately 350
pounds of marijuana. A search of the Gates’ home
revealed marijuana, weapons, and other contraband. The
Illinois Circuit Court ordered suppression of all these
items, on the ground that the affidavit submitted to the
Circuit Judge failed to support the necessary
determination of probable cause to believe that the Gates’
automobile and home contained the contraband in
question. This decision was affirmed in turn by the
Illinois Appellate Court and by a divided vote of the
Supreme Court of Illinois.
The Illinois Supreme Court concluded-and we are
inclined to agree-that, standing alone, the anonymous
letter sent to the Bloomingdale Police Department would
not provide the basis for a magistrate’s determination that
there was probable cause to believe contraband would be
found in the Gates’ car and home. The letter provides
virtually nothing from which one might conclude that its
author is either honest or his information reliable;
likewise, the letter gives absolutely no indication of the
basis for the writer’s predictions regarding the Gates’
criminal activities. Something more was required, then,
before a magistrate could conclude that there was
probable cause to believe that contraband would be found
in the Gates’ home and car. See Aguilar v. Texas, 378
U.S. 108, 109, n. 1, 84 S.Ct. 1509, 1511, n. 1, 12 L.Ed.2d
723 (1964); Nathanson v. United States, 290 U.S. 41, 54
S.Ct. 11, 78 L.Ed. 159 (1933).
The Illinois Supreme Court also properly recognized that
Detective Mader’s affidavit might be capable of
supplementing *228 the anonymous letter with
information sufficient to permit a determination of
probable cause. See **2327 Whiteley v. Warden, 401 U.S.
560, 567, 91 S.Ct. 1031, 1036, 28 L.Ed.2d 306 (1971). In
holding that the affidavit in fact did not contain sufficient
additional information to sustain a determination of
probable cause, the Illinois court applied a “two-pronged
test,” derived from our decision in Spinelli v. United
States, 393 U.S. 410, 89 S.Ct. 584, 21 L.Ed.2d 637
(1969).3 The Illinois Supreme Court, like some others,
apparently understood Spinelli as requiring that the
anonymous letter satisfy each of two independent
requirements before it could be relied on. J.A., at 5.
According to this view, the letter, as supplemented by
Mader’s affidavit, first had to adequately reveal the “basis
of knowledge” of the letter writer-the particular means by
which he came by the information given in his report.
Second, it had to provide *229 facts sufficiently
establishing either the “veracity” of the affiant’s
informant, or, alternatively, the “reliability” of the
informant’s report in this particular case.
The Illinois court, alluding to an elaborate set of legal
rules that have developed among various lower courts to
enforce the “two-pronged test,”4 found that the test had
not been satisfied. First, the “veracity” prong was not
satisfied because, “there was simply no basis [for] ...
conclud [ing] that the anonymous person [who wrote the
letter to the Bloomingdale Police Department] was
credible.” J.A., at 7a. The court indicated that
corroboration by police of details contained in the letter
might never satisfy the “veracity” prong, and in any
event, could not do so if, as in the present case, only
“innocent” details are corroborated. **2328 J.A., at 12a.
In addition, the letter gave no indication of the basis of its
writer’s knowledge of the *230 Gates’ activities. The
Illinois court understood Spinelli as permitting the detail
contained in a tip to be used to infer that the informant
had a reliable basis for his statements, but it thought that
the anonymous letter failed to provide sufficient detail to
permit such an inference. Thus, it concluded that no
showing of probable cause had been made.
We agree with the Illinois Supreme Court that an
49

informant’s “veracity,” “reliability” and “basis of
knowledge” are all highly relevant in determining the
value of his report. We do not agree, however, that these
elements should be understood as entirely separate and
independent requirements to be rigidly exacted in every
case,5 which the opinion of the Supreme Court of Illinois
would imply. Rather, as detailed below, they should be
understood simply as closely intertwined issues that may
usefully illuminate the commonsense, practical question
whether there is “probable cause” to believe that
contraband or evidence is located in a particular place.
III
This totality-of-the-circumstances approach is far more
consistent with our prior treatment of probable cause6
than *231 is any rigid demand that specific “tests” be
satisfied by every informant’s tip. Perhaps the central
teaching of our decisions bearing on the probable cause
standard is that it is a “practical, nontechnical
conception.” Brinegar v. United States, 338 U.S. 160,
176, 69 S.Ct. 1302, 1311, 93 L.Ed. 1879 (1949). “In
dealing with probable cause, ... as the very name implies,
we deal with probabilities. These are not technical; they
are the factual and practical considerations of everyday
life on which reasonable and prudent men, not legal
technicians, act.” Id., at 175, 69 S.Ct., at 1310. Our
observation in United States v. Cortez, 449 U.S. 411, 418,
101 S.Ct. 690, 695, 66 L.Ed.2d 621 (1981), regarding
“particularized suspicion,” is also applicable to the
probable cause standard:
The process does not deal with hard certainties, but with
probabilities. Long before the law of probabilities was
articulated **2329 as such, practical people formulated
certain common-sense conclusions about human
behavior; jurors as factfinders are permitted to do the
same-and *232 so are law enforcement officers. Finally,
the evidence thus collected must be seen and weighed not
in terms of library analysis by scholars, but as understood
by those versed in the field of law enforcement.
As these comments illustrate, probable cause is a fluid
concept-turning on the assessment of probabilities in
particular factual contexts-not readily, or even usefully,
reduced to a neat set of legal rules. Informants’ tips
doubtless come in many shapes and sizes from many
different types of persons. As we said in Adams v.
Williams, 407 U.S. 143, 147, 92 S.Ct. 1921, 1924, 32
L.Ed.2d 612 (1972), “Informants’ tips, like all other clues
and evidence coming to a policeman on the scene may
vary greatly in their value and reliability.” Rigid legal
rules are ill-suited to an area of such diversity. “One
simple rule will not cover every situation.” Ibid.7
*233 Moreover, the “two-pronged test” directs analysis
into two largely independent channels-the informant’s
“veracity” or “reliability” and his “basis of knowledge.”
See nn. 4 and 5 supra. There are persuasive arguments
against according these two elements such independent
status. Instead, they are better understood as relevant
considerations in the totality-of-the-circumstances
analysis that traditionally has guided probable cause
determinations: a deficiency in one may be compensated
for, in determining the overall reliability of a tip, by a
strong showing as to the other, or by some other indicia of
reliability. See, e.g., Adams v. Williams, supra, 407 U.S.,
at 146-147, 92 S.Ct., at 1923-1924; Harris v. United
States, 403 U.S. 573, 91 S.Ct. 2075, 29 L.Ed.2d 723
(1971).
If, for example, a particular informant is known for the
unusual reliability of his predictions of certain types of
criminal activities in a locality, his failure, in a particular
case, to thoroughly set forth the basis of his knowledge
surely should not serve as an absolute bar to a finding of
probable **2330 cause based on his tip. See United States
v. Sellers, 483 F.2d 37 (CA5 1973).8 Likewise, if an
unquestionably honest citizen comes forward with a
report of criminal activity-which if fabricated would
subject him to criminal liability-we have found *234
rigorous scrutiny of the basis of his knowledge
unnecessary. Adams v. Williams, supra. Conversely, even
if we entertain some doubt as to an informant’s motives,
his explicit and detailed description of alleged
wrongdoing, along with a statement that the event was
observed first-hand, entitles his tip to greater weight than
might otherwise be the case. Unlike a totality-of-thecircumstances
analysis, which permits a balanced
assessment of the relative weights of all the various
indicia of reliability (and unreliability) attending an
informant’s tip, the “two-pronged test” has encouraged an
excessively technical dissection of informants’ tips,9 with
undue attention *235 being focused on isolated issues that
cannot sensibly be divorced from the other facts presented
to the magistrate.
As early as Locke v. United States, 7 Cranch. 339, 348, 3
L.Ed. 364 (1813), Chief Justice Marshall observed, in a
closely related context, that “the term ‘probable cause,’
according to its usual acceptation, means less than
evidence which would justify condemnation.... It imports
a seizure made under circumstances which warrant
suspicion.” More recently, we said that “the quanta ... of
proof” appropriate in ordinary judicial proceedings are
50

inapplicable to the decision to issue a warrant. Brinegar,
supra, 338 U.S., at 173, 69 S.Ct., at 1309. Finely-tuned
standards such as proof beyond a reasonable doubt or by a
preponderance of the evidence, useful in formal trials,
have no place in the magistrate’s decision. While an effort
to fix some general, numerically precise degree of
certainty corresponding to “probable cause” may not be
helpful, it is clear that “only the probability, and not a
prima facie showing, of criminal activity is the standard
of probable cause.” Spinelli, supra, 393 U.S., at 419, 89
S.Ct., at 590. See Model Code of Pre-Arraignment
Procedure § 210.1(7) (Proposed Off. Draft 1972); W.
LaFave, Search and Seizure, § 3.2(3) (1978).
We also have recognized that affidavits “are normally
drafted by nonlawyers in the midst and haste of a criminal
investigation. Technical requirements of elaborate
specificity once exacted under common law **2331
pleading have no proper place in this area.” Ventresca,
supra, 380 U.S., at 108, 85 S.Ct., at 745. Likewise, search
and arrest warrants long have been issued by persons who
are neither lawyers nor judges, and who certainly do not
remain abreast of each judicial refinement of the nature of
“probable cause.” See Shadwick v. City of Tampa, 407
U.S. 345, 348-350, 92 S.Ct. 2119, 2121-2122, 32 L.Ed.2d
783 (1972). The rigorous inquiry into the Spinelli prongs
and the complex superstructure of evidentiary and
analytical rules that some have seen implicit in our
Spinelli decision, cannot be reconciled with the fact that
many warrants are-quite properly, ibid.-issued on the
basis of nontechnical, *236 common-sense judgments of
laymen applying a standard less demanding than those
used in more formal legal proceedings. Likewise, given
the informal, often hurried context in which it must be
applied, the “built-in subtleties,” Stanley v. State, 19
Md.App. 507, 313 A.2d 847, 860 (Md.App.1974), of the
“two-pronged test” are particularly unlikely to assist
magistrates in determining probable cause.
Similarly, we have repeatedly said that after-the-fact
scrutiny by courts of the sufficiency of an affidavit should
not take the form of de novo review. A magistrate’s
“determination of probable cause should be paid great
deference by reviewing courts.” Spinelli, supra, 393 U.S.,
at 419, 89 S.Ct., at 590. “A grudging or negative attitude
by reviewing courts toward warrants,” Ventresca, supra,
380 U.S., at 108, 85 S.Ct., at 745, is inconsistent with the
Fourth Amendment’s strong preference for searches
conducted pursuant to a warrant “courts should not
invalidate ... warrant[s] by interpreting affidavit [s] in a
hypertechnical, rather than a commonsense, manner.” Id.,
at 109, 85 S.Ct., at 746.
51
If the affidavits submitted by police officers are subjected
to the type of scrutiny some courts have deemed
appropriate, police might well resort to warrantless
searches, with the hope of relying on consent or some
other exception to the warrant clause that might develop
at the time of the search. In addition, the possession of a
warrant by officers conducting an arrest or search greatly
reduces the perception of unlawful or intrusive police
conduct, by assuring “the individual whose property is
searched or seized of the lawful authority of the executing
officer, his need to search, and the limits of his power to
search.” United States v. Chadwick, 433 U.S. 1, 9, 97
S.Ct. 2476, 2482, 53 L.Ed.2d 538 (1977). Reflecting this
preference for the warrant process, the traditional standard
for review of an issuing magistrate’s probable cause
determination has been that so long as the magistrate had
a “substantial basis for ... conclud[ing]” that a search
would uncover evidence of wrongdoing, the Fourth
Amendment requires no more. Jones v. United States, 362
U.S. 257, 271, 80 S.Ct. 725, 736, 4 L.Ed.2d 697 (1960).
See United States v. *237 Harris, 403 U.S. 573, 577-583,
91 S.Ct. 2075, 2079-2082, 29 L.Ed.2d 723 (1971).10 We
think reaffirmation of this standard better serves the
purpose of encouraging recourse to the warrant procedure
and is more consistent with our traditional deference to
the probable cause determinations of magistrates than is
the “two-pronged test.”
Finally, the direction taken by decisions following
Spinelli poorly serves “the **2332 most basic function of
any government”: “to provide for the security of the
individual and of his property.” Miranda v. Arizona, 384
U.S. 436, 539, 86 S.Ct. 1602, 1661, 16 L.Ed.2d 694
(1966) (WHITE, J., dissenting). The strictures that
inevitably accompany the “two-pronged test” cannot
avoid seriously impeding the task of law enforcement,
see, e.g., n. 9 supra. If, as the Illinois Supreme Court
apparently thought, that test must be rigorously applied in
every case, anonymous tips seldom would be of greatly
diminished value in police work. Ordinary citizens, like
ordinary witnesses, see Federal Rules of Evidence 701,
Advisory Committee Note (1976), generally do not
provide extensive recitations of the basis of their everyday
observations. Likewise, as the Illinois Supreme Court
observed in this case, the veracity of persons supplying
anonymous tips is by hypothesis largely unknown, and
unknowable. As a result, anonymous tips seldom could
survive a rigorous application of either of the Spinelli
prongs. Yet, such tips, particularly when supplemented by
*238 independent police investigation, frequently
contribute to the solution of otherwise “perfect crimes.”
While a conscientious assessment of the basis for
crediting such tips is required by the Fourth Amendment,

a standard that leaves virtually no place for anonymous
citizen informants is not.
For all these reasons, we conclude that it is wiser to
abandon the “two-pronged test” established by our
decisions in Aguilar and Spinelli.11 In its place we
reaffirm the totality-of-the-circumstances analysis that
traditionally has informed probable cause determinations.
See Jones v. United States, supra; United States v.
Ventresca, supra; Brinegar v. United States, supra. The
task of the issuing magistrate is simply to make a
practical, common-sense decision whether, given all the
circumstances set forth in the affidavit before him,
including the “veracity” and “basis of knowledge” of
persons supplying hearsay information, there is a fair
probability that contraband or evidence of a crime will be
found in a particular place. And the duty of a reviewing
court is simply to ensure that the magistrate had a
“substantial basis for ... conclud[ing]” that probable cause
*239 existed. Jones v. United States, supra, 362 U.S., at
271, 80 S.Ct., at 736. We are convinced that this flexible,
easily applied standard will better achieve the
accommodation of public and private interests that the
Fourth Amendment requires than does the approach that
has developed from Aguilar and Spinelli.
[9] [10] [11] Our earlier cases illustrate the limits beyond
which a magistrate may not venture in issuing a warrant.
A sworn statement of an affiant that “he has cause to
suspect and does believe that” liquor illegally brought into
the United States is located on certain premises will not
do. Nathanson v. United States, 290 U.S. 41, 54 S.Ct. 11,
78 L.Ed. 159 (1933). An affidavit must provide the
magistrate with a substantial basis for determining the
existence of probable cause, and the wholly conclusory
statement at issue in Nathanson failed to meet this
requirement. An **2333 officer’s statement that “affiants
have received reliable information from a credible person
and believe” that heroin is stored in a home, is likewise
inadequate. Aguilar v. Texas, 378 U.S. 108, 84 S.Ct.
1509, 12 L.Ed.2d 723 (1964). As in Nathanson, this is a
mere conclusory statement that gives the magistrate
virtually no basis at all for making a judgment regarding
probable cause. Sufficient information must be presented
to the magistrate to allow that official to determine
probable cause; his action cannot be a mere ratification of
the bare conclusions of others. In order to ensure that such
an abdication of the magistrate’s duty does not occur,
courts must continue to conscientiously review the
sufficiency of affidavits on which warrants are issued. But
when we move beyond the “bare bones” affidavits present
in cases such as Nathanson and Aguilar, this area simply
does not lend itself to a prescribed set of rules, like that
52
which had developed from Spinelli. Instead, the flexible,
common-sense standard articulated in Jones, Ventresca,
and Brinegar better serves the purposes of the Fourth
Amendment’s probable cause requirement.
Justice BRENNAN’s dissent suggests in several places
that the approach we take today somehow downgrades the
*240 role of the neutral magistrate, because Aguilar and
Spinelli “preserve the role of magistrates as independent
arbiters of probable cause....” Post, at 2357. Quite the
contrary, we believe, is the case. The essential protection
of the warrant requirement of the Fourth Amendment, as
stated in Johnson v. United States, 333 U.S. 10, 68 S.Ct.
367, 92 L.Ed. 436 (1948), is in “requiring that [the usual
inferences which reasonable men draw from evidence] be
drawn by a neutral and detached magistrate instead of
being judged by the officer engaged in the often
competitive enterprise of ferreting out crime.” Id., at 13-
14, 68 S.Ct., at 369. Nothing in our opinion in any way
lessens the authority of the magistrate to draw such
reasonable inferences as he will from the material
supplied to him by applicants for a warrant; indeed, he is
freer than under the regime of Aguilar and Spinelli to
draw such inferences, or to refuse to draw them if he is so
minded.
The real gist of Justice BRENNAN’s criticism seems to
be a second argument, somewhat at odds with the first,
that magistrates should be restricted in their authority to
make probable cause determinations by the standards laid
down in Aguilar and Spinelli, and that such findings
“should not be authorized unless there is some assurance
that the information on which they are based has been
obtained in a reliable way by an honest or credible
person.” However, under our opinion magistrates remain
perfectly free to exact such assurances as they deem
necessary, as well as those required by this opinion, in
making probable cause determinations. Justice
BRENNAN would apparently prefer that magistrates be
restricted in their findings of probable cause by the
development of an elaborate body of case law dealing
with the “veracity” prong of the Spinelli test, which in
turn is broken down into two “spurs”-the informant’s
“credibility” and the “reliability” of his information,
together with the “basis of knowledge” prong of the
Spinelli test. See n. 4, supra. That such a labyrinthine
body of judicial refinement bears any relationship to
familiar definitions of *241 probable cause is hard to
imagine. Probable cause deals “with probabilities. These
are not technical; they are the factual and practical
considerations of everyday life on which reasonable and
prudent men, not legal technicians, act,” Brinegar v.
United States, 338 U.S. 160, 175, 69 S.Ct. 1302, 1310, 93

L.Ed. 1879 (1949).
Justice BRENNAN’s dissent also suggests that “words
such as ‘practical,’ ‘nontechnical,’ and ‘common sense,’
as used in the Court’s opinion, are but code words for an
overly-permissive attitude towards police practices in
derogation of the rights secured by the Fourth
Amendment.” Infra, p. 2359. An easy, but not a complete,
answer to this rather florid statement would be that
nothing we know about Justice **2334 Rutledge suggests
that he would have used the words he chose in Brinegar
in such a manner. More fundamentally, no one doubts that
“under our Constitution only measures consistent with the
Fourth Amendment may be employed by government to
cure [the horrors of drug trafficking],” post, at 2359; but
this agreement does not advance the inquiry as to which
measures are, and which measures are not, consistent with
the Fourth Amendment. “Fidelity” to the commands of
the Constitution suggests balanced judgment rather than
exhortation. The highest “fidelity” is achieved neither by
the judge who instinctively goes furthest in upholding
even the most bizarre claim of individual constitutional
rights, any more than it is achieved by a judge who
instinctively goes furthest in accepting the most restrictive
claims of governmental authorities. The task of this Court,
as of other courts, is to “hold the balance true,” and we
think we have done that in this case.
IV
[12] Our decisions applying the totality-of-thecircumstances
analysis outlined above have consistently
recognized the value of corroboration of details of an
informant’s tip by independent police work. In Jones v.
United States, supra, 362 U.S., at 269, 80 S.Ct., at 735,
we held that an affidavit relying on hearsay “is not to
*242 be deemed insufficient on that score, so long as a
substantial basis for crediting the hearsay is presented.”
We went on to say that even in making a warrantless
arrest an officer “may rely upon information received
through an informant, rather than upon his direct
observations, so long as the informant’s statement is
reasonably corroborated by other matters within the
officer’s knowledge.” Ibid. Likewise, we recognized the
probative value of corroborative efforts of police officials
in Aguilar -the source of the “two-pronged test”-by
observing that if the police had made some effort to
corroborate the informant’s report at issue, “an entirely
different case” would have been presented. Aguilar,
supra, 378 U.S., at 109, n. 1, 84 S.Ct., at 1511, n. 1.
Our decision in Draper v. United States, 358 U.S. 307, 79
S.Ct. 329, 3 L.Ed.2d 327 (1959), however, is the classic
case on the value of corroborative efforts of police
officials. There, an informant named Hereford reported
that Draper would arrive in Denver on a train from
Chicago on one of two days, and that he would be
carrying a quantity of heroin. The informant also supplied
a fairly detailed physical description of Draper, and
predicted that he would be wearing a light colored
raincoat, brown slacks and black shoes, and would be
walking “real fast.” Id., at 309, 79 S.Ct., at 331. Hereford
gave no indication of the basis for his information.12
On one of the stated dates police officers observed a man
matching this description exit a train arriving from
Chicago; his attire and luggage matched Hereford’s report
and he was *243 walking rapidly. We explained in
Draper that, by this point in his investigation, the
arresting officer “had personally verified every facet of
the information given him by Hereford except whether
petitioner had accomplished his mission and had the three
ounces of heroin on his person or in his bag. And surely,
with every other bit of Hereford’s information being thus
personally verified, [the officer] had ‘reasonable grounds’
to believe that the remaining unverified bit of Hereford’s
information-that Draper would have the heroin with himwas
likewise true,” id., at 313, 79 S.Ct., at 333.
**2335 The showing of probable cause in the present case
was fully as compelling as that in Draper. Even standing
alone, the facts obtained through the independent
investigation of Mader and the DEA at least suggested
that the Gates were involved in drug trafficking. In
addition to being a popular vacation site, Florida is wellknown
as a source of narcotics and other illegal drugs.
See United States v. Mendenhall, 446 U.S. 544, 562, 100
S.Ct. 1870, 1881, 64 L.Ed.2d 497 (1980) (POWELL, J.,
concurring); DEA, Narcotics Intelligence Estimate, The
Supply of Drugs to the U.S. Illicit Market From Foreign
and Domestic Sources 10 (1979). Lance Gates’ flight to
Palm Beach, his brief, overnight stay in a motel, and
apparent immediate return north to Chicago in the family
car, conveniently awaiting him in West Palm Beach, is as
suggestive of a pre-arranged drug run, as it is of an
ordinary vacation trip.
[13] [14] In addition, the magistrate could rely on the
anonymous letter, which had been corroborated in major
part by Mader’s efforts-just as had occurred in Draper.13
The Supreme Court *244 of Illinois reasoned that Draper
involved an informant who had given reliable information
on previous occasions, while the honesty and reliability of
the anonymous informant in this case were unknown to
the Bloomingdale police. While this distinction might be
53

an apt one at the time the police department received the
anonymous letter, it became far less significant after
Mader’s independent investigative work occurred. The
corroboration of the letter’s predictions that the Gates’ car
would be in Florida, that Lance Gates would fly to Florida
in the next day or so, and that he would drive the car north
toward Bloomingdale all indicated, albeit not with
certainty, that the informant’s other assertions also were
true. “Because an informant is right about some things, he
is more probably right about other facts,” Spinelli, supra,
393 U.S., at 427, 89 S.Ct., at 594 (WHITE, J.,
concurring)-including the claim regarding the Gates’
illegal activity. This may well not be the type of
“reliability” or “veracity” necessary to satisfy some views
of the “veracity prong” of Spinelli, but we think it suffices
for the practical, common-sense judgment called for in
making a probable cause determination. It is enough, for
purposes of assessing probable cause, that “corroboration
through other sources of information reduced the *245
chances of a reckless or prevaricating tale,” thus
providing “a substantial basis for crediting the hearsay.”
Jones v. United States, supra, 362 U.S., at 269, 271, 80
S.Ct., at 735, 736.
[15] Finally, the anonymous letter contained a range of
details relating not just to easily obtained facts and
conditions existing at the time of the tip, but to future
**2336 actions of third parties ordinarily not easily
predicted. The letter writer’s accurate information as to
the travel plans of each of the Gates was of a character
likely obtained only from the Gates themselves, or from
someone familiar with their not entirely ordinary travel
plans. If the informant had access to accurate information
of this type a magistrate could properly conclude that it
was not unlikely that he also had access to reliable
information of the Gates’ alleged illegal activities.14 Of
*246 course, the Gates’ travel plans might have been
learned from a talkative neighbor or travel agent; under
the “two-pronged test” developed from Spinelli, the
character of the details in the anonymous letter might well
not permit a sufficiently clear inference regarding the
letter writer’s “basis of knowledge.” But, as discussed
previously, supra, 2332, probable cause does not demand
the certainty we associate with formal trials. It is enough
that there was a fair probability that the writer of the
anonymous letter had obtained his entire story either from
the Gates or someone they trusted. And corroboration of
major portions of the letter’s predictions provides just this
probability. It is apparent, therefore, that the judge issuing
the warrant had a “substantial basis for ... conclud[ing]”
that probable cause to search the Gates’ home and car
existed. The judgment of the Supreme Court of Illinois
therefore must be
54
Reversed.
Justice WHITE, concurring in the judgment.
In my view, the question regarding modification of the
exclusionary rule framed in our order of November 29,
1982, --- U.S. ---- (1982), is properly before us and should
be addressed. I continue to believe that the exclusionary
rule is an inappropriate remedy where law enforcement
officials act in the reasonable belief that a search and
seizure was consistent with the Fourth Amendment-a
position I set forth in Stone v. Powell, 428 U.S. 465, 537-
539, 96 S.Ct. 3027, 3032-3033, 49 L.Ed.2d 1067 (1976).
In this case, it was fully reasonable for the Bloomingdale,
Illinois police to believe that their search of respondents’
house and automobile comported with the Fourth
Amendment as the search was conducted pursuant to a
judicially-issued warrant. The *247 exclusion of
probative evidence where the constable has not blundered
not only sets the criminal free but also fails to serve any
constitutional interest in securing compliance with the
important requirements of the Fourth Amendment. On
this basis, I **2337 concur in the Court’s judgment that
the decision of the Illinois Supreme Court must be
reversed.
I
The Court declines to address the exclusionary rule
question because the Illinois courts were not invited to
modify the rule in the first instance. The Court’s refusal to
face this important question cannot be ascribed to
jurisdictional limitations. I fully agree that the statute
which gives us jurisdiction in this cause, 18 U.S.C. §
1257(3), prevents us from deciding federal constitutional
claims raised here for the first time on review of state
court decisions. Cardinale v. Louisiana, 394 U.S. 437,
438-439, 89 S.Ct. 1161, 1162-1163, 22 L.Ed.2d 398
(1969). But it is equally well-established that “[n]o
particular form of words or phrases is essential, but only
that the claim of invalidity and the ground therefore be
brought to the attention of the state court with fair
precision and in due time.” Street v. New York, 394 U.S.
576, 584, 89 S.Ct. 1354, 1361, 22 L.Ed.2d 572 (1969)
(quoting New York ex rel. Bryant v. Zimmerman, 278 U.S.
63, 67, 49 S.Ct. 61, 63, 73 L.Ed. 184 (1928)).
Notwithstanding the select and controversial instances in
which the Court has reversed a state court decision for
“plain error,”1 we have consistently dismissed for want of
jurisdiction where the federal claim asserted in this Court
was not raised below. But this obviously is not such a

case. As the Court points out, “It is clear in this case that
respondents expressly raised, at every level of the Illinois
judicial system, the claim that the Fourth Amendment had
been violated by the actions of the Illinois *248 police
and that the evidence seized by the officers should be
excluded from their trial.” Ante, at 2323. Until today, we
have not required more.
We have never suggested that the jurisdictional
stipulations of § 1257 require that all arguments on behalf
of, let alone in opposition to, a federal claim be raised and
decided below.2 See R. Stern & E. Gressman, Supreme
Court Practice 230 (1978). Dewey v. Des Moines, 173
U.S. 193, 19 S.Ct. 379, 43 L.Ed. 665 (1898) distinguished
the raising of constitutional claims and the making of
arguments in support of or in opposition to those claims.
“If the question were only an enlargement of the one
mentioned in the assignment of errors, or if it were so
connected with it in substance as to form but another
ground or reason for alleging the invalidity of the
personal judgment, we should have no hesitation in
holding the assignment sufficient to permit the question to
be now raised and argued. Parties are not confined here
to the same arguments which were advanced in the courts
below upon a federal question there discussed. **2338 ”
173 U.S., at 197-198, 19 S.Ct., at 380-381 (emphasis
added).3
*249 Under Dewey, which the Court hails as the “fullest
treatment of the subject,” ante, at 2322, the exclusionary
rule issue is but another argument pertaining to the Fourth
Amendment question squarely presented in the Illinois
courts.
The presentation and decision of respondent’s Fourth
Amendment claim fully embraces the argument that due
to the nature of the alleged Fourth Amendment violation,
the seized evidence should not be excluded. Our decisions
concerning the scope of the exclusionary rule cannot be
divorced from the Fourth Amendment; they rest on the
relationship of Fourth Amendment interests to the
objectives of the criminal justice system. See, e.g. United
States v. Ceccolini, 435 U.S. 268, 98 S.Ct. 1054, 55
L.Ed.2d 268 (1978); Stone v. Powell, 428 U.S. 465, 96
S.Ct. 3037, 49 L.Ed.2d 1067 (1976).4 Similarly, the issues
surrounding a proposed good faith modification are
intricately and inseverably tied to the nature of the Fourth
Amendment violation: the degree of probable cause, the
presence of a warrant, and the clarity of previously
announced Fourth Amendment principles all inform the
*250 good faith issue. The Court’s own holding that the
duty of a reviewing court is simply to ensure that the
magistrate had a “substantial basis” for concluding that
55
probable cause existed, ante, at 2334, is itself but a
variation on the good-faith theme. See Brief of Petitioner
on Reargument at 4-26.
As a jurisdictional requirement, I have no doubt that the
exclusionary rule question is before us as an indivisible
element of the claim that the Constitution requires
exclusion of certain evidence seized in violation of the
Fourth Amendment. As a prudential matter, I am
unmoved by the Court’s lengthy discourse as to why it
must avoid the question. First, the Court turns on its head
the axiom that “ ‘due regard for the appropriate
relationship of this Court to state courts,’ McGoldrick v.
Compagnie Generale, 309 U.S. 430, 434-435, 60 S.Ct.
670, 672-673, 84 L.Ed. 849 (1940), demands that those
courts be given an opportunity to consider the
constitutionality of the actions of state officials” ante, at
2323. This statement, written to explain why a state
statute should not be struck down on federal grounds not
raised in the state courts,5 **2339 hardly applies when the
question is whether a rule of federal law articulated by
this Court should now be narrowed to reduce the scope of
federal intrusion into the state’s administration of criminal
justice. Insofar as modifications of the federal
exclusionary *251 rule are concerned, the Illinois courts
are bound by this Court’s pronouncements. Cf. Oregon v.
Hass, 420 U.S. 714, 719, 95 S.Ct. 1215, 1219, 43 L.Ed.2d
570 (1975). I see little point in requiring a litigant to
request a state court to overrule or modify one of this
Court’s precedents. Far from encouraging the stability of
our precedents, the Court’s proposed practice could well
undercut stare decisis. Either the presentation of such
issues to the lower courts will be a completely futile
gesture or the lower courts are now invited to depart from
this Court’s decisions whenever they conclude such a
modification is in order.6
The Court correctly notes that Illinois may choose to
pursue a different course with respect to the state
exclusionary rule. If this Court were to formulate a “good
faith” exception to the federal exclusionary rule, the
Illinois Supreme Court would be free to consider on
remand whether the state exclusionary rule should be
modified accordingly. The possibility that it might have
relied upon the state exclusionary rule had the “goodfaith”
question been posed does not constitute
independent and adequate state grounds. “The possibility
that the state court might have reached the same
conclusion if it had decided the question purely as a
matter of state law does not create an adequate and
independent state ground that relieves this Court of the
necessity of considering the federal question.” United Air
Lines v. Mahin, 410 U.S. 623, 630-631, 93 S.Ct. 1186,
1191-1192, 35 L.Ed.2d 545 (1973); Beecher v. Alabama,

389 U.S. 35, 37, n. 3, 88 S.Ct. 189, 190, n. 3, 19 L.Ed.2d
35 (1967); C. Wright, Federal Courts § 107, pp. 747-748
(4th ed. 1983). Nor does having the state court first decide
whether the federal exclusionary rule should be modifiedand
presentation of the federal question does not insure
that the equivalent state law issue will be *252 raised or
decided7-avoid the unnecessary decision of a federal
question. The Court still must reach a federal question to
decide the instant case. Thus, in today’s opinion, the
Court eschews modification of the exclusionary rule in
favor of interring the test established by Aguilar v. Texas,
378 U.S. 108, 84 S.Ct. 1509, 12 L.Ed.2d 723 (1964) and
Spinelli v. United States, 393 U.S. 410, 89 S.Ct. 584, 21
L.Ed.2d 637 (1969). Nor is the exclusionary rule question
avoided-it is simply deferred until “another day.”
It also appears that the Court, in disposing of the case,
does not strictly follow its own prudential advice. The
Illinois Supreme Court found not only a violation of the
Fourth Amendment but also of Article I, § 6 of the Illinois
Constitution which also provides assurance against
unreasonable searches and seizures. Taking the Court’s
new prudential standards on their own terms, the Illinois
courts should be given the opportunity to consider in the
first instance whether a “totality of the circumstances” test
should replace the more precise rules of Aguilar and
Spinelli. The Illinois Supreme Court may decide to retain
the established test for purposes **2340 of its state
constitution just as easily as it could decide to retain an
unmodified exclusionary rule.8
Finally, the Court correctly notes that a fully-developed
record is helpful if not indispensable for the decision of
many issues. I too resist the decision of a constitutional
question *253 when such guidance is necessary, but the
question of whether the exclusionary rule should be
modified is an issue of law which obviously goes far
beyond and depends little on the subjective good faith of
the police officers that searched the Gates’ property.
Moreover, the case comes here with a fully developed
record as to the actions of the Bloomingdale, Illinois
police. If further factual development of whether the
officers in this case acted in good faith were important,
that issue should logically be considered on remand,
following this Court’s statement of the proper legal
standards.9
The Court’s straining to avoid coming to grips with the
exclusionary rule issue today may be hard for the country
to understand-particularly given earlier statements by
some members of the Court.10 The question has been
fully briefed and argued by the parties and amici curiae,
including the United States.11 The issue is central to the
enforcement of law and the administration of justice
throughout the nation. The Court of Appeals for the
56
second largest federal circuit *254 has already adopted
such an exception, United States v. Williams, 622 F.2d
830 (CA5 1980) (en banc), cert. denied, 449 U.S. 1127,
101 S.Ct. 946, 67 L.Ed.2d 114 (1981), and the new
Eleventh Circuit is presumably bound by its decision.
Several members of this Court have for some time
expressed the need to consider modifying the
exclusionary rule, ante, at 2325, and Congress as well has
been active in exploring the question. See The
Exclusionary Rule Bills, Hearings before the
Subcommittee on Criminal Law of the Senate Judiciary
Committee, 97th Cong.; 1st and 2d Sess. At least one
state has already enacted a good faith exception.
Colo.Rev.Stat.Tit. 16, Art. 3, § 308. Of course, if there is
a jurisdictional barrier to deciding the issue, none of these
considerations are relevant. But if no such procedural
obstacle exists, I see it as our responsibility to end the
uncertainty and decide whether the rule will be modified.
The question of whether probable cause existed for the
issuance of a warrant and whether the evidence seized
must be excluded in this case should follow our
reconsideration of the framework by which such issues, as
they **2341 arise from the Fourth Amendment, are to be
handled.
A
II
The exclusionary rule is a remedy adopted by this Court
to effectuate the Fourth Amendment right of citizens “to
be secure in their persons, houses, papers, and effects,
against unreasonable searches and seizures ...” Although
early opinions suggested that the Constitution required
exclusion of all illegally obtained evidence, the
exclusionary rule “has never been interpreted to proscribe
the introduction of illegally seized evidence in all
proceedings or against all persons.” Stone v. Powell, 428
U.S. 465, 486, 96 S.Ct. 3037, 3048, 49 L.Ed.2d 1067
(1976). Because of the inherent trustworthiness of seized
tangible evidence and the resulting social costs from its
loss through suppression, application *255 of the
exclusionary rule has been carefully “restricted to those
areas where its remedial objectives are thought most
efficaciously observed.” United States v. Calandra, 414
U.S. 338, 348, 94 S.Ct. 613, 620, 38 L.Ed.2d 561 (1974).
Even at criminal trials the exclusionary rule has not been
applied indiscriminately to ban all illegally obtained
evidence without regard to the costs and benefits of doing
so. Infra, at 2341. These developments, borne of years of
experience with the exclusionary rule in operation,

forcefully suggest that the exclusionary rule be more
generally modified to permit the introduction of evidence
obtained in the reasonable good-faith belief that a search
or seizure was in accord with the Fourth Amendment.
This evolvement in the understanding of the proper scope
of the exclusionary rule embraces several lines of cases.
First, standing to invoke the exclusionary rule has been
limited to situations where the Government seeks to use
such evidence against the victim of the unlawful search.
Brown v. United States, 411 U.S. 223, 93 S.Ct. 1565, 36
L.Ed.2d 208 (1973); Alderman v. United States, 394 U.S.
165, 89 S.Ct. 961, 22 L.Ed.2d 176 (1969); Wong Sun v.
United States, 371 U.S. 471, 491-492, 83 S.Ct. 407, 419-
420, 9 L.Ed.2d 441 (1963); Rakas v. Illinois, 439 U.S.
128, 99 S.Ct. 421, 58 L.Ed.2d 387 (1978).
Second, the rule has not been applied in proceedings other
than the trial itself. In United States v. Calandra, 414 U.S.
338, 94 S.Ct. 613, 38 L.Ed.2d 561 (1974), the Court
refused to extend the rule to grand jury proceedings. “Any
incremental deterrent effect which might be achieved by
extending the rule to grand jury proceedings is uncertain
at best.... We therefore decline to embrace a view that
would achieve a speculative and undoubtedly minimal
advance in the deterrence of police misconduct at the
expense of substantially impeding the role of the grand
jury.” Id., at 348, 94 S.Ct., at 620. Similarly, in United
States v. Janis, 428 U.S. 433, 96 S.Ct. 3021, 49 L.Ed.2d
1046 (1976), the exclusionary rule was not extended to
forbid the use in the federal civil proceedings of evidence
illegally seized by state officials, since the likelihood of
deterring unlawful police conduct was not sufficient to
outweigh the social costs imposed by the exclusion.
*256 Third, even at a criminal trial, the same analysis has
led us to conclude that the costs of excluding probative
evidence outweighed the deterrence benefits in several
circumstances. We have refused to prohibit the use of
illegally seized evidence for the purpose of impeaching a
defendant who testifies in his own behalf. United States v.
Havens, 446 U.S. 620, 100 S.Ct. 1912, 64 L.Ed.2d 559
(1980); Walder v. United States, 347 U.S. 62, 74 S.Ct.
354, 98 L.Ed. 503 (1954). We have also declined to adopt
a “per se or ‘but for’ rule” that would make inadmissible
any evidence which comes to light through a chain of
causation that began with an illegal arrest. Brown v.
Illinois, 422 U.S. 590, 603, 95 S.Ct. 2254, ----, 45
L.Ed.2d 416 (1975). And we have held that testimony of a
live witness may be admitted, notwithstanding that the
testimony was derived from a concededly unconstitutional
search. United States v. Ceccolini, 435 U.S. 268, 98 S.Ct.
1054, 55 L.Ed.2d 268 (1978). Nor is exclusion required
**2342 when law enforcement agents act in good-faith
reliance upon a statute or ordinance that is subsequently
held to be unconstitutional. United States v. Peltier, 422
U.S. 531, 95 S.Ct. 2313, 45 L.Ed.2d 374 (1977),
Michigan v. DeFillippo, 443 U.S. 31, 99 S.Ct. 2627, 61
L.Ed.2d 343 (1979).12 Cf. United States v. Caceres, 440
U.S. 741, 754-757, 99 S.Ct. 1465, 1472-1474, 59 L.Ed.2d
733 (1979) (exclusion not *257 required of evidence
tainted by violation of an executive department’s rules
concerning electronic eavesdropping).
A similar balancing approach is employed in our
decisions limiting the scope of the exclusionary remedy
for Fifth Amendment violations, Oregon v. Hass, 420
U.S. 714, 95 S.Ct. 1215, 43 L.Ed.2d 570 (1975); Harris v.
New York, 401 U.S. 222, 91 S.Ct. 643, 28 L.Ed.2d 1
(1971); Michigan v. Tucker, 417 U.S. 433, 94 S.Ct. 2357,
41 L.Ed.2d 182 (1974), and our cases considering
whether Fourth Amendment decisions should be applied
retroactively, United States v. Peltier, supra, 422 U.S., at
538-539, 95 S.Ct., at 2318; Williams v. United States, 401
U.S. 646, 654-655, 91 S.Ct. 1148, 1153-1154, 28 L.Ed.2d
388 (1971) (plurality opinion); Desist v. United States,
394 U.S., at 244, 249-250, 89 S.Ct., at 1030, 1033-1034,
22 L.Ed.2d 248; Linkletter v. Walker, 381 U.S. 618, 636-
639, 85 S.Ct. 1731, 1741-1743, 14 L.Ed.2d 601. But see
United States v. Johnson, --- U.S. ----, 102 S.Ct. 2579, 73
L.Ed.2d 202 (1982).
These cases reflect that the exclusion of evidence is not a
personal constitutional right but a remedy, which, like all
remedies, must be sensitive to the costs and benefits of its
imposition. The trend and direction of our exclusionary
rule decisions indicate not a lesser concern with
safeguarding the Fourth Amendment but a fuller
appreciation of the high costs incurred when probative,
reliable evidence is barred because of investigative error.
The primary cost, of course, is that the exclusionary rule
interferes with the truthseeking function of a criminal trial
by barring relevant and trustworthy evidence.13 We will
never know how many guilty defendants go free as a
result of the rule’s operation. But any rule of evidence
that denies the jury access to clearly probative and
reliable evidence must bear a heavy burden of
justification, *258 and must be carefully limited to the
circumstances in which it will pay its way by deterring
official lawlessness. I do not presume that modification of
the exclusionary rule will, by itself, significantly reduce
the crime rate-but that **2343 is no excuse for
indiscriminate application of the rule.
The suppression doctrine entails other costs as well. It
would be surprising if the suppression of evidence
57

garnered in good-faith, but by means later found to violate
the Fourth Amendment, did not deter legitimate as well as
unlawful police activities. To the extent the rule operates
to discourage police from reasonable and proper
investigative actions, it hinders the solution and even the
prevention of crime. A tremendous burden is also placed
on the state and federal judicial systems. One study
reveals that one-third of federal defendants going to trial
file Fourth Amendment suppression motions, and 70% to
90% of these involve formal hearings. Comptroller
General of the United States, Impact of the Exclusionary
Rule on Federal Criminal Prosecutions 10 (1979).
The rule also exacts a heavy price in undermining public
confidence in the reasonableness of the standards that
govern the criminal justice system. “[A]lthough the
[exclusionary] rule is thought to deter unlawful police
activity in part through the nurturing of respect for Fourth
Amendment values, if applied indiscriminately it may
well have the opposite effect of generating disrespect for
the law and the administration of justice.” Stone v.
Powell, 428 U.S., at 490-491, 96 S.Ct., at 3050-3051. As
THE CHIEF JUSTICE observed in his separate opinion in
Stone v. Powell, 428 U.S., at 490, 96 S.Ct., at 3050: “The
disparity in particular cases between the error committed
by the police officer and the windfall afforded a guilty
defendant by application of the rule is contrary to the idea
of proportionality that is essential to the concept of
justice.”
For these reasons, “application of the [exclusionary] rule
has been restricted to those areas where its remedial
objectives are thought most efficaciously served.” United
States *259 v. Calandra, supra, 414 U.S., at 348, 94
S.Ct., at 620.14 The reasoning of our recent cases strongly
suggests that there is insufficient justification to suppress
evidence at a criminal trial which was seized in the
reasonable belief that the Fourth Amendment was not
violated. The deterrent effect of the exclusionary rule
**2344 has never been established by empirical evidence,
despite *260 repeated attempts. United States v. Janis,
428 U.S., at 449-453, 96 S.Ct., at 3029-3031; Irvine v.
California, 347 U.S. 128, 136, 74 S.Ct. 381, 385, 98
L.Ed. 561 (1954). But accepting that the rule deters some
police misconduct, it is apparent as a matter of logic that
there is little if any deterrence when the rule is invoked to
suppress evidence obtained by a police officer acting in
the reasonable belief that his conduct did not violate the
Fourth Amendment. As we initially observed in Michigan
v. Tucker, 417 U.S., at 447, 94 S.Ct., at 2365, and
reiterated in United States v. Peltier, 422 U.S., at 539, 95
S.Ct., at 2318:
58
“The deterrent purpose of the exclusionary rule
necessarily assumes that the police have engaged in
willful, or at the very least negligent, conduct which has
deprived the defendant of some right. By refusing to
admit evidence gained as a result of such conduct, the
courts hope to instill in those particular investigating
officers, or in their future counterparts, a greater degree of
care toward the rights of an accused. Where the official
action was pursued in complete good faith, however, the
deterrence rationale loses much of its force.”
The Court in Peltier continued, 422 U.S., at 542, 95 S.Ct.,
at 2320:
“If the purpose of the exclusionary rule is to deter
unlawful police conduct then evidence obtained
from a search should be suppressed only if it can
be said that the law enforcement officer had
knowledge, or may properly be charged with
knowledge, that the search was unconstitutional
under the Fourth Amendment.”
See also United States v. Janis, 428 U.S., at 459, n. 35, 96
S.Ct., at 3034, n. 35 (“[T]he officers here were clearly
acting in good faith ... a factor that the Court has
recognized reduces significantly the potential deterrent
effect of exclusion.”) The deterrent value of the
exclusionary sanction is most effective when officers
engage in searches and seizures under circumstances “so
lacking in indicia of probable cause as to render official
belief in its existence entirely unreasonable.” Brown v.
Illinois, 422 U.S. 590, 610-611, 95 S.Ct. 2254, 2265-
2266, 45 L.Ed.2d 416 (1975) (POWELL, J., concurring).
On the *261 other hand, when officers perform their tasks
in the good-faith belief that their action comported with
constitutional requirements, the deterrent function of the
exclusionary rule is so minimal, if not non-existent, that
the balance clearly favors the rule’s modification.15
*262 **2345 B
There are several types of Fourth Amendment violations
that may be said to fall under the rubric of “good faith.”
“There will be those occasions where the trial or appellate
court will disagree on the issue of probable cause, no
matter how reasonable the grounds for arrest appeared to
the officer and though reasonable men could easily differ
on the question. It also happens that after the events at
issue have occurred, the law may change, dramatically or
ever so slightly, but in any event sufficiently to require
the trial judge to hold that there was not probable cause to
make the arrest and to seize the evidence offered by the
prosecution....” Stone v. Powell, 428 U.S., at 539-540, 96

S.Ct., at 3073-3074. (WHITE, J., dissenting). The
argument for a good-faith exception is strongest,
however, when law enforcement officers have reasonably
relied on a judicially-issued search warrant.
This Court has never set forth a rationale for applying the
exclusionary rule to suppress evidence obtained pursuant
to a search warrant; it has simply done so without
considering whether Fourth Amendment interests will be
advanced. It is my view that they generally will not be.
When officers have dutifully obtained a search warrant
from a judge or magistrate, and execute the warrant as
directed by its terms, exclusion of the evidence thus
obtained cannot be expected to deter future reliance on
such warrants. The warrant is prima-facie proof that the
officers acted reasonably in conducting the search or
seizure; “once the warrant issues, there is literally nothing
more the policeman can do in seeking to comply with the
law.” Stone v. Powell, 428 U.S., at 498, 96 S.Ct., at 3054
(BURGER, C.J., concurring).16 As Justice STEVENS
*263 put it in writing for the Court in United States v.
Ross, 456 U.S. 798, 823, n. 32, 102 S.Ct. 2157, 2172, n.
32, 72 L.Ed.2d 572 (1982): “A warrant issued by a
magistrate normally suffices to establish,” that a law
enforcement officer has “acted in good faith in conducting
the search.” Nevertheless, the warrant may be invalidated
because of a technical defect or because, as in this case,
the judge issued a warrant on information later
determined to fall short of probable cause. Excluding
evidence for these reasons can have no possible deterrent
effect on future police conduct, unless it is to make
officers less willing to do their duty. Indeed, applying the
exclusionary rule to warrant searches may well reduce
incentives for police to utilize the preferred warrant
procedure when a warrantless search may be permissible
under one of the established exceptions to the warrant
requirement. See ante, at 2331; Brown v. Illinois, 422
U.S., at 611, and n. 3, 95 S.Ct., at 2266, and n. 3
(POWELL, J., concurring); P. Johnson, New Approaches
to Enforcing the Fourth Amendment 11 (Working Paper,
1978). See also United States v. United States District
Court, 407 U.S. 297, 316-317, 92 S.Ct. 2125, 2136-2137,
32 L.Ed.2d 752 (1972); United States v. Ventresca, 380
U.S. 102, 106-107, 85 S.Ct. 741, 744-745, 13 L.Ed.2d
684 (1965).
**2346 Opponents of the proposed “reasonable belief”
exception suggest that such a modification would allow
magistrates and judges to flout the probable cause
requirements in issuing warrants. This is a novel concept:
the exclusionary rule was adopted to deter unlawful
searches by police, not to punish the errors of magistrates
and judges. Magistrates must be neutral and detached
59
from law enforcement operations and I would not
presume that a modification of the exclusionary rule will
lead magistrates to abdicate their responsibility to apply
the law.17 In any event, I would apply the exclusionary
*264 rule when it is plainly evident that a magistrate or
judge had no business issuing a warrant. See, e.g., Aguilar
v. Texas, 378 U.S. 108, 84 S.Ct. 1509, 12 L.Ed.2d 723
(1964); Nathanson v. United States, 290 U.S. 41, 54 S.Ct.
11, 78 L.Ed. 159 (1933). Similarly, the good-faith
exception would not apply if the material presented to the
magistrate or judge is false or misleading, Franks v.
Delaware, 438 U.S. 154, 98 S.Ct. 2674, 57 L.Ed.2d 667,
or so clearly lacking in probable cause that no welltrained
officer could reasonably have thought that a
warrant should issue.
Another objection is that a reasonable belief exception
will encompass all searches and seizures on the frontier of
the Fourth Amendment, that such cases will escape
review on the question of whether the officer’s action was
permissible, denying needed guidance from the courts and
freezing Fourth Amendment law in its present state.
These fears are unjustified. The premise of the argument
is that a court must first decide the reasonable belief issue
before turning to the question of whether a Fourth
Amendment violation has occurred. I see no need for such
an inflexible practice. When a Fourth Amendment case
presents a novel question of law whose resolution is
necessary to guide future action by law enforcement
officers and magistrates, there is sufficient reason for the
Court to decide the violation issue before turning to the
good-faith question. Indeed, it may be difficult to *265
determine whether the officers acted reasonably until the
Fourth Amendment issue is resolved.18 **2347 In other
circumstances, however, a suppression motion poses no
Fourth Amendment question of broad import-the issue is
simply whether the facts in a given case amounted to
probable cause-in these cases, it would be prudent for a
reviewing court to immediately turn to the question of
whether the officers acted in good faith. Upon finding that
they had, there would generally be no need to consider the
probable cause question. I doubt that our Fourth
Amendment jurisprudence would suffer thereby. It is not
entirely clear to me that the law in this area has benefitted
from the constant pressure of fully-litigated suppression
motions. The result usually has been that initially brightline
rules have disappeared in a sea of ever-finer
distinctions. Moreover, there is much to be said for
having Fourth Amendment jurisprudence *266 evolve in
part, albeit perhaps at a slower pace, in other settings.19
Finally, it is contended that a good-faith exception will be
difficult to apply in practice. This concern appears
grounded in the assumption that courts would inquire into

the subjective belief of the law enforcement officers
involved. I would eschew such investigations. “Sending
state and federal courts into the minds of police officers
would produce a grave and fruitless mis-allocation of
judicial resources.” Massachusetts v. Painten, 389 U.S.
560, 565, 88 S.Ct. 660, 663, 19 L.Ed.2d 770 (1968)
(WHITE, J., dissenting). Moreover, “[s]ubjective intent
alone ... does not make otherwise lawful conduct illegal or
unconstitutional.” Scott v. United States, 436 U.S. 128, 98
S.Ct. 1717, 56 L.Ed.2d 168 (1978). Just last Term, we
modified the qualified immunity public officials enjoy in
suits seeking damages against federal officials for alleged
deprivations of constitutional rights, eliminating the
subjective component of the standard. See Harlow v.
Fitzgerald, 457 U.S. 800, 102 S.Ct. 2727, 73 L.Ed.2d 396
(1982). Although *267 searches pursuant to a warrant will
rarely require any deep inquiry into reasonableness, I
would measure the reasonableness of a particular search
or seizure only by objective standards. Even for
warrantless searches, the requirement should be no more
difficult to apply than the closely related good-faith test
which governs civil suits under 42 U.S.C. § 1983. In
addition, the burden will likely be offset by the reduction
in the number of cases which will require elongated
considerations of the probable cause question, and will be
greatly outweighed by the advantages in limiting the bite
of the exclusionary rule to the field in which it is most
likely to have its intended effects.
III
Since a majority of the Court deems it inappropriate to
address the good faith issue, I briefly address the question
that the Court does reach-whether the warrant authorizing
the search and seizure of respondents’ car and home was
constitutionally **2348 valid. Abandoning the “twopronged
test” of Aguilar v. Texas, 378 U.S. 108, 84 S.Ct.
1509, 12 L.Ed.2d 723 (1964), and Spinelli v. United
States, 393 U.S. 410, 89 S.Ct. 584, 21 L.Ed.2d 637
(1969), the Court upholds the validity of the warrant
under a new “totality of the circumstances” approach.
Although I agree that the warrant should be upheld, I
reach this conclusion in accordance with the Aguilar-
Spinelli framework.
A
For present purposes, the Aguilar-Spinelli rules can be
summed up as follows. First, an affidavit based on an
informer’s tip, standing alone, cannot provide probable
60
cause for issuance of a warrant unless the tip includes
information that apprises the magistrate of the informant’s
basis for concluding that the contraband is where he
claims it is (the “basis of knowledge” prong), and the
affiant informs the magistrate of his basis for believing
that the informant is credible (the “veracity” prong).
Aguilar, supra, 378 U.S., at 114, 84 S.Ct., at 1514; *268
Spinelli, supra, 393 U.S., at 412-413, 416, 89 S.Ct., at
586-587, 589.20 Second, if a tip fails under either or both
of the two prongs, probable cause may yet be established
by independent police investigatory work that
corroborates the tip to such an extent that it supports
“both the inference that the informer was generally
trustworthy and that he made his charge on the basis of
information obtained in a reliable way.” Spinelli, supra, at
417, 89 S.Ct., at 589. In instances where the officers rely
on corroboration, the ultimate question is whether the
corroborated tip “is as trustworthy as a tip which would
pass Aguilar ‘s tests without independent corroboration.”
Id., at 415, 89 S.Ct., at 588.
In the present case, it is undisputed that the anonymous
tip, by itself, did not furnish probable cause. The question
is whether those portions of the affidavit describing the
results of the police investigation of the respondents,
when considered in light of the tip, “would permit the
suspicions engendered by the informant’s report to ripen
into a judgment that a crime was probably being
committed.” Spinelli, supra, at 418, 89 S.Ct., at 590. The
Illinois Supreme Court concluded that the corroboration
was insufficient to permit such a ripening. App. 9a. The
court reasoned as follows:
“[T]he nature of the corroborating evidence in this case
would satisfy neither the “basis of knowledge” nor the
*269 “veracity” prong of Aguilar. Looking to the affidavit
submitted as support for Detective Mader’s request that a
search warrant issue, we note that the corroborative
evidence here was only of innocent activity. Mader’s
independent investigation revealed only that Lance and
Sue Gates lived on Greenway Drive; that Lance Gates
booked passage on a flight to Florida; that upon arriving
he entered a room registered to his wife; and that he and
his wife left the hotel together by car. The corroboration
of innocent activity is insufficient to support a finding of
probable cause.” App. 12a.
In my view, the lower court’s characterization of the
Gates’ activity here as totally “innocent” is dubious. In
fact, the behavior was quite suspicious. I agree with the
**2349 Court, ante, at 2333, that Lance Gates’ flight to
Palm Beach, an area known to be a source of narcotics,
the brief overnight stay in a motel, and apparent
immediate return North, suggest a pattern that trained

law-enforcement officers have recognized as indicative of
illicit drug-dealing activity.21
Even, however, had the corroboration related only to
completely innocuous activities, this fact alone would not
preclude the issuance of a valid warrant. The critical issue
is not whether the activities observed by the police are
innocent or suspicious. Instead, the proper focus should
be on whether the actions of the suspects, whatever their
nature, give rise to an inference that the informant is
credible and that he obtained his information in a reliable
manner.
Thus, in Draper v. United States, 358 U.S. 307, 79 S.Ct.
329, 3 L.Ed.2d 327 (1959), an informant stated on Sept. 7
that Draper would be carrying narcotics when he arrived
by train in Denver on the morning of Sept. 8 or Sept. 9.
The informant also provided the police with a detailed
physical description *270 of the clothes Draper would be
wearing when he alighted from the train. The police
observed Draper leaving a train on the morning of Sept. 9,
and he was wearing the precise clothing described by the
informant. The Court held that the police had probable
cause to arrest Draper at this point, even though the police
had seen nothing more than the totally innocent act of a
man getting off a train carrying a briefcase. As we later
explained in Spinelli, the important point was that the
corroboration showed both that the informant was
credible,i.e. that he “had not been fabricating his report
out of whole cloth,” Spinelli, supra, 393 U.S., at 417, 89
S.Ct., at 589, and that he had an adequate basis of
knowledge for his allegations, “since the report was of the
sort which in common experience may be recognized as
having been obtained in a reliable way.” Id., at 417-418,
89 S.Ct., at 589-590. The fact that the informer was able
to predict, two days in advance, the exact clothing Draper
would be wearing dispelled the possibility that his tip was
just based on rumor or “an off-hand remark heard at a
neighborhood bar.” Id., at 417, 89 S.Ct., at 589. Probably
Draper had planned in advance to wear these specific
clothes so that an accomplice could identify him. A clear
inference could therefore be drawn that the informant was
either involved in the criminal scheme himself or that he
otherwise had access to reliable, inside information.22
*271 **2350 As in Draper, the police investigation in the
present case satisfactorily demonstrated that the
informant’s tip was as trustworthy as one that would
alone satisfy the Aguilar tests. The tip predicted that Sue
Gates would drive to Florida, that Lance Gates would fly
there a few days after May 3, and that Lance would then
drive the car back. After the police corroborated these
facts,23 the magistrate could reasonably have inferred, as
he apparently did, that the informant, who had specific
61
knowledge of these unusual travel plans, did not make up
his story and that he obtained his information in a reliable
way. It is theoretically possible, as respondents insist, that
the tip could have been supplied by a “vindictive travel
agent” and that the Gates’ activities, although unusual,
might not have been unlawful.24 But Aguilar and Spinelli,
like our other cases, do not require that certain guilt be
established before a warrant may properly be issued.
“[O]nly the probability, and not a prima facie showing,
*272 of criminal activity is the standard of probable
cause.” Spinelli, supra, at 419, 89 S.Ct., at 590 (citing
Beck v. Ohio, 379 U.S. 89, 96, 85 S.Ct. 223, 228, 13
L.Ed.2d 142 (1964)). I therefore conclude that the
judgment of the Illinois Supreme Court invalidating the
warrant must be reversed.
B
The Court agrees that the warrant was valid, but, in the
process of reaching this conclusion, it overrules the
Aguilar-Spinelli tests and replaces them with a “totality of
the circumstances” standard. As shown above, it is not at
all necessary to overrule Aguilar-Spinelli in order to
reverse the judgment below. Therefore, because I am
inclined to believe that, when applied properly, the
Aguilar-Spinelli rules play an appropriate role in probable
cause determinations, and because the Court’s holding
may foretell an evisceration of the probable cause
standard, I do not join the Court’s holding.
The Court reasons, ante, at 2329, that the “veracity” and
“basis of knowledge” tests are not independent, and that a
deficiency as to one can be compensated for by a strong
showing as to the other. Thus, a finding of probable cause
may be based on a tip from an informant “known for the
unusual reliability of his predictions” or from “an
unquestionably honest citizen,” even if the report fails
thoroughly to set forth the basis upon which the
information was obtained. Ibid. If this is so, then it must
follow a fortiori that “the affidavit of an officer, known
by the magistrate to be honest and experienced, stating
that [contraband] is located in a certain building” must be
acceptable. Spinelli, 393 U.S., at 424, 89 S.Ct., at 593
(WHITE, J., concurring). It would be “quixotic” if a
similar statement from an honest informant, but not one
from an honest officer, could furnish probable cause. Ibid.
But we have repeatedly held that the unsupported
assertion or belief of an officer does not satisfy the
probable cause requirement. See, e.g., Whiteley v.
Warden, 401 U.S. 560, 564-565, 91 S.Ct. 1031, 1034-
1035, 28 L.Ed.2d 306; *273 Jones v. United States, 362

U.S. 257, 269, 80 S.Ct. 725, 735, 4 L.Ed.2d 697 (1960);
Nathanson v. United States, 290 U.S. 41, 54 S.Ct. 11, 78
L.Ed. 159 (1933).25 Thus, this portion of today’s holding
can be read as implicitly rejecting the teachings of these
prior holdings.
**2351 The Court may not intend so drastic a result.
Indeed, the Court expressly reaffirms, ante, at 2332, the
validity of cases such as Nathanson that have held that, no
matter how reliable the affiant-officer may be, a warrant
should not be issued unless the affidavit discloses
supporting facts and circumstances. The Court limits
these cases to situations involving affidavits containing
only “bare conclusions” and holds that, if an affidavit
contains anything more, it should be left to the issuing
magistrate to decide, based solely on “practical[ity]” and
“common-sense,” whether there is a fair probability that
contraband will be found in a particular place. Ibid.
Thus, as I read the majority opinion, it appears that the
question whether the probable cause standard is to be
diluted is left to the common-sense judgments of issuing
magistrates. I am reluctant to approve any standard that
does not expressly require, as a prerequisite to issuance of
a warrant, some showing of facts from which an inference
may be drawn that the informant is credible and that his
information was obtained in a reliable way. The Court is
correctly concerned with the fact that some lower courts
have been applying Aguilar-Spinelli in an unduly rigid
manner.26 I believe, however, that with clarification of the
rule of corroborating *274 information, the lower courts
are fully able to properly interpret Aguilar-Spinelli and
avoid such unduly-rigid applications. I may be wrong; it
ultimately may prove to be the case that the only
profitable instruction we can provide to magistrates is to
rely on common sense. But the question whether a
particular anonymous tip provides the basis for issuance
of a warrant will often be a difficult one, and I would at
least attempt to provide more precise guidance by
clarifying Aguilar-Spinelli and the relationship of those
cases with Draper before totally abdicating our
responsibility in this area. Hence, I do not join the Court’s
opinion rejecting the Aguilar-Spinelli rules.
Justice BRENNAN, with whom Justice MARSHALL
joins, dissenting.
Although I join Justice STEVENS’ dissenting opinion
and agree with him that the warrant is invalid even under
the Court’s newly announced “totality of the
circumstances” test, see post, at 2361-2362, and n. 8, I
write separately to dissent from the Court’s unjustified
62
and ill-advised rejection of the two-prong test for
evaluating the validity of a warrant based on hearsay
announced in Aguilar v. Texas, 378 U.S. 108, 84 S.Ct.
1509, 12 L.Ed.2d 723 (1964), and refined in Spinelli v.
United States, 393 U.S. 410, 89 S.Ct. 584, 21 L.Ed.2d 637
(1969).
I
The Court’s current Fourth Amendment jurisprudence, as
reflected by today’s unfortunate decision, patently
disregards Justice Jackson’s admonition in Brinegar v.
United States, 338 U.S. 160, 69 S.Ct. 1302, 93 L.Ed. 1879
(1949):
“[Fourth Amendment rights] ... are not mere second-class
rights but belong in the catalog of indispensable
freedoms. Among deprivations of rights, none is so
effective in cowing a population, crushing the spirit of the
individual and putting terror in every heart. *275
Uncontrolled search and seizure is one of the first and
most effective weapons in the arsenal of every arbitrary
government....
“But the right to be secure against searches and seizures is
one of the most difficult to protect. Since the officers are
themselves the chief invaders, there is no enforcement
outside of court.” Id., at 180-181, 69 S.Ct., at 1313
(Jackson, J., dissenting).
**2352 In recognition of the judiciary’s role as the only
effective guardian of Fourth Amendment rights, this
Court has developed over the last half century a set of
coherent rules governing a magistrate’s consideration of a
warrant application and the showings that are necessary to
support a finding of probable cause. We start with the
proposition that a neutral and detached magistrate, and
not the police, should determine whether there is probable
cause to support the issuance of a warrant. In Johnson v.
United States, 333 U.S. 10, 68 S.Ct. 367, 92 L.Ed. 436
(1948), the Court stated:
“The point of the Fourth Amendment, which often is not
grasped by zealous officers, is not that it denies law
enforcement the support of the usual inferences which
reasonable men draw from evidence. Its protection
consists in requiring that those inferences be drawn by a
neutral and detached magistrate instead of being judged
by the officer engaged in the often competitive enterprise
of ferreting out crime.... When the right of privacy must
reasonably yield to the right of search is, as a rule, to be
decided by a judicial officer, not by a policeman or

government enforcement agent.” Id., at 13-14, 68 S.Ct., at
368-369 (footnote omitted).
See also Whiteley v. Warden, 401 U.S. 560, 564, 91 S.Ct.
1031, 1034, 28 L.Ed.2d 306 (1971); Spinelli v. United
States, supra, 393 U.S., at 415, 89 S.Ct., at 588; United
States v. Ventresca, 380 U.S. 102, 109, 85 S.Ct. 741, 746,
13 L.Ed.2d 684 (1965); Aguilar v. Texas, supra, 378 U.S.,
at 111, 84 S.Ct., at 1512; *276 Jones v. United States, 362
U.S. 257, 270-271, 80 S.Ct. 725, 736-737, 4 L.Ed.2d 697
(1960); Giordenello v. United States, 357 U.S. 480, 486,
78 S.Ct. 1245, 1250, 2 L.Ed.2d 1503 (1958); United
States v. Lefkowitz, 285 U.S. 452, 464, 52 S.Ct. 420, 423,
76 L.Ed. 877 (1932).
In order to emphasize the magistrate’s role as an
independent arbiter of probable cause and to insure that
searches or seizures are not effected on less than probable
cause, the Court has insisted that police officers provide
magistrates with the underlying facts and circumstances
that support the officers’ conclusions. In Nathanson v.
United States, 290 U.S. 41, 54 S.Ct. 11, 78 L.Ed. 159
(1933), the Court held invalid a search warrant that was
based on a customs agent’s “mere affirmation of
suspicion and belief without any statement of adequate
supporting facts.” Id., at 46, 54 S.Ct., at 12. The Court
stated that “[u]nder the Fourth Amendment, an officer
may not properly issue a warrant to search a private
dwelling unless he can find probable cause therefor from
facts or circumstances presented to him under oath or
affirmation. Mere affirmance of belief or suspicion is not
enough.” Id., at 47, 54 S.Ct., at 13.
In Giordenello v. United States, supra, the Court
reviewed an arrest warrant issued under the Federal Rules
of Criminal Procedure based on a complaint sworn to by a
Federal Bureau of Narcotics agent. Id., 357 U.S., at 481,
78 S.Ct., at 1247.1 Based on the agent’s testimony at the
suppression hearing, the Court noted that “until the
warrant was issued ... [the agent’s] suspicions of
petitioner’s guilt derived entirely from information given
him by law enforcement officers and other persons in
Houston, none of whom either appeared before the
Commissioner or submitted affidavits.” Id., at 485, 78
S.Ct., at 1249. The Court found it unnecessary to decide
whether a warrant could be based solely on hearsay
information, for the complaint was “defective in not
providing a sufficient basis upon which a *277 finding of
probable cause could be made.” Ibid. In particular, the
**2353 complaint contained no affirmative allegation that
the agent spoke with personal knowledge nor did it
indicate any sources for the agent’s conclusion. Id., at
486, 78 S.Ct., at 1250. The Court expressly rejected the
argument that these deficiencies could be cured by “the
Commissioner’s reliance upon a presumption that the
complaint was made on the personal knowledge of the
complaining officer.” Ibid.
As noted, the Court did not decide the hearsay question
lurking in Giordenello. The use of hearsay to support the
issuance of a warrant presents special problems because
informants, unlike police officers, are not regarded as
presumptively reliable or honest. Moreover, the basis for
an informant’s conclusions is not always clear from an
affidavit that merely reports those conclusions. If the
conclusory allegations of a police officer are insufficient
to support a finding of probable cause, surely the
conclusory allegations of an informant should a fortiori
be insufficient.
In Jones v. United States, supra, the Court considered
“whether an affidavit which sets out personal
observations relating to the existence of cause to search is
to be deemed insufficient by virtue of the fact that it sets
out not the affiant’s observations but those of another.”
362 U.S., at 269, 80 S.Ct., at 735. The Court held that
hearsay information can support the issuance of a warrant
“so long as a substantial basis for crediting the hearsay is
presented.” Ibid. The Court found that there was a
substantial basis for crediting the hearsay involved in
Jones. The informant’s report was based on the
informant’s personal knowledge, and the informant
previously had provided accurate information. Moreover,
the informant’s story was corroborated by other sources.
Finally, the defendant was known to the police to be a
narcotics user. Id., at 271, 80 S.Ct., at 736.
Aguilar v. Texas, 378 U.S. 108, 84 S.Ct. 1509, 12 L.Ed.2d
723 (1964), merely made explicit what was implicit in
Jones. In considering a search warrant based on hearsay,
the Court reviewed Nathanson *278 and Giordenello and
noted the requirement established by those cases that an
officer provide the magistrate with the underlying facts or
circumstances that support the officer’s conclusion that
there is probable cause to justify the issuance of a
warrant. The Court stated:
“The vice in the present affidavit is at least as great as in
Nathanson and Giordenello. Here, the ‘mere conclusion’
that petitioner possessed narcotics was not even that of
the affiant himself; it was that of an unidentified
informant. The affidavit here not only ‘contains no
affirmative allegation that the affiant spoke with personal
knowledge of the matters contained therein,’ it does not
even contain an ‘affirmative allegation’ that the affiant’s
unidentified source ‘spoke with personal knowledge.’ For
all that appears, the source here merely suspected,
63

elieved or concluded that there were narcotics in
petitioner’s possession. The magistrate here certainly
could not ‘judge for himself the persuasiveness of the
facts relied on ... to show probable cause.’ He necessarily
accepted ‘without question’ the informant’s ‘suspicion,’
‘belief’ or ‘mere conclusion.’ ” Id., at 113-114, 84 S.Ct.,
at 1513-1514 (footnote omitted).2
While recognizing that a warrant may be based on
hearsay, the Court established the following standard:
“[T]he magistrate must be informed of some of the
underlying circumstances from which the informant
concluded *279 that **2354 the narcotics were where he
claimed they were, and some of the underlying
circumstances from which the officer concluded that the
informant, whose identity need not be disclosed ... was
‘credible’ or his information ‘reliable.’ Otherwise, ‘the
inferences from the facts which lead to the complaint’
will be drawn not ‘by a neutral and detached magistrate,’
as the Constitution requires, but instead, by a police
officer ‘engaged in the often competitive enterprise of
ferreting out crime’ ... or, as in this case, by an
unidentified informant.” Id., at 114-115, 84 S.Ct., at
1513-1514 (footnote omitted).
The Aguilar standard was refined in Spinelli v. United
States, 393 U.S. 410, 89 S.Ct. 584, 21 L.Ed.2d 637
(1969). In Spinelli, the Court reviewed a search warrant
based on an affidavit that was “more ample,” id., at 413,
than the one in Aguilar. The affidavit in Spinelli contained
not only a tip from an informant, but also a report of an
independent police investigation that allegedly
corroborated the informant’s tip. Ibid. Under these
circumstances, the Court stated that it was “required to
delineate the manner in which Aguilar ‘s two-pronged test
should be applied....” Ibid.
The Court held that the Aguilar test should be applied to
the tip, and approved two additional ways of satisfying
that test. First, the Court suggested that if the tip
contained sufficient detail describing the accused’s
criminal activity it might satisfy Aguilar ‘s basis of
knowledge prong. Id., at 416, 89 S.Ct., at 589. Such detail
might assure the magistrate that he is “relying on
something more substantial than a casual rumor
circulating in the underworld or an accusation based
merely on an individual’s general reputation.” Ibid.
Although the tip in the case before it did not meet this
standard, “[t]he detail provided by the informant in
Draper v. United States, 358 U.S. 307, 79 S.Ct. 329, 3
L.Ed.2d 327 (1959), provide[d] a suitable benchmark,”
ibid., because “[a] magistrate, when confronted with such
detail, could reasonably infer that the informant *280 had
gained his information in a reliable way.” Id., at 417, 89
S.Ct., at 589 (footnote omitted).3
**2355 Second, the Court stated that police corroboration
of the details of a tip could provide a basis for satisfying
Aguilar. Id., at 417, 89 S.Ct., at 589. *281 The Court’s
opinion is not a model of clarity on this issue since it
appears to suggest that corroboration can satisfy both the
basis of knowledge and veracity prongs of Aguilar. Id., at
417-418, 89 S.Ct., at 589-590.4 Justice WHITE’s
concurring opinion, however, points the way to a proper
reading of the Court’s opinion. After reviewing the
Court’s decision in Draper v. United States, supra, Justice
WHITE concluded that “[t]he thrust of Draper is not that
the verified facts have independent significance with
respect to proof of [another unverified fact].” Id., at 427,
89 S.Ct., at 594. In his view, “[t]he argument instead
relates to the reliability of the source: because an
informant is right about some things, he is more probably
right about other facts, usually the critical, unverified
facts.” Ibid. Justice WHITE then pointed out that prior
cases had rejected “the notion that the past *282
reliability of an officer is sufficient reason for believing
his current assertions.” Ibid. Justice WHITE went on to
state:
“Nor would it suffice, I suppose, if a reliable informant
states there is gambling equipment in Apartment 607 and
then proceeds to describe in detail Apartment 201, a
description which is verified before applying for the
warrant. He was right about 201, but that hardly makes
him more believable about the equipment in 607. But
what if he states that there are narcotics locked in a safe in
Apartment 300, which is described in detail, and the
apartment manager verifies everything but the contents of
the safe I doubt that the report about the narcotics is
made appreciably more believable by the verification. The
informant could still have gotten his information
concerning the safe from others about whom nothing is
known or could have inferred the presence of narcotics
from circumstances which a magistrate would find
unacceptable.” Id., at 427, 89 S.Ct., at 594.
I find this reasoning persuasive. Properly understood,
therefore, Spinelli stands for the proposition that
corroboration of certain details in a tip may be sufficient
to satisfy the veracity, but not the basis of knowledge,
prong of Aguilar. As noted, Spinelli also suggests that in
some limited circumstances considerable detail in an
informant’s tip may be adequate to satisfy the basis of
knowledge prong of Aguilar.5
*283 **2356 Although the rules drawn from the cases
discussed above are cast in procedural terms, they
64

advance an important underlying substantive value:
Findings of probable cause, and attendant intrusions,
should not be authorized unless there is some assurance
that the information on which they are based has been
obtained in a reliable way by an honest or credible person.
As applied to police officers, the rules focus on the way in
which the information was acquired. As applied to
informants, the rules focus both on the honesty or
credibility of the informant and on the reliability of the
way in which the information was acquired. Insofar as it
is more complicated, an evaluation of affidavits based on
hearsay involves a more difficult inquiry. This suggests a
need to structure the inquiry in an effort to insure greater
accuracy. The standards announced in Aguilar, as refined
by Spinelli, fulfill that need. The standards inform the
police of what information they have to provide and
magistrates of what information they should demand. The
standards also inform magistrates of the subsidiary
findings they must make in order to arrive at an ultimate
finding of probable cause. Spinelli, properly understood,
directs the magistrate’s attention to the possibility that the
presence of self-verifying detail might satisfy Aguilar ‘s
basis of knowledge prong and that corroboration of the
details of a tip might satisfy Aguilar ‘s veracity prong. By
requiring police to provide certain crucial information to
magistrates and by structuring magistrates’ probable
cause inquiries, Aguilar and Spinelli assure the
magistrate’s role as an independent arbiter of probable
cause, insure greater accuracy in probable cause
determinations, and advance the substantive value
identified above.
Until today the Court has never squarely addressed the
application of the Aguilar and Spinelli standards to tips
from anonymous informants. Both Aguilar and Spinelli
dealt with tips from informants known at least to the
police. See also, e.g., Adams v. Williams, 407 U.S. 143,
146, 92 S.Ct. 1921, 1923, 32 L.Ed.2d 612 (1972); United
States v. Harris, 403 U.S. 573, 575, 91 S.Ct. 2075, 2078,
29 L.Ed.2d 723 (1971); Whiteley v. Warden, 401 U.S.
560, 565, 91 S.Ct. 1031, 1035, 28 L.Ed.2d 306 (1971);
*284 McCray v. Illinois, 386 U.S. 300, 302, 87 S.Ct.
1056, 1057, 18 L.Ed.2d 62 (1967); Jones v. United States,
362 U.S. 257, 268-269, 80 S.Ct. 725, 735, 4 L.Ed.2d 697
(1960). And surely there is even more reason to subject
anonymous informants’ tips to the tests established by
Aguilar and Spinelli. By definition nothing is known
about an anonymous informant’s identity, honesty, or
reliability. One commentator has suggested that
anonymous informants should be treated as presumptively
unreliable. See Comment, Anonymous Tips,
Corroboration, and Probable Cause: Reconciling The
Spinelli/Draper Dichotomy in Illinois v. Gates, 20
65
Am.Crim.L.Rev. 99, 107 (1982). See also Adams v.
Williams, supra, 407 U.S., at 146, 92 S.Ct., at 1923
(suggesting that an anonymous telephone tip provides a
weaker case for a Terry stop than a tip from an informant
known to the police who had provided information in the
past); United States v. Harris, supra, 403 U.S., at 599, 91
S.Ct., at 2089 (Harlan, J., dissenting) (“We cannot assume
that the ordinary law-abiding citizen has qualms about
[appearing before a magistrate]”). In any event, there
certainly is no basis for treating anonymous informants as
presumptively reliable. Nor is there any basis for
assuming that the information provided by an anonymous
informant has been obtained in a reliable way. If we are
unwilling to accept conclusory allegations from the
police, who are presumptively reliable, or from
informants who are known, at **2357 least to the police,
there cannot possibly be any rational basis for accepting
conclusory allegations from anonymous informants.
To suggest that anonymous informants’ tips are subject to
the tests established by Aguilar and Spinelli is not to
suggest that they can never provide a basis for a finding
of probable cause. It is conceivable that police
corroboration of the details of the tip might establish the
reliability of the informant under Aguilar ‘s veracity
prong, as refined in Spinelli, and that the details in the tip
might be sufficient to qualify under the “self-verifying
detail” test established by Spinelli as a means of satisfying
Aguilar ‘s basis of knowledge prong. The Aguilar and
Spinelli tests must be applied to anonymous informants’
tips, however, if we are to continue to insure *285 that
findings of probable cause, and attendant intrusions, are
based on information provided by an honest or credible
person who has acquired the information in a reliable
way.6
In light of the important purposes served by Aguilar and
Spinelli, I would not reject the standards they establish. If
anything, I simply would make more clear that Spinelli,
properly understood, does not depart in any fundamental
way from the test established by Aguilar. For reasons I
shall next state, I do not find persuasive the Court’s
justifications for rejecting the test established by Aguilar
and refined by Spinelli.
*286 II
In rejecting the Aguilar-Spinelli standards, the Court
suggests that a “totality-of-the-circumstances approach is
far more consistent with our prior treatment of probable
cause than is any rigid demand that specific ‘tests’ be
satisfied by every informant’s tip.” Ante, at 2328

(footnote omitted). In support of this proposition the
Court relies on several cases that purportedly reflect this
approach, ante, at 2328, n. 6, n. 7, and on the “practical,
nontechnical,” ante, at 2329, nature of probable cause.
Only one of the cases cited by the Court in support of its
“totality-of-the-circumstances” approach, Jaben v. United
States, 381 U.S. 214, 85 S.Ct. 1365, 14 L.Ed.2d 345
(1965), was decided subsequent to Aguilar. It is by no
means inconsistent with Aguilar.7 The other three cases8
cited by the **2358 Court as supporting its *287 totality
of the circumstances approach were decided before
Aguilar. In any event, it is apparent from the Court’s
discussion of them, see ante, at 2329, n. 7, that they are
not inconsistent with Aguilar.
In addition, one can concede that probable cause is a
“practical, nontechnical” concept without betraying the
values that Aguilar and Spinelli reflect. As noted, see
supra, at 2347, Aguilar and Spinelli require the police to
provide magistrates with certain crucial information. They
also provide structure for magistrates’ probable cause
inquiries. In so doing, Aguilar and Spinelli preserve the
role of magistrates as independent arbiters of probable
cause, insure greater accuracy in probable cause
determinations, and advance the substantive value of
precluding findings of probable cause, and attendant
intrusions, based on anything less than information from
an honest or credible person who has acquired his
information in a reliable way. Neither the standards nor
their effects are inconsistent with a “practical,
nontechnical” conception of probable cause. Once a
magistrate has determined that he has information before
him that he can reasonably say has been obtained in a
reliable way by a credible person, he has ample room to
use his common sense and to apply a practical,
nontechnical conception of probable cause.
It also should be emphasized that cases such as
Nathanson v. United States, 290 U.S. 41, 54 S.Ct. 11, 78
L.Ed. 159 (1933), and Giordenello v. United States, 357
U.S. 480, 78 S.Ct. 1245, 2 L.Ed.2d 1503 (1958),
discussed supra, at 2352, directly contradict the Court’s
suggestion, ante, at 2329, that a strong showing on one
prong of the Aguilar test should compensate for a
deficient showing on the other. If the conclusory
allegations of a presumptively reliable police officer are
insufficient to establish probable cause, there is no
conceivable reason why the conclusory allegations of an
anonymous informant should not be insufficient as well.
Moreover, contrary to the Court’s implicit suggestion,
Aguilar and Spinelli do not stand as an insuperable barrier
to the use *288 of even anonymous informants’ tips to
66
establish probable cause. See supra, at 2330. It is no
justification for rejecting them outright that some courts
may have employed an overly technical version of the
Aguilar-Spinelli standards, see ante, at 2330, and n. 9.
The Court also insists that the Aguilar-Spinelli standards
must be abandoned because they are inconsistent with the
fact that non-lawyers frequently serve as magistrates.
Ante, at 2332. To the contrary, the standards help to
structure probable cause inquiries and, properly
interpreted, may actually help a non-lawyer magistrate in
making a probable cause determination. Moreover, the
Aguilar and Spinelli tests are not inconsistent with
deference to magistrates’ determinations of probable
cause. Aguilar expressly acknowledged that reviewing
courts “will pay substantial deference to judicial
determinations of probable cause....” 378 U.S., at 111, 84
S.Ct., at 1512. In Spinelli, the Court noted that it was not
retreating from the proposition **2359 that magistrates’
determinations of probable cause “should be paid great
deference by reviewing courts....” 393 U.S., at 419, 89
S.Ct., at 590. It is also noteworthy that the language from
United States v. Ventresca, 380 U.S. 102, 108-109, 85
S.Ct. 741, 745-746, 13 L.Ed.2d 684 (1965), which the
Court repeatedly quotes, see ante, at 2330, 2331, and n.
10, brackets the following passage, which the Court does
not quote:
“This is not to say that probable cause can be made out by
affidavits which are purely conclusory, stating only the
affiant’s or an informer’s belief that probable cause exists
without detailing any of the ‘underlying circumstances’
upon which that belief is based. See Aguilar v. Texas,
supra. Recital of some of the underlying circumstances in
the affidavit is essential if the magistrate is to perform his
detached function and not serve merely as a rubber stamp
for the police. However, where these circumstances are
detailed, where reason for crediting the source of the
information is given, and when a magistrate has found
probable cause, the courts should not *289 invalidate the
warrant by interpreting the affidavit in a hypertechnical,
rather than a commonsense, manner.” 380 U.S., at 108-
109, 85 S.Ct., at 745-746.9
At the heart of the Court’s decision to abandon Aguilar
and Spinelli appears to be its belief that “the direction
taken by decisions following Spinelli poorly serves ‘the
most basic function of any government: to provide for the
security of the individual and of his property.’ ” Ante, at
2331. This conclusion rests on the judgment that Aguilar
and Spinelli “seriously imped[e] the task of law
enforcement,” ibid., and render anonymous tips valueless
in police work. Ibid. Surely, the Court overstates its case.
See supra, at 2331. But of particular concern to all

Americans must be that the Court gives virtually no
consideration to the value of insuring that findings of
probable cause are based on information that a magistrate
can reasonably say has been obtained in a reliable *290
way by an honest or credible person. I share Justice
WHITE’s fear that the Court’s rejection of Aguilar and
Spinelli and its adoption of a new totality-of-thecircumstances
test, ante, at 2332, “may foretell an
evisceration of the probable cause standard....” Ante, at
2334 (WHITE, J., concurring in the judgment).
III
The Court’s complete failure to provide any persuasive
reason for rejecting Aguilar and Spinelli doubtlessly
reflects impatience with what it perceives to be “overly
technical” rules governing searches and seizures under the
Fourth Amendment. Words such as “practical,”
“nontechnical,” and “commonsense,” as used in the
Court’s opinion, are but code words for an overly
permissive attitude towards police practices in derogation
of the rights secured by the Fourth Amendment. Everyone
shares the Court’s concern over the **2360 horrors of
drug trafficking, but under our Constitution only measures
consistent with the Fourth Amendment may be employed
by government to cure this evil. We must be ever mindful
of Justice Stewart’s admonition in Coolidge v. New
Hampshire, 403 U.S. 443, 91 S.Ct. 2022, 29 L.Ed.2d 564
(1971), that “[i]n times of unrest, whether caused by
crime or racial conflict or fear of internal subversion, this
basic law and the values that it represents may appear
unrealistic or ‘extravagant’ to some. But the values were
those of the authors of our fundamental constitutional
concepts.” Id., at 455, 91 S.Ct., at 2032 (plurality
opinion). In the same vein, Glasser v. United States, 315
U.S. 60, 62 S.Ct. 457, 86 L.Ed. 680 (1942), warned that
“[s]teps innocently taken may, one by one, lead to the
irretrievable impairment of substantial liberties.” Id., at
86, 62 S.Ct., at 472.
Rights secured by the Fourth Amendment are particularly
difficult to protect because their “advocates are usually
criminals.” Draper v. United States, 358 U.S. 307, 314,
79 S.Ct. 329, 333, 3 L.Ed.2d 327 (1959) (Douglas, J.,
dissenting). But the rules “we fashion [are] for the
innocent and guilty alike.” Ibid. See also Kolender v.
Lawson, --- U.S. ----, ----, 103 S.Ct. 1855, 1861, 75
L.Ed.2d 903 (1983) (BRENNAN, J., concurring);
Brinegar v. United States, 338 U.S. 160, 181, 69 S.Ct.
1302, 1313, 93 L.Ed. 1879 (1949) (Jackson, J.,
dissenting). *291 By replacing Aguilar and Spinelli with a
67
test that provides no assurance that magistrates, rather
than the police, or informants, will make determinations
of probable cause; imposes no structure on magistrates’
probable cause inquiries; and invites the possibility that
intrusions may be justified on less than reliable
information from an honest or credible person, today’s
decision threatens to “obliterate one of the most
fundamental distinctions between our form of
government, where officers are under the law, and the
police-state where they are the law.” Johnson v. United
States, 333 U.S. 10, 17, 68 S.Ct. 367, 370, 92 L.Ed. 436
(1948).
Justice STEVENS, with whom Justice BRENNAN joins,
dissenting.
The fact that Lance and Sue Gates made a 22-hour
nonstop drive from West Palm Beach, Florida, to
Bloomingdale, Illinois, only a few hours after Lance had
flown to Florida provided persuasive evidence that they
were engaged in illicit activity. That fact, however, was
not known to the magistrate when he issued the warrant to
search their home.
What the magistrate did know at that time was that the
anonymous informant had not been completely accurate
in his or her predictions. The informant had indicated that
“Sue drives their car to Florida where she leaves it to be
loaded up with drugs.... Sue flies back after she drops the
car off in Florida.” App. 1a (emphasis added). Yet
Detective Mader’s affidavit reported that she “left the
West Palm Beach area driving the Mercury northbound.”
App. 12a.
The discrepancy between the informant’s predictions and
the facts known to Detective Mader is significant for three
reasons. First, it cast doubt on the informant’s hypothesis
that the Gates already had “over $100,000 worth of drugs
in their basement,” App. 1a. The informant had predicted
an itinerary that always kept one *292 spouse in
Bloomingdale, suggesting that the Gates did not want to
leave their home unguarded because something valuable
was hidden within. That inference obviously could not be
drawn when it was known that the pair was actually
together over a thousand miles from home.
Second, the discrepancy made the Gates’ conduct seem
substantially less unusual than the informant had
predicted it would be. It would have been odd if, as
predicted, Sue had driven down to Florida on Wednesday,
left the car, and flown right back to Illinois. But the mere
facts that **2361 Sue was in West Palm Beach with the
car,1 that she was joined by her husband at the Holiday

Inn on Friday,2 and that the couple drove north together
the next morning3 are neither unusual nor probative of
criminal activity.
*293 Third, the fact that the anonymous letter contained a
material mistake undermines the reasonableness of
relying on it as a basis for making a forcible entry into a
private home.4
Of course, the activities in this case did not stop when the
magistrate issued the warrant. The Gates drove all night to
Bloomingdale, the officers searched the car and found
400 pounds of marijuana, and then they searched the
house.5 However, none of these subsequent events may be
considered in evaluating the warrant,6 and the search of
the house was legal only if the warrant was valid. Vale v.
Louisiana, 399 U.S. 30, 33-35, 90 S.Ct. 1969, 1971-1972,
26 L.Ed.2d 409 (1970). I cannot accept the Court’s casual
conclusion that, before the Gates arrived in
Bloomingdale, there was probable cause to justify a valid
entry and search of a private home. No one knows who
the informant in this case was, or what motivated him or
her to write the note. Given that the note’s predictions
were faulty in one *294 significant respect, and were
corroborated by nothing except ordinary **2362 innocent
activity, I must surmise that the Court’s evaluation of the
warrant’s validity has been colored by subsequent
events.7
Although the foregoing analysis is determinative as to the
house search, the car search raises additional issues
because “there is a constitutional difference between
houses and cars.” Chambers v. Maroney, 399 U.S. 42, 52,
90 S.Ct. 1975, 1981, 26 L.Ed.2d 419 (1970). Cf. Payton
v. New York, 445 U.S. 573, 589-590, 100 S.Ct. 1371,
1381-1382, 63 L.Ed.2d 639 (1980). An officer who has
probable cause to suspect that a highly movable
automobile contains contraband does not need a valid
warrant in order to search it. This point was developed in
our opinion in United States v. Ross, 456 U.S. 798, 102
S.Ct. 2157, 72 L.Ed.2d 572 (1982), which was not
decided until after the Illinois Supreme Court rendered its
decision in this case. Under Ross, the car search may have
been valid if the officers had probable cause after the
Gates arrived.
In apologizing for its belated realization that we should
not have ordered reargument in this case, the Court today
shows high regard for the appropriate relationship of this
Court to state courts. Ante, at 2323. When the Court
discusses the merits, however, it attaches no weight to the
conclusions of the Circuit Judge of DuPage County,
Illinois, of the three judges of the Second District of the
Illinois Appellate Court, or of the five justices of the
Illinois Supreme Court, all of whom concluded that the
warrant was not based on probable cause. In a fact-bound
inquiry of this sort, the judgment of three levels of state
courts, all of whom are better able to evaluate the
probable reliability of anonymous informants in *295
Bloomingdale, Illinois, than we are, should be entitled to
at least a presumption of accuracy.8 I would simply vacate
the judgment of the Illinois Supreme Court and remand
the case for reconsideration in the light of our intervening
decision in United States v. Ross.
Parallel Citations
103 S.Ct. 2317, 76 L.Ed.2d 527, 54 USLW 2230
Footnotes
* The syllabus constitutes no part of the opinion of the Court but has been prepared by the Reporter of Decisions for the convenience
of the reader. See United States v. Detroit Lumber Co., 200 U.S. 321, 337, 26 S.Ct. 282, 287, 50 L.Ed. 499.
1 The apparent rule of Crowell v. Randell, supra, that a federal claim have been both raised and addressed in state court was
generally not understood in the literal fashion in which it was phrased. See R. Robertson & F. Kirkham, Jurisdiction of the
Supreme Court of the United States § 60 (1951). Instead, the Court developed the rule that a claim would not be considered here
unless it had been either raised or squarely considered and resolved in state court. See, e.g., McGoldrick v. Compagnie Generale,
309 U.S. 430, 435-436, 60 S.Ct. 670, 673, 84 L.Ed. 849 (1940); State Farm Mutual Insurance Co. v. Duel, 324 U.S. 154, 160, 65
S.Ct. 573, 576, 89 L.Ed. 812 (1945).
2 In Dewey, certain assessments had been levied against the owner of property abutting a street paved by the city; a state trial court
ordered that the property be forfeited when the assessments were not paid, and in addition, held appellant personally liable for the
amount by which the assessments exceeded the value of the lots. In state court the appellant argued that the imposition of personal
liability against him violated the Due Process Clause of the Fourteenth Amendment, because he had not received personal notice of
the assessment proceedings. In this Court, he also attempted to argue that the assessment itself constituted a taking under the
Fourteenth Amendment. The Court held that, beyond arising from a single factual occurrence, the two claims “are not in anywise
necessarily connected,” id., at 198, 19 S.Ct., at 381. Because of this, we concluded that appellant’s taking claim could not be
considered.
68

3 In Spinelli, police officers observed Mr. Spinelli going to and from a particular apartment, which the telephone company said
contained two telephones with stated numbers. The officers also were “informed by a confidential reliable informant that William
Spinelli [was engaging in illegal gambling activities]” at the apartment, and that he used two phones, with numbers corresponding
to those possessed by the police. The officers submitted an affidavit with this information to a magistrate and obtained a warrant to
search Spinelli’s apartment. We held that the magistrate could have made his determination of probable cause only by “abdicating
his constitutional function,” id., at 416, 89 S.Ct., at 589. The Government’s affidavit contained absolutely no information regarding
the informant’s reliability. Thus, it did not satisfy Aguilar ‘s requirement that such affidavits contain “some of the underlying
circumstances” indicating that “the informant ... was ‘credible’ ” or that “his information [was] ‘reliable.’ ” Aguilar, supra, 378
U.S., at 114, 84 S.Ct., at 1514. In addition, the tip failed to satisfy Aguilar ‘s requirement that it detail “some of the underlying
circumstances from which the informant concluded that ... narcotics were where he claimed they were. We also held that if the tip
concerning Spinelli had contained “sufficient detail” to permit the magistrate to conclude “that he [was] relying on something more
substantial than a casual rumor circulating in the underworld or an accusation based merely on an individual’s general reputation,”
393 U.S., at 416, 89 S.Ct., at 589, then he properly could have relied on it; we thought, however, that the tip lacked the requisite
detail to permit this “self-verifying detail” analysis.
4 See, e.g., Stanley v. State, 19 Md.App. 507, 313 A.2d 847 (Md.App.1974). In summary, these rules posit that the “veracity” prong
of the Spinelli test has two “spurs”-the informant’s “credibility” and the “reliability” of his information. Various interpretations are
advanced for the meaning of the “reliability” spur of the “veracity” prong. Both the “basis of knowledge” prong and the “veracity”
prong are treated as entirely separate requirements, which must be independently satisfied in every case in order to sustain a
determination of probable cause. See n. 5, infra. Some ancillary doctrines are relied on to satisfy certain of the foregoing
requirements. For example, the “self-verifying detail” of a tip may satisfy the “basis of knowledge” requirement, although not the
“credibility” spur of the “veracity” prong. See J.A. 10a. Conversely, corroboration would seem not capable of supporting the “basis
of knowledge” prong, but only the “veracity” prong. Id., at 12a.
The decision in Stanley, while expressly approving and conscientiously attempting to apply the “two-pronged test” observes that
“[t]he built-in subtleties [of the test] are such, however, that a slipshod application calls down upon us the fury of Murphy’s Law.”
313 A.2d, at 860 (footnote omitted). The decision also suggested that it is necessary “to evolve analogous guidelines [to hearsay
rules employed in trial settings] for the reception of hearsay in a probable cause setting.” Id., at 857.
5 The entirely independent character that the Spinelli prongs have assumed is indicated both by the opinion of the Illinois Supreme
Court in this case, and by decisions of other courts. One frequently cited decision, Stanley v. State, 19 Md.App. 507, 313 A.2d 847,
861 (Md.App.1974), remarks that “the dual requirements represented by the ‘two-pronged test’ are ‘analytically severable’ and an
‘overkill’ on one prong will not carry over to make up for a deficit on the other prong.” See also n. 9, infra.
6 Our original phrasing of the so-called “two-pronged test” in Aguilar v. Texas, 378 U.S. 108, 84 S.Ct. 1509, 12 L.Ed.2d 723 (1969),
suggests that the two prongs were intended simply as guides to a magistrate’s determination of probable cause, not as inflexible,
independent requirements applicable in every case. In Aguilar, we required only that:
the magistrate must be informed of some of the underlying circumstances from which the informant concluded that ... narcotics
were where he claimed they were, and some of the underlying circumstances from which the officer concluded that the informant
... was ‘credible’ or his information ‘reliable.’ ” Id., at 114, 84 S.Ct., at 1514 (emphasis added).
As our language indicates, we intended neither a rigid compartmentalization of the inquiries into an informant’s “veracity,”
“reliability” and “basis of knowledge,” nor that these inquiries be elaborate exegeses of an informant’s tip. Rather, we required
only that some facts bearing on two particular issues be provided to the magistrate. Our decision in Jaben v. United States, 381
U.S. 214, 85 S.Ct. 1365, 14 L.Ed.2d 345 (1965), demonstrated this latter point. We held there that a criminal complaint showed
probable cause to believe the defendant had attempted to evade the payment of income taxes. We commented that:
“Obviously any reliance upon factual allegations necessarily entails some degree of reliability upon the credibility of the
source.... Nor does it indicate that each factual allegation which the affiant puts forth must be independently documented, or
that each and every fact which contributed to his conclusions be spelled out in the complaint.... It simply requires that
enough information be presented to the Commissioner to enable him to make the judgment that the charges are not
capricious and are sufficiently supported to justify bringing into play the further steps of the criminal process.” Id., at 224-
225, 85 S.Ct., at 1371 (emphasis added).
7 The diversity of informants’ tips, as well as the usefulness of the totality-of-the-circumstances approach to probable cause, is
reflected in our prior decisions on the subject. In Jones v. United States, 362 U.S. 257, 271, 80 S.Ct. 725, 736, 4 L.Ed.2d 697
(1960), we held that probable cause to search petitioners’ apartment was established by an affidavit based principally on an
informant’s tip. The unnamed informant claimed to have purchased narcotics from petitioners at their apartment; the affiant stated
that he had been given correct information from the informant on a prior occasion. This, and the fact that petitioners had admitted
to police officers on another occasion that they were narcotics users, sufficed to support the magistrate’s determination of probable
69

cause.
Likewise, in Rugendorf v. United States, 376 U.S. 528, 84 S.Ct. 825, 11 L.Ed.2d 887 (1964), the Court upheld a magistrate’s
determination that there was probable cause to believe that certain stolen property would be found in petitioner’s apartment. The
affidavit submitted to the magistrate stated that certain furs had been stolen, and that a confidential informant, who previously had
furnished confidential information, said that he saw the furs in petitioner’s home. Moreover, another confidential informant, also
claimed to be reliable, stated that one Schweihs had stolen the furs. Police reports indicated that petitioner had been seen in
Schweihs’ company and a third informant stated that petitioner was a fence for Schweihs.
Finally, in Ker v. California, 374 U.S. 23, 83 S.Ct. 1623, 10 L.Ed.2d 726 (1963), we held that information within the knowledge of
officers who searched the Ker’s apartment provided them with probable cause to believe drugs would be found there. The officers
were aware that one Murphy had previously sold marijuana to a police officer; the transaction had occurred in an isolated area, to
which Murphy had led the police. The night after this transaction, police observed Ker and Murphy meet in the same location.
Murphy approached Ker’s car, and, although police could see nothing change hands, Murphy’s modus operandi was identical to
what it had been the night before. Moreover, when police followed Ker from the scene of the meeting with Murphy he managed to
lose them after performing an abrupt U-turn. Finally, the police had a statement from an informant who had provided reliable
information previously, that Ker was engaged in selling marijuana, and that his source was Murphy. We concluded that “To say
that this coincidence of information was sufficient to support a reasonable belief of the officers that Ker was illegally in possession
of marijuana is to indulge in understatement.” Id., at 36, 83 S.Ct., at 1631.
8 Compare Stanley v. State, 19 Md.App. 507, 313 A.2d 847, 861 (Md.App.1974), reasoning that “Even assuming ‘credibility’
amounting to sainthood, the judge still may not accept the bare conclusion of a sworn and known and trusted police-affiant.”
9 Some lower court decisions, brought to our attention by the State, reflect a rigid application of such rules. In Bridger v. State, 503
S.W.2d 801 (Tex.Cr.App.1974), the affiant had received a confession of armed robbery from one of two suspects in the robbery; in
addition, the suspect had given the officer $800 in cash stolen during the robbery. The suspect also told the officer that the gun
used in the robbery was hidden in the other suspect’s apartment. A warrant issued on the basis of this was invalidated on the
ground that the affidavit did not satisfactorily describe how the accomplice had obtained his information regarding the gun.
Likewise, in People v. Palanza, 55 Ill.App.3d 1028, 13 Ill.Dec. 752, 371 N.E.2d 687 (Ill.App.1978), the affidavit submitted in
support of an application for a search warrant stated that an informant of proven and uncontested reliability had seen, in
specifically described premises, “a quantity of a white crystalline substance which was represented to the informant by a white
male occupant of the premises to be cocaine. Informant has observed cocaine on numerous occasions in the past and is thoroughly
familiar with its appearance. The informant states that the white crystalline powder he observed in the above described premises
appeared to him to be cocaine.” The warrant issued on the basis of the affidavit was invalidated because “There is no indication as
to how the informant or for that matter any other person could tell whether a white substance was cocaine and not some other
substance such as sugar or salt.” Id., 13 Ill.Dec., at 754, 371 N.E.2d, at 689.
Finally, in People v. Brethauer, 174 Colo. 29, 482 P.2d 369 (Colo.1971), an informant, stated to have supplied reliable information
in the past, claimed that L.S.D. and marijuana were located on certain premises. The affiant supplied police with drugs, which were
tested by police and confirmed to be illegal substances. The affidavit setting forth these, and other, facts was found defective under
both prongs of Spinelli.
10 We also have said that “Although in a particular case it may not be easy to determine when an affidavit demonstrates the existence
of probable cause, the resolution of doubtful or marginal cases in this area should be largely determined by the preference to be
accorded to warrants,” Ventresca, supra, 380 U.S., at 109, 85 S.Ct., at 746. This reflects both a desire to encourage use of the
warrant process by police officers and a recognition that once a warrant has been obtained, intrusion upon interests protected by the
Fourth Amendment is less severe than otherwise may be the case. Even if we were to accept the premise that the accurate
assessment of probable cause would be furthered by the “two-pronged test,” which we do not, these Fourth Amendment policies
would require a less rigorous standard than that which appears to have been read into Aguilar and Spinelli.
11 The Court’s decision in Spinelli has been the subject of considerable criticism, both by members of this Court and others. Justice
BLACKMUN, concurring in United States v. Harris, 403 U.S. 573, 585-586, 91 S.Ct. 2075, 2082-2083, 29 L.Ed.2d 723 (1971),
noted his long-held view “that Spinelli ... was wrongly decided” by this Court. Justice Black similarly would have overruled that
decision. Ibid. Likewise, a noted commentator has observed that “[t]he Aguilar-Spinelli formulation has provoked apparently
ceaseless litigation.” 8A Moore’s Federal Practice 41.04 (1981).
Whether the allegations submitted to the magistrate in Spinelli would, under the view we now take, have supported a finding of
probable cause, we think it would not be profitable to decide. There are so many variables in the probable cause equation that one
determination will seldom be a useful “precedent” for another. Suffice it to say that while we in no way abandon Spinelli ‘s
concern for the trustworthiness of informers and for the principle that it is the magistrate who must ultimately make a finding of
probable cause, we reject the rigid categorization suggested by some of its language.
12 The tip in Draper might well not have survived the rigid application of the “two-pronged test” that developed following Spinelli.
70

The only reference to Hereford’s reliability was that he had “been engaged as a ‘special employee’ of the Bureau of Narcotics at
Denver for about six months, and from time to time gave information to [the police] for small sums of money, and that [the officer]
had always found the information given by Hereford to be accurate and reliable.” 358 U.S., at 309, 79 S.Ct., at 331. Likewise, the
tip gave no indication of how Hereford came by his information. At most, the detailed and accurate predictions in the tip indicated
that, however Hereford obtained his information, it was reliable.
13 The Illinois Supreme Court thought that the verification of details contained in the anonymous letter in this case amounted only to
“the corroboration of innocent activity,” J.A. 12a, and that this was insufficient to support a finding of probable cause. We are
inclined to agree, however, with the observation of Justice Moran in his dissenting opinion that “In this case, just as in Draper,
seemingly innocent activity became suspicious in the light of the initial tip.” J.A. 18a. And it bears noting that all of the
corroborating detail established in Draper, supra, was of entirely innocent activity-a fact later pointed out by the Court in both
Jones v. United States, 362 U.S. 257, 269-270, 80 S.Ct. 725, 735-736, 4 L.Ed.2d 697 (1960), and Ker v. California, 374 U.S. 23,
36, 83 S.Ct. 1623, 1631, 10 L.Ed.2d 726 (1963).
This is perfectly reasonable. As discussed previously, probable cause requires only a probability or substantial chance of criminal
activity, not an actual showing of such activity. By hypothesis, therefore, innocent behavior frequently will provide the basis for a
showing of probable cause; to require otherwise would be to sub silentio impose a drastically more rigorous definition of probable
cause than the security of our citizens demands. We think the Illinois court attempted a too rigid classification of the types of
conduct that may be relied upon in seeking to demonstrate probable cause. See Brown v. Texas, 443 U.S. 47, 52, n. 2, 99 S.Ct.
2637, 2641, n. 2, 61 L.Ed.2d 357 (1979). In making a determination of probable cause the relevant inquiry is not whether particular
conduct is “innocent” or “guilty,” but the degree of suspicion that attaches to particular types of non-criminal acts.
14 The dissent seizes on one inaccuracy in the anonymous informant’s letter-its statement that Sue Gates would fly from Florida to
Illinois, when in fact she drove-and argues that the probative value of the entire tip was undermined by this allegedly “material
mistake.” We have never required that informants used by the police be infallible, and can see no reason to impose such a
requirement in this case. Probable cause, particularly when police have obtained a warrant, simply does not require the perfection
the dissent finds necessary.
Likewise, there is no force to the dissent’s argument that the Gates’ action in leaving their home unguarded undercut the
informant’s claim that drugs were hidden there. Indeed, the line-by-line scrutiny that the dissent applies to the anonymous letter is
akin to that we find inappropriate in reviewing magistrate’s decisions. The dissent apparently attributes to the magistrate who
issued the warrant in this case the rather implausible notion that persons dealing in drugs always stay at home, apparently out of
fear that to leave might risk intrusion by criminals. If accurate, one could not help sympathizing with the self-imposed isolation of
people so situated. In reality, however, it is scarcely likely that the magistrate ever thought that the anonymous tip “kept one
spouse” at home, much less that he relied on the theory advanced by the dissent. The letter simply says that Sue would fly from
Florida to Illinois, without indicating whether the Gates’ made the bitter choice of leaving the drugs in their house, or those in their
car, unguarded. The magistrate’s determination that there might be drugs or evidence of criminal activity in the Gates’ home was
well-supported by the less speculative theory, noted in text, that if the informant could predict with considerable accuracy the
somewhat unusual travel plans of the Gates, he probably also had a reliable basis for his statements that the Gates’ kept a large
quantity of drugs in their home and frequently were visited by other drug traffickers there.
1 See e.g., Eddings v. Oklahoma, 455 U.S. 104, 102 S.Ct. 869, 71 L.Ed.2d 1 (1982); Wood v. Georgia, 450 U.S. 261, 101 S.Ct. 1097,
67 L.Ed.2d 220 (1980); Vachon v. New Hampshire, 414 U.S. 478, 94 S.Ct. 664, 38 L.Ed.2d 666 (1974) (per curiam ). Of course, to
the extent these cases were correctly decided, they indicate a fortiori that the exclusionary rule issue in this case is properly before
us.
2 The Court has previously relied on issues and arguments not raised in the state court below in order to dispose of a federal question
that was properly raised. In Stanley v. Illinois, 405 U.S. 645, 658, 92 S.Ct. 1208, 1216, 31 L.Ed.2d 551 (1972), the Court held that
unmarried fathers could not be denied a hearing on parental fitness that was afforded other Illinois parents. Although this issue was
not presented in the Illinois courts, the Court found that it could properly be considered: “we dispose of the case on the
constitutional premise raised below, reaching the result by a method of analysis readily available to the state court. For the same
reason, the strictures of Cardinale ... and Hill, have been fully observed.” 405 U.S., at 658, n. 10, 92 S.Ct., at 1216, n. 10. The
dissent argued that the Court was deciding a due process claim instead of an equal protection one, but there was no suggestion that
it mattered at all that the Court had relied on a different type of equal protection argument.
3 As the Court explains, ante, at 2322, n. 2, in Dewey, appellant argued only that the imposition of personal liability against him
violated the Due Process Clause of the Fourteenth Amendment, because he had not received personal notice of the assessment
proceedings. In this Court, appellant sought to raise a takings argument for the first time. The Court declined to pass on the issue
because, although arising from a single factual occurrence the two claims “are not in anywise necessarily connected,” 173 U.S., at
198, 19 S.Ct., at 380.
71

4 The Court relies on these cases for the surprising assertion that the Fourth Amendment and exclusionary rule questions are
“distinct.” I had understood the very essence of Rakas v. Illinois, 439 U.S. 128, 99 S.Ct. 421, 58 L.Ed.2d 387 (1978) to be that
standing to seek exclusion of evidence could not be divorced from substantive Fourth Amendment rights. Past decisions finding
that the remedy of exclusion is not always appropriate upon the finding of a Fourth Amendment violation acknowledge the close
relationship of the issues. For example, in United States v. Ceccolini it was said: “The constitutional question under the Fourth
Amendment was phrased in Wong Sun v. United States, 371 U.S. 471, 83 S.Ct. 407, 9 L.Ed.2d 441 (1963), as whether ‘the
connection between the lawless conduct of the police and the discovery of the challenged evidence has become so attenuated as to
dissipate the taint.’ ” 435 U.S., at 275-276, 98 S.Ct., at 1059-1060. It is also surprising to learn that the issues in Stone v. Powell are
“distinct” from the Fourth Amendment.
5 Consider the full context of the statement in McGoldrick:
“In cases coming here from state courts in which a state statute is assailed as unconstitutional, there are reasons of peculiar force
which should lead us to refrain from deciding questions not presented or decided in the highest court of the state whose judicial
action we are called upon to review. Apart from the reluctance with which every court should proceed to set aside legislation as
unconstitutional on grounds not properly presented, due regard for the appropriate relationship of this Court to state courts requires
us to decline to consider and decide questions affecting the validity of state statutes not urged or considered there. It is for these
reasons that this Court, where the constitutionality of a statute has been upheld in the state court, consistently refuses to consider
any grounds of attack not raised or decided in that court.” 309 U.S., at 434, 60 S.Ct., at 672.
6 The Court observes that “although the Illinois courts applied the federal exclusionary rule, there was never ‘any real contest’ upon
the point.” Ante, at 2324. But the proper forum for a “real contest” on the continued vitality of the exclusionary rule that has
developed from our decisions in Weeks v. United States, 232 U.S. 383, 34 S.Ct. 341, 58 L.Ed. 652 (1914) and Mapp v. Ohio, 367
U.S. 643, 81 S.Ct. 1684, 6 L.Ed.2d 1081 (1961) is this Court.
7 Nor is there any reason for the Illinois courts to decide that question in advance of this Court’s decision on the federal exclusionary
rule. Until the federal rule is modified, the state law question is entirely academic. The state courts should not be expected to
render such purely advisory decisions.
8 Respondents press this very argument. Brief of Respondent at 24-27; Brief for Respondent on Reargument, at 6. Of course, under
traditional principles the possibility that the state court might reach a different conclusion in interpreting its state constitution does
not make it improper for us to decide the federal issue. Delaware v. Prouse, 440 U.S. 648, 651-653, 99 S.Ct. 1391, 1394-1395, 59
L.Ed.2d 660 (1979); Zacchini v. Scripps-Howard Broadcasting Co., 433 U.S. 562, 568, 97 S.Ct. 2849, 2854, 53 L.Ed.2d 965
(1977).
9 It also should be noted that the requirement that the good faith issue be presented to the Illinois courts has little to do with whether
the record is complete. I doubt that the raising of the good faith issue below would have been accompanied by any different record.
And this Court may dismiss a writ of certiorari as improvidently granted when the record makes decision of a federal question
unwise. See, e.g., Minnick v. Calif. Department of Corrections, 452 U.S. 105, 101 S.Ct. 2211, 68 L.Ed.2d 706 (1981).
10 In California v. Minjares, 443 U.S. 916, 928, 100 S.Ct. 9, 15, 61 L.Ed.2d 892 (1979) (REHNQUIST, J., joined by THE CHIEF
JUSTICE, dissenting from the denial of stay), the author of today’s opinion for the Court urged that the parties be directed to brief
whether the exclusionary rule should be retained. In Minjares, like this case, respondents had raised a Fourth Amendment claim
but petitioners had not attacked the validity of the exclusionary rule in the state court. See also Robbins v. California, 453 U.S. 420,
437, 101 S.Ct. 2841, 2851, 69 L.Ed.2d 744 (REHNQUIST, J., dissenting) (advocating overruling of Mapp v. Ohio, 367 U.S. 643,
81 S.Ct. 1684, 6 L.Ed.2d 1081 (1961)).
11 Ironically, in Mapp v. Ohio, supra, petitioners did not ask the Court to partially overrule Wolf v. Colorado, 338 U.S. 25, 69 S.Ct.
1359, 93 L.Ed. 1782 (1949). The sole argument to apply the exclusionary rule to the states is found in a single paragraph in an
amicus brief filed by the American Civil Liberties Union.
12 To be sure, Peltier and DeFillippo did not modify the exclusionary rule itself. Peltier held that Almeida-Sanchez v. United States,
413 U.S. 266, 93 S.Ct. 2535, 37 L.Ed.2d 596 (1973), was not to be given retroactive effect; DeFillippo upheld the validity of an
arrest made in good-faith reliance on an ordinance subsequently declared unconstitutional. The effect of these decisions, of course,
was that evidence was not excluded because of the officer’s reasonable belief that he was acting lawfully, and the Court’s
reasoning, as I discuss below, infra, at 2343-2344, leads inexorably to the more general modification of the exclusionary rule I
favor. Indeed, Justice BRENNAN recognized this in his dissent in Peltier, 422 U.S., at 551-552, 95 S.Ct., at 2324-2325.
I recognize that we have held that the exclusionary rule required suppression of evidence obtained in searches carried out pursuant
to statutes, not previously declared unconstitutional, which purported to authorize the searches in question without probable cause
and without a valid warrant. See, e.g., Torres v. Puerto Rico, 442 U.S. 465, 99 S.Ct. 2425, 61 L.Ed.2d 1 (1979); Almeida-Sanchez
72

v. United States, supra; Sibron v. New York, 392 U.S. 40, 88 S.Ct. 1889, 20 L.Ed.2d 917 (1968); Berger v. New York, 388 U.S. 41,
87 S.Ct. 1873, 18 L.Ed.2d 1040 (1967). The results in these cases may well be different under a “good-faith” exception to the
exclusionary rule.
13 The effects of the exclusionary rule are often felt before a case reaches trial. A recent study by the National Institute of Justice of
felony arrests in California during the years 1976-1979 “found a major impact of the exclusionary rule on state prosecutions.”
National Institute of Justice, The Effects of the Exclusionary Rule: A Study in California 2 (1982). The study found that 4.8% of
the more than 4,000 felony cases declined for prosecution were rejected because of search and seizure problems. The exclusionary
rule was found to have a particularly pronounced effect in drug cases; prosecutors rejected approximately 30% of all felony drug
arrests because of search and seizure problems.
14 Our decisions applying the exclusionary rule have referred to the “imperative of judicial integrity,” Elkins v. United States, 364
U.S. 206, 222, 80 S.Ct. 1437, 1446, 4 L.Ed.2d 1669 (1960), although recent opinions of the Court make clear that the primary
function of the exclusionary rule is to deter violations of the Fourth Amendment, Stone v. Powell, 428 U.S., at 486, 96 S.Ct., at
3048; United States v. Janis, 428 U.S. 433, 446, 96 S.Ct. 3021, 3028, 49 L.Ed.2d 1046 (1976); United States v. Calandra, 414 U.S.
338, 348, 94 S.Ct. 613, 620, 38 L.Ed.2d 561 (1974). I do not dismiss the idea that the integrity of the courts may be compromised
when illegally seized evidence is admitted, but I am convinced that the force of the argument depends entirely on the type of search
or seizure involved. At one extreme, there are lawless invasions of personal privacy that shock the conscience and the admission of
evidence so obtained must be suppressed as a matter of Due Process, entirely aside from the Fourth Amendment. See, e.g., Rochin
v. California, 342 U.S. 165, 72 S.Ct. 205, 96 L.Ed. 183 (1952). Also deserving of exclusionary treatment are searches and seizures
perpetrated in intentional and flagrant disregard of Fourth Amendment principles. But the question of exclusion must be viewed
through a different lens when a Fourth Amendment violation occurs because the police have reasonably erred in assessing the
facts, mistakenly conducted a search authorized under a presumably valid statute, or relied in good-faith upon a warrant not
supported by probable cause. In these circumstances, the integrity of the courts is not implicated. The violation of the Fourth
Amendment is complete before the evidence is admitted. Thus, “[t]he primary meaning of ‘judicial integrity’ in the context of
evidentiary rules is that the courts must not commit or encourage violations of the Constitution.” United States v. Janis, supra, 428
U.S., at 458, n. 35, 96 S.Ct., at 3034, n. 35. Cf. United States v. Peltier, 422 U.S., at 537, 95 S.Ct., at 2317 (“The teaching of these
retroactivity cases is that if the law enforcement officers reasonably believed in good faith that evidence they had seized was
admissible at trial, the ‘imperative of judicial integrity’ is not offended by the introduction into evidence of that material even if
decisions subsequent to the search or seizure have broadened the exclusionary rule to encompass evidence seized in that manner.”)
I am content that the interests in judicial integrity run along with rather than counter to the deterrence concept, and that to focus
upon the latter is to promote, not denigrate, the former.
15 It has been suggested that the deterrence function of the exclusionary rule has been understated by viewing the rule as aimed at
special deterrence, when, in fact, the exclusionary rule is directed at “affecting the wider audience of law enforcement officials and
society at large.” W. LaFave, 1 Search and Seizure 6 (1983 Supp.). See also W. Mertens and S. Wasserstrom, “The Good Faith
Exception to the Exclusionary Rule: Deregulating the Police and Derailing the Law,” 70 Georgetown L.J. 365, 399-401 (1981). I
agree that the exclusionary rule’s purpose is not only, or even primarily, to deter the individual police officer involved in the
instant case. It appears that this objection assumes that the proposed modification of the exclusionary rule will turn only the
subjective “good-faith” of the officer. Grounding the modification in objective reasonableness, however, retains the value of the
exclusionary rule as an incentive for the law enforcement profession as a whole to conduct themselves in accord with the Fourth
Amendment. Dunaway v. New York, 442 U.S. 200, 221, 99 S.Ct. 2248, 2261, 60 L.Ed.2d 824 (1979) (STEVENS, J., concurring).
Indeed, the present indiscriminate application of the exclusionary rule may hinder the educative and deterrent function of the
suppression remedy. “Instead of disciplining their employees, police departments generally have adopted the attitude that the
courts cannot be satisfied, that the rules are hopelessly complicated and subject to change, and that the suppression of evidence is
the court’s problem and not the departments’.” J. Kaplan, The Limits of the Exclusionary Rule, 26 Stan.L.Rev. 1027, 1050 (1974).
If evidence is suppressed only when a law enforcement officer should have known that he was violating the Fourth Amendment,
police departments may look more seriously at the officer’s misconduct when suppression is invoked. Moreover, by providing that
evidence gathered in good-faith reliance on a reasonable rule will not be excluded, a good-faith exception creates an incentive for
police departments to formulate rules governing activities of officers in the search and seizure area. Many commentators, including
proponents of the exclusionary sanction, recognize that the formulation of such rules by police departments, and the training
necessary to implement these guidelines in practice, is perhaps the most effective means of protecting Fourth Amendment rights.
See K. Davis, Discretionary Justice (1971); McGowan, Rule-Making and the Police, 70 Mich.L.Rev. 659 (1972); A. Amsterdam,
Perspectives on the Fourth Amendment, 58 Minn.L.Rev. 349, 416-431 (1974).
16 The Attorney General’s Task Force on Violent Crime concluded that the situation in which an officer relies on a duly authorized
warrant
“is a particularly compelling example of good faith. A warrant is a judicial mandate to an officer to conduct a search or
make an arrest, and the officer has a sworn duty to carry out its provisions. Accordingly, we believe that there should be a
73

ule which states that evidence obtained pursuant to and within the scope of a warrant is prima facie the result of good faith
on the part of the officer seizing the evidence.”
Final Report 55 (1981).
17 Much is made of Shadwick v. City of Tampa, 407 U.S. 345, 92 S.Ct. 2119, 32 L.Ed.2d 783 (1971), where we held that magistrates
need not be legally trained. Shadwick’s holding was quite narrow. First, the Court insisted that “an issuing magistrate must meet
two tests. He must be neutral and detached, and he must be capable of determining whether probable cause exists for the requested
arrest or search.” 407 U.S., at 345, 92 S.Ct., at 2119. Second, in Shadwick, the court clerk’s authority extended only to the
relatively straightforward task of issuing arrest warrants for breach of municipal ordinances. To issue search warrants, an
individual must be capable of making the probable cause judgments involved. In this regard, I reject the Court’s insinuation that it
is too much to expect that persons who issue warrants remain abreast of judicial refinements of probable cause. Ante, at 2330.
Finally, as indicated in text, I do not propose that a warrant clearly lacking a basing in probable cause can support a “good-faith”
defense to invocation of the exclusionary rule.
18 Respondents and some amici contend that this practice would be inconsistent with the Article III requirement of an actual case or
controversy. I have no doubt that a defendant who claims that he has been subjected to an unlawful search or seizure and seeks
suppression of the evidentiary fruits thereof raises a live controversy within the Article III authority of federal courts to adjudicate.
It is fully appropriate for a court to decide whether there has been a wrong before deciding what remedy to impose. When
questions of good-faith immunity have arisen under 42 U.S.C. § 1983, we have not been constrained to reach invariably the
immunity question before the violation issue. Compare O’Connor v. Donaldson, 422 U.S. 563, 95 S.Ct. 2486, 45 L.Ed.2d 396
(1975) (finding constitutional violation and remanding for consideration of good-faith defense) with Procunier v. Navarette, 434
U.S. 555, 566, n. 14, 98 S.Ct. 855, 862, n. 14, 55 L.Ed.2d 24 (1978) (finding good-faith defense first). Similarly, we have exercised
discretion in at times deciding the merits of a claim even though the error was harmless, while on other occasions resolving the
case solely by reliance on the harmless error doctrine. Compare Milton v. Wainwright, 407 U.S. 371, 372, 92 S.Ct. 2174, 2175, 33
L.Ed.2d 1 (1972) (declining to decide whether admission of confession was constitutional violation because error, if any, was
harmless beyond a reasonable doubt), with Coleman v. Alabama, 399 U.S. 1, 90 S.Ct. 1999, 26 L.Ed.2d 387 (1970) (upholding
right to counsel at preliminary hearing and remanding for harmless error determination).
19 For example, a pattern or practice of official conduct that is alleged to violate Fourth Amendment rights may be challenged by an
aggrieved individual in a suit for declaratory or injunctive relief. See, e.g., Zurcher v. Stanford Daily, 436 U.S. 547, 98 S.Ct. 1970,
56 L.Ed.2d 525 (1978). (Of course, there are limits on the circumstances in which such actions will lie. Rizzo v. Goode, 423 U.S.
362, 96 S.Ct. 598, 46 L.Ed.2d 561 (1976); Los Angeles v. Lyons, 461 U.S. 95, 103 S.Ct. 1660, 75 L.Ed.2d 675 (1983)). Although a
municipality is not liable under 42 U.S.C. § 1983 on a theory of respondeat superior, local governing bodies are subject to suit for
constitutional torts resulting from implementation of local ordinances, regulations, policies, or even customary practices. Monell v.
Department of Social Services, 436 U.S. 658, 98 S.Ct. 2018, 56 L.Ed.2d 611 (1978). Such entities enjoy no immunity defense that
might impede resolution of the substantive constitutional issue. Owen v. City of Independence, 445 U.S. 622, 100 S.Ct. 1398, 63
L.Ed.2d 673 (1980). In addition, certain state courts may continue to suppress, as a matter of state law, evidence in state trials for
any Fourth Amendment violation. These cases would likely provide a sufficient supply of state criminal cases in which to resolve
unsettled questions of Fourth Amendment law. As a final alternative, I would entertain the possibility of according the benefits of a
new Fourth Amendment rule to the party in whose case the rule is first announced. See Stovall v. Denno, 388 U.S. 293, 301, 87
S.Ct. 1967, 1972, 18 L.Ed.2d 1199 (1967).
20 The “veracity” prong is satisfied by a recitation in the affidavit that the informant previously supplied accurate information to the
police, see McCray v. Illinois, 386 U.S. 300, 303-304, 87 S.Ct. 1056, 1058-1059, 18 L.Ed.2d 62 (1967), or by proof that the
informant gave his information against his penal interest, see United States v. Harris, 403 U.S. 573, 583-584, 91 S.Ct. 2075, 2082-
2083, 29 L.Ed.2d 723 (1971) (plurality opinion). The “basis of knowledge” prong is satisfied by a statement from the informant
that he personally observed the criminal activity, or, if he came by the information indirectly, by a satisfactory explanation of why
his sources were reliable, or, in the absence of a statement detailing the manner in which the information was gathered, by a
description of the accused’s criminal activity in sufficient detail that the magistrate may infer that the informant is relying on
something more substantial than casual rumor or an individual’s general reputation. Spinelli v. United States, 393 U.S. 410, 416, 89
S.Ct. 584, 589, 21 L.Ed.2d 637 (1969).
21 See ante, at 2333; United States v. Mendenhall, 446 U.S. 544, 562, 100 S.Ct. 1870, 1881, 64 L.Ed.2d 497 (1980) (POWELL, J.,
concurring).
22 Thus, as interpreted in Spinelli, the Court in Draper held that there was probable cause because “the kind of information related by
the informant [was] not generally sent ahead of a person’s arrival in a city except to those who are intimately connected with
making careful arrangements for meeting him.” Spinelli, supra, 393 U.S., at 426, 89 S.Ct., at 594 (WHITE, J., concurring). As I
said in Spinelli, the conclusion that Draper itself was based on this fact is far from inescapable. Prior to Spinelli, Draper was
74

susceptible to the interpretation that it stood for the proposition that “the existence of the tenth and critical fact is made sufficiently
probable to justify the issuance of a warrant by verifying nine other facts coming from the same source.” Spinelli, supra, at 426-
427, 89 S.Ct., at 594-595 (WHITE, J., concurring). But it now seems clear that the Court in Spinelli rejected this reading of
Draper.
Justice BRENNAN, post, at 2354-2355, erroneously interprets my Spinelli concurrence as espousing the view that “corroboration
of certain details in a tip may be sufficient to satisfy the veracity, but not the basis of knowledge, prong of Aguilar.” Others have
made the same mistake. See, e.g., Comment, 20 Am.Crim.L.Rev. 99, 105 (1982). I did not say that corroboration could never
satisfy the basis of knowledge prong. My concern was, and still is, that the prong might be deemed satisfied on the basis of
corroboration of information that does not in any way suggest that the informant had an adequate basis of knowledge for his report.
If, however, as in Draper, the police corroborate information from which it can be inferred that the informant’s tip was grounded
on inside information, this corroboration is sufficient to satisfy the basis of knowledge prong. Spinelli, supra, at 426, 89 S.Ct., at
594 (WHITE, J., concurring). The rules would indeed be strange if, as Justice BRENNAN suggests, post, at 2356, the basis of
knowledge prong could be satisfied by detail in the tip alone, but not by independent police work.
23 Justice STEVENS is correct, post, at 2360, that one of the informant’s predictions proved to be inaccurate. However, I agree with
the Court, ante, at 2335, n. 14, that an informant need not be infallible.
24 It is also true, as Justice STEVENS points out, post, at 2360, n. 3, that the fact that respondents were last seen leaving West Palm
Beach on a northbound interstate highway is far from conclusive proof that they were heading directly to Bloomington.
25 I have already indicated my view, supra, at 2329-2330, that such a “bare-bones” affidavit could not be the basis for a good-faith
issuance of a warrant.
26 Bridger v. State, 503 S.W.2d 801 (Tex.Cr.App.1974), and People v. Palanza, 55 Ill.App.3d 1028, 13 Ill.Dec. 752, 371 N.E.2d 687
(Ill.App.1978), which the Court describes ante, at 2330, n. 9, appear to me to be excellent examples of overly-technical
applications of the Aguilar-Spinelli standard. The holdings in these cases could easily be disapproved without reliance on a
“totality of the circumstances” analysis.
1 Although the warrant was issued under the Federal Rules of Criminal Procedure, the Court stated that “[t]he provisions of these
Rules must be read in light of the constitutional requirements they implement.” Giordenello v. United States, 357 U.S. 480, 485,
78 S.Ct. 1245, 1249, 2 L.Ed.2d 1503 (1958). See Aguilar v. Texas, 378 U.S. 108, 112, n. 3, 84 S.Ct. 1509, 1512, n. 3, 12 L.Ed.2d
723 (1964) (“The principles announced in Giordenello derived ... from the Fourth Amendment, and not from our supervisory
power”).
2 The Court noted that approval of the affidavit before it “would open the door to easy circumvention of the rule announced in
Nathanson and Giordenello.” Aguilar v. Texas, supra, at 114, n. 4, 84 S.Ct., at 1514, n. 4. The Court stated:
“A police officer who arrived at the ‘suspicion,’ ‘belief’ or ‘mere conclusion’ that narcotics were in someone’s possession could
not obtain a warrant. But he could convey this conclusion to another police officer, who could then secure the warrant by swearing
that he had ‘received reliable information from a credible person’ that the narcotics were in someone’s possession.” Ibid.
3 There is some tension between Draper v. United States, 358 U.S. 307, 79 S.Ct. 329, 3 L.Ed.2d 327 (1959), and Aguilar. In Draper,
the Court considered the validity of a warrantless arrest based on an informant’s tip and police corroboration of certain details of
the tip. The informant, who in the past had always given accurate and reliable information, told the police that Draper was peddling
narcotics. The informant later told the police that Draper had left for Chicago by train to pick up some heroin and would return by
train on the morning of one of two days. The informant gave the police a detailed physical description of Draper and of the
clothing he was wearing. The informant also said that Draper would be carrying a tan zipper bag and that he walked very fast. 358
U.S., at 309, 79 S.Ct., at 331.
On the second morning specified by the informant, the police saw a man “having the exact physical attributes and wearing the
precise clothing described by [the informant], alight from an incoming Chicago train and start walking ‘fast’ toward the exit.” Id.,
at 309-310, 79 S.Ct., at 331. The man was carrying a tan zipper bag. The police arrested him and searched him incident to the
arrest. Ibid.
The Court found that the arrest had been based on probable cause. Having verified every detail of the tip “except whether [Draper]
had accomplished his mission and had the three ounces of heroin on his person or in his bag,” id., at 313, 79 S.Ct., at 333, the
police “had ‘reasonable grounds’ to believe that the remaining unverified bit of [the informant’s] information ... was likewise true.”
Ibid.
There is no doubt that the tip satisfied Aguilar’s veracity prong. The informant had given accurate information in the past.
Moreover, under Spinelli, the police corroborated most of the details of the informant’s tip. See Spinelli v. United States, 393 U.S.,
at 417, 89 S.Ct., at 589; id., at 426-427, 89 S.Ct., at 594-595 (WHITE, J., concurring); infra, at 2354, and n. 4. There is some
question, however, about whether the tip satisfied Aguilar ‘s basis of knowledge prong. The fact that an informant is right about
75

most things may suggest that he is credible, but it does not establish that he has acquired his information in a reliable way. See
Spinelli v. United States, supra, at 426-427, 89 S.Ct., at 594-595 (WHITE, J., concurring). Spinelli ‘s “self-verifying detail”
element resolves this tension. As one commentator has suggested, “under Spinelli, the Draper decision is sound as applied to its
facts.” Note, The Informer’s Tip As Probable Cause for Search or Arrest, 54 Cornell L.Rev. 958, 964, n. 34 (1969).
4 The Court stated that the FBI’s independent investigative efforts could not “support both the inference that the informer was
generally trustworthy and that he had made his charge against Spinelli on the basis of information obtained in a reliable way.”
Spinelli v. United States, supra, at 417, 89 S.Ct., at 589. The Court suggested that Draper again provided “a relevant comparison.”
Ibid. Once the police had corroborated most of the details of the tip in Draper “[i]t was ... apparent that the informant had not been
fabricating his report out of whole cloth; since the report was of the sort which in common experience may be recognized as having
been obtained in a reliable way, it was perfectly clear that probable cause had been established.” Id., at 417-418, 89 S.Ct., at 589-
590.
It is the Court’s citation of Draper which creates most of the confusion. The informant’s credibility was not at issue in Draper
irrespective of the corroboration of the details of his tip. See n. 3, supra. The Court’s opinion, therefore, might be read as
suggesting that corroboration also could satisfy Aguilar’s basis of knowledge test. I think it is more likely, however, especially in
view of the discussion infra, at 2356, that the Court simply was discussing an alternative means of satisfying Aguilar ‘s veracity
prong, using the facts of Draper as an example, and relying on its earlier determination that the detail of the tip in Draper was selfverifying.
See 393 U.S., at 416-417, 89 S.Ct., at 589-590. It is noteworthy that although the affiant in Spinelli had sworn that the
informer was reliable, “he [had] offered the magistrate no reason in support of this conclusion.” Id., at 416, 89 S.Ct., at 589.
Aguilar ‘s veracity prong, therefore, was not satisfied. Ibid.
5 After concluding that the tip was not sufficient to support a finding of probable cause, the Court stated:
“This is not to say that the tip was so insubstantial that it could not properly have counted in the magistrate’s determination. Rather,
it needed some further support. When we look to the other parts of the application, however, we find nothing alleged which would
permit the suspicions engendered by the informant’s report to ripen into a judgment that a crime was probably being committed.”
Spinelli v. United States, 393 U.S., at 418, 89 S.Ct., at 590.
The Court went on to suggest that corroboration of incriminating facts would be needed. See ibid.
6 As noted, supra, at 2353-2356, Aguilar and Spinelli inform the police of what information they have to provide and magistrates of
what information they should demand. This advances the important process value, which is intimately related to substantive Fourth
Amendment concerns, of having magistrates, rather than police, or informants, determine whether there is probable cause to
support the issuance of a warrant. We want the police to provide magistrates with the information on which they base their
conclusions so that magistrates can perform their important function. When the police rely on facts about which they have personal
knowledge, requiring them to disclose those facts to magistrates imposes no significant burden on the police. When the police rely
on information obtained from confidential informants, requiring the police to disclose the facts on which the informants based their
conclusions imposes a more substantial burden on the police, but it is one that they can meet because they presumably have access
to their confidential informants.
In cases in which the police rely on information obtained from an anonymous informant, the police, by hypothesis, cannot obtain
further information from the informant regarding the facts and circumstances on which the informant based his conclusion. When
the police seek a warrant based solely on an anonymous informants’ tip, therefore, they are providing the magistrate with all the
information on which they have based their conclusion. In this respect, the command of Aguilar and Spinelli has been met and the
process value identified above has been served. But Aguilar and Spinelli advance other values which argue for their application
even to anonymous informants’ tips. They structure the magistrate’s probable cause inquiry and, more importantly, they guard
against findings of probable cause, and attendant intrusions, based on anything other than information which magistrates
reasonably can conclude has been obtained in a reliable way by an honest or credible person.
7 In Jaben v. United States, 381 U.S. 214, 85 S.Ct. 1365, 14 L.Ed.2d 345 (1965), the Court considered whether there was probable
cause to support a complaint charging petitioner with willfully filing a false tax return. Id., at 221, 85 S.Ct., at 1369. After
reviewing the extensive detail contained in the complaint, id., at 223, 85 S.Ct., at 1370, the Court expressly distinguished tax
offenses from other types of offenses:
“Some offenses are subject to putative establishment by blunt and concise factual allegations, e.g., ‘A saw narcotics in B ‘s
possession,’ whereas ‘A saw B file a false tax return’ does not mean very much in a tax evasion case. Establishment of grounds for
belief that the offense of tax evasion has been committed often requires a reconstruction of the taxpayer’s income from many
individually unrevealing facts which are not susceptible of a concise statement in a complaint. Furthermore, unlike narcotics
informants, for example, whose credibility may often be suspect, the sources in this tax evasion case are much less likely to
produce false or untrustworthy information. Thus, whereas some supporting information concerning the credibility of informants in
narcotics cases or other common garden varieties of crime may be required, such information is not so necessary in the context of
the case before us.” Id., at 223-224, 85 S.Ct., at 1370-1371.
Obviously, Jaben is not inconsistent with Aguilar and involved no general rejection of the Aguilar standards.
76

8 Rugendorf v. United States, 376 U.S. 528, 84 S.Ct. 825, 11 L.Ed.2d 887 (1964); Ker v. California, 374 U.S. 23, 83 S.Ct. 1623, 10
L.Ed.2d 726 (1963); Jones v. United States, 362 U.S. 257, 80 S.Ct. 725, 4 L.Ed.2d 697 (1960).
9 The Court also argues that “[i]f the affidavits submitted by police officers are subjected to the type of scrutiny some courts have
deemed appropriate, police might well resort to warrantless searches, with the hope of relying on consent or some other exception
to the warrant clause that might develop at the time of the search.” Ante, at 2331. If the Court is suggesting, as it appears to be, that
the police will intentionally disregard the law, it need only be noted in response that the courts are not helpless to deal with such
conduct. Moreover, as was noted in Coolidge v. New Hampshire, 403 U.S. 443, 91 S.Ct. 2022, 29 L.Ed.2d 564 (1971):
“[T]he most basic constitutional rule in this area is that ‘searches conducted outside the judicial process, without prior approval by
judge or magistrate, are per se unreasonable under the Fourth Amendment-subject only to a few specifically established and welldelineated
exceptions.’ The exceptions are ‘jealously and carefully drawn,’ and there must be ‘a showing by those who seek
exemption ... that the exigencies of the situation made that course imperative.’ ‘[T]he burden is on those seeking the exemption to
show the need for it.’ ” Id., at 454-455, 91 S.Ct., at 2031-2032 (plurality opinion) (footnotes omitted).
It therefore would appear to be not only inadvisable, but also unavailing, for the police to conduct warrantless searches in “the
hope of relying on consent or some other exception to the warrant clause that might develop at the time of the search.” Ante, at
2331.
1 The anonymous note suggested that she was going down on Wednesday, App. 1a, but for all the officers knew she had been in
Florida for a month. App. 10b-13b.
2 Lance does not appear to have behaved suspiciously in flying down to Florida. He made a reservation in his own name and gave an
accurate home phone number to the airlines. Compare Florida v. Royer, ---U.S. ----, ----, n. 2, 103 S.Ct. 1319, 1322, n. 2, 75
L.Ed.2d 229 (1983); United States v. Mendenhall, 446 U.S. 544, 548, 100 S.Ct. 1870, 1874, 64 L.Ed.2d 497 (1980) (Stewart, J.,
announcing the judgment). And Detective Mader’s affidavit does not report that he did any of the other things drug couriers are
notorious for doing, such as paying for the ticket in cash, Royer, supra, 460 U.S., at ----, n. 2, 103 S.Ct., at 1322, n. 2, dressing
casually, ibid., looking pale and nervous, ibid.; Mendenhall, supra, 446 U.S., at 548, 100 S.Ct., at 1874, improperly filling out
baggage tags, Royer, supra, 460 U.S., at ----, n. 2, 103 S.Ct., at 1322, n. 2, carrying American Tourister luggage, ibid., not carrying
any luggage, Mendenhall, supra, 446 U.S., at 564-565, 100 S.Ct., at 1882-1883 (POWELL, J., concurring in part and concurring in
the judgment), or changing airlines en route, ibid.
3 Detective Mader’s affidavit hinted darkly that the couple had set out upon “that interstate highway commonly used by travelers to
the Chicago area.” But the same highway is also commonly used by travelers to Disney World, Sea World, and Ringling Brothers
and Barnum and Bailey Circus World. It is also the road to Cocoa Beach, Cape Canaveral, and Washington, D.C. I would venture
that each year dozens of perfectly innocent people fly to Florida, meet a waiting spouse, and drive off together in the family car.
4 The Court purports to rely on the proposition that “if the [anonymous] informant could predict with considerable accuracy the
somewhat unusual travel plans of the Gates, he probably also had a reliable basis for his statements that the Gates kept a large
quantity of drugs in their home.” Ante, at 2336, n. 14 (emphasis added). Even if this syllogism were sound, but see Spinelli v.
United States, 393 U.S. 410, 427, 89 S.Ct. 584, 594, 21 L.Ed.2d 637 (1969) (WHITE, J., concurring), its premises are not met in
this case.
5 The officers did not enter the unoccupied house as soon as the warrant issued; instead, they waited until the Gates returned. It is
unclear whether they waited because they wanted to execute the warrant without unnecessary property damage or because they had
doubts about whether the informant’s tip was really valid. In either event their judgment is to be commended.
6 It is a truism that “a search warrant is valid only if probable cause has been shown to the magistrate and that an inadequate showing
may not be rescued by post-search testimony on information known to the searching officers at the time of the search.” Rice v.
Wolff, 513 F.2d 1280 (CA8 1975). See Coolidge v. New Hampshire, 403 U.S. 443, 450-451, 91 S.Ct. 2022, 2029-2030, 29 L.Ed.2d
564 (1971); Whiteley v. Warden, 401 U.S. 560, 565, n. 8, 91 S.Ct. 1031, 1035, n. 8, 28 L.Ed.2d 306 (1971); Aguilar v. Texas, 378
U.S. 108, 109, n. 1, 84 S.Ct. 1509, 1511, n. 1, 12 L.Ed.2d 723 (1964); Jones v. United States, 357 U.S. 493, 497-498, 78 S.Ct.
1253, 1256-1257, 2 L.Ed.2d 1514 (1958); Giordenello v. United States, 357 U.S. 480, 486, 78 S.Ct. 1245, 1250, 2 L.Ed.2d 1503
(1958); Taylor v. United States, 286 U.S. 1, 6, 52 S.Ct. 466, 467, 76 L.Ed. 951 (1932); Agnello v. United States, 269 U.S. 20, 33,
46 S.Ct. 4, 6, 70 L.Ed. 145 (1925).
7 Draper v. United States, 358 U.S. 307, 79 S.Ct. 329, 3 L.Ed.2d 327 (1959), affords no support for today’s holding. That case did
not involve an anonymous informant. On the contrary, as the Court twice noted, Mr. Hereford was “employed for that purpose and
[his] information had always been found accurate and reliable.” Id., at 313, 79 S.Ct., at 333; see id., at 309, 79 S.Ct., at 331. In this
case, the police had no prior experience with the informant, and some of his or her information in this case was unreliable and
77

inaccurate.
8 The Court holds that what were heretofore considered two independent “prongs”-“veracity” and “basis of knowledge”-are now to
be considered together as circumstances whose totality must be appraised. Ante, at 2329. “A deficiency in one may be compensated
for, in determining the overall reliability of a tip, by a strong showing as to the other, or by some other indicia of reliability.” Ibid.
Yet in this case, the lower courts found neither factor present. App. 12a. And the supposed “other indicia” in the affidavit take the
form of activity that is not particularly remarkable. I do not understand how the Court can find that the “totality” so far exceeds the
sum of its “circumstances.”
End of Document
© 2012 Thomson Reuters. No claim to original U.S. Government Works.
78

104 S.Ct. 1652
Supreme Court of the United States
UNITED STATES, Petitioner
v.
Bradley Thomas JACOBSEN and Donna Marie
Jacobsen.
No. 82-1167. | Argued Dec. 7, 1983. | Decided April
2, 1984.
Opinion
*111 Justice STEVENS delivered the opinion of the
Court.
During their examination of a damaged package, the
employees of a private freight carrier observed a white
powdery substance, originally concealed within eight
layers of wrappings. They summoned a federal agent,
who removed a trace of the powder, subjected it to a
chemical test and determined that it was cocaine. The
question presented is whether the Fourth Amendment
required the agent to obtain a warrant before he did so.
The relevant facts are not in dispute. Early in the morning
of May 1, 1981, a supervisor at the Minneapolis-St. Paul
airport Federal Express office asked the office manager to
look at a package that had been damaged and torn by a
forklift. They then opened the package in order to
examine its contents pursuant to a written company policy
regarding insurance claims.
The container was an ordinary cardboard box wrapped in
brown paper. Inside the box five or six pieces of crumpled
newspaper covered a tube about 10 inches long; the tube
was made of the silver tape used on basement ducts. The
supervisor and office manager cut open the tube, and
found a series of four zip-lock plastic bags, the outermost
enclosing the other three and the innermost containing
about six and a half ounces of white powder. When they
observed the white powder in the innermost bag, they
notified the Drug Enforcement Administration. Before the
first DEA agent arrived, they replaced the plastic bags in
the tube and put the tube and the newspapers back into the
box.
When the first federal agent arrived, the box, still
wrapped in brown paper, but with a hole punched in its
79
side and the top open, was placed on a desk. The agent
saw that one end of the tube had been slit open; he
removed the four plastic bags from the tube and saw the
white powder. He then opened each of the four bags and
removed a trace of the *112 white substance with a knife
blade. A field test made on the spot identified the
substance as cocaine.1
In due course, other agents arrived, made a second field
test, rewrapped the package, obtained a warrant to search
the place to which it was addressed, executed the warrant,
and arrested respondents. After they were indicted for the
crime of possessing an illegal substance with intent to
distribute, their motion to suppress the evidence on the
ground that the warrant was the product of an illegal
search and seizure was denied; they were tried and
convicted, and appealed. The Court of Appeals reversed.
It held that the validity of the search warrant depended on
the validity of the agents’ warrantless test of the white
powder,2 that **1656 the testing constituted a significant
expansion of the earlier private search, and that a warrant
was required. 683 F.2d 296 (CA8 1982).
As the Court of Appeals recognized, its decision
conflicted with a decision of another court of appeals on
comparable facts, United States v. Barry, 673 F.2d 912
(CA6), cert. denied, 459 U.S. 927, 103 S.Ct. 238, 74
L.Ed.2d 188 (1982).3 For that reason, and because *113
field tests play an important role in the enforcement of the
narcotics laws, we granted certiorari, 460 U.S. 1021, 103
S.Ct. 1271, 75 L.Ed.2d 493 (1983).
I
[1] [2] [3] The first clause of the Fourth Amendment
provides that the “right of the people to be secure in their
persons, houses, papers and effects, against unreasonable
searches and seizures, shall not be violated....” This text
protects two types of expectations, one involving
“searches,” the other “seizures.” A “search” occurs when
an expectation of privacy that society is prepared to
consider reasonable is infringed.4 A “seizure” of property
occurs when there is some meaningful interference with
an individual’s possessory interests in that property.5 This
Court has also consistently construed this protection as
proscribing only governmental action; it is wholly
inapplicable “to a search or seizure, even an unreasonable
one, effected by a private individual not acting as an agent
of the Government or with the participation or knowledge

of any governmental official.” Walter v. *114 United
States, 447 U.S. 649, 662, 100 S.Ct. 2395, 2404, 65
L.Ed.2d 410 (1980) (BLACKMUN, J., dissenting).6
[4] [5] [6] When the wrapped parcel involved in this case
was delivered to the **1657 private freight carrier, it was
unquestionably an “effect” within the meaning of the
Fourth Amendment. Letters and other sealed packages are
in the general class of effects in which the public at large
has a legitimate expectation of privacy; warrantless
searches of such effects are presumptively unreasonable.7
Even when government agents may lawfully seize such a
package to prevent loss or destruction of suspected
contraband, the Fourth Amendment requires that they
obtain a warrant before examining the contents of such a
package.8 Such a warrantless search could not be
characterized as reasonable simply because, after the
official invasion of privacy occurred, contraband is
discovered.9 Conversely, in this case the fact that agents
of the private carrier independently opened the package
and made an examination that might have been
impermissible for a government agent *115 cannot render
otherwise reasonable official conduct unreasonable. The
reasonableness of an official invasion of the citizen’s
privacy must be appraised on the basis of the facts as they
existed at the time that invasion occurred.
[7] The initial invasions of respondents’ package were
occasioned by private action. Those invasions revealed
that the package contained only one significant item, a
suspicious looking tape tube. Cutting the end of the tube
and extracting its contents revealed a suspicious looking
plastic bag of white powder. Whether those invasions
were accidental or deliberate,10 and whether they were
reasonable or unreasonable, they did not violate the
Fourth Amendment because of their private character.
[8] The additional invasions of respondents’ privacy by
the government agent must be tested by the degree to
which they exceeded the scope of the private search. That
standard was adopted by a majority of the Court in Walter
v. United States, 447 U.S. 649, 100 S.Ct. 2395, 65
L.Ed.2d 410 (1980). In Walter a private party had opened
a misdirected carton, found rolls of motion picture films
that appeared to be contraband, and turned the carton over
to the Federal Bureau of Investigation. Later, without
obtaining a warrant, FBI agents obtained a projector and
viewed the films. While there was no single opinion of
the Court, a majority did agree on the appropriate analysis
of a governmental search which follows on the heels of a
private one. Two Justices took the position:
“If a properly authorized official search is limited by the
80
particular terms of its authorization, at least the same kind
of strict limitation must be applied **1658 to any official
*116 use of a private party’s invasion of another person’s
privacy. Even though some circumstances-for example, if
the results of the private search are in plain view when
materials are turned over to the Government-may justify
the Government’s reexamination of the materials, surely
the Government may not exceed the scope of the private
search unless it has the right to make an independent
search. In these cases, the private party had not actually
viewed the films. Prior to the Government’s screening
one could only draw inferences about what was on the
films. The projection of the films was a significant
expansion of the search that had been conducted
previously by a private party and therefore must be
characterized as a separate search.” Id., at 657, 100 S.Ct.,
at 2401 (opinion of STEVENS, J., joined by Stewart, J.)
(footnote omitted).11
Four additional Justices, while disagreeing with this
characterization of the scope of the private search, were
also of the view that the legality of the governmental
search must be tested by the scope of the antecedent
private search.
“Under these circumstances, since the L’Eggs employees
so fully ascertained the nature of the films before
contacting the authorities, we find that the FBI’s
subsequent viewing of the movies on a projector did not
‘change the nature of the search’ and was not an
additional search subject to the warrant requirement.” Id.,
at 663-664, 100 S.Ct., at 2405-2406 (BLACKMUN, J.,
dissenting, joined by BURGER, C.J., POWELL and
REHNQUIST, JJ.) (footnote omitted) (quoting *117
United States v. Sanders, 592 F.2d 788, 793-794 (CA5
1979), rev’d sub nom. Walter v. United States, 447 U.S.
649, 100 S.Ct. 2395, 65 L.Ed.2d 410 (1980)).12
[9] This standard follows from the analysis applicable
when private parties reveal other kinds of private
information to the authorities. It is well-settled that when
an individual reveals private information to another, he
assumes the risk that his confidant will reveal that
information to the authorities, and if that occurs the
Fourth Amendment does not prohibit governmental use of
that information. Once frustration of the original
expectation of privacy occurs, the Fourth Amendment
does not prohibit governmental use of the now-nonprivate
information: “This Court has held repeatedly that the
Fourth Amendment does not prohibit the obtaining of
information revealed to a third party and conveyed by him
to Government authorities, even if the information is
revealed on the assumption that it will be used only for a
limited purpose and the confidence placed in a third party

will not be betrayed.” United States v. Miller, 425 U.S.
435, 443, 96 S.Ct. 1619, 1624, 48 L.Ed.2d 71 (1976).13
The Fourth Amendment is implicated only if the
authorities use information with respect **1659 to which
the expectation of privacy has not already been frustrated.
In such a case the authorities have not relied on what is in
effect a private *118 search, and therefore presumptively
violate the Fourth Amendment if they act without a
warrant.14
In this case, the federal agents’ invasions of respondents’
privacy involved two steps: first, they removed the tube
from the box, the plastic bags from the tube and a trace of
powder from the innermost bag; second, they made a
chemical test of the powder. Although we ultimately
conclude that both actions were reasonable for essentially
the same reason, it is useful to discuss them separately.
II
[10] When the first federal agent on the scene initially
saw the package, he knew it contained nothing of
significance except a tube containing plastic bags and,
ultimately, white powder. It is not entirely clear that the
powder was visible to him before he removed the tube
from the box.15 Even if the white *119 powder was not
itself in “plain view” because it was still enclosed in so
many containers and covered with papers, there was a
virtual certainty that nothing else of significance was in
the package and that a manual inspection of the tube and
its contents would not tell him anything more than he
already had been told. Respondents do not dispute that the
Government could utilize the Federal Express employees’
testimony concerning the contents of the package. If that
is the case, it hardly infringed respondents’ privacy for the
agents to reexamine the contents of the open package by
brushing aside a crumpled newspaper and picking up the
tube. The advantage the Government gained thereby was
merely avoiding the risk of a flaw in the employees’
recollection, rather than in further infringing respondents’
privacy. Protecting the risk of misdescription hardly
enhances any legitimate privacy interest, and is not
protected by the Fourth Amendment.16 Respondents
**1660 could have no privacy interest in the contents of
the package, since it remained unsealed and since the
Federal Express employees had just examined the
package and had, of their own accord, invited the federal
agent to their offices for the express purpose of viewing
its contents. The agent’s viewing of what a private party
had freely made available for his inspection did not
81
violate the Fourth Amendment. *120 See Coolidge v. New
Hampshire, 403 U.S. 443, 487-490, 91 S.Ct. 2022, 2048-
2050, 29 L.Ed.2d 564 (1971); Burdeau v. McDowell, 256
U.S. 465, 475-476, 41 S.Ct. 574, 576, 65 L.Ed. 1048
(1921).
Similarly, the removal of the plastic bags from the tube
and the agent’s visual inspection of their contents enabled
the agent to learn nothing that had not previously been
learned during the private search.17 It infringed no
legitimate expectation of privacy and hence was not a
“search” within the meaning of the Fourth Amendment.
[11] While the agents’ assertion of dominion and control
over the package and its contents did constitute a
“seizure,”18 that *121 seizure was not unreasonable. The
fact that, prior to the field test, respondents’ privacy
interest in the contents of the package had been largely
compromised, is highly relevant to the reasonableness of
the agents’ conduct in this respect. The agents had already
learned a great deal about the contents of the package
from the Federal Express employees, all of which was
consistent with what they could see. The package itself,
which had previously been opened, remained unsealed,
and the Federal Express employees had invited the agents
to examine its contents. Under these circumstances, the
package could no longer support any expectation of
privacy; it was just like a balloon “the distinctive
character [of which] spoke volumes as to its contents,
particularly to the trained eye of the officer,” Texas v.
Brown, 460 U.S. ----, ----, 103 S.Ct. 1535, 1545, 75
L.Ed.2d 502 (1983) (plurality opinion); see also id., at ----
, 103 S.Ct., at 1543 (POWELL, J., concurring in the
judgment); or the hypothetical gun case in Arkansas v.
Sanders, 442 U.S. 753, 764-765, n. 13, 99 S.Ct. 2586,
2593-2594, n. 13, 61 L.Ed.2d 235 (1979). **1661 Such
containers may be seized, at least temporarily, without a
warrant.19 Accordingly, since it was apparent that the
tube and plastic bags contained contraband and little else,
this warrantless seizure was reasonable,20 for it is wellsettled
that it is constitutionally reasonable for law
enforcement officials to seize “effects” that cannot
support a justifiable expectation *122 of privacy without a
warrant, based on probable cause to believe they contain
contraband.21
III
[12] The question remains whether the additional
intrusion occasioned by the field test, which had not been
conducted by the Federal Express agents and therefore

exceeded the scope of the private search, was an unlawful
“search” or “seizure” within the meaning of the Fourth
Amendment.
The field test at issue could disclose only one fact
previously unknown to the agent-whether or not a
suspicious white powder was cocaine. It could tell him
nothing more, not even whether the substance was sugar
or talcum powder. We must first determine whether this
can be considered a “search” subject to the Fourth
Amendment-did it infringe an expectation of privacy that
society is prepared to consider reasonable
The concept of an interest in privacy that society is
prepared to recognize as reasonable is, by its very nature,
critically different from the mere expectation, however
well justified, that certain facts will not come to the
attention of the authorities.22 Indeed, this distinction
underlies the rule that *123 Government may utilize
information voluntarily disclosed to a governmental
informant, despite the criminal’s reasonable expectation
that his associates would not disclose confidential
information to the authorities. See United States v. White,
401 U.S. 745, 751-752, 91 S.Ct. 1122, 1125-1126, 28
L.Ed.2d 453 (1971) (plurality opinion).
A chemical test that merely discloses whether or not a
particular substance is cocaine does not compromise any
legitimate interest in privacy. This conclusion is not
dependent on the result of any particular **1662 test. It is
probably safe to assume that virtually all of the tests
conducted under circumstances comparable to those
disclosed by this record would result in a positive finding;
in such cases, no legitimate interest has been
compromised. But even if the results are negative-merely
disclosing that the substance is something other than
cocaine-such a result reveals nothing of special interest.
Congress has decided-and there is no question about its
power to do so-to treat the interest in “privately”
possessing cocaine as illegitimate; thus governmental
conduct that can reveal whether a substance is cocaine,
and no other arguably “private” fact, compromises no
legitimate privacy interest.23
This conclusion is dictated by United States v. Place, 462
U.S. 696, 103 S.Ct. 2637, 77 L.Ed.2d 110 (1983), in
which the Court held that subjecting luggage to a “sniff
test” by a trained narcotics detection dog was not a
“search” within the meaning of the Fourth Amendment:
*124 “A ‘canine sniff’ by a well-trained narcotics
detection dog, however, does not require opening of the
luggage. It does not expose noncontraband items that
otherwise would remain hidden from public view, as
82
does, for example, an officer’s rummaging through the
contents of the luggage. Thus, the manner in which
information is obtained through this investigative
technique is much less intrusive than a typical search.
Moreover, the sniff discloses only the presence or absence
of narcotics, a contraband item. Thus, despite the fact that
the sniff tells the authorities something about the contents
of the luggage, the information obtained is limited.” Id., at
----, 103 S.Ct., at 2644.24
Here, as in Place, the likelihood that official conduct of
the kind disclosed by the record will actually compromise
any legitimate interest in privacy seems much too remote
to characterize the testing as a search subject to the Fourth
Amendment.
We have concluded, in Part II, supra, that the initial
“seizure” of the package and its contents was reasonable.
Nevertheless, as Place also holds, a seizure lawful at its
inception can nevertheless violate the Fourth Amendment
because its manner of execution unreasonably infringes
possessory interests protected by the Fourth
Amendment’s prohibition on “unreasonable seizures.”25
Here, the field test did affect respondents’ possessory
interests protected by the Amendment, since by
destroying a quantity of the powder it converted *125
what had been only a temporary deprivation of possessory
interests into a permanent one. To assess the
reasonableness of this conduct, “[w]e must balance the
nature and quality of the intrusion on the individual’s
Fourth Amendment interests against the importance of the
governmental interests alleged to justify the intrusion.”
Id., at ----, 103 S.Ct., at 2642.26
**1663 Applying this test, we conclude that the
destruction of the powder during the course of the field
test was reasonable. The law enforcement interests
justifying the procedure were substantial; the suspicious
nature of the material made it virtually certain that the
substance tested was in fact contraband. Conversely,
because only a trace amount of material was involved, the
loss of which appears to have gone unnoticed by
respondents, and since the property had already been
lawfully detained, the “seizure” could, at most, have only
a de minimis impact on any protected property interest.
Cf. Cardwell v. Lewis, 417 U.S. 583, 591-592, 94 S.Ct.
2464, 2469-2470, 41 L.Ed.2d 325 (1974) (plurality
opinion) (examination of automobile’s tires and taking of
paint scrapings was a de minimis invasion of
constitutional interests).27 Under these circumstances, the
safeguards of a warrant would only minimally advance
Fourth Amendment interests. This warrantless “seizure”
was reasonable.28

*126 In sum, the federal agents did not infringe any
constitutionally protected privacy interest that had not
already been frustrated as the result of private conduct. To
the extent that a protected possessory interest was
infringed, the infringement was de minimis and
constitutionally reasonable. The judgment of the Court of
Appeals is
Reversed.
Justice WHITE, concurring in part and concurring in the
judgment.
It is relatively easy for me to concur in the judgment in
this case, since in my view the case should be judged on
the basis of the Magistrate’s finding that, when the first
DEA agent arrived, the “tube was in plain view in the box
and the bags of white powder were visible from the end of
the tube.” App. to Pet. for Cert. 18a. Although this finding
was challenged before the District Court, that court found
it unnecessary to pass on the issue. Id., at 12a-13a. As I
understand its opinion, however, the Court of Appeals
accepted the Magistrate’s finding: the Federal Express
manager “placed the bags back in the tube, leaving them
visible from the tube’s end, and placed the tube back in
the box”; he later gave the box to the DEA agent, who
“removed the tube from the open box, took the bags out
of the tube, and extracted a sample of powder.” 683 F.2d
296, 297 (CA8 1982). At the very least, the Court of
Appeals assumed that *127 the contraband was in plain
view. The Court of Appeals then proceeded to consider
whether the federal agent’s field test was an illegal
extension of the private search, and it invalidated the field
test solely for that reason.
Particularly since respondents argue here that whether or
not the contraband was in plain view when the federal
agent **1664 arrived is irrelevant and that the only issue
is the validity of the field test, see, e.g., Brief for
Respondents 25, n. 11; Tr. of Oral Arg. 28, I would
proceed on the basis that the clear plastic bags were in
plain view when the agent arrived and that the agent thus
properly observed the suspected contraband. On that
basis, I agree with the Court’s conclusion in Part III that
the Court of Appeals erred in holding that the type of
chemical test conducted here violated the Fourth
Amendment.
The Court, however, would not read the Court of
Appeals’ opinion as having accepted the Magistrate’s
finding. It refuses to assume that the suspected contraband
83
was visible when the first DEA agent arrived on the
scene, conducts its own examination of the record, and
devotes a major portion of its opinion to a discussion that
would be unnecessary if the facts were as found by the
Magistrate. The Court holds that even if the bags were not
visible when the agent arrived, his removal of the tube
from the box and the plastic bags from the tube and his
subsequent visual examination of the bags’ contents
“infringed no legitimate expectation of privacy and hence
was not a ‘search’ within the meaning of the Fourth
Amendment” because these actions “enabled the agent to
learn nothing that had not previously been learned during
the private search.” Ante, at 1660 (footnote omitted). I
disagree with the Court’s approach for several reasons.
First, as I have already said, respondents have abandoned
any attack on the Magistrate’s findings; they assert that it
is irrelevant whether the suspected contraband was in
plain view when the first DEA agent arrived and argue
only that the plastic bags could not be opened and their
contents tested *128 without a warrant. In short, they
challenge only the expansion of the private search, place
no reliance on the fact that the plastic bags containing the
suspected contraband might not have been left in plain
view by the private searchers, and do not contend that
their Fourth Amendment rights were violated by the
duplication of the private search they alleged in the
District Court was necessitated by the condition to which
the private searchers returned the package. In these
circumstances, it would be the better course for the Court
to decide the case on the basis of the facts found by the
Magistrate and not rejected by the Court of Appeals, to
consider only whether the alleged expansion of the private
search by the field test violated the Fourth Amendment,
and to leave for another day the question whether federal
agents could have duplicated the prior private search had
that search not left the contraband in plain view.
Second, if the Court feels that the Magistrate may have
erred in concluding that the white powder was in plain
view when the first agent arrived and believes that
respondents have not abandoned their challenge to the
agent’s duplication of the prior private search, it
nevertheless errs in responding to that challenge. The task
of reviewing the Magistrate’s findings belongs to the
District Court and the Court of Appeals in the first
instance. We should request that they perform that
function, particularly since if the Magistrate’s finding that
the contraband was in plain view when the federal agent
arrived were to be sustained, there would be no need to
address the difficult constitutional question decided today.
The better course, therefore, would be to remand the case

after rejecting the Court of Appeals’ decision invalidating
the field test as an illegal expansion of the private search.
Third, if this case must be judged on the basis that the
plastic bags and their contents were concealed when the
first agent arrived, I disagree with the Court’s conclusion
that the agent could, without a warrant, uncover or
unwrap the tube *129 and remove its contents simply
because a private party had previously done so. The
remainder of this opinion will address this issue.
The governing principles with respect to the constitutional
protection afforded closed containers and packages may
be **1665 readily discerned from our cases. The Court
has consistently rejected proposed distinctions between
worthy and unworthy containers and packages, United
States v. Ross, 456 U.S. 798, 815, 822-823, 102 S.Ct.
2157, 2171-2172, 72 L.Ed.2d 572 (1982); Robbins v.
California, 453 U.S. 420, 425-426, 101 S.Ct. 2841, 2845-
2846, 69 L.Ed.2d 744 (1981) (plurality opinion), and has
made clear that “the Fourth Amendment provides
protection to the owner of every container that conceals
its contents from plain view” and does not otherwise
unmistakably reveal its contents. United States v. Ross,
supra, 456 U.S., at 822-823, 102 S.Ct., at 2171-2172; see
Robbins v. California, supra, 453 U.S., at 427-428, 101
S.Ct., at 2846-2847 (plurality opinion); Arkansas v.
Sanders, 442 U.S. 753, 764, n. 13, 99 S.Ct. 2586, 2593, n.
13, 61 L.Ed.2d 235 (1979). Although law-enforcement
officers may sometimes seize such containers and
packages pending issuance of warrants to examine their
contents, United States v. Place, 462 U.S. ----, ----, 103
S.Ct. 2637, 2641, 77 L.Ed.2d 110 (1983); Texas v. Brown,
460 U.S. ----, ----, 103 S.Ct. 1535, 1547, 75 L.Ed.2d 502
(1983) (STEVENS, J., concurring in the judgment), the
mere existence of probable cause to believe that a
container or package contains contraband plainly cannot
justify a warrantless examination of its contents. Ante, at
1657; United States v. Ross, supra, 456 U.S., at 809-812,
102 S.Ct., at 2164-2166; Arkansas v. Sanders, supra, 442
U.S., at 762, 99 S.Ct., at 2592; United States v. Chadwick,
433 U.S. 1, 13, and n. 8, 97 S.Ct. 2476, 2485, and n. 8, 53
L.Ed.2d 538 (1977).
This well-established prohibition of warrantless searches
has applied notwithstanding the manner in which the
police obtained probable cause. The Court now for the
first time sanctions warrantless searches of closed or
covered containers or packages whenever probable cause
exists as a result of a prior private search. It declares, in
fact, that governmental inspections following on the heels
of private searches are not searches at all as long as the
84
police do no more than the private parties have already
done. In reaching this conclusion, the Court excessively
expands our prior decisions recognizing *130 that the
Fourth Amendment proscribes only governmental action.
Burdeau v. McDowell, 256 U.S. 465, 41 S.Ct. 574, 65
L.Ed. 1048 (1921); Coolidge v. New Hampshire, 403 U.S.
443, 487-490, 91 S.Ct. 2022, 2048-2050, 29 L.Ed.2d 564
(1971).
As the Court observes, the Fourth Amendment “is wholly
inapplicable ‘to a search or seizure, even an unreasonable
one, effected by a private individual not acting as an agent
of the Government or with the participation or knowledge
of any governmental official.’ ” Ante, at 1656 (quoting
Walter v. United States, 447 U.S. 649, 662, 100 S.Ct.
2395, 2404, 65 L.Ed.2d 410 (1980) (BLACKMUN, J.,
dissenting)). Where a private party has revealed to the
police information he has obtained during a private search
or exposed the results of his search to plain view, no
Fourth Amendment interest is implicated because the
police have done no more than fail to avert their eyes.
Coolidge v. New Hampshire, supra, 403 U.S., at 489, 91
S.Ct., at 2049.
The private-search doctrine thus has much in common
with the plain-view doctrine, which is “grounded on the
proposition that once police are lawfully in a position to
observe an item first-hand, its owner’s privacy interest in
that item is lost ....” Illinois v. Andreas, 463 U.S. ----, ----,
103 S.Ct. 3319, 3324, 77 L.Ed.2d 1003 (1983) (emphasis
added). It also shares many of the doctrinal underpinnings
of cases establishing that “the Fourth Amendment does
not prohibit the obtaining of information revealed to a
third party and conveyed by him to Government
authorities,” United States v. Miller, 425 U.S. 435, 443,
96 S.Ct. 1619, 1624, 48 L.Ed.2d 71 (1976), although the
analogy is imperfect since the risks assumed by a person
whose belongings are subjected to a private search are not
comparable to those assumed by one who voluntarily
chooses to reveal his secrets to a companion.
**1666 Undoubtedly, the fact that a private party has
conducted a search “that might have been impermissible
for a government agent cannot render otherwise
reasonable official conduct unreasonable.” Ante, at 1657.
But the fact that a repository of personal property
previously was searched by a private party has never been
used to legitimize governmental conduct that otherwise
would be subject to challenge under *131 the Fourth
Amendment. If government agents are unwilling or
unable to rely on information or testimony provided by a
private party concerning the results of a private search

and that search has not left incriminating evidence in
plain view, the agents may wish to duplicate the private
search to observe first-hand what the private party has
related to them or to examine and seize the suspected
contraband the existence of which has been reported. The
information provided by the private party clearly would
give the agents probable cause to secure a warrant
authorizing such actions. Nothing in our previous cases
suggests, however, that the agents may proceed to
conduct their own search of the same or lesser scope as
the private search without first obtaining a warrant.
Walter v. United States, 447 U.S., at 660-662, 100 S.Ct.,
at 2403-2404 (WHITE, J., concurring in part and
concurring in the judgment).
Walter v. United States, on which the majority heavily
relies in opining that “[t]he additional invasions of
respondents’ privacy by the government agent must be
tested by the degree to which they exceeded the scope of
the private search,” ante, at 1657, does not require that
conclusion. Justice STEVENS’ opinion in Walter does
contain language suggesting that the government is free to
do all of what was done earlier by the private searchers.
But this language was unnecessary to the decision, as
Justice STEVENS himself recognized in leaving open the
question whether “the Government would have been
required to obtain a warrant had the private party been the
first to view [the films],” 447 U.S., at 657, n. 9, 100 S.Ct.,
at 2402, n. 9, and in emphasizing that “[e]ven though
some circumstances-for example, if the results of the
private search are in plain view when materials are
turned over to the Government-may justify the
Government’s re-examination of the materials, surely the
Government may not exceed the scope of the private
search unless it has the right to make an independent
search.” Id., at 657, 100 S.Ct., at 2401 (emphasis added).
Nor does Justice BLACKMUN’S dissent in Walter
necessarily support today’s holding, for it emphasized that
the opened containers *132 turned over to the government
agents “clearly revealed the nature of their contents,” id.,
at 663, 100 S.Ct., at 2405; see id., at 665, 100 S.Ct., at
2406, and the facts of this case, at least as viewed by the
Court, do not support such a conclusion.
Today’s decision also is not supported by the majority’s
reference to cases involving the transmission of
previously private information to the police by a third
party who has been made privy to that information. Ante,
at 1658-1659. The police may, to be sure, use confidences
revealed to them by a third party to establish probable
cause or for other purposes, and the third party may
testify about those confidences at trial without violating
85
the Fourth Amendment. But we have never intimated
until now that an individual who reveals that he stores
contraband in a particular container or location to an
acquaintance who later betrays his confidence has no
expectation of privacy in that container or location and
that the police may thus search it without a warrant.
That, I believe, is the effect of the Court’s opinion. If a
private party breaks into a locked suitcase, a locked car,
or even a locked house, observes incriminating
information, returns the object of his search to its prior
locked condition, and then reports his findings to the
police, the majority apparently would allow the police to
duplicate the prior search on the ground that the private
search vitiated the owner’s expectation of privacy. As
Justice STEVENS has previously observed, this
conclusion **1667 cannot rest on the proposition that the
owner no longer has a subjective expectation of privacy
since a person’s expectation of privacy cannot be altered
by subsequent events of which he was unaware. Walter v.
United States, supra, at 659, n. 12, 100 S.Ct., at 2403 n.
12.
The majority now ignores an individual’s subjective
expectations and suggests that “[t]he reasonableness of an
official invasion of a citizen’s privacy must be appraised
on the basis of the facts as they existed at the time that
invasion occurred.” Ante, at 1657. On that view, however,
the reasonableness of a particular individual’s remaining
expectation of privacy should turn entirely on whether the
private *133 search left incriminating evidence or
contraband in plain view. Cf. Walter v. United States,
supra, at 663, 665, 100 S.Ct., at 2405, 2406
(BLACKMUN, J., dissenting). If the evidence or
contraband is not in plain view and not in a container that
clearly announces its contents at the end of a private
search, the government’s subsequent examination of the
previously searched object necessarily constitutes an
independent, governmental search that infringes Fourth
Amendment privacy interests. Id., at 662, 100 S.Ct., at
2404 (WHITE, J., concurring in part and concurring in the
judgment).
The majority opinion is particularly troubling when one
considers its logical implications. I would be hard-pressed
to distinguish this case, which involves a private search,
from (1) one in which the private party’s knowledge, later
communicated to the government, that a particular
container concealed contraband and nothing else arose
from his presence at the time the container was sealed; (2)
one in which the private party learned that a container
concealed contraband and nothing else when it was

previously opened in his presence; or (3) one in which the
private party knew to a certainty that a container
concealed contraband and nothing else as a result of
conversations with its owner. In each of these cases, the
approach adopted by the Court today would seem to
suggest that the owner of the container has no legitimate
expectation of privacy in its contents and that government
agents opening that container without a warrant on the
strength of information provided by the private party
would not violate the Fourth Amendment.
Because I cannot accept the majority’s novel extension of
the private-search doctrine and its implications for the
entire concept of legitimate expectations of privacy, I
concur only in Part III of its opinion and in the judgment.
Justice BRENNAN, with whom Justice MARSHALL
joins, dissenting.
This case presents two questions: first whether law
enforcement officers may conduct a warrantless search of
the *134 contents of a container merely because a private
party has previously examined the container’s contents
and informed the officers of its suspicious nature; and
second, whether law enforcement officers may conduct a
chemical field test of a substance once the officers have
legitimately located the substance. Because I disagree
with the Court’s treatment of each of these issues, I
respectfully dissent.
I
I agree entirely with Justice WHITE that the Court has
expanded the reach of the private-search doctrine far
beyond its logical bounds. Ante, at 1655-1658 (WHITE,
J., concurring in the judgment). It is difficult to
understand how respondents can be said to have no
expectation of privacy in a closed container simply
because a private party has previously opened the
container and viewed its contents. I also agree with
Justice WHITE, however, that if the private party presents
the contents of a container to a law enforcement officer in
such a manner that the contents are plainly visible, the
officer’s visual inspection of the contents does not
constitute a “search” within the meaning of the Fourth
Amendment. Because the record in this case is unclear on
the question whether the contents of respondents’ package
were plainly **1668 visible when the Federal Express
employee showed the package to the DEA officer, I
would remand the case for further factfinding on this
central issue.
II
As noted, I am not persuaded that the DEA officer
actually came upon respondents’ cocaine without
violating the Fourth Amendment and accordingly, I need
not address the legality of the chemical field test. Since
the Court has done so, however, I too will address the
question, assuming, arguendo, that the officer committed
neither an unconstitutional search nor an unconstitutional
seizure prior to the point at which he took the sample of
cocaine out of the plastic bags to conduct the test.
*135 A
I agree that, under the hypothesized circumstances, the
field test in this case was not a search within the meaning
of the Fourth Amendment for the following reasons:
First, the officer came upon the white powder innocently;
second, under the hypothesized circumstances,
respondents could not have had a reasonable expectation
of privacy in the chemical identity of the powder because
the DEA agents were already able to identify it as
contraband with virtual certainty, Texas v. Brown, 460
U.S. ----, ----, 103 S.Ct. 1535, 1547, 75 L.Ed.2d 502
(1983) (STEVENS, J., concurring in the judgment); and
third, the test required the destruction of only a minute
quantity of the powder. The Court, however, has reached
this conclusion on a much broader ground, relying on two
factors alone to support the proposition that the field test
was not a search; first, the fact that the test revealed only
whether or not the substance was cocaine, without
providing any further information; and second, the
assumption that an individual does not have a reasonable
expectation of privacy in such a fact.
The Court asserts that its “conclusion is dictated by
United States v. Place,” ante, at 1662, in which the Court
stated that a “canine sniff” of a piece of luggage did not
constitute a search because it “is less intrusive than a
typical search,” and because it “discloses only the
presence or absence of narcotics, a contraband item.” 462
U.S. ----, ----, 103 S.Ct. 2637, 2644, 77 L.Ed.2d 110
(1983). Presumably, the premise of Place was that an
individual could not have a reasonable expectation of
86

privacy in the presence or absence of narcotics in his
luggage. The validity of the canine sniff in that case,
however, was neither briefed by the parties nor addressed
by the courts below. Indeed, since the Court ultimately
held that the defendant’s luggage had been impermissibly
seized, its discussion of the question was wholly
unnecessary to its judgment. In short, as Justice
BLACKMUN pointed out at the time, “the Court [was]
certainly in no position to consider all the ramifications of
this important issue.” Id., at ----, 103 S.Ct., at 2644-45.
*136 Nonetheless, the Court concluded that
“the canine sniff is sui generis. We are aware of no other
investigative procedure that is so limited both in the
manner in which the information is obtained and in the
content of the information revealed by the procedure.
Therefore, we conclude that the particular course of
investigation that the agents intended to pursue hereexposure
of respondent’s luggage, which was located in a
public place, to a trained canine-did not constitute a
‘search’ within the meaning of the Fourth Amendment.”
Id., at ----, 103 S.Ct., at 2644-45.
As it turns out, neither the Court’s knowledge nor its
imagination regarding criminal investigative techniques
proved very sophisticated, for within one year we have
learned of another investigative procedure that shares
with the dog sniff the same defining characteristics that
led the Court to suggest that the dog sniff was not a
search.
Before continuing along the course that the Court so
hastily charted in Place, it is only prudent to take this
opportunity-in **1669 my view, the first real opportunityto
consider the implications of the Court’s new Fourth
Amendment jurisprudence. Indeed, in light of what these
two cases have taught us about contemporary lawenforcement
methods, it is particularly important that we
analyze the basis upon which the Court has redefined the
term “search” to exclude a broad class of surveillance
techniques. In my view, such an analysis demonstrates
that, although the Court’s conclusion is correct in this
case, its dictum in Place was dangerously incorrect. More
important, however, the Court’s reasoning in both cases is
fundamentally misguided and could potentially lead to the
development of a doctrine wholly at odds with the
principles embodied in the Fourth Amendment.
Because the requirements of the Fourth Amendment
apply only to “searches” and “seizures,” an investigative
technique *137 that falls within neither category need not
87
be reasonable and may be employed without a warrant
and without probable cause, regardless of the
circumstances surrounding its use. The prohibitions of the
Fourth Amendment are not, however, limited to any
preconceived conceptions of what constitutes a search or
a seizure; instead we must apply the constitutional
language to modern developments according to the
fundamental principles that the Fourth Amendment
embodies. Katz v. United States, 389 U.S. 347, 88 S.Ct.
507, 19 L.Ed.2d 576 (1967). See Amsterdam,
Perspectives on the Fourth Amendment, 58 Minn.L.Rev.
349, 356 (1974). Before excluding a class of surveillance
techniques from the reach of the Fourth Amendment,
therefore, we must be certain that none of the techniques
so excluded threatens the areas of personal security and
privacy that the Amendment is intended to protect.
What is most startling about the Court’s interpretation of
the term “search,” both in this case and in Place, is its
exclusive focus on the nature of the information or item
sought and revealed through the use of a surveillance
technique, rather than on the context in which the
information or item is concealed. Combining this
approach with the blanket assumption, implicit in Place
and explicit in this case, that individuals in our society
have no reasonable expectation of privacy in the fact that
they have contraband in their possession, the Court adopts
a general rule that a surveillance technique does not
constitute a search if it reveals only whether or not an
individual possesses contraband.
It is certainly true that a surveillance technique that
identifies only the presence or absence of contraband is
less intrusive than a technique that reveals the precise
nature of an item regardless of whether it is contraband.
But by seizing upon this distinction alone to conclude that
the first type of technique, as a general matter, is not a
search, the Court has foreclosed any consideration of the
circumstances under which the technique is used, and
may very well have paved *138 the way for technology to
override the limits of law in the area of criminal
investigation.
For example, under the Court’s analysis in these cases,
law enforcement officers could release a trained cocainesensitive
dog-to paraphrase the California Court of
Appeal, a “canine cocaine connoisseur”-to roam the
streets at random, alerting the officers to people carrying
cocaine. Cf. People v. Evans, 65 Cal.App.3d 924, 932,
134 Cal.Rptr. 436, 440 (1977). Or, if a device were
developed that, when aimed at a person, would detect
instantaneously whether the person is carrying cocaine,

there would be no Fourth Amendment bar, under the
Court’s approach, to the police setting up such a device
on a street corner and scanning all passersby. In fact, the
Court’s analysis is so unbounded that if a device were
developed that could detect, from the outside of a
building, the presence of cocaine inside, there would be
no constitutional obstacle to the police cruising through a
residential neighborhood and using the device to identify
all homes in which the drug is present. In short, under the
interpretation of the Fourth Amendment first suggested in
Place and first **1670 applied in this case, these
surveillance techniques would not constitute searches and
therefore could be freely pursued whenever and wherever
law enforcement officers desire. Hence, at some point in
the future, if the Court stands by the theory it has adopted
today, search warrants, probable cause, and even
“reasonable suspicion” may very well become notions of
the past. Fortunately, we know from precedents such as
Katz v. United States, supra, overruling the “trespass”
doctrine of Goldman v. United States, 316 U.S. 129, 62
S.Ct. 993, 86 L.Ed. 1322 (1942), and Olmstead v. United
States, 277 U.S. 438, 48 S.Ct. 564, 72 L.Ed. 944 (1928),
that this Court ultimately stands ready to prevent this
Orwellian world from coming to pass.
Although the Court accepts, as it must, the fundamental
proposition that an investigative technique is a search
within the meaning of the Fourth Amendment if it
intrudes upon a privacy expectation that society considers
to be reasonable, *139 ante, at 1661, the Court has
entirely omitted from its discussion the considerations
that have always guided our decisions in this area. In
determining whether a reasonable expectation of privacy
has been violated, we have always looked to the context
in which an item is concealed, not to the identity of the
concealed item. Thus in cases involving searches for
physical items, the Court has framed its analysis first in
terms of the expectation of privacy that normally attends
the location of the item and ultimately in terms of the
legitimacy of that expectation. In United States v.
Chadwick, 433 U.S. 1, 97 S.Ct. 2476, 53 L.Ed.2d 538
(1977), for example, we held that “no less than one who
locks the doors of his home against intruders, one who
safeguards his possessions [by locking them in a
footlocker] is due the protection of the Fourth
Amendment ...” Id., at 11, 97 S.Ct., at 2483. Our holding
was based largely on the observation that, “[b]y placing
personal effects inside a double-locked footlocker,
respondents manifested an expectation that the contents
would remain free from public examination.” Ibid. The
Court made the same point in United States v. Ross, 456
U.S. 798, 822, 102 S.Ct. 2157, 2171, 72 L.Ed.2d 572
88
(1982), where it held that the “Fourth Amendment
provides protection to the owner of every container that
conceals its contents from plain view.” The fact that a
container contains contraband, which indeed it usually
does in such cases, has never altered our analysis.
Similarly, in Katz v. United States, supra, we held that
electronic eavesdropping constituted a search under the
Fourth Amendment because it violated a reasonable
expectation of privacy. In reaching that conclusion, we
focused upon the private context in which the
conversation in question took place, stating that “[w]hat a
person knowingly exposes to the public ... is not a subject
of Fourth Amendment protection.... But what he seeks to
preserve as private, even in an area accessible to the
public, may be constitutionally protected.” Id., 389 U.S.,
at 351-352, 88 S.Ct., at 511-512. Again, the fact that the
conversations involved in Katz were incriminating did not
alter our consideration of the *140 privacy issue. Nor did
such a consideration affect our analysis in Payton v. New
York, 445 U.S. 573, 100 S.Ct. 1371, 63 L.Ed.2d 639
(1980), in which we reaffirmed the principle that the
home is private even though it may be used to harbor a
fugitive.
In sum, until today this Court has always looked to the
manner in which an individual has attempted to preserve
the private nature of a particular fact before determining
whether there is a reasonable expectation of privacy upon
which the government may not intrude without substantial
justification. And it has always upheld the general
conclusion that searches constitute at least “those more
extensive intrusions that significantly jeopardize the sense
of security which is the paramount concern of Fourth
Amendment liberties.” United States v. White, 401 U.S.
745, 786, 91 S.Ct. 1122, 1143, 28 L.Ed.2d 453 (1971)
(Harlan, J., dissenting).
**1671 Nonetheless, adopting the suggestion in Place,
the Court has veered away from this sound and wellsettled
approach and has focused instead solely on the
product of the would-be search. In so doing, the Court has
ignored the fundamental principle that “[a] search
prosecuted in violation of the Constitution is not made
lawful by what it brings to light.” Byars v. United States,
273 U.S. 28, 29, 47 S.Ct. 248, 249, 71 L.Ed. 520 (1927).
The unfortunate product of this departure from precedent
is an undifferentiated rule allowing law enforcement
officers free rein in utilizing a potentially broad range of
surveillance techniques that reveal only whether or not
contraband is present in a particular location. The Court’s
new rule has rendered irrelevant the circumstances

surrounding the use of the technique, the accuracy of the
technique, and the privacy interest upon which it intrudes.
Furthermore, the Court’s rule leaves no room to consider
whether the surveillance technique is employed randomly
or selectively, a consideration that surely implicates
Fourth Amendment concerns. See LaFave, 2 Search and
Seizure § 2.2(f). Although a technique that reveals only
the presence or absence of illegal *141 activity intrudes
less into the private life of an individual under
investigation than more conventional techniques, the fact
remains that such a technique does intrude. In my view,
when the investigation intrudes upon a domain over
which the individual has a reasonable expectation of
privacy, such as his home or a private container, it is
plainly a search within the meaning of the Fourth
Amendment. Surely it cannot be that the individual’s
reasonable expectation of privacy dissipates simply
because a sophisticated surveillance technique is
employed.
This is not to say that the limited nature of the intrusion
has no bearing on the general Fourth Amendment inquiry.
Although there are very few exceptions to the general rule
that warrantless searches are presumptively unreasonable,
the isolated exceptions that do exist are based on a
“balancing [of] the need to search against the invasion
which the search entails.” Camara v. Municipal Court,
387 U.S. 523, 537, 87 S.Ct. 1727, 1735, 18 L.Ed.2d 930
(1967). Hence it may be, for example, that the limited
intrusion effected by a given surveillance technique
renders the employment of the technique, under particular
circumstances, a “reasonable” search under the Fourth
Amendment. See United States v. Place, 462 U.S. ----, ---
-, 103 S.Ct. 2637, 2653, 77 L.Ed.2d 110 (1983)
(BLACKMUN, J., concurring in the judgment) (“a dog
sniff may be a search, but a minimally intrusive one that
could be justified in this situation under Terry”). At least
under this well-settled approach, the Fourth Amendment
inquiry would be broad enough to allow consideration of
the method by which a surveillance technique is
employed as well as the circumstances attending its use.
More important, however, it is only under this approach
that law enforcement procedures, like those involved in
this case and in Place, may continue to be governed by
the safeguards of the Fourth Amendment.
depends on *142 whether the technique intrudes upon a
reasonable expectation of privacy. This inquiry, in turn,
depends primarily on the private nature of the area or item
subjected to the intrusion. In cases involving techniques
used to locate or identify a physical item, the manner in
which a person has attempted to shield the item’s
existence or identity from public scrutiny will usually be
the key to determining whether a reasonable expectation
of privacy has been violated. Accordingly, the use of
techniques like the dog sniff at issue in Place constitutes a
search whenever the police employ such techniques to
secure any information about an item that is concealed in
a container that we are prepared to view as supporting a
reasonable expectation of privacy. The same would be
true if a more technologically **1672 sophisticated
method were developed to take the place of the dog.
In this case, the chemical field test was used to determine
whether certain white powder was cocaine. Upon visual
inspection of the powder in isolation, one could not
identify it as cocaine. In the abstract, therefore, it is
possible that an individual could keep the powder in such
a way as to preserve a reasonable expectation of privacy
in its identity. For instance, it might be kept in a
transparent pharmaceutical vial and disguised as
legitimate medicine. Under those circumstances, the use
of a chemical field test would constitute a search.
However, in this case, as hypothesized above, see supra,
at 1668, the context in which the powder was found could
not support a reasonable expectation of privacy. In
particular, the substance was found in four plastic bags,
which had been inside a tube wrapped with tape and sent
to respondents via Federal Express. It was essentially
inconceivable that a legal substance would be packaged in
this manner for transport by a common carrier. Thus,
viewing the powder as they did at the offices of Federal
Express, the DEA agent could identify it with “virtual
certainty”; it was essentially as though the chemical
identity of the powder was *143 plainly visible. See Texas
v. Brown, supra, 460 U.S., at ----, 103 S.Ct., at 1547
(1983) (STEVENS, J., concurring in the judgment).
Under these circumstances, therefore, respondents had no
reasonable expectation of privacy in the identity of the
powder, and the use of the chemical field test did not
constitute a “search” violative of the Fourth Amendment.
B
In sum, the question whether the employment of a
particular surveillance technique constitutes a search
89
Parallel Citations
104 S.Ct. 1652, 80 L.Ed.2d 85

Footnotes
* The syllabus constitutes no part of the opinion of the Court but has been prepared by the Reporter of Decisions for the convenience
of the reader. See United States v. Detroit Lumber Co., 200 U.S. 321, 337, 26 S.Ct. 282, 287, 50 L.Ed. 499.
1 As the test is described in the evidence, it involved the use of three test tubes. When a substance containing cocaine is placed in
one test tube after another, it will cause liquids to take on a certain sequence of colors. Such a test discloses whether or not the
substance is cocaine, but there is no evidence that it would identify any other substances.
2 The Court of Appeals did not hold that the facts would not have justified the issuance of a warrant without reference to the test
results; the court merely held that the facts recited in the warrant application, which relied almost entirely on the results of the field
tests, would not support the issuance of the warrant if the field test was itself unlawful. “It is elementary that in passing on the
validity of a warrant, the reviewing court may consider only information brought to the magistrate’s attention.” Spinelli v. United
States, 393 U.S. 410, 413, n. 3, 89 S.Ct. 584, 587 n. 3, 21 L.Ed.2d 637 (1969) (emphasis in original) (quoting Aguilar v. Texas, 378
U.S. 108, 109, n. 1, 84 S.Ct. 1509, 1511 n. 1, 12 L.Ed.2d 723 (1964)). See Illinois v. Gates, 462 U.S. ----, ----, 103 S.Ct. 2317,
2331, 76 L.Ed.2d 527 (1983).
3 See also People v. Adler, 50 N.Y.2d 730, 409 N.E.2d 888, 431 N.Y.S.2d 412, cert. denied, 449 U.S. 1014, 101 S.Ct. 573, 66
L.Ed.2d 473 (1980); cf. United States v. Andrews, 618 F.2d 646 (CA10) (upholding warrantless field test without discussion), cert.
denied, 449 U.S. 824, 101 S.Ct. 84, 66 L.Ed.2d 26 (1980).
4 See Illinois v. Andreas, 463 U.S. ----, ----, 103 S.Ct. 3319, 3323, 77 L.Ed.2d 1003 (1983); United States v. Knotts, 460 U.S. ----, ---
-, 103 S.Ct. 1081, 1085, 75 L.Ed.2d 55 (1983); Smith v. Maryland, 442 U.S. 735, 739-741, 99 S.Ct. 2577, 2579-2580, 61 L.Ed.2d
220 (1979); Terry v. Ohio, 392 U.S. 1, 9, 88 S.Ct. 1868, 1873, 20 L.Ed.2d 889 (1968).
5 See United States v. Place, 462 U.S. 696, 103 S.Ct. 2637, 77 L.Ed.2d 110 (1983); id., at ----, 103 S.Ct., at 2649 (BRENNAN, J.,
concurring in the result); Texas v. Brown, 460 U.S. ----, ----, 103 S.Ct. 1535, 1547, 75 L.Ed.2d 502 (1983) (STEVENS, J.,
concurring in the judgment); see also United States v. Chadwick, 433 U.S. 1, 13-14, n. 8, 97 S.Ct. 2476, 2484-2485, n. 8, 53
L.Ed.2d 538 (1977); Hale v. Henkel, 201 U.S. 43, 76, 26 S.Ct. 370, 379, 50 L.Ed. 652 (1906). While the concept of a “seizure” of
property is not much discussed in our cases, this definition follows from our oft-repeated definition of the “seizure” of a person
within the meaning of the Fourth Amendment-meaningful interference, however brief, with an individual’s freedom of movement.
See Michigan v. Summers, 452 U.S. 692, 696, 101 S.Ct. 2587, 2590, 69 L.Ed.2d 340 (1981); Reid v. Georgia, 448 U.S. 438, 440,
n. *, 100 S.Ct. 2752, 2753, n. *, 65 L.Ed.2d 890 (1980) (per curiam); United States v. Mendenhall, 446 U.S. 544, 551-554, 100
S.Ct. 1870, 1875-1877, 64 L.Ed.2d 497 (1980) (opinion of Stewart, J.); Brown v. Texas, 443 U.S. 47, 50, 99 S.Ct. 2637, 2640, 61
L.Ed.2d 357 (1979); United States v. Brignoni-Ponce, 422 U.S. 873, 878, 95 S.Ct. 2574, 2578, 45 L.Ed.2d 607 (1975); Cupp v.
Murphy, 412 U.S. 291, 294-295, 93 S.Ct. 2000, 2003-2004, 36 L.Ed.2d 900 (1973); Davis v. Mississippi, 394 U.S. 721, 726-727,
89 S.Ct. 1394, 1397-1398, 22 L.Ed.2d 676 (1969); Terry v. Ohio, 392 U.S. 1, 16, 19, n. 16, 88 S.Ct. 1868, 1879, n. 16, 20 L.Ed.2d
889 (1968).
6 See id., 447 U.S., at 656, 100 S.Ct. at 2401 (opinion of STEVENS, J.); id., at 660-661, 100 S.Ct., at 2403-2404 (WHITE, J.,
concurring in part and concurring in the judgment); United States v. Janis, 428 U.S. 433, 455-456, n. 31, 96 S.Ct. 3021, 3032-
3033, n. 31, 49 L.Ed.2d 1046 (1976); Coolidge v. New Hampshire, 403 U.S. 443, 487-490, 91 S.Ct. 2022, 2048-2050, 29 L.Ed.2d
564 (1971); Burdeau v. McDowell, 256 U.S. 465, 41 S.Ct. 574, 65 L.Ed. 1048 (1921).
7 United States v. Chadwick, 433 U.S. 1, 10, 97 S.Ct. 2476, 2482, 53 L.Ed.2d 538 (1977); United States v. Van Leeuwen, 397 U.S.
249, 251, 90 S.Ct. 1029, 1031, 25 L.Ed.2d 282 (1970); Ex parte Jackson, 96 U.S. 727, 733, 6 Otto 727, 733, 24 L.Ed. 877 (1878);
see also Walter, 447 U.S., at 654-655, 100 S.Ct., at 2400-2401 (opinion of STEVENS, J.).
8 See, e.g., United States v. Place, 462 U.S. ----, ----, 103 S.Ct. 2637, 2641, 77 L.Ed.2d 110 (1983); United States v. Ross, 456 U.S.
798, 809-812, 102 S.Ct. 2157, 2164-2166, 72 L.Ed.2d 572 (1982); Robbins v. California, 453 U.S. 420, 426, 101 S.Ct. 2841, 2845,
69 L.Ed.2d 744 (1981) (plurality opinion); Arkansas v. Sanders, 442 U.S. 753, 762, 99 S.Ct. 2586, 2592, 61 L.Ed.2d 235 (1979);
United States v. Chadwick, 433 U.S. 1, 13 and n. 8, 97 S.Ct. 2476, 2485 and n. 8, 53 L.Ed.2d 538 (1977); United States v. Van
Leeuwen, 397 U.S. 249, 90 S.Ct. 1029, 25 L.Ed.2d 282 (1970). There is, of course, a well recognized exception for customs
searches; but that exception is not involved in this case.
9 See Whiteley v. Warden, 401 U.S. 560, 567, n. 11, 91 S.Ct. 1031, 1036, n. 11, 28 L.Ed.2d 306 (1971); Wong Sun v. United States,
371 U.S. 471, 484, 83 S.Ct. 407, 415, 9 L.Ed.2d 441 (1963); Rios v. United States, 364 U.S. 253, 261-262, 80 S.Ct. 1431, 1436-
90

1437, 4 L.Ed.2d 1688 (1960); Henry v. United States, 361 U.S. 98, 103 (1959); Miller v. United States, 357 U.S. 301, 312, 78 S.Ct.
1190, 1197, 2 L.Ed.2d 1332 (1958); United States v. Di Re, 332 U.S. 581, 595, 68 S.Ct. 222, 228, 92 L.Ed. 210 (1948); Byars v.
United States, 273 U.S. 28, 29, 47 S.Ct. 248, 249, 71 L.Ed. 520 (1927).
10 A post-trial affidavit indicates that an agent of Federal Express may have opened the package because he was suspicious about its
contents, and not because of damage from a forklift. However, the lower courts found no governmental involvement in the private
search, a finding not challenged by respondents. The affidavit thus is of no relevance to the issue we decide.
11 See also id., 447 U.S., at 658-659, 100 S.Ct., at 2402-2403 (footnotes omitted) (“The fact that the cartons were unexpectedly
opened by a third party before the shipment was delivered to its intended consignee does not alter the consignor’s legitimate
expectation of privacy. The private search merely frustrated that expectation in part. It did not simply strip the remaining
unfrustrated portion of that expectation of all Fourth Amendment protection.”).
12 In Walter, a majority of the Court found a violation of the Fourth Amendment. For present purposes, the disagreement between the
majority and the dissenters in that case with respect to the comparison between the private search and the official search is less
significant than the agreement on the standard to be applied in evaluating the relationship between the two searches.
13 See Smith v. Maryland, 442 U.S. 735, 743-744, 99 S.Ct. 2577, 2581-2582, 61 L.Ed.2d 220 (1979); United States v. White, 401 U.S.
745, 749-753, 91 S.Ct. 1122, 1124-1126, 28 L.Ed.2d 453 (1971) (plurality opinion); Osborn v. United States, 385 U.S. 323, 326-
331, 87 S.Ct. 429, 431-433, 17 L.Ed.2d 394 (1966); Hoffa v. United States, 385 U.S. 293, 300-303, 87 S.Ct. 408, 412-414, 17
L.Ed.2d 374 (1966); Lewis v. United States, 385 U.S. 206, 87 S.Ct. 424, 17 L.Ed.2d 312 (1966); Lopez v. United States, 373 U.S.
427, 437-439, 83 S.Ct. 1381, 1387-1388, 10 L.Ed.2d 462 (1963); On Lee v. United States, 343 U.S. 747, 753-754, 72 S.Ct. 967,
971-972, 96 L.Ed. 1270 (1952). See also United States v. Henry, 447 U.S. 264, 272, 100 S.Ct. 2183, 2187, 65 L.Ed.2d 115 (1980);
United States v. Caceres, 440 U.S. 741, 744, 750-751, 99 S.Ct. 1465, 1467, 1470-1471, 59 L.Ed.2d 733 (1979).
14 See Katz v. United States, 389 U.S. 347, 88 S.Ct. 507, 19 L.Ed.2d 576 (1967); Berger v. New York, 388 U.S. 41, 87 S.Ct. 1873, 18
L.Ed.2d 1040 (1967); Silverman v. United States, 365 U.S. 505, 81 S.Ct. 679, 5 L.Ed.2d 734 (1961).
15 Daniel Stegemoller, the Federal Express office manager, testified at the suppression hearing that the white substance was not
visible without reentering the package at the time the first agent arrived. App. 42-43; 58. As Justice WHITE points out, the
magistrate found that the “tube was in plain view in the box and the bags of white powder were visible from the end of the tube.”
App. to Pet. for Cert. 18a. The bags were, however, only visible if one picked up the tube and peered inside through a small
aperture; even then, what was visible was only the translucent bag that contained the white powder. The powder itself was barely
visible, and surely was not so plainly in view that the agents did “no more than fail to avert their eyes,” post, at 1665. In any event,
respondents filed objections to the magistrate’s report with the District Court. The District Court declined to resolve respondents’
objection, ruling that fact immaterial and assuming for purposes of its decision “that the newspaper in the box covered the gray
tube and that neither the gray tube nor the contraband could be seen when the box was turned over to the DEA agents.” App. to
Pet. for Cert. 12a-13a. At trial, the federal agent first on the scene testified that the powder was not visible until after he pulled the
plastic bags out of the tube. App. 71-72. Respondents continue to argue this case on the assumption that the Magistrate’s report is
incorrect. Brief for Respondents 2-3. As our discussion will make clear, we agree with the District Court that it does not matter
whether the loose piece of newspaper covered the tube at the time the agent first saw the box.
16 See United States v. Caceres, 440 U.S. 741, 750-751, 99 S.Ct. 1465, 1470-1471, 59 L.Ed.2d 733 (1979); United States v. White,
401 U.S. 745, 749-753, 91 S.Ct. 1122, 1124-1126, 28 L.Ed.2d 453 (1971) (plurality opinion); United States v. Osborn, 385 U.S.
323, 326-331, 87 S.Ct. 429, 431-433, 17 L.Ed.2d 394 (1966); On Lee v. United States, 343 U.S. 747, 753-754, 72 S.Ct. 967, 971-
972, 96 L.Ed. 1270 (1952). For example, in Lopez v. United States, 373 U.S. 427, 83 S.Ct. 1381, 10 L.Ed.2d 462 (1963), the Court
wrote: “Stripped to its essentials, petitioner’s argument amounts to saying that he has a constitutional right to rely on possible flaws
in the agent’s memory, or to challenge the agent’s credibility without being beset by corroborating evidence.... For no other
argument can justify excluding an accurate version of a conversation that the agent could testify to from memory. We think the risk
that petitioner took in offering a bribe to Davis fairly included the risk that the offer would be accurately reproduced in court....”
Id., at 439, 83 S.Ct., at 1388 (footnote omitted).
17 We reject Justice WHITE’s suggestion that this case is indistinguishable from one in which the police simply learn from a private
party that a container contains contraband, seize it from its owner, and conduct a warrantless search which, as Justice WHITE
properly observes, would be unconstitutional. Here, the Federal Express employees who were lawfully in possession of the
package invited the agent to examine its contents; the governmental conduct was made possible only because private parties had
compromised the integrity of this container. Justice WHITE would have this case turn on the fortuity of whether the Federal
91

Express agents placed the tube back into the box. But in the context of their previous examination of the package, their
communication of what they had learned to the agent, and their offer to have the agent inspect it, that act surely could not create
any privacy interest with respect to the package that would not otherwise exist. See Illinois v. Andreas, 463 U.S. ----, ----, 103 S.Ct.
3319, 3323, 77 L.Ed.2d 1003 (1983). Thus the precise character of the white powder’s visibility to the naked eye is far less
significant than the facts that the container could no longer support any expectation of privacy, and that it was virtually certain that
it contained nothing but contraband. Contrary to Justice WHITE’s suggestion, we do not “sanction[ ] warrantless searches of
closed or covered containers or packages whenever probable cause exists as a result of a prior private search.” Post, at 1665. A
container which can support a reasonable expectation of privacy may not be searched, even on probable cause, without a warrant.
See United States v. Ross, 456 U.S. 798, 809-812, 102 S.Ct. 2157, 2164-2166, 72 L.Ed.2d 572 (1982); Robbins v. California, 453
U.S. 420, 426-427, 101 S.Ct. 2841, 2845-2846, 69 L.Ed.2d 744 (1981) (plurality opinion); Arkansas v. Sanders, 442 U.S. 753,
764-765, 99 S.Ct. 2586, 2593-2594, 61 L.Ed.2d 235 (1979); United States v. Chadwick, 433 U.S. 1, 97 S.Ct. 2476, 53 L.Ed.2d 538
(1977).
18 Both the Magistrate and the District Court found that the agents took custody of the package from Federal Express after they
arrived. Although respondents had entrusted possession of the items to Federal Express, the decision by governmental authorities
to exert dominion and control over the package for their own purposes clearly constituted a “seizure,” though not necessarily an
unreasonable one. See United States v. Van Leeuwen, 397 U.S. 249, 90 S.Ct. 1029, 25 L.Ed.2d 282 (1970). Indeed, this is one thing
on which the entire Court appeared to agree in Walter.
19 See also United States v. Ross, 456 U.S. 798, 822-823, 102 S.Ct. 2157, 2171-2172, 72 L.Ed.2d 572 (1982); Robbins v. California,
453 U.S. 420, 428-428, 101 S.Ct. 2841, 2846-2847, 69 L.Ed.2d 744 (1981) (plurality opinion).
20 Respondents concede that the agents had probable cause to believe the package contained contraband. Therefore we need not
decide whether the agents could have seized the package based on something less than probable cause. Some seizures can be
justified by an articulable suspicion of criminal activity. See United States v. Place, 462 U.S. 696, 103 S.Ct. 2637, 77 L.Ed.2d 110
(1983).
21 See Place, 462 U.S., at ----, 103 S.Ct., at 2641; Texas v. Brown, 460 U.S., at ----, 103 S.Ct., at 1541 (plurality opinion); id., at ----,
103 S.Ct., at 1547 (STEVENS, J., concurring in the judgment); Payton v. New York, 445 U.S. 573, 587, 100 S.Ct. 1371, 1380, 63
L.Ed.2d 639 (1980); G.M. Leasing Corp. v. United States, 429 U.S. 338, 354, 97 S.Ct. 619, 629, 50 L.Ed.2d 530 (1977); Harris v.
United States, 390 U.S. 234, 236, 88 S.Ct. 992, 993, 19 L.Ed.2d 1067 (1968) (per curiam).
22 “Obviously, however, a ‘legitimate’ expectation of privacy by definition means more than a subjective expectation of not being
discovered. A burglar plying his trade in a summer cabin during the off season may have a thoroughly justified subjective
expectation of privacy, but it is not one which the law recognizes as ‘legitimate.’ His presence, in the words of Jones [v. United
States, 362 U.S. 257, 267, 80 S.Ct. 725, 734, 4 L.Ed.2d 697 (1960) ], is ‘wrongful,’ his expectation of privacy is not one that
society is prepared to recognize as ‘reasonable.’ Katz v. United States, 389 U.S., at 361, 88 S.Ct., at 516 (Harlan, J., concurring).
And it would, of course, be merely tautological to fall back on the notion that those expectations of privacy which are legitimate
depend primarily on cases deciding exclusionary-rule issues in criminal cases. Legitimation of expectations of privacy by law must
have a source outside of the Fourth Amendment, either by reference to concepts of real or personal property law or to
understandings that are recognized and permitted by society.” Rakas v. Illinois, 439 U.S. 128, 143-144, n. 12, 99 S.Ct. 421, 430-
431, n. 12, 58 L.Ed.2d 387 (1978). See also United States v. Knotts, 460 U.S. 276, 103 S.Ct. 1081, 75 L.Ed.2d 55 (1983) (use of a
beeper to track car’s movements infringed no reasonable expectation of privacy); Smith v. Maryland, 442 U.S. 735, 99 S.Ct. 2577,
61 L.Ed.2d 220 (1979) (use of a pen register to record phone numbers dialed infringed no reasonable expectation of privacy).
23 See Loewy, The Fourth Amendment as a Device for Protecting the Innocent, 81 Mich.L.Rev. 1229 (1983). Our discussion, of
course, is confined to possession of contraband. It is not necessarily the case that the purely “private” possession of an article that
cannot be distributed in commerce is itself illegitimate. See Stanley v. Georgia, 394 U.S. 557, 89 S.Ct. 1243, 22 L.Ed.2d 542
(1969).
24 Respondents attempt to distinguish Place arguing that it involved no physical invasion of Place’s effects, unlike the conduct at
issue here. However, as the quotation makes clear, the reason this did not intrude upon any legitimate privacy interest was that the
governmental conduct could reveal nothing about noncontraband items. That rationale is fully applicable here.
25 In Place, the Court held that while the initial seizure of luggage for the purpose of subjecting it to a “dog sniff” test was reasonable,
the seizure became unreasonable because its length unduly intruded upon constitutionally protected interests. See id., 462 U.S., at -
---, 103 S.Ct., at 2645.
92

26 See, e.g., Michigan v. Long, 463 U.S. ----, ----, 103 S.Ct. 3469, 3479, 77 L.Ed.2d 1201 (1983); Delaware v. Prouse, 440 U.S. 648,
654, 99 S.Ct. 1391, 1396, 59 L.Ed.2d 660 (1979); United States v. Brignoni-Ponce, 422 U.S. 873, 878, 95 S.Ct. 2574, 2578, 45
L.Ed.2d 607 (1975); Terry v. Ohio, 392 U.S. 1, 20-21, 88 S.Ct. 1868, 1879-1880, 20 L.Ed.2d 889 (1968); Camara v. Municipal
Court, 387 U.S. 523, 536-537, 87 S.Ct. 1727, 1734-1735, 18 L.Ed.2d 930 (1967).
27 In fact, respondents do not contend that the amount of material tested was large enough to make it possible for them to have
detected its loss. The only description in the record of the amount of cocaine seized is that “[i]t was a trace amount.” App. 75.
28 See Cupp v. Murphy, 412 U.S. 291, 296, 93 S.Ct. 2000, 2004, 36 L.Ed.2d 900 (1973) (warrantless search and seizure limited to
scraping suspect’s fingernails justified even when full search may not be). Cf. Place, 462 U.S., at ----, 103 S.Ct., at 2644-2645
(approving brief warrantless seizure of luggage for purposes of “sniff test” based on its minimal intrusiveness and reasonable belief
that the luggage contained contraband); Van Leeuwen v. United States, 397 U.S. 249, 252-253, 90 S.Ct. 1029, 1032-1033, 25
L.Ed.2d 282 (1970) (detention of package on reasonable suspicion was justified since detention infringed no “significant Fourth
Amendment interest”). Of course, where more substantial invasions of constitutionally protected interests are involved, a
warrantless search or seizure is unreasonable in the absence of exigent circumstances. See, e.g., Steagald v. United States, 451 U.S.
204, 101 S.Ct. 1642, 68 L.Ed.2d 38 (1981); Payton v. New York, 445 U.S. 573, 100 S.Ct. 1371, 63 L.Ed.2d 639 (1980); Dunaway
v. New York, 442 U.S. 200, 99 S.Ct. 2248, 60 L.Ed.2d 824 (1979); United States v. Chadwick, 433 U.S. 1, 97 S.Ct. 2476, 53
L.Ed.2d 538 (1977). We do not suggest, however, that any seizure of a small amount of material is necessarily reasonable. An
agent’s arbitrary decision to take the “white powder” he finds in a neighbor’s sugar bowl, or his medicine cabinet, and subject it to
a field test for cocaine, might well work an unreasonable seizure.
End of Document
93

121 S.Ct. 2038
Supreme Court of the United States
Danny Lee KYLLO, Petitioner,
v.
UNITED STATES.
No. 99–8508. | Argued Feb. 20, 2001. | Decided
June 11, 2001.
Opinion
Justice SCALIA delivered the opinion of the Court.
This case presents the question whether the use of a
thermal-imaging device aimed at a private home from a
public street to **2041 detect relative amounts of heat
within the home constitutes a “search” within the meaning
of the Fourth Amendment.
I
In 1991 Agent William Elliott of the United States
Department of the Interior came to suspect that marijuana
was being grown in the home belonging to petitioner
Danny Kyllo, part of a triplex on Rhododendron Drive in
Florence, Oregon. Indoor marijuana growth typically
requires high-intensity lamps. In order to determine
whether an amount of heat was emanating from
petitioner’s home consistent with the use of such lamps, at
3:20 a.m. on January 16, 1992, Agent Elliott and Dan
Haas used an Agema Thermovision 210 thermal imager to
scan the triplex. Thermal imagers detect infrared
radiation, which virtually all objects emit but which is not
visible to the naked eye. The imager converts radiation
into images based on relative warmth—black *30 is cool,
white is hot, shades of gray connote relative differences;
in that respect, it operates somewhat like a video camera
showing heat images. The scan of Kyllo’s home took only
a few minutes and was performed from the passenger seat
of Agent Elliott’s vehicle across the street from the front
of the house and also from the street in back of the house.
The scan showed that the roof over the garage and a side
wall of petitioner’s home were relatively hot compared to
the rest of the home and substantially warmer than
neighboring homes in the triplex. Agent Elliott concluded
that petitioner was using halide lights to grow marijuana
in his house, which indeed he was. Based on tips from
94
informants, utility bills, and the thermal imaging, a
Federal Magistrate Judge issued a warrant authorizing a
search of petitioner’s home, and the agents found an
indoor growing operation involving more than 100 plants.
Petitioner was indicted on one count of manufacturing
marijuana, in violation of 21 U.S.C. § 841(a)(1). He
unsuccessfully moved to suppress the evidence seized
from his home and then entered a conditional guilty plea.
The Court of Appeals for the Ninth Circuit remanded the
case for an evidentiary hearing regarding the intrusiveness
of thermal imaging. On remand the District Court found
that the Agema 210 “is a non-intrusive device which
emits no rays or beams and shows a crude visual image of
the heat being radiated from the outside of the house”; it
“did not show any people or activity within the walls of
the structure”; “[t]he device used cannot penetrate walls
or windows to reveal conversations or human activities”;
and “[n]o intimate details of the home were observed.”
Supp.App. to Pet. for Cert. 39–40. Based on these
findings, the District Court upheld the validity of the
warrant that relied in part upon the thermal imaging, and
reaffirmed its denial of the motion to suppress. A divided
Court of Appeals initially reversed, 140 F.3d 1249 (1998),
but that *31 opinion was withdrawn and the panel (after a
change in composition) affirmed, 190 F.3d 1041 (1999),
with Judge Noonan dissenting. The court held that
petitioner had shown no subjective expectation of privacy
because he had made no attempt to conceal the heat
escaping from his home, id., at 1046, and even if he had,
there was no objectively reasonable expectation of
privacy because the imager “did not expose any intimate
details of Kyllo’s life,” only “amorphous ‘hot spots’ on
the roof and exterior wall,” id., at 1047. We granted
certiorari. 530 U.S. 1305, 121 S.Ct. 29, 147 L.Ed.2d 1052
(2000).
II
[1] The Fourth Amendment provides that “[t]he right of
the people to be secure in their persons, houses, papers,
and effects, against unreasonable searches and seizures,
shall not be violated.” “At the very core” of the Fourth
Amendment “stands the right of a man to retreat into his
own home and there be free from unreasonable
governmental intrusion.” **2042 Silverman v. United
States, 365 U.S. 505, 511, 81 S.Ct. 679, 5 L.Ed.2d 734
(1961). With few exceptions, the question whether a
warrantless search of a home is reasonable and hence
constitutional must be answered no. See Illinois v.

Rodriguez, 497 U.S. 177, 181, 110 S.Ct. 2793, 111
L.Ed.2d 148 (1990); Payton v. New York, 445 U.S. 573,
586, 100 S.Ct. 1371, 63 L.Ed.2d 639 (1980).
On the other hand, the antecedent question whether or not
a Fourth Amendment “search” has occurred is not so
simple under our precedent. The permissibility of
ordinary visual surveillance of a home used to be clear
because, well into the 20th century, our Fourth
Amendment jurisprudence was tied to common-law
trespass. See, e.g., Goldman v. United States, 316 U.S.
129, 134–136, 62 S.Ct. 993, 86 L.Ed. 1322 (1942);
Olmstead v. United States, 277 U.S. 438, 464–466, 48
S.Ct. 564, 72 L.Ed. 944 (1928). Cf. Silverman v. United
States, supra, at 510–512, 81 S.Ct. 679 (technical trespass
not necessary for Fourth Amendment violation; it suffices
if there is “actual intrusion into a constitutionally
protected area”). Visual surveillance was unquestionably
lawful because “ ‘the *32 eye cannot by the laws of
England be guilty of a trespass.’ ” Boyd v. United States,
116 U.S. 616, 628, 6 S.Ct. 524, 29 L.Ed. 746 (1886)
(quoting Entick v. Carrington, 19 How. St. Tr. 1029, 95
Eng. Rep. 807 (K.B.1765)). We have since decoupled
violation of a person’s Fourth Amendment rights from
trespassory violation of his property, see Rakas v. Illinois,
439 U.S. 128, 143, 99 S.Ct. 421, 58 L.Ed.2d 387 (1978),
but the lawfulness of warrantless visual surveillance of a
home has still been preserved. As we observed in
California v. Ciraolo, 476 U.S. 207, 213, 106 S.Ct. 1809,
90 L.Ed.2d 210 (1986), “[t]he Fourth Amendment
protection of the home has never been extended to require
law enforcement officers to shield their eyes when
passing by a home on public thoroughfares.”
One might think that the new validating rationale would
be that examining the portion of a house that is in plain
public view, while it is a “search”1 despite the absence of
trespass, is not an “unreasonable” one under the Fourth
Amendment. See Minnesota v. Carter, 525 U.S. 83, 104,
119 S.Ct. 469, 142 L.Ed.2d 373 (1998) (BREYER, J.,
concurring in judgment). But in fact we have held that
visual observation is no “search” at all—perhaps in order
to preserve somewhat more intact our doctrine that
warrantless searches are presumptively unconstitutional.
See Dow Chemical Co. v. United States, 476 U.S. 227,
234–235, 239, 106 S.Ct. 1819, 90 L.Ed.2d 226 (1986). In
assessing when a search is not a search, we have applied
somewhat in reverse the principle first enunciated in Katz
v. United States, 389 U.S. 347, 88 S.Ct. 507, 19 L.Ed.2d
576 (1967). Katz involved eavesdropping by means of an
electronic listening device placed on the outside of a
telephone booth—a location not within the catalog
(“persons, houses, papers, and effects”) that the Fourth
95
Amendment protects against unreasonable searches. We
held that the *33 Fourth Amendment nonetheless
protected Katz from the warrantless eavesdropping
because he “justifiably relied” upon the privacy of the
telephone booth. Id., at 353, 88 S.Ct. 507. As Justice
Harlan’s oft-quoted concurrence described it, a Fourth
Amendment search occurs when the government violates
a subjective expectation of privacy that society recognizes
as reasonable. See id., at 361, 88 S.Ct. 507. We have
subsequently applied this principle to hold that a Fourth
Amendment search does not occur—even when the
explicitly protected location of a house is concerned—
unless “the individual manifested a subjective expectation
of privacy **2043 in the object of the challenged search,”
and “society [is] willing to recognize that expectation as
reasonable.” Ciraolo, supra, at 211, 106 S.Ct. 1809. We
have applied this test in holding that it is not a search for
the police to use a pen register at the phone company to
determine what numbers were dialed in a private home,
Smith v. Maryland, 442 U.S. 735, 743–744, 99 S.Ct.
2577, 61 L.Ed.2d 220 (1979), and we have applied the
test on two different occasions in holding that aerial
surveillance of private homes and surrounding areas does
not constitute a search, Ciraolo, supra; Florida v. Riley,
488 U.S. 445, 109 S.Ct. 693, 102 L.Ed.2d 835 (1989).
The present case involves officers on a public street
engaged in more than naked-eye surveillance of a home.
We have previously reserved judgment as to how much
technological enhancement of ordinary perception from
such a vantage point, if any, is too much. While we
upheld enhanced aerial photography of an industrial
complex in Dow Chemical, we noted that we found “it
important that this is not an area immediately adjacent to
a private home, where privacy expectations are most
heightened,” 476 U.S., at 237, n. 4, 106 S.Ct. 1819
(emphasis in original).
III
It would be foolish to contend that the degree of privacy
secured to citizens by the Fourth Amendment has been
*34 entirely unaffected by the advance of technology. For
example, as the cases discussed above make clear, the
technology enabling human flight has exposed to public
view (and hence, we have said, to official observation)
uncovered portions of the house and its curtilage that once
were private. See Ciraolo, supra, at 215, 106 S.Ct. 1809.
The question we confront today is what limits there are
upon this power of technology to shrink the realm of
guaranteed privacy.

[2] [3] The Katz test—whether the individual has an
expectation of privacy that society is prepared to
recognize as reasonable—has often been criticized as
circular, and hence subjective and unpredictable. See 1
W. LaFave, Search and Seizure § 2.1(d), pp. 393–394 (3d
ed.1996); Posner, The Uncertain Protection of Privacy by
the Supreme Court, 1979 S.Ct. Rev. 173, 188; Carter,
supra, at 97, 119 S.Ct. 469 (SCALIA, J., concurring). But
see Rakas, supra, at 143–144, n. 12, 99 S.Ct. 421. While
it may be difficult to refine Katz when the search of areas
such as telephone booths, automobiles, or even the
curtilage and uncovered portions of residences is at issue,
in the case of the search of the interior of homes—the
prototypical and hence most commonly litigated area of
protected privacy—there is a ready criterion, with roots
deep in the common law, of the minimal expectation of
privacy that exists, and that is acknowledged to be
reasonable. To withdraw protection of this minimum
expectation would be to permit police technology to erode
the privacy guaranteed by the Fourth Amendment. We
think that obtaining by sense-enhancing technology any
information regarding the interior of the home that could
not otherwise have been obtained without physical
“intrusion into a constitutionally protected area,”
Silverman, 365 U.S., at 512, 81 S.Ct. 679, constitutes a
search—at least where (as here) the technology in
question is not in general public use. This assures
preservation of that degree of privacy against government
that existed when the Fourth Amendment was adopted.
On the basis of this criterion, the *35 information
obtained by the thermal imager in this case was the
product of a search.2
**2044 [4] [5] The Government maintains, however, that
the thermal imaging must be upheld because it detected
“only heat radiating from the external surface of the
house,” Brief for United States 26. The dissent makes this
its leading point, see post, at 2047, contending that there
is a fundamental difference between what it calls “off-thewall”
observations and “through-the-wall surveillance.”
But just as a thermal imager captures only heat emanating
from a house, so also a powerful directional microphone
picks up only sound emanating from a house-and a
satellite capable of scanning from many miles away
would pick up only visible light emanating from a house.
We rejected such a mechanical interpretation of the
Fourth Amendment in Katz, where the eavesdropping
device picked up only sound waves that reached the
exterior of the phone booth. Reversing that approach
would leave the homeowner at the mercy of advancing
technology—including imaging technology that could
discern all human *36 activity in the home. While the
technology used in the present case was relatively crude,
the rule we adopt must take account of more sophisticated
96
systems that are already in use or in development.3 The
dissent’s reliance on the distinction between “off-thewall”
and “through-the-wall” observation is entirely
incompatible with the dissent’s belief, which we discuss
below, that thermal-imaging observations of the intimate
details of a home are impermissible. The most
sophisticated thermal-imaging devices continue to
measure heat “off-the-wall” rather than “through-thewall”;
the dissent’s disapproval of those more
sophisticated thermal-imaging devices, see post, at 2051,
is an acknowledgement that there is no substance to this
distinction. As for the dissent’s extraordinary assertion
that anything learned through “an inference” cannot be a
search, see post, at 2048–2049, that would validate even
the “through-the-wall” technologies that the dissent
purports to disapprove. Surely the dissent does not believe
that the through-the-wall radar or ultrasound technology
produces an 8–by–10 Kodak glossy that needs no analysis
(i.e., the making of inferences). And, of course, the novel
proposition that inference insulates a search is blatantly
contrary to United States v. Karo, 468 U.S. 705, 104 S.Ct.
3296, 82 L.Ed.2d 530 (1984), where the police “inferred”
from the activation of a beeper that a certain can of ether
was in the home. The police activity *37 was held to be a
search, and the search was held unlawful.4
**2045 [6] The Government also contends that the
thermal imaging was constitutional because it did not
“detect private activities occurring in private areas,” Brief
for United States 22. It points out that in Dow Chemical
we observed that the enhanced aerial photography did not
reveal any “intimate details.” 476 U.S., at 238, 106 S.Ct.
1819. Dow Chemical, however, involved enhanced aerial
photography of an industrial complex, which does not
share the Fourth Amendment sanctity of the home. The
Fourth Amendment’s protection of the home has never
been tied to measurement of the quality or quantity of
information obtained. In Silverman, for example, we
made clear that any physical invasion of the structure of
the home, “by even a fraction of an inch,” was too much,
365 U.S., at 512, 81 S.Ct. 679, and there is certainly no
exception to the warrant requirement for the officer who
barely cracks open the front door and sees nothing but the
nonintimate rug on the vestibule floor. In the home, our
cases show, all details are intimate details, because the
entire area is held safe from prying government eyes.
Thus, in Karo, supra, the only thing detected was a can of
ether in the *38 home; and in Arizona v. Hicks, 480 U.S.
321, 107 S.Ct. 1149, 94 L.Ed.2d 347 (1987), the only
thing detected by a physical search that went beyond what
officers lawfully present could observe in “plain view”
was the registration number of a phonograph turntable.
These were intimate details because they were details of
the home, just as was the detail of how warm—or even

how relatively warm—Kyllo was heating his residence.5
Limiting the prohibition of thermal imaging to “intimate
details” would not only be wrong in principle; it would be
impractical in application, failing to provide “a workable
accommodation between the needs of law enforcement
and the interests protected by the Fourth Amendment,”
Oliver v. United States, 466 U.S. 170, 181, 104 S.Ct.
1735, 80 L.Ed.2d 214 (1984). To begin with, there is no
necessary connection between the sophistication of the
surveillance equipment and the “intimacy” of the details
that it observes—which means that one cannot say (and
the police cannot be assured) that use of the relatively
crude equipment at issue here will always be lawful. The
Agema Thermovision 210 might disclose, for example, at
what hour each night the lady of the house takes her daily
sauna and bath—a detail that many would consider
“intimate”; and a much more sophisticated system might
detect nothing more intimate than the fact that someone
left a closet light on. We could not, in other words,
develop a rule approving only that through-the-wall
surveillance which identifies objects no smaller than 36
by 36 inches, but would have to develop a jurisprudence
specifying which *39 home activities are “intimate” and
which are not. **2046 And even when (if ever) that
jurisprudence were fully developed, no police officer
would be able to know in advance whether his throughthe-wall
surveillance picks up “intimate” details—and
thus would be unable to know in advance whether it is
constitutional.
The dissent’s proposed standard—whether the technology
offers the “functional equivalent of actual presence in the
area being searched,” post, at 2050—would seem quite
similar to our own at first blush. The dissent concludes
that Katz was such a case, but then inexplicably asserts
that if the same listening device only revealed the volume
of the conversation, the surveillance would be
permissible, post, at 2051. Yet if, without technology, the
police could not discern volume without being actually
present in the phone booth, Justice STEVENS should
conclude a search has occurred. Cf. Karo, 468 U.S., at
735, 104 S.Ct. 3296 (STEVENS, J., concurring in part
and dissenting in part) (“I find little comfort in the Court’s
notion that no invasion of privacy occurs until a listener
obtains some significant information by use of the device
.... A bathtub is a less private area when the plumber is
present even if his back is turned”). The same should hold
for the interior heat of the home if only a person present
in the home could discern the heat. Thus the driving force
of the dissent, despite its recitation of the above standard,
appears to be a distinction among different types of
information—whether the “homeowner would even care
if anybody noticed,” post, at 2051. The dissent offers no
97
practical guidance for the application of this standard, and
for reasons already discussed, we believe there can be
none. The people in their houses, as well as the police,
deserve more precision.6
[7] *40 We have said that the Fourth Amendment draws
“a firm line at the entrance to the house,” Payton, 445
U.S., at 590, 100 S.Ct. 1371. That line, we think, must be
not only firm but also bright—which requires clear
specification of those methods of surveillance that require
a warrant. While it is certainly possible to conclude from
the videotape of the thermal imaging that occurred in this
case that no “significant” compromise of the
homeowner’s privacy has occurred, we must take the long
view, from the original meaning of the Fourth
Amendment forward.
“The Fourth Amendment is to be construed in the light of
what was deemed an unreasonable search and seizure
when it was adopted, and in a manner which will
conserve public interests as well as the interests and rights
of individual citizens.” Carroll v. United States, 267 U.S.
132, 149, 45 S.Ct. 280, 69 L.Ed. 543 (1925).
Where, as here, the Government uses a device that is not
in general public use, to explore details of the home that
would previously have been unknowable without physical
intrusion, the surveillance is a “search” and is
presumptively unreasonable without a warrant.
Since we hold the Thermovision imaging to have been an
unlawful search, it will remain for the District Court to
determine whether, without the evidence it provided, the
search warrant issued in this case was supported by
probable cause—and if not, whether there is any other
basis for supporting admission of the evidence that the
search pursuant to the warrant produced.
**2047 *41 * * *
The judgment of the Court of Appeals is reversed; the
case is remanded for further proceedings consistent with
this opinion.
It is so ordered.
Justice STEVENS, with whom THE CHIEF JUSTICE,
Justice O’CONNOR, and Justice KENNEDY join,
dissenting.

There is, in my judgment, a distinction of constitutional
magnitude between “through-the-wall surveillance” that
gives the observer or listener direct access to information
in a private area, on the one hand, and the thought
processes used to draw inferences from information in the
public domain, on the other hand. The Court has crafted a
rule that purports to deal with direct observations of the
inside of the home, but the case before us merely involves
indirect deductions from “off-the-wall” surveillance, that
is, observations of the exterior of the home. Those
observations were made with a fairly primitive thermal
imager that gathered data exposed on the outside of
petitioner’s home but did not invade any constitutionally
protected interest in privacy.1 Moreover, I believe that the
supposedly “bright-line” rule the Court has created in
response to its concerns about future technological
developments is unnecessary, unwise, and inconsistent
with the Fourth Amendment.
I
There is no need for the Court to craft a new rule to
decide this case, as it is controlled by established
principles from *42 our Fourth Amendment
jurisprudence. One of those core principles, of course, is
that “searches and seizures inside a home without a
warrant are presumptively unreasonable.” Payton v. New
York, 445 U.S. 573, 586, 100 S.Ct. 1371, 63 L.Ed.2d 639
(1980) (emphasis added). But it is equally well settled that
searches and seizures of property in plain view are
presumptively reasonable. See id., at 586–587, 100 S.Ct.
1371.2 Whether that property is residential or commercial,
the basic principle is the same: “ ‘What a person
knowingly exposes to the public, even in his own home or
office, is not a subject of Fourth Amendment protection.’
” California v. Ciraolo, 476 U.S. 207, 213, 106 S.Ct.
1809, 90 L.Ed.2d 210 (1986) (quoting Katz v. United
States, 389 U.S. 347, 351, 88 S.Ct. 507, 19 L.Ed.2d 576
(1967)); see Florida v. Riley, 488 U.S. 445, 449–450, 109
S.Ct. 693, 102 L.Ed.2d 835 (1989); California v.
Greenwood, 486 U.S. 35, 40–41, 108 S.Ct. 1625, 100
L.Ed.2d 30 (1988); Dow Chemical Co. v. United States,
476 U.S. 227, 235–236, 106 S.Ct. 1819, 90 L.Ed.2d 226
(1986); **2048 Air Pollution Variance Bd. of Colo. v.
Western Alfalfa Corp., 416 U.S. 861, 865, 94 S.Ct. 2114,
40 L.Ed.2d 607 (1974). That is the principle implicated
here.
While the Court “take[s] the long view” and decides this
case based largely on the potential of yet-to-be-developed
technology that might allow “through-the-wall
98
surveillance,” ante, at 2045–2046; see ante, at 2044, n. 3,
this case involves nothing more than off-the-wall
surveillance by law enforcement officers to gather
information exposed to the general public from the
outside of petitioner’s home. All that the infrared camera
did in this case was passively measure heat emitted *43
from the exterior surfaces of petitioner’s home; all that
those measurements showed were relative differences in
emission levels, vaguely indicating that some areas of the
roof and outside walls were warmer than others. As still
images from the infrared scans show, see Appendix, infra,
no details regarding the interior of petitioner’s home were
revealed. Unlike an x-ray scan, or other possible
“through-the-wall” techniques, the detection of infrared
radiation emanating from the home did not accomplish
“an unauthorized physical penetration into the premises,”
Silverman v. United States, 365 U.S. 505, 509, 81 S.Ct.
679, 5 L.Ed.2d 734 (1961), nor did it “obtain information
that it could not have obtained by observation from
outside the curtilage of the house,” United States v. Karo,
468 U.S. 705, 715, 104 S.Ct. 3296, 82 L.Ed.2d 530
(1984).
Indeed, the ordinary use of the senses might enable a
neighbor or passerby to notice the heat emanating from a
building, particularly if it is vented, as was the case here.
Additionally, any member of the public might notice that
one part of a house is warmer than another part or a
nearby building if, for example, rainwater evaporates or
snow melts at different rates across its surfaces. Such use
of the senses would not convert into an unreasonable
search if, instead, an adjoining neighbor allowed an
officer onto her property to verify her perceptions with a
sensitive thermometer. Nor, in my view, does such
observation become an unreasonable search if made from
a distance with the aid of a device that merely discloses
that the exterior of one house, or one area of the house, is
much warmer than another. Nothing more occurred in this
case.
Thus, the notion that heat emissions from the outside of a
dwelling are a private matter implicating the protections
of the Fourth Amendment (the text of which guarantees
the right of people “to be secure in their ... houses”
against unreasonable searches and seizures (emphasis
added)) is not only unprecedented but also quite difficult
to take seriously. Heat waves, like aromas that are
generated in a kitchen, or *44 in a laboratory or opium
den, enter the public domain if and when they leave a
building. A subjective expectation that they would remain
private is not only implausible but also surely not “one
that society is prepared to recognize as ‘reasonable.’ ”
Katz, 389 U.S., at 361, 88 S.Ct. 507 (Harlan, J.,

concurring).
To be sure, the homeowner has a reasonable expectation
of privacy concerning what takes place within the home,
and the Fourth Amendment’s protection against physical
invasions of the home should apply to their functional
equivalent. But the equipment in this case did not
penetrate the walls of petitioner’s home, and while it did
pick up “details of the home” that were exposed to the
public, ante, at 2045, it did not obtain “any information
regarding the interior of the home,” ante, at 2043
(emphasis added). In the Court’s own words, based on
what the thermal imager “showed” regarding the outside
of petitioner’s home, the officers “concluded” that
petitioner was engaging in illegal activity inside the
home. Ante, at 2041. It would be quite absurd to
characterize their thought processes as “searches,”
regardless of whether they inferred (rightly) that
petitioner was growing marijuana in his house, or
(wrongly) that “the lady of the house [was taking] her
daily sauna and bath.” Ante, at 2045. In either case, the
only conclusions the officers reached concerning the
interior of the home were at least as indirect as those that
might have **2049 been inferred from the contents of
discarded garbage, see California v. Greenwood, 486 U.S.
35, 108 S.Ct. 1625, 100 L.Ed.2d 30 (1988), or pen
register data, see Smith v. Maryland, 442 U.S. 735, 99
S.Ct. 2577, 61 L.Ed.2d 220 (1979), or, as in this case,
subpoenaed utility records, see 190 F.3d 1041, 1043
(C.A.9 1999). For the first time in its history, the Court
assumes that an inference can amount to a Fourth
Amendment violation. See ante, at 2044–2045.3
*45 Notwithstanding the implications of today’s decision,
there is a strong public interest in avoiding constitutional
litigation over the monitoring of emissions from homes,
and over the inferences drawn from such monitoring. Just
as “the police cannot reasonably be expected to avert their
eyes from evidence of criminal activity that could have
been observed by any member of the public,” Greenwood,
486 U.S., at 41, 108 S.Ct. 1625, so too public officials
should not have to avert their senses or their equipment
from detecting emissions in the public domain such as
excessive heat, traces of smoke, suspicious odors,
odorless gases, airborne particulates, or radioactive
emissions, any of which could identify hazards to the
community. In my judgment, monitoring such emissions
with “sense-enhancing technology,” ante, at 2043, and
drawing useful conclusions from such monitoring, is an
entirely reasonable public service.
On the other hand, the countervailing privacy interest is at
best trivial. After all, homes generally are insulated to
keep heat in, rather than to prevent the detection of heat
99
going out, and it does not seem to me that society will
suffer from a rule requiring the rare homeowner who both
intends to engage in uncommon activities that produce
extraordinary amounts of heat, and wishes to conceal that
production from outsiders, to make sure that the
surrounding area is well insulated. Cf. United States v.
Jacobsen, 466 U.S. 109, 122, 104 S.Ct. 1652, 80 L.Ed.2d
85 (1984) (“The concept of an interest in privacy that
society is prepared to recognize as reasonable is, by its
very nature, critically different from the mere expectation,
however well *46 justified, that certain facts will not
come to the attention of the authorities”). The interest in
concealing the heat escaping from one’s house pales in
significance to “the chief evil against which the wording
of the Fourth Amendment is directed,” the “physical entry
of the home,” United States v. United States Dist. Court
for Eastern Dist. of Mich., 407 U.S. 297, 313, 92 S.Ct.
2125, 32 L.Ed.2d 752 (1972), and it is hard to believe that
it is an interest the Framers sought to protect in our
Constitution.
Since what was involved in this case was nothing more
than drawing inferences from off-the-wall surveillance,
rather than any “through-the-wall” surveillance, the
officers’ conduct did not amount to a search and was
perfectly reasonable.4
**2050 II
Instead of trying to answer the question whether the use
of the thermal imager in this case was even arguably
unreasonable, the Court has fashioned a rule that is
intended to provide essential guidance for the day when
“more sophisticated systems” gain the “ability to ‘see’
through walls and other opaque barriers.” Ante, at 2044,
and n. 3. The newly minted rule encompasses “obtaining
[1] by sense-enhancing technology [2] any information
regarding the interior of the home [3] that could not
otherwise have been obtained without physical intrusion
into a constitutionally protected area ... [4] at least where
(as here) the technology in question is not in general
public use.” Ante, at 2043 (internal quotation marks
omitted). In my judgment, the *47 Court’s new rule is at
once too broad and too narrow, and is not justified by the
Court’s explanation for its adoption. As I have suggested,
I would not erect a constitutional impediment to the use of
sense-enhancing technology unless it provides its user
with the functional equivalent of actual presence in the
area being searched.
Despite the Court’s attempt to draw a line that is “not
only firm but also bright,” ante, at 2046, the contours of

its new rule are uncertain because its protection
apparently dissipates as soon as the relevant technology is
“in general public use,” ante, at 2043. Yet how much use
is general public use is not even hinted at by the Court’s
opinion, which makes the somewhat doubtful assumption
that the thermal imager used in this case does not satisfy
that criterion.5 In any event, putting aside its lack of
clarity, this criterion is somewhat perverse because it
seems likely that the threat to privacy will grow, rather
than recede, as the use of intrusive equipment becomes
more readily available.
It is clear, however, that the category of “sense-enhancing
technology” covered by the new rule, ibid., is far too
broad. It would, for example, embrace potential
mechanical substitutes for dogs trained to react when they
sniff narcotics. But in United States v. Place, 462 U.S.
696, 707, 103 S.Ct. 2637, 77 L.Ed.2d 110 (1983), we held
that a dog sniff that “discloses only the presence or
absence of narcotics” does “not constitute a ‘search’
within the meaning of the Fourth Amendment,” and it
must follow that sense-enhancing equipment that
identifies nothing but illegal *48 activity is not a search
either. Nevertheless, the use of such a device would be
unconstitutional under the Court’s rule, as would the use
of other new devices that might detect the odor of deadly
bacteria or chemicals for making a new type of high
explosive, even if the devices (like the dog sniffs) are “so
limited both in the manner in which” they obtain
information and “in the content of the information” they
reveal. Ibid. If nothing more than that sort of information
could be obtained by using the devices in a public place to
monitor emissions from a house, then their use would be
no more objectionable than the use of the thermal imager
in this case.
The application of the Court’s new rule to “any
information regarding the interior of the home,” ante, at
2043, is also unnecessarily broad. If it takes sensitive
equipment to detect an odor that identifies criminal
conduct and nothing else, the fact that the odor emanates
from the interior of a **2051 home should not provide it
with constitutional protection. See supra, at 2050 and this
page. The criterion, moreover, is too sweeping in that
information “regarding” the interior of a home apparently
is not just information obtained through its walls, but also
information concerning the outside of the building that
could lead to (however many) inferences “regarding”
what might be inside. Under that expansive view, I
suppose, an officer using an infrared camera to observe a
man silently entering the side door of a house at night
carrying a pizza might conclude that its interior is now
occupied by someone who likes pizza, and by doing so
100
the officer would be guilty of conducting an
unconstitutional “search” of the home.
Because the new rule applies to information regarding the
“interior” of the home, it is too narrow as well as too
broad. Clearly, a rule that is designed to protect
individuals from the overly intrusive use of senseenhancing
equipment should not be limited to a home. If
such equipment *49 did provide its user with the
functional equivalent of access to a private place—such
as, for example, the telephone booth involved in Katz, or
an office building—then the rule should apply to such an
area as well as to a home. See Katz, 389 U.S., at 351, 88
S.Ct. 507 (“[T]he Fourth Amendment protects people, not
places”).
The final requirement of the Court’s new rule, that the
information “could not otherwise have been obtained
without physical intrusion into a constitutionally protected
area,” ante, at 2043 (internal quotation marks omitted),
also extends too far as the Court applies it. As noted, the
Court effectively treats the mental process of analyzing
data obtained from external sources as the equivalent of a
physical intrusion into the home. See supra, at 2048–
2049. As I have explained, however, the process of
drawing inferences from data in the public domain should
not be characterized as a search.
The two reasons advanced by the Court as justifications
for the adoption of its new rule are both unpersuasive.
First, the Court suggests that its rule is compelled by our
holding in Katz, because in that case, as in this, the
surveillance consisted of nothing more than the
monitoring of waves emanating from a private area into
the public domain. See ante, at 2044. Yet there are critical
differences between the cases. In Katz, the electronic
listening device attached to the outside of the phone booth
allowed the officers to pick up the content of the
conversation inside the booth, making them the functional
equivalent of intruders because they gathered information
that was otherwise available only to someone inside the
private area; it would be as if, in this case, the thermal
imager presented a view of the heat-generating activity
inside petitioner’s home. By contrast, the thermal imager
here disclosed only the relative amounts of heat radiating
from the house; it would be as if, in Katz, the listening
device disclosed only the relative *50 volume of sound
leaving the booth, which presumably was discernible in
the public domain.6 Surely, there is a significant
difference between the general and well-settled
expectation that strangers will not have direct access to
the contents of private communications, on the one hand,
and the rather theoretical expectation that an occasional

homeowner would even care if anybody noticed the
relative amounts of heat emanating from the walls of his
house, on the other. It is pure hyperbole for the Court to
suggest that refusing to extend the holding of Katz to this
case would leave the homeowner at the mercy of
“technology that could discern all human activity in the
home.” Ante, at 2044.
**2052 Second, the Court argues that the permissibility of
“through-the-wall surveillance” cannot depend on a
distinction between observing “intimate details” such as
“the lady of the house [taking] her daily sauna and bath,”
and noticing only “the nonintimate rug on the vestibule
floor” or “objects no smaller than 36 by 36 inches.” Ante,
at 2045–2046. This entire argument assumes, of course,
that the thermal imager in this case could or did perform
“through-the-wall surveillance” that could identify any
detail “that would previously have been unknowable
without physical intrusion.” Ante, at 2046. In fact, the
device could not, see n. 1, supra, and did not, see
Appendix, infra, enable its user to identify either the lady
of the house, the rug on the vestibule floor, or anything
else inside the house, whether smaller or larger than 36 by
36 inches. Indeed, the vague thermal images of
petitioner’s home that are reproduced in the Appendix
were submitted by him to the District Court as part of an
expert report raising the question whether the device
could even take “accurate, consistent infrared images” of
the *51 outside of his house. Defendant’s Exh. 107, p. 4.
But even if the device could reliably show extraordinary
differences in the amounts of heat leaving his home,
drawing the inference that there was something suspicious
occurring inside the residence—a conclusion that officers
far less gifted than Sherlock Holmes would readily
draw—does not qualify as “through-the-wall
surveillance,” much less a Fourth Amendment violation.
Although the Court is properly and commendably
concerned about the threats to privacy that may flow from
advances in the technology available to the law
enforcement profession, it has unfortunately failed to heed
the tried and true counsel of judicial restraint. Instead of
concentrating on the rather mundane issue that is actually
presented by the case before it, the Court has endeavored
to craft an all-encompassing rule for the future. It would
be far wiser to give legislators an unimpeded opportunity
to grapple with these emerging issues rather than to
shackle them with prematurely devised constitutional
constraints.
I respectfully dissent.
Parallel Citations
**2053 *52 APPENDIX
121 S.Ct. 2038, 150 L.Ed.2d 94, 01 Cal. Daily Op. Serv.
4749, 2001 Daily Journal D.A.R. 5879, 14 Fla. L. Weekly
Fed. S 329, 2001 DJCAR 2926
III
Footnotes
* The syllabus constitutes no part of the opinion of the Court but has been prepared by the Reporter of Decisions for the convenience
of the reader. See United States v. Detroit Timber & Lumber Co., 200 U.S. 321, 337, 26 S.Ct. 282, 50 L.Ed. 499.
1 When the Fourth Amendment was adopted, as now, to “search” meant “[t]o look over or through for the purpose of finding
something; to explore; to examine by inspection; as, to search the house for a book; to search the wood for a thief.” N. Webster,
An American Dictionary of the English Language 66 (1828) (reprint 6th ed.1989).
2 The dissent’s repeated assertion that the thermal imaging did not obtain information regarding the interior of the home, post, at
2048 (opinion of STEVENS, J.), is simply inaccurate. A thermal imager reveals the relative heat of various rooms in the home. The
dissent may not find that information particularly private or important, see post, at 2048, 2049, 2051, but there is no basis for
saying it is not information regarding the interior of the home. The dissent’s comparison of the thermal imaging to various
circumstances in which outside observers might be able to perceive, without technology, the heat of the home—for example, by
101

observing snowmelt on the roof, post, at 2048—is quite irrelevant. The fact that equivalent information could sometimes be
obtained by other means does not make lawful the use of means that violate the Fourth Amendment. The police might, for
example, learn how many people are in a particular house by setting up year-round surveillance; but that does not make breaking
and entering to find out the same information lawful. In any event, on the night of January 16, 1992, no outside observer could
have discerned the relative heat of Kyllo’s home without thermal imaging.
3 The ability to “see” through walls and other opaque barriers is a clear, and scientifically feasible, goal of law enforcement research
and development. The National Law Enforcement and Corrections Technology Center, a program within the United States
Department of Justice, features on its Internet Website projects that include a “Radar–Based Through–the–Wall Surveillance
System,” “Handheld Ultrasound Through the Wall Surveillance,” and a “Radar Flashlight” that “will enable law enforcement
officers to detect individuals through interior building walls.” www.nlectc.org/techproj/ (visited May 3, 2001). Some devices may
emit low levels of radiation that travel “through-the-wall,” but others, such as more sophisticated thermal-imaging devices, are
entirely passive, or “off-the-wall” as the dissent puts it.
4 The dissent asserts, post, at 2049, n. 3, that we have misunderstood its point, which is not that inference insulates a search, but that
inference alone is not a search. If we misunderstood the point, it was only in a good-faith effort to render the point germane to the
case at hand. The issue in this case is not the police’s allegedly unlawful inferencing, but their allegedly unlawful thermal-imaging
measurement of the emanations from a house. We say such measurement is a search; the dissent says it is not, because an inference
is not a search. We took that to mean that, since the technologically enhanced emanations had to be the basis of inferences before
anything inside the house could be known, the use of the emanations could not be a search. But the dissent certainly knows better
than we what it intends. And if it means only that an inference is not a search, we certainly agree. That has no bearing, however,
upon whether hi-tech measurement of emanations from a house is a search.
5 The Government cites our statement in California v. Ciraolo, 476 U.S. 207, 106 S.Ct. 1809, 90 L.Ed.2d 210 (1986), noting
apparent agreement with the State of California that aerial surveillance of a house’s curtilage could become “ ‘invasive’ ” if “
‘modern technology’ ” revealed “ ‘those intimate associations, objects or activities otherwise imperceptible to police or fellow
citizens.’ ” Id., at 215, n. 3, 106 S.Ct. 1809 (quoting Brief for State of California 14–15). We think the Court’s focus in this
secondhand dictum was not upon intimacy but upon otherwise-imperceptibility, which is precisely the principle we vindicate
today.
6 The dissent argues that we have injected potential uncertainty into the constitutional analysis by noting that whether or not the
technology is in general public use may be a factor. See post, at 2050. That quarrel, however, is not with us but with this Court’s
precedent. See Ciraolo, supra, at 215, 106 S.Ct. 1809 (“In an age where private and commercial flight in the public airways is
routine, it is unreasonable for respondent to expect that his marijuana plants were constitutionally protected from being observed
with the naked eye from an altitude of 1,000 feet”). Given that we can quite confidently say that thermal imaging is not “routine,”
we decline in this case to reexamine that factor.
1 After an evidentiary hearing, the District Court found:
“[T]he use of the thermal imaging device here was not an intrusion into Kyllo’s home. No intimate details of the home were
observed, and there was no intrusion upon the privacy of the individuals within the home. The device used cannot penetrate walls
or windows to reveal conversations or human activities. The device recorded only the heat being emitted from the home.”
Supp.App. to Pet. for Cert. 40.
2 Thus, for example, we have found consistent with the Fourth Amendment, even absent a warrant, the search and seizure of garbage
left for collection outside the curtilage of a home, California v. Greenwood, 486 U.S. 35, 108 S.Ct. 1625, 100 L.Ed.2d 30 (1988);
the aerial surveillance of a fenced-in backyard from an altitude of 1,000 feet, California v. Ciraolo, 476 U.S. 207, 106 S.Ct. 1809,
90 L.Ed.2d 210 (1986); the aerial observation of a partially exposed interior of a residential greenhouse from 400 feet above,
Florida v. Riley, 488 U.S. 445, 109 S.Ct. 693, 102 L.Ed.2d 835 (1989); the aerial photography of an industrial complex from
several thousand feet above, Dow Chemical Co. v. United States, 476 U.S. 227, 106 S.Ct. 1819, 90 L.Ed.2d 226 (1986); and the
observation of smoke emanating from chimney stacks, Air Pollution Variance Bd. of Colo. v. Western Alfalfa Corp., 416 U.S. 861,
94 S.Ct. 2114, 40 L.Ed.2d 607 (1974).
3 Although the Court credits us with the “novel proposition that inference insulates a search,” ante, at 2044, our point simply is that
an inference cannot be a search, contrary to the Court’s reasoning. See supra, at 2048 and this page. Thus, the Court’s use of
United States v. Karo, 468 U.S. 705, 104 S.Ct. 3296, 82 L.Ed.2d 530 (1984), to refute a point we do not make underscores the fact
that the Court has no real answer (either in logic or in law) to the point we do make. Of course, Karo itself does not provide any
support for the Court’s view that inferences can amount to unconstitutional searches. The illegality in that case was “the
monitoring of a beeper in a private residence” to obtain information that “could not have [been] obtained by observation from
outside,” id., at 714–715, 104 S.Ct. 3296, rather than any thought processes that flowed from such monitoring.
102

4 This view comports with that of all the Courts of Appeals that have resolved the issue. See 190 F.3d 1041 (C.A.9 1999); United
States v. Robinson, 62 F.3d 1325 (C.A.11 1995) (upholding warrantless use of thermal imager); United States v. Myers, 46 F.3d
668 (C.A.7 1995) (same); United States v. Ishmael, 48 F.3d 850 (C.A.5 1995) (same); United States v. Pinson, 24 F.3d 1056
(C.A.8 1994) (same). But see United States v. Cusumano, 67 F.3d 1497 (C.A.10 1995) (warrantless use of thermal imager violated
Fourth Amendment), vacated and decided on other grounds, 83 F.3d 1247 (C.A.10 1996) (en banc).
5 The record describes a device that numbers close to a thousand manufactured units; that has a predecessor numbering in the
neighborhood of 4,000 to 5,000 units; that competes with a similar product numbering from 5,000 to 6,000 units; and that is
“readily available to the public” for commercial, personal, or law enforcement purposes, and is just an 800–number away from
being rented from “half a dozen national companies” by anyone who wants one. App. 18. Since, by virtue of the Court’s new rule,
the issue is one of first impression, perhaps it should order an evidentiary hearing to determine whether these facts suffice to
establish “general public use.”
6 The use of the latter device would be constitutional given Smith v. Maryland, 442 U.S. 735, 741, 99 S.Ct. 2577, 61 L.Ed.2d 220
(1979), which upheld the use of pen registers to record numbers dialed on a phone because, unlike “the listening device employed
in Katz ... pen registers do not acquire the contents of communications.”
End of Document
© 2012 Thomson Reuters. No claim to original U.S. Government Works.
103

125 S.Ct. 834
Supreme Court of the United States
ILLINOIS, Petitioner,
v.
Roy I. CABALLES.
No. 03–923. | Argued Nov. 10, 2004. | Decided Jan.
24, 2005.
Opinion
Justice STEVENS delivered the opinion of the Court.
*406 Illinois State Trooper Daniel Gillette stopped
respondent for speeding on an interstate highway. When
Gillette radioed the police dispatcher to report the stop, a
second trooper, Craig Graham, a member of the Illinois
State Police Drug Interdiction Team, overheard the
transmission and immediately headed for the scene with
his narcotics-detection dog. When they arrived,
respondent’s car was on the shoulder of the road and
respondent was in Gillette’s vehicle. While Gillette was in
the process of writing a warning ticket, Graham walked
his dog around respondent’s car. The dog alerted at the
trunk. Based on that alert, the officers searched the trunk,
found marijuana, and arrested respondent. The entire
incident lasted less than 10 minutes.
*407 Respondent was convicted of a narcotics offense
and sentenced to 12 years’ imprisonment and a $256,136
fine. The trial judge denied his motion to suppress the
seized evidence and to quash his arrest. He held that the
officers had not unnecessarily prolonged the stop and that
the dog alert was sufficiently reliable to provide probable
cause to conduct the search. Although the Appellate Court
affirmed, the Illinois Supreme Court reversed, concluding
that because the canine sniff was performed without any “
‘specific and articulable facts’ ” to suggest drug activity,
the use of the dog “unjustifiably **837 enlarg[ed] the
scope of a routine traffic stop into a drug investigation.”
207 Ill.2d 504, 510, 280 Ill.Dec. 277, 802 N.E.2d 202,
205 (2003).
The question on which we granted certiorari, 541 U.S.
972, 124 S.Ct. 1875, 158 L.Ed.2d 466 (2004), is narrow:
“Whether the Fourth Amendment requires reasonable,
articulable suspicion to justify using a drug-detection dog
to sniff a vehicle during a legitimate traffic stop.” Pet. for
104
Cert. i. Thus, we proceed on the assumption that the
officer conducting the dog sniff had no information about
respondent except that he had been stopped for speeding;
accordingly, we have omitted any reference to facts about
respondent that might have triggered a modicum of
suspicion.
[1] [2] Here, the initial seizure of respondent when he was
stopped on the highway was based on probable cause and
was concededly lawful. It is nevertheless clear that a
seizure that is lawful at its inception can violate the
Fourth Amendment if its manner of execution
unreasonably infringes interests protected by the
Constitution. United States v. Jacobsen, 466 U.S. 109,
124, 104 S.Ct. 1652, 80 L.Ed.2d 85 (1984). A seizure that
is justified solely by the interest in issuing a warning
ticket to the driver can become unlawful if it is prolonged
beyond the time reasonably required to complete that
mission. In an earlier case involving a dog sniff that
occurred during an unreasonably prolonged traffic stop,
the Illinois Supreme Court held that use of the dog and
the subsequent discovery *408 of contraband were the
product of an unconstitutional seizure. People v. Cox, 202
Ill.2d 462, 270 Ill.Dec. 81, 782 N.E.2d 275 (2002). We
may assume that a similar result would be warranted in
this case if the dog sniff had been conducted while
respondent was being unlawfully detained.
In the state-court proceedings, however, the judges
carefully reviewed the details of Officer Gillette’s
conversations with respondent and the precise timing of
his radio transmissions to the dispatcher to determine
whether he had improperly extended the duration of the
stop to enable the dog sniff to occur. We have not
recounted those details because we accept the state court’s
conclusion that the duration of the stop in this case was
entirely justified by the traffic offense and the ordinary
inquiries incident to such a stop.
Despite this conclusion, the Illinois Supreme Court held
that the initially lawful traffic stop became an unlawful
seizure solely as a result of the canine sniff that occurred
outside respondent’s stopped car. That is, the court
characterized the dog sniff as the cause rather than the
consequence of a constitutional violation. In its view, the
use of the dog converted the citizen-police encounter from
a lawful traffic stop into a drug investigation, and because
the shift in purpose was not supported by any reasonable
suspicion that respondent possessed narcotics, it was
unlawful. In our view, conducting a dog sniff would not
change the character of a traffic stop that is lawful at its
inception and otherwise executed in a reasonable manner,

unless the dog sniff itself infringed respondent’s
constitutionally protected interest in privacy. Our cases
hold that it did not.
[3] [4] Official conduct that does not “compromise any
legitimate interest in privacy” is not a search subject to
the Fourth Amendment. Jacobsen, 466 U.S., at 123, 104
S.Ct. 1652. We have held that any interest in possessing
contraband cannot be deemed “legitimate,” and thus,
governmental conduct that only reveals the possession of
contraband “compromises no legitimate privacy interest.”
Ibid. This is because the expectation *409 “that certain
facts will not come to the attention of the authorities” is
not the same as an interest **838 in “privacy that society
is prepared to consider reasonable.” Id., at 122, 104 S.Ct.
1652 (punctuation omitted). In United States v. Place, 462
U.S. 696, 103 S.Ct. 2637, 77 L.Ed.2d 110 (1983), we
treated a canine sniff by a well-trained narcotics-detection
dog as “sui generis ” because it “discloses only the
presence or absence of narcotics, a contraband item.” Id.,
at 707, 103 S.Ct. 2637; see also Indianapolis v. Edmond,
531 U.S. 32, 40, 121 S.Ct. 447, 148 L.Ed.2d 333 (2000).
Respondent likewise concedes that “drug sniffs are
designed, and if properly conducted are generally likely,
to reveal only the presence of contraband.” Brief for
Respondent 17. Although respondent argues that the error
rates, particularly the existence of false positives, call into
question the premise that drug-detection dogs alert only to
contraband, the record contains no evidence or findings
that support his argument. Moreover, respondent does not
suggest that an erroneous alert, in and of itself, reveals
any legitimate private information, and, in this case, the
trial judge found that the dog sniff was sufficiently
reliable to establish probable cause to conduct a fullblown
search of the trunk.
[5] [6] Accordingly, the use of a well-trained narcoticsdetection
dog—one that “does not expose noncontraband
items that otherwise would remain hidden from public
view,” Place, 462 U.S., at 707, 103 S.Ct. 2637—during a
lawful traffic stop, generally does not implicate legitimate
privacy interests. In this case, the dog sniff was performed
on the exterior of respondent’s car while he was lawfully
seized for a traffic violation. Any intrusion on
respondent’s privacy expectations does not rise to the
level of a constitutionally cognizable infringement.
[7] This conclusion is entirely consistent with our recent
decision that the use of a thermal-imaging device to detect
the growth of marijuana in a home constituted an
unlawful search. Kyllo v. United States, 533 U.S. 27, 121
S.Ct. 2038, 150 L.Ed.2d 94 (2001). Critical to that
decision was the fact that the device was capable of
105
detecting lawful activity—in that case, intimate details in
a *410 home, such as “at what hour each night the lady of
the house takes her daily sauna and bath.” Id., at 38, 121
S.Ct. 2038. The legitimate expectation that information
about perfectly lawful activity will remain private is
categorically distinguishable from respondent’s hopes or
expectations concerning the nondetection of contraband in
the trunk of his car. A dog sniff conducted during a
concededly lawful traffic stop that reveals no information
other than the location of a substance that no individual
has any right to possess does not violate the Fourth
Amendment.
The judgment of the Illinois Supreme Court is vacated,
and the case is remanded for further proceedings not
inconsistent with this opinion.
It is so ordered.
THE CHIEF JUSTICE took no part in the decision of this
case.
Justice SOUTER, dissenting.
I would hold that using the dog for the purposes of
determining the presence of marijuana in the car’s trunk
was a search unauthorized as an incident of the speeding
stop and unjustified on any other ground. I would
accordingly affirm the judgment of the Supreme Court of
Illinois, and I respectfully dissent.
In United States v. Place, 462 U.S. 696, 103 S.Ct. 2637,
77 L.Ed.2d 110 (1983), we categorized the sniff of the
narcotics-seeking dog as “sui generis” under the Fourth
Amendment and held it was not a search. Id., at 707, 103
S.Ct. 2637. The classification rests not only upon the
limited nature **839 of the intrusion, but on a further
premise that experience has shown to be untenable, the
assumption that trained sniffing dogs do not err. What we
have learned about the fallibility of dogs in the years since
Place was decided would itself be reason to call for
reconsidering Place’s decision against treating the
intentional use of a trained dog as a search. The portent of
this very case, however, adds insistence *411 to the call,
for an uncritical adherence to Place would render the
Fourth Amendment indifferent to suspicionless and
indiscriminate sweeps of cars in parking garages and
pedestrians on sidewalks; if a sniff is not preceded by a
seizure subject to Fourth Amendment notice, it escapes
Fourth Amendment review entirely unless it is treated as a
search. We should not wait for these developments to
occur before rethinking Place’s analysis, which invites
such untoward consequences.1

At the heart both of Place and the Court’s opinion today
is the proposition that sniffs by a trained dog are sui
generis because a reaction by the dog in going alert is a
response to nothing but the presence of contraband.2 See
ibid. (“[T]he sniff discloses only the presence or absence
of narcotics, a contraband item”); ante, at 838 (assuming
that “a canine sniff by a well-trained narcotics-detection
dog” will only reveal “ ‘the presence or absence of
narcotics, a contraband item’ ” (quoting Place, supra, at
707, 103 S.Ct. 2637)). Hence, the argument goes, because
the sniff can only reveal the presence of items devoid of
any legal use, the sniff “does not implicate legitimate
privacy interests” and is not to be treated as a search.
Ante, at 838.
The infallible dog, however, is a creature of legal fiction.
Although the Supreme Court of Illinois did not get into
the sniffing averages of drug dogs, their supposed
infallibility is belied by judicial opinions describing welltrained
animals sniffing and alerting with less than perfect
accuracy, whether *412 owing to errors by their handlers,
the limitations of the dogs themselves, or even the
pervasive contamination of currency by cocaine. See, e.g.,
United States v. Kennedy, 131 F.3d 1371, 1378 (C.A.10
1997) (describing a dog that had a 71% accuracy rate);
United States v. Scarborough, 128 F.3d 1373, 1378, n. 3
(C.A.10 1997) (describing a dog that erroneously alerted
4 times out of 19 while working for the postal service and
8% of the time over its entire career); United States v.
Limares, 269 F.3d 794, 797 (C.A.7 2001) (accepting as
reliable a dog that gave false positives between 7% and
38% of the time); Laime v. State, 347 Ark. 142, 159, 60
S.W.3d 464, 476 (2001) (speaking of a dog that made
between 10 and 50 errors); United States v. $242,484.00,
351 F.3d 499, 511 (C.A.11 2003) (noting that because as
much as 80% of all currency in circulation contains drug
residue, a dog alert “is of little value”), vacated on other
grounds by rehearing en banc, 357 F.3d 1225 (C.A.11
2004); United States v. Carr, 25 F.3d 1194, 1214–1217
(C.A.3 1994) (Becker, J., concurring in part and
dissenting in part) (“[A] **840 substantial portion of
United States currency ... is tainted with sufficient traces
of controlled substances to cause a trained canine to alert
to their presence”). Indeed, a study cited by Illinois in this
case for the proposition that dog sniffs are “generally
reliable” shows that dogs in artificial testing situations
return false positives anywhere from 12.5% to 60% of the
time, depending on the length of the search. See Reply
Brief for Petitioner 13; Federal Aviation Admin., K.
Garner et al., Duty Cycle of the Detector Dog: A Baseline
Study 12 (Apr.2001) (prepared by Auburn U. Inst. for
Biological Detection Systems). In practical terms, the
evidence is clear that the dog that alerts hundreds of times
106
will be wrong dozens of times.
Once the dog’s fallibility is recognized, however, that
ends the justification claimed in Place for treating the
sniff as sui generis under the Fourth Amendment: the
sniff alert does not necessarily signal hidden contraband,
and opening the container or enclosed space whose
emanations the dog has *413 sensed will not necessarily
reveal contraband or any other evidence of crime. This is
not, of course, to deny that a dog’s reaction may provide
reasonable suspicion, or probable cause, to search the
container or enclosure; the Fourth Amendment does not
demand certainty of success to justify a search for
evidence or contraband. The point is simply that the sniff
and alert cannot claim the certainty that Place assumed,
both in treating the deliberate use of sniffing dogs as sui
generis and then taking that characterization as a reason
to say they are not searches subject to Fourth Amendment
scrutiny. And when that aura of uniqueness disappears,
there is no basis in Place’s reasoning, and no good reason
otherwise, to ignore the actual function that dog sniffs
perform. They are conducted to obtain information about
the contents of private spaces beyond anything that
human senses could perceive, even when conventionally
enhanced. The information is not provided by
independent third parties beyond the reach of
constitutional limitations, but gathered by the
government’s own officers in order to justify searches of
the traditional sort, which may or may not reveal evidence
of crime but will disclose anything meant to be kept
private in the area searched. Thus in practice the
government’s use of a trained narcotics dog functions as a
limited search to reveal undisclosed facts about private
enclosures, to be used to justify a further and complete
search of the enclosed area. And given the fallibility of
the dog, the sniff is the first step in a process that may
disclose “intimate details” without revealing contraband,
just as a thermal-imaging device might do, as described in
Kyllo v. United States, 533 U.S. 27, 121 S.Ct. 2038, 150
L.Ed.2d 94 (2001).3
**841 *414 It makes sense, then, to treat a sniff as the
search that it amounts to in practice, and to rely on the
body of our Fourth Amendment cases, including Kyllo, in
deciding whether such a search is reasonable. As a
general proposition, using a dog to sniff for drugs is
subject to the rule that the object of enforcing criminal
laws does not, without more, justify suspicionless Fourth
Amendment intrusions. See Indianapolis v. Edmond, 531
U.S. 32, 41–42, 121 S.Ct. 447, 148 L.Ed.2d 333 (2000).
Since the police claim to have had no particular suspicion
that Caballes was violating any drug law,4 this sniff
search must stand or fall on its being ancillary to the
traffic stop that led up to it. It is true that the police had

probable cause to stop the car for an offense committed in
the officer’s presence, which Caballes concedes could
have justified his arrest. See Brief for Respondent 31.
There is no occasion to consider authority incident to
arrest, however, see Knowles v. Iowa, 525 U.S. 113, 119
S.Ct. 484, 142 L.Ed.2d 492 (1998), for the police did
nothing more than detain Caballes long enough to check
his record and write a ticket. As a consequence, the
reasonableness of the search must be assessed in relation
to the actual delay the police chose to impose, and as
Justice GINSBURG points out in her opinion, post, at
844, the Fourth Amendment consequences of stopping for
a traffic citation are settled law.
*415 In Berkemer v. McCarty, 468 U.S. 420, 439–440,
104 S.Ct. 3138, 82 L.Ed.2d 317 (1984), followed in
Knowles, supra, at 117, 119 S.Ct. 484, we held that the
analogue of the common traffic stop was the limited
detention for investigation authorized by Terry v. Ohio,
392 U.S. 1, 88 S.Ct. 1868, 20 L.Ed.2d 889 (1968). While
Terry authorized a restricted incidental search for
weapons when reasonable suspicion warrants such a
safety measure, id., at 25–26, 88 S.Ct. 1868, the Court
took care to keep a Terry stop from automatically
becoming a foot in the door for all investigatory purposes;
the permissible intrusion was bounded by the justification
for the detention, id., at 29–30, 88 S.Ct. 1868.5 Although
facts disclosed by enquiry within this limit might give
grounds to go further, the government could not otherwise
take advantage of a suspect’s immobility to search for
evidence unrelated to the reason for the detention. That
has to be the rule unless Terry is going to become an open
sesame for general searches, and that rule requires
holding that the police do not have reasonable grounds to
conduct sniff searches for drugs simply because they have
stopped someone to receive a ticket for a highway
offense. Since the police had no indication of illegal
activity beyond the speed of the car in this case, the sniff
search should be held unreasonable under the Fourth
Amendment and its fruits should be suppressed.
Nothing in the case relied upon by the Court, United
States v. Jacobsen, 466 U.S. 109, 104 S.Ct. 1652, 80
L.Ed.2d 85 (1984), unsettled the limit of reasonable
enquiry adopted in Terry. In Jacobsen, the Court found
that no Fourth Amendment search occurred when federal
agents analyzed **842 powder they had already lawfully
obtained. The Court noted that because the test could only
reveal whether the powder was cocaine, the owner had no
legitimate privacy interest at stake. 466 U.S., at 123, 104
S.Ct. 1652. *416 As already explained, however, the use
of a sniffing dog in cases like this is significantly different
and properly treated as a search that does indeed implicate
Fourth Amendment protection.
In Jacobsen, once the powder was analyzed, that was
effectively the end of the matter: either the powder was
cocaine, a fact the owner had no legitimate interest in
concealing, or it was not cocaine, in which case the test
revealed nothing about the powder or anything else that
was not already legitimately obvious to the police. But in
the case of the dog sniff, the dog does not smell the
disclosed contraband; it smells a closed container. An
affirmative reaction therefore does not identify a
substance the police already legitimately possess, but
informs the police instead merely of a reasonable chance
of finding contraband they have yet to put their hands on.
The police will then open the container and discover
whatever lies within, be it marijuana or the owner’s
private papers. Thus, while Jacobsen could rely on the
assumption that the enquiry in question would either show
with certainty that a known substance was contraband or
would reveal nothing more, both the certainty and the
limit on disclosure that may follow are missing when the
dog sniffs the car.6
*417 The Court today does not go so far as to say
explicitly that sniff searches by dogs trained to sense
contraband always get a free pass under the Fourth
Amendment, since it reserves judgment on the
constitutional significance of sniffs assumed to be more
intrusive than a dog’s walk around a stopped car, ante, at
838. For this reason, I do not take the Court’s reliance on
Jacobsen as actually signaling recognition of a broad
authority to conduct suspicionless sniffs for drugs in any
parked car, about which Justice GINSBURG is rightly
concerned, post, at 845–846, or on the person of any
pedestrian minding his own business on a sidewalk. But
the Court’s stated reasoning provides no apparent
stopping point short of such excesses. For the sake of
providing a workable framework to analyze cases on facts
like these, which are certain to come along, I would treat
the dog sniff as the familiar search it is in fact, **843
subject to scrutiny under the Fourth Amendment.7
Justice GINSBURG, with whom Justice SOUTER joins,
dissenting.
Illinois State Police Trooper Daniel Gillette stopped Roy
Caballes for driving 71 miles per hour in a zone with a
posted *418 speed limit of 65 miles per hour. Trooper
Craig Graham of the Drug Interdiction Team heard on the
radio that Trooper Gillette was making a traffic stop.
Although Gillette requested no aid, Graham decided to
come to the scene to conduct a dog sniff. Gillette
informed Caballes that he was speeding and asked for the
107

usual documents—driver’s license, car registration, and
proof of insurance. Caballes promptly provided the
requested documents but refused to consent to a search of
his vehicle. After calling his dispatcher to check on the
validity of Caballes’ license and for outstanding warrants,
Gillette returned to his vehicle to write Caballes a
warning ticket. Interrupted by a radio call on an unrelated
matter, Gillette was still writing the ticket when Trooper
Graham arrived with his drug-detection dog. Graham
walked the dog around the car, the dog alerted at
Caballes’ trunk, and, after opening the trunk, the troopers
found marijuana. 207 Ill.2d 504, 506–507, 280 Ill.Dec.
277, 278, 802 N.E.2d 202, 203 (2003).
The Supreme Court of Illinois held that the drug evidence
should have been suppressed. Id., at 506, 280 Ill.Dec., at
278, 802 N.E.2d, at 202. Adhering to its decision in
People v. Cox, 202 Ill.2d 462, 270 Ill.Dec. 81, 782 N.E.2d
275 (2002), the court employed a two-part test taken from
Terry v. Ohio, 392 U.S. 1, 88 S.Ct. 1868, 20 L.Ed.2d 889
(1968), to determine the overall reasonableness of the
stop. 207 Ill.2d, at 508, 280 Ill.Dec., at 278, 802 N.E.2d,
at 204. The court asked first “whether the officer’s action
was justified at its inception,” and second “whether it was
reasonably related in scope to the circumstances which
justified the interference in the first place.” Ibid. (quoting
People v. Brownlee, 186 Ill.2d 501, 518–519, 239 Ill.Dec.
25, 34, 713 N.E.2d 556, 565 (1999) (in turn quoting
Terry, 392 U.S., at 19–20, 88 S.Ct. 1868)). “[I]t is
undisputed,” the court observed, “that the traffic stop was
properly initiated”; thus, the dispositive inquiry trained on
the “second part of the Terry test,” in which “[t]he State
bears the burden of establishing that the conduct remained
within the scope of the stop.” 207 Ill.2d, at 509, 280
Ill.Dec., at 279, 802 N.E.2d, at 204.
*419 The court concluded that the State failed to offer
sufficient justification for the canine sniff: “The police did
not detect the odor of marijuana in the car or note any
other evidence suggesting the presence of illegal drugs.”
Ibid. Lacking “specific and articulable facts” supporting
the canine sniff, ibid. (quoting Cox, 202 Ill.2d, at 470–
471, 270 Ill.Dec. 81, 782 N.E.2d, at 281), the court ruled,
“the police impermissibly broadened the scope of the
traffic stop in this case into a drug investigation.” 207
Ill.2d, at 509, 280 Ill.Dec., at 279, 802 N.E.2d, at 204.1 I
would affirm the Illinois **844 Supreme Court’s
judgment and hold that the drug sniff violated the Fourth
Amendment.
In Terry v. Ohio, the Court upheld the stop and
subsequent frisk of an individual based on an officer’s
observation of suspicious behavior and his reasonable
108
belief that the suspect was armed. See 392 U.S., at 27–28,
88 S.Ct. 1868. In a Terry-type investigatory stop, “the
officer’s action [must be] justified at its inception, and ...
reasonably related in scope to the circumstances which
justified the interference in the first place.” Id., at 20, 88
S.Ct. 1868. In applying Terry, the Court has several times
indicated that the limitation on “scope” is not confined to
the duration of the seizure; it also encompasses the
manner in which the seizure is conducted. See, e.g.,
Hiibel v. Sixth Judicial Dist. Court of Nev., Humboldt
Cty., 542 U.S. 177, 188, 124 S.Ct. 2451, 2459, 159
L.Ed.2d 292 (2004) (an officer’s request that an
individual identify himself “has an immediate relation to
the purpose, rationale, and practical demands of a Terry
stop”); United States v. Hensley, 469 U.S. 221, 235, 105
S.Ct. 675, 83 L.Ed.2d 604 (1985) (examining, under
Terry, *420 both “the length and intrusiveness of the stop
and detention”); Florida v. Royer, 460 U.S. 491, 500, 103
S.Ct. 1319, 75 L.Ed.2d 229 (1983) (plurality opinion)
(“[A]n investigative detention must be temporary and last
no longer than is necessary to effectuate the purpose of
the stop [and] the investigative methods employed should
be the least intrusive means reasonably available to verify
or dispel the officer’s suspicion ....”).
“A routine traffic stop,” the Court has observed, “is a
relatively brief encounter and ‘is more analogous to a socalled
Terry stop ... than to a formal arrest.’ ” Knowles v.
Iowa, 525 U.S. 113, 117, 119 S.Ct. 484, 142 L.Ed.2d 492
(1998) (quoting Berkemer v. McCarty, 468 U.S. 420, 439,
104 S.Ct. 3138, 82 L.Ed.2d 317 (1984)); see also ante, at
841 (SOUTER, J., dissenting) (The government may not
“take advantage of a suspect’s immobility to search for
evidence unrelated to the reason for the detention.”).2 I
would apply Terry’s reasonable-relation test, as the
Illinois Supreme Court did, to determine whether the
canine sniff impermissibly expanded the scope of the
initially valid seizure of Caballes.
It is hardly dispositive that the dog sniff in this case may
not have lengthened the duration of the stop. Cf. ante, at
837 (“A seizure ... can become unlawful if it is prolonged
beyond the time reasonably required to complete [the
initial] mission.”). Terry, it merits repetition, instructs that
**845 any investigation must be “reasonably related in
scope to the circumstances which justified the
interference in the first place.” 392 U.S., at 20, 88 S.Ct.
1868 (emphasis added). The unwarranted *421 and
nonconsensual expansion of the seizure here from a
routine traffic stop to a drug investigation broadened the
scope of the investigation in a manner that, in my
judgment, runs afoul of the Fourth Amendment.3
The Court rejects the Illinois Supreme Court’s judgment

and, implicitly, the application of Terry to a traffic stop
converted, by calling in a dog, to a drug search. The Court
so rules, holding that a dog sniff does not render a seizure
that is reasonable in time unreasonable in scope. Ante, at
837. Dog sniffs that detect only the possession of
contraband may be employed without offense to the
Fourth Amendment, the Court reasons, because they
reveal no lawful activity and hence disturb no legitimate
expectation of privacy. Ante, at 837–838.
In my view, the Court diminishes the Fourth
Amendment’s force by abandoning the second Terry
inquiry (was the police action “reasonably related in
scope to the circumstances [justifiying] the [initial]
interference”). 392 U.S., at 20, 88 S.Ct. 1868. A drugdetection
dog is an intimidating animal. Cf. United States
v. Williams, 356 F.3d 1268, 1276 (C.A.10 2004) (McKay,
J., dissenting) (“drug dogs are not lap dogs”). Injecting
such an animal into a routine traffic stop changes the
character of the encounter between the police and the
motorist. The stop becomes broader, more adversarial,
and (in at least some cases) longer. Caballes—who, as far
as Troopers Gillette and Graham knew, was guilty solely
of driving six miles per hour over the speed limit—was
exposed to the embarrassment and intimidation of being
investigated, on a public thoroughfare, for drugs. Even if
the drug sniff is not characterized as a Fourth Amendment
“search,” cf. Indianapolis *422 v. Edmond, 531 U.S. 32,
40, 121 S.Ct. 447, 148 L.Ed.2d 333 (2000); United States
v. Place, 462 U.S. 696, 707, 103 S.Ct. 2637, 77 L.Ed.2d
110 (1983), the sniff surely broadened the scope of the
traffic-violation-related seizure.
The Court has never removed police action from Fourth
Amendment control on the ground that the action is well
calculated to apprehend the guilty. See, e.g., United States
v. Karo, 468 U.S. 705, 717, 104 S.Ct. 3296, 82 L.Ed.2d
530 (1984) (Fourth Amendment warrant requirement
applies to police monitoring of a beeper in a house even if
“the facts [justify] believing that a crime is being or will
be committed and that monitoring the beeper wherever it
goes is likely to produce evidence of criminal activity.”);
see also Minnesota v. Carter, 525 U.S. 83, 110, 119 S.Ct.
469, 142 L.Ed.2d 373 (1998) (GINSBURG, J., dissenting)
(“Fourth Amendment protection, reserved for the
innocent only, would have little force in regulating police
behavior toward either the innocent or the guilty.”). Under
today’s decision, every traffic stop could become an
occasion to call in the dogs, to the distress and
embarrassment of the law-abiding population.
The Illinois Supreme Court, it seems to me, correctly
apprehended the danger in allowing the police to search
109
for contraband despite the absence of cause to suspect its
presence. Today’s decision, in contrast, clears the way for
suspicionless, **846 dog-accompanied drug sweeps of
parked cars along sidewalks and in parking lots. Compare,
e.g., United States v. Ludwig, 10 F.3d 1523, 1526–1527
(C.A.10 1993) (upholding a search based on a canine drug
sniff of a parked car in a motel parking lot conducted
without particular suspicion), with United States v. Quinn,
815 F.2d 153, 159 (C.A.1 1987) (officers must have
reasonable suspicion that a car contains narcotics at the
moment a dog sniff is performed), and Place, 462 U.S., at
706–707, 103 S.Ct. 2637 (Fourth Amendment not
violated by a dog sniff of a piece of luggage that was
seized, pre-sniff, based on suspicion of drugs). Nor would
motorists have constitutional grounds for complaint
should police with dogs, stationed at long traffic lights,
circle cars waiting for the red signal to turn green.
*423 Today’s decision also undermines this Court’s
situation-sensitive balancing of Fourth Amendment
interests in other contexts. For example, in Bond v. United
States, 529 U.S. 334, 338–339, 120 S.Ct. 1462, 146
L.Ed.2d 365 (2000), the Court held that a bus passenger
had an expectation of privacy in a bag placed in an
overhead bin and that a police officer’s physical
manipulation of the bag constituted an illegal search. If
canine drug sniffs are entirely exempt from Fourth
Amendment inspection, a sniff could substitute for an
officer’s request to a bus passenger for permission to
search his bag, with this significant difference: The
passenger would not have the option to say “No.”
The dog sniff in this case, it bears emphasis, was for drug
detection only. A dog sniff for explosives, involving
security interests not presented here, would be an entirely
different matter. Detector dogs are ordinarily trained not
as all-purpose sniffers, but for discrete purposes. For
example, they may be trained for narcotics detection or
for explosives detection or for agricultural products
detection. See, e.g., U.S. Customs & Border Protection,
Canine Enforcement Training Center Training Program
Course
Descriptions,
http://www.cbp.gov/xp/cgov/border_security/canines/trai
ning_program.xml (all Internet materials as visited Dec.
16, 2004, and available in Clerk of Court’s case file)
(describing Customs training courses in narcotics
detection); Transportation Security Administration,
Canine and Explosives Program, http://
www.tsa.gov/public/displaytheme=32 (describing
Transportation Security Administration’s explosives
detection canine program); U.S. Dept. of Agriculture,
Animal and Plant Health Inspection Service, USDA’s
Detector Dogs: Protecting American Agriculture

(Oct.2001), available at http://www.aphis.usda.
gov/oa/pubs/detdogs.pdf (describing USDA Beagle
Brigade detector dogs trained to detect prohibited fruits,
plants, and meat); see also Jennings, Origins and History
of Security and Detector Dogs, in Canine Sports Medicine
and Surgery 16, 18–19 (M. Bloomberg, J. Dee, & R.
Taylor eds.1998) (describing narcotics-detector *424 dogs
used by Border Patrol and Customs, and bomb detector
dogs used by the Federal Aviation Administration and the
Secret Service, but noting the possibility in some
circumstances of cross training dogs for multiple tasks);
S. Chapman, Police Dogs in North America 64, 70–79
(1990) (describing narcotics- and explosives-detection
dogs and noting the possibility of cross training). There is
no indication in this case that the dog accompanying
Trooper Graham was trained for anything other than drug
detection. See 207 Ill.2d, at 507, 280 Ill.Dec., at 278, 802
N.E.2d, at 203 (“Trooper Graham arrived with his drugdetection
dog ....”); Brief for Petitioner 3 (“Trooper
Graham arrived with a drug-detection dog ....”).
**847 This Court has distinguished between the general
interest in crime control and more immediate threats to
public safety. In Michigan Dept. of State Police v. Sitz,
496 U.S. 444, 110 S.Ct. 2481, 110 L.Ed.2d 412 (1990),
this Court upheld the use of a sobriety traffic checkpoint.
Balancing the State’s interest in preventing drunk driving,
the extent to which that could be accomplished through
the checkpoint program, and the degree of intrusion the
stops involved, the Court determined that the State’s
checkpoint program was consistent with the Fourth
Amendment. Id., at 455, 110 S.Ct. 2481. Ten years after
Sitz, in Indianapolis v. Edmond, 531 U.S. 32, 121 S.Ct.
447, 148 L.Ed.2d 333, this Court held that a drug
interdiction checkpoint violated the Fourth Amendment.
Despite the illegal narcotics traffic that the Nation is
struggling to stem, the Court explained, a “general interest
in crime control” did not justify the stops. Id., at 43–44,
121 S.Ct. 447 (internal quotation marks omitted). The
Court distinguished the sobriety checkpoints in Sitz on the
ground that those checkpoints were designed to eliminate
an “immediate, vehicle-bound threat to life and limb.”
531 U.S., at 43, 121 S.Ct. 447.
The use of bomb-detection dogs to check vehicles for
explosives without doubt has a closer kinship to the
sobriety checkpoints in Sitz than to the drug checkpoints
in Edmond. As the Court observed in Edmond: “[T]he
Fourth Amendment would almost certainly permit an
appropriately tailored *425 roadblock set up to thwart an
imminent terrorist attack ....” 531 U.S., at 44, 121 S.Ct.
447. Even if the Court were to change course and
characterize a dog sniff as an independent Fourth
Amendment search, see ante, p. 838 (SOUTER, J.,
dissenting), the immediate, present danger of explosives
would likely justify a bomb sniff under the special needs
doctrine. See, e.g., ante, at 843, n. 7 (SOUTER, J.,
dissenting); Griffin v. Wisconsin, 483 U.S. 868, 873, 107
S.Ct. 3164, 97 L.Ed.2d 709 (1987) (permitting exceptions
to the warrant and probable-cause requirements for a
search when “special needs, beyond the normal need for
law enforcement,” make those requirements impracticable
(quoting New Jersey v. T.L. O., 469 U.S. 325, 351, 105
S.Ct. 733, 83 L.Ed.2d 720 (1985) (Blackmun, J.,
concurring in judgment))).
* * *
For the reasons stated, I would hold that the police
violated Caballes’ Fourth Amendment rights when,
without cause to suspect wrongdoing, they conducted a
dog sniff of his vehicle. I would therefore affirm the
judgment of the Illinois Supreme Court.
Parallel Citations
125 S.Ct. 834, 160 L.Ed.2d 842, 73 BNA USLW 4111,
05 Cal. Daily Op. Serv. 648, 2005 Daily Journal D.A.R.
849, 18 Fla. L. Weekly Fed. S 100
Footnotes
* The syllabus constitutes no part of the opinion of the Court but has been prepared by the Reporter of Decisions for the convenience
of the reader. See United States v. Detroit Timber & Lumber Co., 200 U.S. 321, 337, 26 S.Ct. 282, 50 L.Ed. 499.
1 I also join Justice GINSBURG’s dissent, post, p. 843. Without directly reexamining the soundness of the Court’s analysis of
government dog sniffs in Place, she demonstrates that investigation into a matter beyond the subject of the traffic stop here offends
the rule in Terry v. Ohio, 392 U.S. 1, 88 S.Ct. 1868, 20 L.Ed.2d 889 (1968), the analysis I, too, adopt.
2 Another proffered justification for sui generis status is that a dog sniff is a particularly nonintrusive procedure. United States v.
Place, 462 U.S. 696, 707, 103 S.Ct. 2637, 77 L.Ed.2d 110 (1983). I agree with Justice GINSBURG that the introduction of a dog
to a traffic stop (let alone an encounter with someone walking down the street) can in fact be quite intrusive. Post, at 845.
110

3 Kyllo was concerned with whether a search occurred when the police used a thermal-imaging device on a house to detect heat
emanations associated with high-powered marijuana-growing lamps. In concluding that using the device was a search, the Court
stressed that the “Government [may not] us[e] a device ... to explore details of the home that would previously have been
unknowable without physical intrusion.” 533 U.S., at 40, 121 S.Ct. 2038. Any difference between the dwelling in Kyllo and the
trunk of the car here may go to the issue of the reasonableness of the respective searches, but it has no bearing on the question of
search or no search. Nor is it significant that Kyllo’s imaging device would disclose personal details immediately, whereas they
would be revealed only in the further step of opening the enclosed space following the dog’s alert reaction; in practical terms the
same values protected by the Fourth Amendment are at stake in each case. The justifications required by the Fourth Amendment
may or may not differ as between the two practices, but if constitutional scrutiny is in order for the imager, it is in order for the
dog.
4 Despite the remarkable fact that the police pulled over a car for going 71 miles an hour on I–80, the State maintains that excessive
speed was the only reason for the stop, and the case comes to us on that assumption.
5 Thus, in Place itself, the Government officials had independent grounds to suspect that the luggage in question contained
contraband before they employed the dog sniff. 462 U.S., at 698, 103 S.Ct. 2637 (describing how Place had acted suspiciously in
line at the airport and had labeled his luggage with inconsistent and fictional addresses).
6 It would also be error to claim that some variant of the plain-view doctrine excuses the lack of justification for the dog sniff in this
case. When an officer observes an object left by its owner in plain view, no search occurs because the owner has exhibited “no
intention to keep [the object] to himself.” Katz v. United States, 389 U.S. 347, 361, 88 S.Ct. 507, 19 L.Ed.2d 576 (1967) (Harlan,
J., concurring). In contrast, when an individual conceals his possessions from the world, he has grounds to expect some degree of
privacy. While plain view may be enhanced somewhat by technology, see, e.g., Dow Chemical Co. v. United States, 476 U.S. 227,
106 S.Ct. 1819, 90 L.Ed.2d 226 (1986) (allowing for aerial surveillance of an industrial complex), there are limits. As Kyllo v.
United States, 533 U.S. 27, 33, 121 S.Ct. 2038, 150 L.Ed.2d 94 (2001), explained in treating the thermal-imaging device as outside
the plain-view doctrine, “[w]e have previously reserved judgment as to how much technological enhancement of ordinary
perception” turns mere observation into a Fourth Amendment search. While Kyllo laid special emphasis on the heightened privacy
expectations that surround the home, closed car trunks are accorded some level of privacy protection. See, e.g., New York v. Belton,
453 U.S. 454, 460, n. 4, 101 S.Ct. 2860, 69 L.Ed.2d 768 (1981) (holding that even a search incident to arrest in a vehicle does not
itself permit a search of the trunk). As a result, if Fourth Amendment protections are to have meaning in the face of superhuman,
yet fallible, techniques like the use of trained dogs, those techniques must be justified on the basis of their reasonableness, lest
everything be deemed in plain view.
7 I should take care myself to reserve judgment about a possible case significantly unlike this one. All of us are concerned not to
prejudge a claim of authority to detect explosives and dangerous chemical or biological weapons that might be carried by a terrorist
who prompts no individualized suspicion. Suffice it to say here that what is a reasonable search depends in part on demonstrated
risk. Unreasonable sniff searches for marijuana are not necessarily unreasonable sniff searches for destructive or deadly material if
suicide bombs are a societal risk.
1 The Illinois Supreme Court held insufficient to support a canine sniff Gillette’s observations that (1) Caballes said he was moving
to Chicago, but his only visible belongings were two sport coats in the backseat; (2) the car smelled of air freshener; (3) Caballes
was dressed for business, but was unemployed; and (4) Caballes seemed nervous. Even viewed together, the court said, these
observations gave rise to “nothing more than a vague hunch” of “possible wrongdoing.” 207 Ill.2d 504, 509–510, 280 Ill.Dec., at
279–280, 802 N.E.2d 202, 204–205 (2003). This Court proceeds on “the assumption that the officer conducting the dog sniff had
no information about [Caballes].” Ante, at 837.
2 The Berkemer Court cautioned that by analogizing a traffic stop to a Terry stop, it did “not suggest that a traffic stop supported by
probable cause may not exceed the bounds set by the Fourth Amendment on the scope of a Terry stop.” 468 U.S., at 439, n. 29, 104
S.Ct. 3138. This Court, however, looked to Terry earlier in deciding that an officer acted reasonably when he ordered a motorist
stopped for driving with expired license tags to exit his car, Pennsylvania v. Mimms, 434 U.S. 106, 109–110, 98 S.Ct. 330, 54
L.Ed.2d 331 (1977) (per curiam), and later reaffirmed the Terry analogy when evaluating a police officer’s authority to search a
vehicle during a routine traffic stop, Knowles, 525 U.S., at 117, 119 S.Ct. 484.
3 The question whether a police officer inquiring about drugs without reasonable suspicion unconstitutionally broadens a traffic
investigation is not before the Court. Cf. Florida v. Bostick, 501 U.S. 429, 434, 111 S.Ct. 2382, 115 L.Ed.2d 389 (1991) (police
questioning of a bus passenger, who might have just said “No,” did not constitute a seizure).
End of Document
111
© 2012 Thomson Reuters. No claim to original U.S. Government Works.

417 F.3d 692
United States Court of Appeals,
Seventh Circuit.
UNITED STATES of America, Plaintiff-Appellee,
v.
David C. BROCK, Defendant-Appellant.
No. 03-2279. | Argued April 8, 2005. | Decided Aug.
2, 2005.
Opinion
FLAUM, Chief Judge.
A federal jury convicted defendant-appellant David C.
Brock of several counts of possessing with intent to
distribute large quantities of narcotics and being a felon in
possession of a firearm. Brock appeals his conviction and
his 360-month sentence. For the reasons that follow, we
affirm the conviction and order a limited remand of
Brock’s sentence pursuant to our decision in United States
v. Paladino, 401 F.3d 471 (7th Cir.2005).
I. Background
On April 9, 2002, a team of federal and state law
enforcement officers executed a federal search warrant at
defendant’s residence, 3375 Payton Avenue in
Indianapolis, Indiana (“3375”). The officers conducted a
thorough search of the home and, over several hours,
recovered evidence including cocaine, methamphetamine,
marijuana, $35,000 in cash, numerous loaded firearms,
and ammunition. Brock was not present during the search,
but three individuals were found in the home who
identified themselves as Reginald Godsey, Kelly Knox,
and Steven Hayden. Indianapolis police officer David
Miller placed handcuffs on these individuals, and after
informing them of their Miranda rights, proceeded to
question them. Godsey told police that he lived next door
at 3381 Payton Avenue (“3381”), and that he watched
over both houses. He gave the police a key to 3381 and
consented to a search of the common areas of that
residence.
Godsey also informed police that Brock rented a room at
3381, which he used as a “stash house.” According to
Godsey, Brock transported methamphetamine between
112
3381 and 3375 using a silver suitcase and was storing 16
to 17 pounds of methamphetamine inside a safe in his
room at 3381. Police had recovered a silver suitcase
during the search of 3375.
After receiving this information from Godsey, Officer
Miller returned to the office to prepare an affidavit and
obtain a search warrant for the entire 3381 residence.
Other officers entered 3381 through the rear door using
Godsey’s key. The house at 3381 Payton Avenue
consisted of a kitchen, a living room, and three separate
locked bedrooms. The police found a shotgun in plain
view in the living room. Godsey provided a key to his
bedroom and authorized police to search it. Officers
found in Godsey’s room a small amount of narcotics
consistent with personal use. Another bedroom in the
southwest corner of the residence had a pile of clothes
directly in front of the locked door and a sign on the door
stating: “Stay Out. David.” Officer Ron Mills, a canine
officer with the Indianapolis police department, was
called to 3381 with Yoba, his drugsniffing dog, to
corroborate the presence of narcotics. The dog alerted to
the presence *694 of narcotics while sniffing just outside
Brock’s locked bedroom.
Officer Miller prepared an affidavit in which he detailed
all of the evidence recovered from 3375, including utility
bills for the 3381 residence in Brock’s name. Miller also
included in the affidavit the information provided by
Godsey as well as the dog’s alert to the southwest
bedroom of 3381. Based on that evidence, a judge issued
a search warrant authorizing a search of 3381 and seizure
of “Methamphetamine, Cocaine, an extract of Coca,
Marijuana, Cannabis, all monies, papers, records,
documents, electronic information, or any other
documentation which indicates or tends to indicate a
violation or a conspiracy to violate the Indiana Controlled
Substance Act.” When Officer Miller returned with the
search warrant, police forcibly entered the southwest
bedroom. They recovered several firearms from inside a
closet, an ammunition box labeled “David Brock,” and a
safe, which the officers forcibly opened to find seventeen
pounds of methamphetamine and one pound of cocaine.
Godsey, Hayden, and Knox all denied ownership of the
drugs and weapons seized from both residences. They
were released and were not charged in connection with
this case.
Brock was indicted on six counts: two counts of
possession with intent to distribute 500 grams or more of
methamphetamine in violation of 21 U.S.C. § 841(a)(1);
two counts of possession with intent to distribute cocaine

(500 grams and an unspecified amount) in violation of 21
U.S.C. § 841(a)(1); and two counts of being a felon in
possession of numerous firearms and ammunition in
violation of 18 U.S.C. § 922(g)(1).
Prior to trial, defendant moved to suppress the evidence
recovered from 3381 on the grounds that the dog sniff
was an illegal warrantless search and the search warrant
was not otherwise supported by probable cause. The
district court denied the motion following a hearing, and
Brock proceeded to trial.
At trial, the government introduced the evidence seized
during the searches of 3375 and 3381, including 8.42
kilograms of methamphetamine, 1.037 kilograms of
cocaine, and 21 firearms. The government also presented
two witnesses, Joel Dyer and Scott Lewis, who testified
that they had engaged in additional methamphetamine
transactions with Brock at the 3375 residence. The jury
convicted Brock on all six counts.
II. Discussion
In this appeal, Brock contends that the district court erred
in denying his motion to suppress, arguing that the
warrantless dog sniff inside his home violated the Fourth
Amendment. Brock also challenges several rulings made
by the district court during the course of his trial. Finally,
Brock contests his sentence and seeks a Paladino remand.
We address each argument in turn.
A. Motion to Suppress
The Fourth Amendment to the United States Constitution
provides:
The right of the people to be secure in their
persons, houses, papers and effects, against
unreasonable searches and seizures, shall not be
violated, and no Warrants shall issue, but upon
probable cause, supported by Oath or affirmation,
and particularly describing the place to be
searched, and the persons or things to be seized.
U.S. Const. amend. IV. With few exceptions, the Fourth
Amendment prohibits the warrantless entry of a person’s
home to make an arrest or conduct a search. *695 Kyllo v.
United States, 533 U.S. 27, 31, 121 S.Ct. 2038, 150
L.Ed.2d 94 (2001); Illinois v. Rodriguez, 497 U.S. 177,
181, 110 S.Ct. 2793, 111 L.Ed.2d 148 (1990); Payton v.
New York, 445 U.S. 573, 586, 100 S.Ct. 1371, 63 L.Ed.2d
113
639 (1980). “A ‘search’ occurs when an expectation of
privacy that society is prepared to consider reasonable is
infringed.” United States v. Jacobsen, 466 U.S. 109, 113,
104 S.Ct. 1652, 80 L.Ed.2d 85 (1984); see also Kyllo, 533
U.S. at 33, 121 S.Ct. 2038 (quoting California v. Ciraolo,
476 U.S. 207, 211, 106 S.Ct. 1809, 90 L.Ed.2d 210
(1986)) (a Fourth Amendment search of a home does not
occur “unless the individual manifested a subjective
expectation of privacy in the object of the challenged
search and society is willing to recognize that expectation
as reasonable”).
[1] Brock contends that the canine sniff outside his locked
bedroom door constituted an illegal warrantless search,
and that the warrant to search 3381, which was issued in
reliance on that sniff, violated the federal and Indiana
Constitutions. The government argues that the dog sniff
was not a search at all because the police were lawfully
present inside Brock’s residence with Godsey’s consent,
and Brock possessed no reasonable expectation that his
drugs would go undetected.
At oral argument, the government relied primarily on the
Supreme Court’s recent decision in Illinois v. Caballes,
543 U.S. 405, 125 S.Ct. 834, 160 L.Ed.2d 842 (2005),
issued after the parties submitted their briefs in this case.
The Court held in Caballes that a dog sniff of a vehicle
during a traffic stop, conducted absent reasonable
suspicion of illegal drug activity, did not violate the
Fourth Amendment because it did not implicate any
legitimate privacy interest. Id. at 837-38. The Court
explained that, because there is no legitimate interest in
possessing contraband, the use of a well-trained narcoticsdetection
dog that “only reveals the possession of
narcotics ‘compromises no legitimate privacy interest’ ”
and does not violate the Fourth Amendment. Id. (quoting
Jacobsen, 466 U.S. at 123, 104 S.Ct. 1652).
Caballes relied on the Court’s opinion in United States v.
Place, 462 U.S. 696, 103 S.Ct. 2637, 77 L.Ed.2d 110
(1983), which held that a canine sniff of a traveler’s
luggage in the airport was not a search within the meaning
of the Fourth Amendment because the information
obtained through this investigative technique revealed
only the presence or absence of narcotics. As the Court
explained,
the canine sniff is sui generis. We are aware of no
other investigative procedure that is so limited
both in the manner in which the information is
obtained and in the content of the information
revealed by the procedure.
Id. at 707, 103 S.Ct. 2637. Adhering to this reasoning, the

Court held in Jacobsen that a chemical field test of a
substance found inside a package was not a Fourth
Amendment search because the test “merely discloses
whether or not a particular substance is cocaine.” 466
U.S. at 123, 104 S.Ct. 1652. As there is no legitimate
interest in possessing cocaine, the field test did not
compromise any legitimate privacy interest. Id.; see also
Indianapolis v. Edmond, 531 U.S. 32, 40, 121 S.Ct. 447,
148 L.Ed.2d 333 (2000) (officers’ practice of walking a
narcotics-detection dog around the exterior of each car at
a drug interdiction checkpoint does not transform the
seizure into a search).
Defendant tries to distinguish these cases on the ground
that he has a far greater privacy interest inside his home,
particularly inside the bedroom, than one has in a public
space or even a car. He relies on the Court’s decision in
Kyllo, which held that the use of a thermal-imaging
device to detect relative amounts *696 of heat within a
private home was a Fourth Amendment search and must
be supported by probable cause and a warrant. In Kyllo,
the Court held that where the government uses “a device
that is not in general public use, to explore details of the
home that would previously have been unknowable
without physical intrusion, the surveillance is a ‘search’
and is presumptively unreasonable without a warrant.” Id.
at 40, 121 S.Ct. 2038.
Kyllo does not support defendant’s position. The Kyllo
Court did reaffirm the important privacy interest in one’s
home. See id. at 37, 121 S.Ct. 2038 (“In the home, our
cases show, all details are intimate details, because the
entire area is held safe from prying government eyes.”).
However, as the Court subsequently explained in
Caballes, it was essential to Kyllo’s holding that the
imaging device was capable of detecting not only illegal
activity inside the home, but also lawful activity,
including such intimate details as “at what hour each
night the lady of the house takes her daily sauna and
bath.” Caballes, 125 S.Ct. at 838 (quoting Kyllo, 533 U.S.
at 38, 121 S.Ct. 2038). As the Court emphasized, an
expectation of privacy regarding lawful activity is
“categorically distinguishable” from one’s “hopes or
expectations concerning the nondetection of contraband in
the trunk of his car.” Id. Based on this reasoning, we hold
that the dog sniff inside Brock’s residence was not a
Fourth Amendment search because it detected only the
presence of contraband and did not provide any
information about lawful activity over which Brock had a
legitimate expectation of privacy.1
This conclusion is consistent with previous decisions of
this Court, as well as those of the majority of our sister
circuits, which have held that canine sniffs used only to
114
detect the presence of contraband are not Fourth
Amendment searches. See United States v. Vasquez, 909
F.2d 235, 238 (7th Cir.1990) (collecting cases) (canine
sniff of a private garage from a public alley was not a
warrantless search). Accord United States v. Reed, 141
F.3d 644, 650 (6th Cir.1998) (where canine team was
lawfully present inside a home, the canine sniff itself was
not a Fourth Amendment search); United States v. Reyes,
349 F.3d 219, 224 (5th Cir.2003) (dog sniff of passengers
exiting bus from distance of four to five feet was not a
Fourth Amendment search); United States v. Roby, 122
F.3d 1120, 1125 (8th Cir.1997) (defendant’s reasonable
expectation of privacy in his hotel room did not extend to
hallway outside his room, and no warrant was needed to
bring trained dog to conduct a narcotics sniff in hallway);
United States v. Lingenfelter, 997 F.2d 632, 638 (9th
Cir.1993) (canine sniff of a commercial warehouse was
not a search because defendant “could have no legitimate
expectation that a narcotics canine would not detect the
odor of marijuana”); United States v. Colyer, 878 F.2d
469, 477 (D.C.Cir.1989) (dog sniff of a sleeper car from
train’s public corridor was not a search because it was not
overly intrusive and “did not expose noncontraband items
that otherwise would remain hidden from view”). But see
United States v. Thomas, 757 F.2d 1359, 1366-67 (2d
Cir.1985) (canine sniff of doorway outside defendant’s
apartment was a search *697 because it impermissibly
intruded on defendant’s legitimate expectation that the
contents of his closed apartment would not be sensed
from outside his door).
Whatever subjective expectation Brock might have had
that his possession of narcotics would remain private, that
expectation is not one “that society is prepared to consider
reasonable.” Jacobsen, 466 U.S. at 113, 104 S.Ct. 1652.
The Second Circuit’s holding to the contrary in Thomas,
on which defendant relies, has been rightly criticized. See
Lingenfelter, 997 F.2d at 638 (Thomas’s implication “that
a person has a reasonable expectation that even
contraband items hidden in his dwelling place will not be
revealed” is inconsistent with Supreme Court precedent);
Colyer, 878 F.2d at 475 (questioning correctness of
Thomas’s assertion that possessor of contraband “had a
legitimate expectation that the contents of his closed
apartment would remain private”).
[2] Critical to our holding that the dog sniff in this case
was not a Fourth Amendment search is the fact that police
were lawfully present inside the common areas of the
residence with the consent of Brock’s roommate. While
Brock contends that he had a legitimate expectation that
the contents of his locked bedroom would remain private,
he does not contest in any meaningful way Godsey’s

authority to allow police inside the common areas of their
shared home.2 It is well settled that a third party with
common authority over a home may consent to a search,
obviating the need for a search warrant. United States v.
Matlock, 415 U.S. 164, 171, 94 S.Ct. 988, 39 L.Ed.2d 242
(1974); United States v. Aghedo, 159 F.3d 308, 310 (7th
Cir.1998). Third-party consents to search shared property
are based on a “reduced expectation of privacy in the
premises or things shared with another.” United States v.
Ladell, 127 F.3d 622, 624 (7th Cir.1997). When someone
shares an apartment or a home with another individual, he
“ordinarily assumes the risk that a co-tenant might
consent to a search, at least to all common areas and those
areas to which the other has access.” Id. Once Godsey
authorized the police to explore the common areas of
3381, the entry of a narcotics-sniffing dog into that space
did not infringe on any legitimate privacy interest.
Everything behind Brock’s locked bedroom door
remained undetected except the narcotics, which Brock
had no right to possess in the first place. The dog sniff
from the common area of defendant’s residence, where
police were present by consent, did not violate
defendant’s Fourth Amendment rights, and the district
court did not err in denying Brock’s motion to suppress.
B. Trial Rulings
Defendant claims that the district court committed several
errors in conducting the trial. He argues that the court
improperly limited his cross-examination of a government
witness and abused its discretion in refusing to give a
missing witness instruction. Brock contends that these
errors deprived him of a fair trial and warrant reversal of
his conviction.
1. Cross-Examination
[3] Defendant argues that the district court abused its
discretion in limiting his *698 cross-examination of Joel
Dyer, one of the government witnesses who testified that
he sold large quantities of methamphetamine to Brock and
later purchased the drug from him. Prior to Brock’s trial,
Dyer had been charged in an unrelated case in state court.
Those state charges were later dropped, and federal
authorities brought charges against Dyer arising out of the
same conduct. Dyer was federal custody at the time of his
testimony in Brock’s trial. During her cross-examination
of Dyer, defense counsel attempted to discredit his
testimony by showing that Dyer cooperated with the
government and testified against defendant for the
purpose of avoiding habitual offender status on his state
115
charges.
Defense counsel questioned Dyer about his prior felony
convictions, and the government objected. The court held
a side bar during which the parties spent several minutes
debating the factual underpinnings of defendant’s bias
theory and the most appropriate way for defense counsel
to question Dyer. The district court proposed a specific
question, and the following exchange took place:
The Court: You can ask him if he was ever promised
anything in the state court in exchange for his
cooperation.
Defense Counsel: Okay.
Prosecutor: And I think it is clear that he never cooperated
or provided any cooperation until January 30, 2003.
The Court: You can ask him, because if he wasn’t, he
wasn’t, and if he was, he was, and you will be satisfied.
Defense Counsel: Right.
* * * * * *
Defense Counsel: To be clear, I can ask him if he was
promised anything in state court, as far as dismissal or
anything
Prosecutor: In exchange for cooperation.
The Court: Right, you can ask that.
(Tr. at 252-53.)
Defense counsel then proceeded to ask Dyer several
questions about whether he was promised or received any
benefit in exchange for his testimony against Brock. Dyer
replied that he did not, and testified in response to further
questions that he was not approached about cooperating in
Brock’s case until January 2003, after his state charges
were dismissed and federal charges were brought against
him.
Brock now argues that the district court deprived him of
his Sixth Amendment right to confront adverse witnesses
by limiting his opportunity to question Dyer about his
potential bias to a single question. The government
contends that defendant waived or at least forfeited his
opportunity to make this argument because his trial
counsel indicated that she was “satisfied” with the district
court’s proposed question and did not formally object.
Defense counsel’s assent to the district court’s instruction

did not constitute waiver or forfeiture. During the lengthy
side bar, counsel thoroughly explained the basis for her
questioning Dyer about his criminal record. She was not
obligated to object formally after the district court
instructed her to proceed with a specific question in order
to preserve the issue for our review. We conclude,
however, that defendant’s argument fails on the merits.
The Confrontation Clause of the Sixth Amendment
guarantees the right of a criminal defendant “to be
confronted with the witnesses against him.” U.S. Const.
amend. VI. The right to cross-examination is, of course,
not unlimited. Trial courts have wide latitude “to impose
reasonable limits on such cross-examination based on
concerns about, among other things, harassment,
prejudice, confusion of the issues, *699 the witness’
safety, or interrogation that is repetitive or only
marginally relevant.” United States v. McGee, 408 F.3d
966, 975 (7th Cir.2005) (quoting Delaware v. Van
Arsdall, 475 U.S. 673, 679, 106 S.Ct. 1431, 89 L.Ed.2d
674 (1986)). The trial court violates the Sixth Amendment
only where it has so abused its discretion as to prevent the
jury from making a discriminating appraisal of the
witness’s testimony. United States. v. Valles, 41 F.3d 355,
359 (7th Cir.1994).
Far from defendant’s contention that the district court
limited the cross-examination to a single question, the
record reflects that the court allowed defense counsel to
question Dyer repeatedly about his motivation for
testifying against Brock, over the government’s objection.
Although Dyer denied any motivation other than a desire
to tell the truth, the district court allowed defense counsel
ample opportunity to present the bias theory to the jury
without permitting an open-ended inquiry into the
witness’s unrelated criminal history. The district court did
not abuse its discretion in placing this limitation on
defendant’s cross-examination.
2. Missing Witness Instruction
[4] Defendant also contends that the district court abused
its discretion in declining to give a “missing witness
instruction” with respect to Godsey. Defendant asked the
district court to instruct the jury that it could infer from
the government’s failure to call Godsey that his testimony
would have been unfavorable to the government.
[5] “To establish entitlement to a missing witness
instruction, a defendant must prove two things: first, that
the absent witness was peculiarly within the government’s
power to produce; and second, that the testimony would
have elucidated issues in the case and would not merely
116
have been cumulative.” United States v. Gant, 396 F.3d
906, 910 (7th Cir.2005) (quoting Valles, 41 F.3d at 360).
Although the missing witness instruction is generally
disfavored, the district court has broad discretion in
determining whether to give it. Id.
Brock did not prove that Godsey was within the
government’s power to produce, and in fact agreed with
the government’s representation that Godsey could not be
located despite efforts to arrest him on unrelated charges.
Accordingly, the district court did not abuse its discretion
in declining to give the instruction.
C. Sentence
The district court sentenced Brock to 360 months on the
drug counts and a concurrent 120 months on the felon-inpossession
counts. The court based its guidelines
calculation on the 8.42 kilograms of methamphetamine
and one kilogram of cocaine seized from the 3375 and
3381 residences, as well as an additional 7.22 kilograms
of methamphetamine based on the testimony of Dyer and
Lewis. This quantity far exceeds the 1.5 kilograms
expressly charged in the indictment, and the jury did not
find Brock guilty of having possessed any specific
amount above this threshold. The court also enhanced the
sentence because defendant possessed a firearm during
the course of the offense. Based on Brock’s criminal
history category II, the guidelines yielded a range of 324
to 405 months. The district court imposed a sentence in
the middle of the range “due to the large amount of drugs
and weapons possessed and his prior criminal convictions
for drug dealing.”
[6] Defendant does not contend that the district court
miscalculated his guidelines range, but argues correctly
that, under *700 United States v. Booker, 543 U.S. 220,
125 S.Ct. 738, 160 L.Ed.2d 621 (2005), the sentence
violated the Sixth Amendment because it exceeded the
maximum sentence authorized by the jury verdict.
Because he did not raise this Sixth Amendment argument
before the district court, we ask whether the violation
constitutes plain error. Paladino, 401 F.3d at 481. To
determine whether the prejudice prong of the plain error
test has been satisfied, we order a “limited remand to
permit the sentencing judge to determine whether he
would (if required to resentence) reimpose his original
sentence.” Id. at 484.
III. Conclusion
For the foregoing reasons, Brock’s conviction is

AFFIRMED. We retain jurisdiction and REMAND to the
district court pursuant to the procedure set forth in
Paladino.
Footnotes
1 Defendant’s contention that the dog could have been wrong in alerting to his bedroom, even if supported, would not affect whether
the sniff itself was a search. A false alert would not reveal any private information about what was behind Brock’s door, although
the dog’s error rate might affect whether a warrant issued in reliance on the dog sniff was supported by probable cause. In any
event, Brock does not challenge Yoba’s qualifications, nor does he argue that the totality of the evidence, including the dog’s alert
to his bedroom, was insufficient to support the search warrant.
2 At oral argument, Brock’s attorney disputed whether Godsey had consented to the search of 3381. In denying Brock’s motion to
suppress, the district court found that he had, and defendant has pointed to nothing in the record to support a finding to the
contrary. In fact, the record provides ample support for the conclusion that Godsey voluntarily cooperated with police, informing
them of the contents of 3381, and giving them a key to the house.
End of Document
© 2012 Thomson Reuters. No claim to original U.S. Government Works.
117

132 S.Ct. 945
Supreme Court of the United States
UNITED STATES, Petitioner
v.
Antoine JONES.
No. 10–1259. | Argued Nov. 8, 2011. | Decided Jan.
23, 2012.
Opinion
Justice SCALIA delivered the opinion of the Court.
We decide whether the attachment of a Global–
Positioning–System (GPS) tracking device to an
individual’s vehicle, and subsequent use of that device to
monitor the vehicle’s movements on public streets,
constitutes a search or seizure within the meaning of the
Fourth Amendment.
I
In 2004 respondent Antoine Jones, owner and operator of
a nightclub in the District of Columbia, came under
suspicion of trafficking in narcotics and was made the
target of an investigation by a joint FBI and Metropolitan
Police Department task force. Officers employed various
investigative techniques, including visual surveillance of
the nightclub, installation of a camera focused on the front
door of the club, and a pen register and wiretap covering
Jones’s cellular phone.
Based in part on information gathered from these sources,
in 2005 the Government applied to the United States
District Court for the District of Columbia for a warrant
authorizing the use of an electronic tracking device on the
Jeep Grand Cherokee registered to Jones’s wife. A
warrant issued, authorizing installation of the device in
the District of Columbia and within 10 days.
On the 11th day, and not in the District of Columbia but
in Maryland,1 agents installed a GPS tracking device on
the undercarriage of the Jeep while it was parked in a
public parking lot. Over the next 28 days, the Government
used the device to track the vehicle’s movements, and
once had to replace the device’s battery when the vehicle
was parked in a different public lot in Maryland. By
118
means of signals from multiple satellites, the device
established the vehicle’s location within 50 to 100 feet,
and communicated that location by cellular phone to a
Government computer. It relayed more than 2,000 pages
of data over the 4–week period.
The Government ultimately obtained a multiple-count
indictment charging Jones and several alleged coconspirators
with, as relevant here, conspiracy to
distribute and possess with intent to distribute five
kilograms or more of cocaine and 50 grams or more of
cocaine base, in violation of 21 U.S.C. §§ 841 and 846.
Before trial, Jones filed a motion to suppress evidence
obtained through the GPS device. The District Court
granted the motion only in part, suppressing the data
obtained while the vehicle was parked in the garage
adjoining Jones’s residence. 451 F.Supp.2d 71, 88 (2006).
It held the remaining data admissible, because “ ‘[a]
person traveling in an automobile on public thoroughfares
has no reasonable expectation of privacy in his
movements from one place to another.’ ” Ibid. (quoting
United States v. Knotts, 460 U.S. 276, 281, 103 S.Ct.
1081, 75 L.Ed.2d 55 (1983)). Jones’s trial in October
2006 produced a hung jury on the conspiracy count.
In March 2007, a grand jury returned another indictment,
charging Jones and others with the same conspiracy. The
Government introduced at trial the same GPS-derived
locational data admitted in the first trial, which connected
Jones to the alleged conspirators’ stash house that
contained $850,000 in cash, 97 kilograms of *949
cocaine, and 1 kilogram of cocaine base. The jury
returned a guilty verdict, and the District Court sentenced
Jones to life imprisonment.
The United States Court of Appeals for the District of
Columbia Circuit reversed the conviction because of
admission of the evidence obtained by warrantless use of
the GPS device which, it said, violated the Fourth
Amendment. United States v. Maynard, 615 F.3d 544
(2010). The D.C. Circuit denied the Government’s
petition for rehearing en banc, with four judges
dissenting. 625 F.3d 766 (2010). We granted certiorari,
564 U.S. ––––, 131 S.Ct. 3064, 180 L.Ed.2d 885 (2011).
II
A
[1] [2] The Fourth Amendment provides in relevant part

that “[t]he right of the people to be secure in their persons,
houses, papers, and effects, against unreasonable searches
and seizures, shall not be violated.” It is beyond dispute
that a vehicle is an “effect” as that term is used in the
Amendment. United States v. Chadwick, 433 U.S. 1, 12,
97 S.Ct. 2476, 53 L.Ed.2d 538 (1977). We hold that the
Government’s installation of a GPS device on a target’s
vehicle,2 and its use of that device to monitor the
vehicle’s movements, constitutes a “search.”
It is important to be clear about what occurred in this
case: The Government physically occupied private
property for the purpose of obtaining information. We
have no doubt that such a physical intrusion would have
been considered a “search” within the meaning of the
Fourth Amendment when it was adopted. Entick v.
Carrington, 95 Eng. Rep. 807 (C.P. 1765), is a “case we
have described as a ‘monument of English freedom’
‘undoubtedly familiar’ to ‘every American statesman’ at
the time the Constitution was adopted, and considered to
be ‘the true and ultimate expression of constitutional law’
” with regard to search and seizure. Brower v. County of
Inyo, 489 U.S. 593, 596, 109 S.Ct. 1378, 103 L.Ed.2d 628
(1989) (quoting Boyd v. United States, 116 U.S. 616, 626,
6 S.Ct. 524, 29 L.Ed. 746 (1886)). In that case, Lord
Camden expressed in plain terms the significance of
property rights in search-and-seizure analysis:
“[O]ur law holds the property of every man so sacred, that
no man can set his foot upon his neighbour’s close
without his leave; if he does he is a trespasser, though he
does no damage at all; if he will tread upon his
neighbour’s ground, he must justify it by law.” Entick,
supra, at 817.
The text of the Fourth Amendment reflects its close
connection to property, since otherwise it would have
referred simply to “the right of the people to be secure
against unreasonable searches and seizures”; the phrase
“in their persons, houses, papers, and effects” would have
been superfluous.
Consistent with this understanding, our Fourth
Amendment jurisprudence was tied to common-law
trespass, at least until the latter half of the 20th century.
Kyllo v. United States, 533 U.S. 27, 31, 121 S.Ct. 2038,
150 L.Ed.2d 94 (2001); Kerr, The *950 Fourth
Amendment and New Technologies: Constitutional
Myths and the Case for Caution, 102 Mich. L.Rev. 801,
816 (2004). Thus, in Olmstead v. United States, 277 U.S.
438, 48 S.Ct. 564, 72 L.Ed. 944 (1928), we held that
wiretaps attached to telephone wires on the public streets
did not constitute a Fourth Amendment search because
“[t]here was no entry of the houses or offices of the
119
defendants,” id., at 464, 48 S.Ct. 564.
Our later cases, of course, have deviated from that
exclusively property-based approach. In Katz v. United
States, 389 U.S. 347, 351, 88 S.Ct. 507, 19 L.Ed.2d 576
(1967), we said that “the Fourth Amendment protects
people, not places,” and found a violation in attachment
of an eavesdropping device to a public telephone booth.
Our later cases have applied the analysis of Justice
Harlan’s concurrence in that case, which said that a
violation occurs when government officers violate a
person’s “reasonable expectation of privacy,” id., at 360,
88 S.Ct. 507. See, e.g., Bond v. United States, 529 U.S.
334, 120 S.Ct. 1462, 146 L.Ed.2d 365 (2000); California
v. Ciraolo, 476 U.S. 207, 106 S.Ct. 1809, 90 L.Ed.2d 210
(1986); Smith v. Maryland, 442 U.S. 735, 99 S.Ct. 2577,
61 L.Ed.2d 220 (1979).
[3] [4] The Government contends that the Harlan standard
shows that no search occurred here, since Jones had no
“reasonable expectation of privacy” in the area of the Jeep
accessed by Government agents (its underbody) and in the
locations of the Jeep on the public roads, which were
visible to all. But we need not address the Government’s
contentions, because Jones’s Fourth Amendment rights do
not rise or fall with the Katz formulation. At bottom, we
must “assur[e] preservation of that degree of privacy
against government that existed when the Fourth
Amendment was adopted.” Kyllo, supra, at 34, 121 S.Ct.
2038. As explained, for most of our history the Fourth
Amendment was understood to embody a particular
concern for government trespass upon the areas (“persons,
houses, papers, and effects”) it enumerates.3 Katz did not
repudiate that understanding. Less than two years later the
Court upheld defendants’ contention that the Government
could not introduce against them conversations between
other people obtained by warrantless placement of
electronic surveillance devices in their homes. The
opinion rejected the dissent’s contention that there was no
Fourth Amendment violation “unless the conversational
privacy of the homeowner himself is invaded.”4 *951
Alderman v. United States, 394 U.S. 165, 176, 89 S.Ct.
961, 22 L.Ed.2d 176 (1969). “[W]e [do not] believe that
Katz, by holding that the Fourth Amendment protects
persons and their private conversations, was intended to
withdraw any of the protection which the Amendment
extends to the home....” Id., at 180, 89 S.Ct. 961.
[5] [6] More recently, in Soldal v. Cook County, 506 U.S.
56, 113 S.Ct. 538, 121 L.Ed.2d 450 (1992), the Court
unanimously rejected the argument that although a
“seizure” had occurred “in a ‘technical’ sense” when a
trailer home was forcibly removed, id., at 62, 113 S.Ct.
538, no Fourth Amendment violation occurred because
law enforcement had not “invade[d] the [individuals’]

privacy,” id., at 60, 113 S.Ct. 538. Katz, the Court
explained, established that “property rights are not the
sole measure of Fourth Amendment violations,” but did
not “snuf[f] out the previously recognized protection for
property.” 506 U.S., at 64, 113 S.Ct. 538. As Justice
Brennan explained in his concurrence in Knotts, Katz did
not erode the principle “that, when the Government does
engage in physical intrusion of a constitutionally
protected area in order to obtain information, that
intrusion may constitute a violation of the Fourth
Amendment.” 460 U.S., at 286, 103 S.Ct. 1081 (opinion
concurring in judgment). We have embodied that
preservation of past rights in our very definition of
“reasonable expectation of privacy” which we have said
to be an expectation “that has a source outside of the
Fourth Amendment, either by reference to concepts of
real or personal property law or to understandings that are
recognized and permitted by society.” Minnesota v.
Carter, 525 U.S. 83, 88, 119 S.Ct. 469, 142 L.Ed.2d 373
(1998) (internal quotation marks omitted). Katz did not
narrow the Fourth Amendment’s scope.5
The Government contends that several of our post-Katz
cases foreclose the conclusion that what occurred here
constituted a search. It relies principally on two cases in
which we rejected Fourth Amendment challenges to
“beepers,” electronic tracking devices that represent
another form of electronic monitoring. The first case,
Knotts, upheld against Fourth Amendment challenge the
use of a “beeper” that had been placed in a container of
chloroform, allowing law enforcement to monitor the
location of the container. 460 U.S., at 278, 103 S.Ct.
1081. We said that there had been no infringement of
Knotts’ reasonable expectation of privacy since the
information obtained—the location of the automobile
carrying the container on public roads, and the location of
the off-loaded container in open fields near Knotts’
cabin—had been voluntarily conveyed to the *952
public.6 Id., at 281–282, 103 S.Ct. 1081. But as we have
discussed, the Katz reasonable-expectation-of-privacy test
has been added to, not substituted for, the common-law
trespassory test. The holding in Knotts addressed only the
former, since the latter was not at issue. The beeper had
been placed in the container before it came into Knotts’
possession, with the consent of the then-owner. 460 U.S.,
at 278, 103 S.Ct. 1081. Knotts did not challenge that
installation, and we specifically declined to consider its
effect on the Fourth Amendment analysis. Id., at 279, n.
**, 103 S.Ct. 1081 Knotts would be relevant, perhaps, if
the Government were making the argument that what
would otherwise be an unconstitutional search is not such
where it produces only public information. The
Government does not make that argument, and we know
120
of no case that would support it.
The second “beeper” case, United States v. Karo, 468
U.S. 705, 104 S.Ct. 3296, 82 L.Ed.2d 530 (1984), does
not suggest a different conclusion. There we addressed
the question left open by Knotts, whether the installation
of a beeper in a container amounted to a search or seizure.
468 U.S., at 713, 104 S.Ct. 3296. As in Knotts, at the time
the beeper was installed the container belonged to a third
party, and it did not come into possession of the defendant
until later. 468 U.S., at 708, 104 S.Ct. 3296. Thus, the
specific question we considered was whether the
installation “with the consent of the original owner
constitute[d] a search or seizure ... when the container is
delivered to a buyer having no knowledge of the presence
of the beeper.” Id., at 707, 104 S.Ct. 3296 (emphasis
added). We held not. The Government, we said, came into
physical contact with the container only before it
belonged to the defendant Karo; and the transfer of the
container with the unmonitored beeper inside did not
convey any information and thus did not invade Karo’s
privacy. See id., at 712, 104 S.Ct. 3296. That conclusion
is perfectly consistent with the one we reach here. Karo
accepted the container as it came to him, beeper and all,
and was therefore not entitled to object to the beeper’s
presence, even though it was used to monitor the
container’s location. Cf. On Lee v. United States, 343
U.S. 747, 751–752, 72 S.Ct. 967, 96 L.Ed. 1270 (1952)
(no search or seizure where an informant, who was
wearing a concealed microphone, was invited into the
defendant’s business). Jones, who possessed the Jeep at
the time the Government trespassorily inserted the
information-gathering device, is on much different
footing.
The Government also points to our exposition in New
York v. Class, 475 U.S. 106, 106 S.Ct. 960, 89 L.Ed.2d 81
(1986), that “[t]he exterior of a car ... is thrust into the
public eye, and thus to examine it does not constitute a
‘search.’ ” Id., at 114, 106 S.Ct. 960. That statement is of
marginal relevance here since, as the Government
acknowledges, “the officers in this case did more than
conduct a visual inspection of respondent’s vehicle,”
Brief for United States 41 (emphasis added). By attaching
the device to the Jeep, officers encroached on a protected
area. In Class itself we suggested that this would make a
difference, for we concluded that an officer’s momentary
reaching into the interior of a vehicle did constitute a
search.7 475 U.S., at 114–115, 106 S.Ct. 960.
*953 [7] Finally, the Government’s position gains little
support from our conclusion in Oliver v. United States,
466 U.S. 170, 104 S.Ct. 1735, 80 L.Ed.2d 214 (1984),
that officers’ information-gathering intrusion on an “open

field” did not constitute a Fourth Amendment search even
though it was a trespass at common law, id., at 183, 104
S.Ct. 1735. Quite simply, an open field, unlike the
curtilage of a home, see United States v. Dunn, 480 U.S.
294, 300, 107 S.Ct. 1134, 94 L.Ed.2d 326 (1987), is not
one of those protected areas enumerated in the Fourth
Amendment. Oliver, supra, at 176–177, 104 S.Ct. 1735.
See also Hester v. United States, 265 U.S. 57, 59, 44 S.Ct.
445, 68 L.Ed. 898 (1924). The Government’s physical
intrusion on such an area—unlike its intrusion on the
“effect” at issue here—is of no Fourth Amendment
significance.8
B
[8] The concurrence begins by accusing us of applying
“18th-century tort law.” Post, at 957. That is a distortion.
What we apply is an 18th-century guarantee against
unreasonable searches, which we believe must provide at
a minimum the degree of protection it afforded when it
was adopted. The concurrence does not share that belief.
It would apply exclusively Katz ‘s reasonable-expectationof-privacy
test, even when that eliminates rights that
previously existed.
The concurrence faults our approach for “present[ing]
particularly vexing problems” in cases that do not involve
physical contact, such as those that involve the
transmission of electronic signals. Post, at 962. We
entirely fail to understand that point. For unlike the
concurrence, which would make Katz the exclusive test,
we do not make trespass the exclusive test. Situations
involving merely the transmission of electronic signals
without trespass would remain subject to Katz analysis.
In fact, it is the concurrence’s insistence on the
exclusivity of the Katz test that needlessly leads us into
“particularly vexing problems” in the present case. This
Court has to date not deviated from the understanding that
mere visual observation does not constitute a search. See
Kyllo, 533 U.S., at 31–32, 121 S.Ct. 2038. We
accordingly held in Knotts that “[a] person traveling in an
automobile on public thoroughfares has no reasonable
expectation of privacy in his movements from one place
to another.” 460 U.S., at 281, 103 S.Ct. 1081. Thus, even
assuming that the concurrence is correct to say that
“[t]raditional surveillance” of Jones for a 4–week period
“would have required a large team of agents, multiple
vehicles, and perhaps aerial assistance,” post, at 963, our
cases suggest that such visual observation is
constitutionally *954 permissible. It may be that
achieving the same result through electronic means,
121
without an accompanying trespass, is an unconstitutional
invasion of privacy, but the present case does not require
us to answer that question.
And answering it affirmatively leads us needlessly into
additional thorny problems. The concurrence posits that
“relatively short-term monitoring of a person’s
movements on public streets” is okay, but that “the use of
longer term GPS monitoring in investigations of most
offenses ” is no good. Post, at 964 (emphasis added). That
introduces yet another novelty into our jurisprudence.
There is no precedent for the proposition that whether a
search has occurred depends on the nature of the crime
being investigated. And even accepting that novelty, it
remains unexplained why a 4–week investigation is
“surely” too long and why a drug-trafficking conspiracy
involving substantial amounts of cash and narcotics is not
an “extraordinary offens[e]” which may permit longer
observation. See post, at 964. What of a 2–day monitoring
of a suspected purveyor of stolen electronics Or of a 6–
month monitoring of a suspected terrorist We may have
to grapple with these “vexing problems” in some future
case where a classic trespassory search is not involved
and resort must be had to Katz analysis; but there is no
reason for rushing forward to resolve them here.
III
[9] The Government argues in the alternative that even if
the attachment and use of the device was a search, it was
reasonable—and thus lawful—under the Fourth
Amendment because “officers had reasonable suspicion,
and indeed probable cause, to believe that [Jones] was a
leader in a large-scale cocaine distribution conspiracy.”
Brief for United States 50–51. We have no occasion to
consider this argument. The Government did not raise it
below, and the D.C. Circuit therefore did not address it.
See 625 F.3d, at 767 (Ginsburg, Tatel, and Griffith, JJ.,
concurring in denial of rehearing en banc). We consider
the argument forfeited. See Sprietsma v. Mercury Marine,
537 U.S. 51, 56, n. 4, 123 S.Ct. 518, 154 L.Ed.2d 466
(2002).
* * *
The judgment of the Court of Appeals for the D.C. Circuit
is affirmed.
It is so ordered.
Justice SOTOMAYOR, concurring.

I join the Court’s opinion because I agree that a search
within the meaning of the Fourth Amendment occurs, at a
minimum, “[w]here, as here, the Government obtains
information by physically intruding on a constitutionally
protected area.” Ante, at 950, n. 3. In this case, the
Government installed a Global Positioning System (GPS)
tracking device on respondent Antoine Jones’ Jeep
without a valid warrant and without Jones’ consent, then
used that device to monitor the Jeep’s movements over
the course of four weeks. The Government usurped Jones’
property for the purpose of conducting surveillance on
him, thereby invading privacy interests long afforded, and
undoubtedly entitled to, Fourth Amendment protection.
See, e.g., Silverman v. United States, 365 U.S. 505, 511–
512, 81 S.Ct. 679, 5 L.Ed.2d 734 (1961).
Of course, the Fourth Amendment is not concerned only
with trespassory intrusions on property. See, e.g., Kyllo v.
United States, 533 U.S. 27, 31–33, 121 S.Ct. 2038, 150
L.Ed.2d 94 (2001). Rather, even in the absence of a
trespass, “a Fourth Amendment search occurs when the
government violates a subjective expectation of privacy
that society recognizes *955 as reasonable.” Id., at 33,
121 S.Ct. 2038; see also Smith v. Maryland, 442 U.S. 735,
740–741, 99 S.Ct. 2577, 61 L.Ed.2d 220 (1979); Katz v.
United States, 389 U.S. 347, 361, 88 S.Ct. 507, 19
L.Ed.2d 576 (1967) (Harlan, J., concurring). In Katz, this
Court enlarged its then-prevailing focus on property rights
by announcing that the reach of the Fourth Amendment
does not “turn upon the presence or absence of a physical
intrusion.” Id., at 353, 88 S.Ct. 507. As the majority’s
opinion makes clear, however, Katz ‘s reasonableexpectation-of-privacy
test augmented, but did not
displace or diminish, the common-law trespassory test
that preceded it. Ante, at 951. Thus, “when the
Government does engage in physical intrusion of a
constitutionally protected area in order to obtain
information, that intrusion may constitute a violation of
the Fourth Amendment.” United States v. Knotts, 460
U.S. 276, 286, 103 S.Ct. 1081, 75 L.Ed.2d 55 (1983)
(Brennan, J., concurring in judgment); see also, e.g.,
Rakas v. Illinois, 439 U.S. 128, 144, n. 12, 99 S.Ct. 421,
58 L.Ed.2d 387 (1978). Justice ALITO’s approach, which
discounts altogether the constitutional relevance of the
Government’s physical intrusion on Jones’ Jeep, erodes
that longstanding protection for privacy expectations
inherent in items of property that people possess or
control. See post, at 959 – 961 (opinion concurring in
judgment). By contrast, the trespassory test applied in the
majority’s opinion reflects an irreducible constitutional
minimum: When the Government physically invades
personal property to gather information, a search occurs.
The reaffirmation of that principle suffices to decide this
122
case.
Nonetheless, as Justice ALITO notes, physical intrusion is
now unnecessary to many forms of surveillance. Post, at
961 – 963. With increasing regularity, the Government
will be capable of duplicating the monitoring undertaken
in this case by enlisting factory- or owner-installed
vehicle tracking devices or GPS-enabled smartphones.
See United States v. Pineda–Moreno, 617 F.3d 1120,
1125 (C.A.9 2010) (Kozinski, C.J., dissenting from denial
of rehearing en banc). In cases of electronic or other novel
modes of surveillance that do not depend upon a physical
invasion on property, the majority opinion’s trespassory
test may provide little guidance. But “[s]ituations
involving merely the transmission of electronic signals
without trespass would remain subject to Katz analysis.”
Ante, at 953. As Justice ALITO incisively observes, the
same technological advances that have made possible
nontrespassory surveillance techniques will also affect the
Katz test by shaping the evolution of societal privacy
expectations. Post, at 962 – 963. Under that rubric, I agree
with Justice ALITO that, at the very least, “longer term
GPS monitoring in investigations of most offenses
impinges on expectations of privacy.” Post, at 964.
In cases involving even short-term monitoring, some
unique attributes of GPS surveillance relevant to the Katz
analysis will require particular attention. GPS monitoring
generates a precise, comprehensive record of a person’s
public movements that reflects a wealth of detail about
her familial, political, professional, religious, and sexual
associations. See, e.g., People v. Weaver, 12 N.Y.3d 433,
441–442, 882 N.Y.S.2d 357, 909 N.E.2d 1195, 1199
(2009) (“Disclosed in [GPS] data ... will be trips the
indisputably private nature of which takes little
imagination to conjure: trips to the psychiatrist, the plastic
surgeon, the abortion clinic, the AIDS treatment center,
the strip club, the criminal defense attorney, the by-thehour
motel, the union meeting, the mosque, synagogue or
church, the gay bar and on and on”). The *956
Government can store such records and efficiently mine
them for information years into the future. Pineda–
Moreno, 617 F.3d, at 1124 (opinion of Kozinski, C.J.).
And because GPS monitoring is cheap in comparison to
conventional surveillance techniques and, by design,
proceeds surreptitiously, it evades the ordinary checks
that constrain abusive law enforcement practices: “limited
police resources and community hostility.” Illinois v.
Lidster, 540 U.S. 419, 426, 124 S.Ct. 885, 157 L.Ed.2d
843 (2004).
Awareness that the Government may be watching chills
associational and expressive freedoms. And the

Government’s unrestrained power to assemble data that
reveal private aspects of identity is susceptible to abuse.
The net result is that GPS monitoring—by making
available at a relatively low cost such a substantial
quantum of intimate information about any person whom
the Government, in its unfettered discretion, chooses to
track—may “alter the relationship between citizen and
government in a way that is inimical to democratic
society.” United States v. Cuevas–Perez, 640 F.3d 272,
285 (C.A.7 2011) (Flaum, J., concurring).
I would take these attributes of GPS monitoring into
account when considering the existence of a reasonable
societal expectation of privacy in the sum of one’s public
movements. I would ask whether people reasonably
expect that their movements will be recorded and
aggregated in a manner that enables the Government to
ascertain, more or less at will, their political and religious
beliefs, sexual habits, and so on. I do not regard as
dispositive the fact that the Government might obtain the
fruits of GPS monitoring through lawful conventional
surveillance techniques. See Kyllo, 533 U.S., at 35, n. 2,
121 S.Ct. 2038; ante, at 954 (leaving open the possibility
that duplicating traditional surveillance “through
electronic means, without an accompanying trespass, is an
unconstitutional invasion of privacy”). I would also
consider the appropriateness of entrusting to the
Executive, in the absence of any oversight from a
coordinate branch, a tool so amenable to misuse,
especially in light of the Fourth Amendment’s goal to
curb arbitrary exercises of police power to and prevent “a
too permeating police surveillance,” United States v. Di
Re, 332 U.S. 581, 595, 68 S.Ct. 222, 92 L.Ed. 210
(1948).*
*957 More fundamentally, it may be necessary to
reconsider the premise that an individual has no
reasonable expectation of privacy in information
voluntarily disclosed to third parties. E.g., Smith, 442
U.S., at 742, 99 S.Ct. 2577; United States v. Miller, 425
U.S. 435, 443, 96 S.Ct. 1619, 48 L.Ed.2d 71 (1976). This
approach is ill suited to the digital age, in which people
reveal a great deal of information about themselves to
third parties in the course of carrying out mundane tasks.
People disclose the phone numbers that they dial or text to
their cellular providers; the URLs that they visit and the e-
mail addresses with which they correspond to their
Internet service providers; and the books, groceries, and
medications they purchase to online retailers. Perhaps, as
Justice ALITO notes, some people may find the
“tradeoff” of privacy for convenience “worthwhile,” or
come to accept this “diminution of privacy” as
“inevitable,” post, at 962, and perhaps not. I for one doubt
that people would accept without complaint the
123
warrantless disclosure to the Government of a list of
every Web site they had visited in the last week, or
month, or year. But whatever the societal expectations,
they can attain constitutionally protected status only if our
Fourth Amendment jurisprudence ceases to treat secrecy
as a prerequisite for privacy. I would not assume that all
information voluntarily disclosed to some member of the
public for a limited purpose is, for that reason alone,
disentitled to Fourth Amendment protection. See Smith,
442 U.S., at 749, 99 S.Ct. 2577 (Marshall, J., dissenting)
(“Privacy is not a discrete commodity, possessed
absolutely or not at all. Those who disclose certain facts
to a bank or phone company for a limited business
purpose need not assume that this information will be
released to other persons for other purposes”); see also
Katz, 389 U.S., at 351–352, 88 S.Ct. 507 (“[W]hat [a
person] seeks to preserve as private, even in an area
accessible to the public, may be constitutionally
protected”).
Resolution of these difficult questions in this case is
unnecessary, however, because the Government’s
physical intrusion on Jones’ Jeep supplies a narrower
basis for decision. I therefore join the majority’s opinion.
Justice ALITO, with whom Justice GINSBURG, Justice
BREYER, and Justice KAGAN join, concurring in the
judgment.
This case requires us to apply the Fourth Amendment’s
prohibition of unreasonable searches and seizures to a
21st-century surveillance technique, the use of a Global
Positioning System (GPS) device to monitor a vehicle’s
movements for an extended period of time. Ironically, the
Court has chosen to decide this case based on 18thcentury
tort law. By attaching a small GPS device1 to the
underside of the vehicle that respondent drove, the law
enforcement officers in this case engaged in conduct that
might have provided grounds in 1791 for a suit for
trespass to chattels.2 And for this reason, the Court
concludes, *958 the installation and use of the GPS
device constituted a search. Ante, at 948 – 949.
This holding, in my judgment, is unwise. It strains the
language of the Fourth Amendment; it has little if any
support in current Fourth Amendment case law; and it is
highly artificial.
I would analyze the question presented in this case by
asking whether respondent’s reasonable expectations of
privacy were violated by the long-term monitoring of the
movements of the vehicle he drove.

I
A
The Fourth Amendment prohibits “unreasonable searches
and seizures,” and the Court makes very little effort to
explain how the attachment or use of the GPS device fits
within these terms. The Court does not contend that there
was a seizure. A seizure of property occurs when there is
“some meaningful interference with an individual’s
possessory interests in that property,” United States v.
Jacobsen, 466 U.S. 109, 113, 104 S.Ct. 1652, 80 L.Ed.2d
85 (1984), and here there was none. Indeed, the success of
the surveillance technique that the officers employed was
dependent on the fact that the GPS did not interfere in any
way with the operation of the vehicle, for if any such
interference had been detected, the device might have
been discovered.
The Court does claim that the installation and use of the
GPS constituted a search, see ante, at 948 – 949, but this
conclusion is dependent on the questionable proposition
that these two procedures cannot be separated for
purposes of Fourth Amendment analysis. If these two
procedures are analyzed separately, it is not at all clear
from the Court’s opinion why either should be regarded
as a search. It is clear that the attachment of the GPS
device was not itself a search; if the device had not
functioned or if the officers had not used it, no
information would have been obtained. And the Court
does not contend that the use of the device constituted a
search either. On the contrary, the Court accepts the
holding in United States v. Knotts, 460 U.S. 276, 103
S.Ct. 1081, 75 L.Ed.2d 55 (1983), that the use of a
surreptitiously planted electronic device to monitor a
vehicle’s movements on public roads did not amount to a
search. See ante, at 951.
The Court argues—and I agree—that “we must ‘assur[e]
preservation of that degree of privacy against government
that existed when the Fourth Amendment was adopted.’ ”
Ante, at 950 (quoting Kyllo v. United States, 533 U.S. 27,
34, 121 S.Ct. 2038, 150 L.Ed.2d 94 (2001)). But it is
almost impossible to think of late–18th-century situations
that are analogous to what took place in this case. (Is it
possible to imagine a case in which a constable secreted
himself somewhere in a coach and remained there for a
period of time in order to monitor the movements of the
coach’s owner3) The Court’s theory seems to be that the
concept of a search, as originally understood,
comprehended any technical trespass that led to the
gathering of evidence, but we know that this is incorrect.
At common law, any unauthorized intrusion on private
124
property was actionable, see Prosser & Keeton 75, but a
trespass on open fields, as opposed to the “curtilage” of a
home, does not fall within the scope of the Fourth
Amendment because private property outside the curtilage
*959 is not part of a “hous[e]” within the meaning of the
Fourth Amendment. See Oliver v. United States, 466 U.S.
170, 104 S.Ct. 1735, 80 L.Ed.2d 214 (1984); Hester v.
United States, 265 U.S. 57, 44 S.Ct. 445, 68 L.Ed. 898
(1924).
B
The Court’s reasoning in this case is very similar to that
in the Court’s early decisions involving wiretapping and
electronic eavesdropping, namely, that a technical
trespass followed by the gathering of evidence constitutes
a search. In the early electronic surveillance cases, the
Court concluded that a Fourth Amendment search
occurred when private conversations were monitored as a
result of an “unauthorized physical penetration into the
premises occupied” by the defendant. Silverman v. United
States, 365 U.S. 505, 509, 81 S.Ct. 679, 5 L.Ed.2d 734
(1961). In Silverman, police officers listened to
conversations in an attached home by inserting a “spike
mike” through the wall that this house shared with the
vacant house next door. Id., at 506, 81 S.Ct. 679. This
procedure was held to be a search because the mike made
contact with a heating duct on the other side of the wall
and thus “usurp[ed] ... an integral part of the premises.”
Id., at 511, 81 S.Ct. 679.
By contrast, in cases in which there was no trespass, it
was held that there was no search. Thus, in Olmstead v.
United States, 277 U.S. 438, 48 S.Ct. 564, 72 L.Ed. 944
(1928), the Court found that the Fourth Amendment did
not apply because “[t]he taps from house lines were made
in the streets near the houses.” Id., at 457, 48 S.Ct. 564.
Similarly, the Court concluded that no search occurred in
Goldman v. United States, 316 U.S. 129, 135, 62 S.Ct.
993, 86 L.Ed. 1322 (1942), where a “detectaphone” was
placed on the outer wall of defendant’s office for the
purpose of overhearing conversations held within the
room.
This trespass-based rule was repeatedly criticized. In
Olmstead, Justice Brandeis wrote that it was “immaterial
where the physical connection with the telephone wires
was made.” 277 U.S., at 479, 48 S.Ct. 564 (dissenting
opinion). Although a private conversation transmitted by
wire did not fall within the literal words of the Fourth
Amendment, he argued, the Amendment should be
understood as prohibiting “every unjustifiable intrusion

y the government upon the privacy of the individual.”
Id., at 478, 48 S.Ct. 564. See also, e.g., Silverman, supra,
at 513, 81 S.Ct. 679 (Douglas, J., concurring) (“The
concept of ‘an unauthorized physical penetration into the
premises,’ on which the present decision rests seems to
me beside the point. Was not the wrong ... done when the
intimacies of the home were tapped, recorded, or
revealed The depth of the penetration of the electronic
device—even the degree of its remoteness from the inside
of the house—is not the measure of the injury”);
Goldman, supra, at 139, 62 S.Ct. 993 (Murphy, J.,
dissenting) (“[T]he search of one’s home or office no
longer requires physical entry, for science has brought
forth far more effective devices for the invasion of a
person’s privacy than the direct and obvious methods of
oppression which were detested by our forebears and
which inspired the Fourth Amendment”).
Katz v. United States, 389 U.S. 347, 88 S.Ct. 507, 19
L.Ed.2d 576 (1967), finally did away with the old
approach, holding that a trespass was not required for a
Fourth Amendment violation. Katz involved the use of a
listening device that was attached to the outside of a
public telephone booth and that allowed police officers to
eavesdrop on one end of the target’s phone conversation.
This procedure *960 did not physically intrude on the
area occupied by the target, but the Katz Court,
“repudiate[ed]” the old doctrine, Rakas v. Illinois, 439
U.S. 128, 143, 99 S.Ct. 421, 58 L.Ed.2d 387 (1978), and
held that “[t]he fact that the electronic device employed ...
did not happen to penetrate the wall of the booth can have
no constitutional significance,” 389 U.S., at 353, 88 S.Ct.
507 (“[T]he reach of th[e] [Fourth] Amendment cannot
turn upon the presence or absence of a physical intrusion
into any given enclosure”); see Rakas, supra, at 143, 99
S.Ct. 421 (describing Katz as holding that the “capacity to
claim the protection for the Fourth Amendment depends
not upon a property right in the invaded place but upon
whether the person who claims the protection of the
Amendment has a legitimate expectation of privacy in the
invaded place”); Kyllo, supra, at 32, 121 S.Ct. 2038 (“We
have since decoupled violation of a person’s Fourth
Amendment rights from trespassory violation of his
property”). What mattered, the Court now held, was
whether the conduct at issue “violated the privacy upon
which [the defendant] justifiably relied while using the
telephone booth.” Katz, supra, at 353, 88 S.Ct. 507.
Under this approach, as the Court later put it when
addressing the relevance of a technical trespass, “an
actual trespass is neither necessary nor sufficient to
establish a constitutional violation.” United States v.
Karo, 468 U.S. 705, 713, 104 S.Ct. 3296, 82 L.Ed.2d 530
(1984) (emphasis added). Ibid. (“Compar[ing] Katz v.
125
United States, 389 U.S. 347 [88 S.Ct. 507, 19 L.Ed.2d
576] (1967) (no trespass, but Fourth Amendment
violation), with Oliver v. United States, 466 U.S. 170 [104
S.Ct. 1735, 80 L.Ed.2d 214] (1984) (trespass, but no
Fourth Amendment violation)”). In Oliver, the Court
wrote:
“The existence of a property right is but one element in
determining whether expectations of privacy are
legitimate. ‘The premise that property interests control the
right of the Government to search and seize has been
discredited.’ Katz, 389 U.S., at 353 [88 S.Ct. 507],
(quoting Warden v. Hayden, 387 U.S. 294, 304 [87 S.Ct.
1642, 18 L.Ed.2d 782] (1967); some internal quotation
marks omitted).” 466 U.S., at 183, 104 S.Ct. 1735.
II
The majority suggests that two post-Katz decisions—
Soldal v. Cook County, 506 U.S. 56, 113 S.Ct. 538, 121
L.Ed.2d 450 (1992), and Alderman v. United States, 394
U.S. 165, 89 S.Ct. 961, 22 L.Ed.2d 176 (1969)—show
that a technical trespass is sufficient to establish the
existence of a search, but they provide little support.
In Soldal, the Court held that towing away a trailer home
without the owner’s consent constituted a seizure even if
this did not invade the occupants’ personal privacy. But in
the present case, the Court does not find that there was a
seizure, and it is clear that none occurred.
In Alderman, the Court held that the Fourth Amendment
rights of homeowners were implicated by the use of a
surreptitiously planted listening device to monitor thirdparty
conversations that occurred within their home. See
394 U.S., at 176–180, 89 S.Ct. 961. Alderman is best
understood to mean that the homeowners had a legitimate
expectation of privacy in all conversations that took place
under their roof. See Rakas, 439 U.S., at 144, n. 12, 99
S.Ct. 421 (citing Alderman for the proposition that “the
Court has not altogether abandoned use of property
concepts in determining the presence or absence of the
privacy interests protected by that Amendment”); 439
U.S., at 153, 99 S.Ct. 421 (Powell, J., concurring) (citing
Alderman *961 for the proposition that “property rights
reflect society’s explicit recognition of a person’s
authority to act as he wishes in certain areas, and
therefore should be considered in determining whether an
individual’s expectations of privacy are reasonable”);
Karo, supra, at 732, 104 S.Ct. 3296 (Stevens, J.,
concurring in part and dissenting in part) (citing Alderman
in support of the proposition that “a homeowner has a

easonable expectation of privacy in the contents of his
home, including items owned by others”).
In sum, the majority is hard pressed to find support in
post-Katz cases for its trespass-based theory.
III
Disharmony with a substantial body of existing case law
is only one of the problems with the Court’s approach in
this case.
I will briefly note four others. First, the Court’s reasoning
largely disregards what is really important (the use of a
GPS for the purpose of long-term tracking) and instead
attaches great significance to something that most would
view as relatively minor (attaching to the bottom of a car
a small, light object that does not interfere in any way
with the car’s operation). Attaching such an object is
generally regarded as so trivial that it does not provide a
basis for recovery under modern tort law. See Prosser &
Keeton § 14, at 87 (harmless or trivial contact with
personal property not actionable); D. Dobbs, Law of Torts
124 (2000) (same). But under the Court’s reasoning, this
conduct may violate the Fourth Amendment. By contrast,
if long-term monitoring can be accomplished without
committing a technical trespass—suppose, for example,
that the Federal Government required or persuaded auto
manufacturers to include a GPS tracking device in every
car—the Court’s theory would provide no protection.
Second, the Court’s approach leads to incongruous
results. If the police attach a GPS device to a car and use
the device to follow the car for even a brief time, under
the Court’s theory, the Fourth Amendment applies. But if
the police follow the same car for a much longer period
using unmarked cars and aerial assistance, this tracking is
not subject to any Fourth Amendment constraints.
In the present case, the Fourth Amendment applies, the
Court concludes, because the officers installed the GPS
device after respondent’s wife, to whom the car was
registered, turned it over to respondent for his exclusive
use. See ante, at 951. But if the GPS had been attached
prior to that time, the Court’s theory would lead to a
different result. The Court proceeds on the assumption
that respondent “had at least the property rights of a
bailee,” ante, at 949, n. 2, but a bailee may sue for a
trespass to chattel only if the injury occurs during the term
of the bailment. See 8A Am.Jur.2d, Bailment § 166, pp.
685–686 (2009). So if the GPS device had been installed
before respondent’s wife gave him the keys, respondent
126
would have no claim for trespass—and, presumably, no
Fourth Amendment claim either.
Third, under the Court’s theory, the coverage of the
Fourth Amendment may vary from State to State. If the
events at issue here had occurred in a community property
State4 or a State that has adopted the Uniform Marital
Property Act,5 respondent would likely be an owner of the
vehicle, and it would not matter whether the *962 GPS
was installed before or after his wife turned over the keys.
In non-community-property States, on the other hand, the
registration of the vehicle in the name of respondent’s
wife would generally be regarded as presumptive
evidence that she was the sole owner. See 60 C.J. S.,
Motor Vehicles § 231, pp. 398–399 (2002); 8 Am.Jur.2d,
Automobiles § 1208, pp. 859–860 (2007).
Fourth, the Court’s reliance on the law of trespass will
present particularly vexing problems in cases involving
surveillance that is carried out by making electronic, as
opposed to physical, contact with the item to be tracked.
For example, suppose that the officers in the present case
had followed respondent by surreptitiously activating a
stolen vehicle detection system that came with the car
when it was purchased. Would the sending of a radio
signal to activate this system constitute a trespass to
chattels Trespass to chattels has traditionally required a
physical touching of the property. See Restatement
(Second) of Torts § 217 and Comment e (1963 and 1964);
Dobbs, supra, at 123. In recent years, courts have
wrestled with the application of this old tort in cases
involving unwanted electronic contact with computer
systems, and some have held that even the transmission of
electrons that occurs when a communication is sent from
one computer to another is enough. See, e.g.,
CompuServe, Inc. v. Cyber Promotions, Inc., 962 F.Supp.
1015, 1021 (S.D.Ohio 1997); Thrifty–Tel, Inc. v. Bezenek,
46 Cal.App.4th 1559, 1566, n. 6, 54 Cal.Rptr.2d 468
(1996). But may such decisions be followed in applying
the Court’s trespass theory Assuming that what matters
under the Court’s theory is the law of trespass as it existed
at the time of the adoption of the Fourth Amendment, do
these recent decisions represent a change in the law or
simply the application of the old tort to new situations
IV
A
The Katz expectation-of-privacy test avoids the problems
and complications noted above, but it is not without its

own difficulties. It involves a degree of circularity, see
Kyllo, 533 U.S., at 34, 121 S.Ct. 2038, and judges are apt
to confuse their own expectations of privacy with those of
the hypothetical reasonable person to which the Katz test
looks. See Minnesota v. Carter, 525 U.S. 83, 97, 119
S.Ct. 469, 142 L.Ed.2d 373 (1998) (SCALIA, J.,
concurring). In addition, the Katz test rests on the
assumption that this hypothetical reasonable person has a
well-developed and stable set of privacy expectations. But
technology can change those expectations. Dramatic
technological change may lead to periods in which
popular expectations are in flux and may ultimately
produce significant changes in popular attitudes. New
technology may provide increased convenience or
security at the expense of privacy, and many people may
find the tradeoff worthwhile. And even if the public does
not welcome the diminution of privacy that new
technology entails, they may eventually reconcile
themselves to this development as inevitable.6
On the other hand, concern about new intrusions on
privacy may spur the enactment of legislation to protect
against these intrusions. This is what ultimately happened
*963 with respect to wiretapping. After Katz, Congress
did not leave it to the courts to develop a body of Fourth
Amendment case law governing that complex subject.
Instead, Congress promptly enacted a comprehensive
statute, see 18 U.S.C. §§ 2510–2522 (2006 ed. and Supp.
IV), and since that time, the regulation of wiretapping has
been governed primarily by statute and not by case law.7
In an ironic sense, although Katz overruled Olmstead,
Chief Justice Taft’s suggestion in the latter case that the
regulation of wiretapping was a matter better left for
Congress, see 277 U.S., at 465–466, 48 S.Ct. 564, has
been borne out.
B
Recent years have seen the emergence of many new
devices that permit the monitoring of a person’s
movements. In some locales, closed-circuit television
video monitoring is becoming ubiquitous. On toll roads,
automatic toll collection systems create a precise record
of the movements of motorists who choose to make use of
that convenience. Many motorists purchase cars that are
equipped with devices that permit a central station to
ascertain the car’s location at any time so that roadside
assistance may be provided if needed and the car may be
found if it is stolen.
Perhaps most significant, cell phones and other wireless
devices now permit wireless carriers to track and record
127
the location of users—and as of June 2011, it has been
reported, there were more than 322 million wireless
devices in use in the United States.8 For older phones, the
accuracy of the location information depends on the
density of the tower network, but new “smart phones,”
which are equipped with a GPS device, permit more
precise tracking. For example, when a user activates the
GPS on such a phone, a provider is able to monitor the
phone’s location and speed of movement and can then
report back real-time traffic conditions after combining
(“crowdsourcing”) the speed of all such phones on any
particular road.9 Similarly, phone-location-tracking
services are offered as “social” tools, allowing consumers
to find (or to avoid) others who enroll in these services.
The availability and use of these and other new devices
will continue to shape the average person’s expectations
about the privacy of his or her daily movements.
V
In the pre-computer age, the greatest protections of
privacy were neither constitutional nor statutory, but
practical. Traditional surveillance for any extended period
of time was difficult and costly and therefore rarely
undertaken. The surveillance at issue in this case—
constant monitoring of the location of a vehicle for four
weeks—would have required a large team of agents,
multiple vehicles, and perhaps aerial assistance.10 Only an
investigation of unusual importance could have justified
such an expenditure of law enforcement *964 resources.
Devices like the one used in the present case, however,
make long-term monitoring relatively easy and cheap. In
circumstances involving dramatic technological change,
the best solution to privacy concerns may be legislative.
See, e.g., Kerr, 102 Mich. L.Rev., at 805–806. A
legislative body is well situated to gauge changing public
attitudes, to draw detailed lines, and to balance privacy
and public safety in a comprehensive way.
To date, however, Congress and most States have not
enacted statutes regulating the use of GPS tracking
technology for law enforcement purposes. The best that
we can do in this case is to apply existing Fourth
Amendment doctrine and to ask whether the use of GPS
tracking in a particular case involved a degree of intrusion
that a reasonable person would not have anticipated.
Under this approach, relatively short-term monitoring of a
person’s movements on public streets accords with
expectations of privacy that our society has recognized as
reasonable. See Knotts, 460 U.S., at 281–282, 103 S.Ct.
1081. But the use of longer term GPS monitoring in

investigations of most offenses impinges on expectations
of privacy. For such offenses, society’s expectation has
been that law enforcement agents and others would not—
and indeed, in the main, simply could not—secretly
monitor and catalogue every single movement of an
individual’s car for a very long period. In this case, for
four weeks, law enforcement agents tracked every
movement that respondent made in the vehicle he was
driving. We need not identify with precision the point at
which the tracking of this vehicle became a search, for the
line was surely crossed before the 4–week mark. Other
cases may present more difficult questions. But where
uncertainty exists with respect to whether a certain period
of GPS surveil lance is long enough to constitute a Fourth
Amendment search, the police may always seek a
warrant.11 We also need not consider whether prolonged
GPS monitoring in the context of investigations involving
extraordinary offenses would similarly intrude on a
constitutionally protected sphere of privacy. In such
cases, long-term tracking might have been mounted using
previously available techniques.
For these reasons, I conclude that the lengthy monitoring
that occurred in this case constituted a search under the
Fourth Amendment. I therefore agree with the majority
that the decision of the Court of Appeals must be
affirmed.
Parallel Citations
181 L.Ed.2d 911, 80 BNA USLW 4125, 12 Cal. Daily
Op. Serv. 887, 2012 Daily Journal D.A.R. 895, 23 Fla. L.
Weekly Fed. S 102
Footnotes
* The syllabus constitutes no part of the opinion of the Court but has been prepared by the Reporter of Decisions for the convenience
of the reader. See United States v. Detroit Timber & Lumber Co., 200 U.S. 321, 337, 26 S.Ct. 282, 50 L.Ed. 499.
1 In this litigation, the Government has conceded noncompliance with the warrant and has argued only that a warrant was not
required. United States v. Maynard, 615 F.3d 544, 566, n. * (C.A.D.C. 2010).
2 As we have noted, the Jeep was registered to Jones’s wife. The Government acknowledged, however, that Jones was “the exclusive
driver.” Id., at 555, n. * (internal quotation marks omitted). If Jones was not the owner he had at least the property rights of a
bailee. The Court of Appeals concluded that the vehicle’s registration did not affect his ability to make a Fourth Amendment
objection, ibid., and the Government has not challenged that determination here. We therefore do not consider the Fourth
Amendment significance of Jones’s status.
3 Justice ALITO’s concurrence (hereinafter concurrence) doubts the wisdom of our approach because “it is almost impossible to
think of late–18th–century situations that are analogous to what took place in this case.” Post, at 958 (opinion concurring in
judgment). But in fact it posits a situation that is not far afield—a constable’s concealing himself in the target’s coach in order to
track its movements. Ibid. There is no doubt that the information gained by that trespassory activity would be the product of an
unlawful search—whether that information consisted of the conversations occurring in the coach, or of the destinations to which
the coach traveled.
In any case, it is quite irrelevant whether there was an 18th-century analog. Whatever new methods of investigation may be
devised, our task, at a minimum, is to decide whether the action in question would have constituted a “search” within the original
meaning of the Fourth Amendment. Where, as here, the Government obtains information by physically intruding on a
constitutionally protected area, such a search has undoubtedly occurred.
4 Thus, the concurrence’s attempt to recast Alderman as meaning that individuals have a “legitimate expectation of privacy in all
conversations that [take] place under their roof,” post, at 960, is foreclosed by the Court’s opinion. The Court took as a given that
the homeowner’s “conversational privacy” had not been violated.
5 The concurrence notes that post-Katz we have explained that “ ‘an actual trespass is neither necessary nor sufficient to establish a
constitutional violation.’ ” Post, at 960 (quoting United States v. Karo, 468 U.S. 705, 713, 104 S.Ct. 3296, 82 L.Ed.2d 530 (1984)).
That is undoubtedly true, and undoubtedly irrelevant. Karo was considering whether a seizure occurred, and as the concurrence
explains, a seizure of property occurs, not when there is a trespass, but “when there is some meaningful interference with an
individual’s possessory interests in that property.” Post, at 958 (internal quotation marks omitted). Likewise with a search.
Trespass alone does not qualify, but there must be conjoined with that what was present here: an attempt to find something or to
obtain information.
Related to this, and similarly irrelevant, is the concurrence’s point that, if analyzed separately, neither the installation of the device
nor its use would constitute a Fourth Amendment search. See ibid. Of course not. A trespass on “houses” or “effects,” or a Katz
invasion of privacy, is not alone a search unless it is done to obtain information; and the obtaining of information is not alone a
128

search unless it is achieved by such a trespass or invasion of privacy.
6 Knotts noted the “limited use which the government made of the signals from this particular beeper,” 460 U.S., at 284, 103 S.Ct.
1081; and reserved the question whether “different constitutional principles may be applicable” to “dragnet-type law enforcement
practices” of the type that GPS tracking made possible here, ibid.
7 The Government also points to Cardwell v. Lewis, 417 U.S. 583, 94 S.Ct. 2464, 41 L.Ed.2d 325 (1974), in which the Court
rejected the claim that the inspection of an impounded vehicle’s tire tread and the collection of paint scrapings from its exterior
violated the Fourth Amendment. Whether the plurality said so because no search occurred or because the search was reasonable is
unclear. Compare id., at 591, 94 S.Ct. 2464 (opinion of Blackmun, J.) (“[W]e fail to comprehend what expectation of privacy was
infringed”), with id., at 592, 94 S.Ct. 2464 (“Under circumstances such as these, where probable cause exists, a warrantless
examination of the exterior of a car is not unreasonable ...”).
8 Thus, our theory is not that the Fourth Amendment is concerned with “any technical trespass that led to the gathering of evidence.”
Post, at 958 (ALITO, J., concurring in judgment) (emphasis added). The Fourth Amendment protects against trespassory searches
only with regard to those items (“persons, houses, papers, and effects”) that it enumerates. The trespass that occurred in Oliver may
properly be understood as a “search,” but not one “in the constitutional sense.” 466 U.S., at 170, 183, 104 S.Ct. 1735.
* United States v. Knotts, 460 U.S. 276, 103 S.Ct. 1081, 75 L.Ed.2d 55 (1983), does not foreclose the conclusion that GPS
monitoring, in the absence of a physical intrusion, is a Fourth Amendment search. As the majority’s opinion notes, Knotts reserved
the question whether “ ‘different constitutional principles may be applicable’ ” to invasive law enforcement practices such as GPS
tracking. See ante, at 952, n. 6 (quoting 460 U.S., at 284, 103 S.Ct. 1081).
United States v. Karo, 468 U.S. 705, 104 S.Ct. 3296, 82 L.Ed.2d 530 (1984), addressed the Fourth Amendment implications of the
installation of a beeper in a container with the consent of the container’s original owner, who was aware that the beeper would be
used for surveillance purposes. Id., at 707, 104 S.Ct. 3296. Owners of GPS-equipped cars and smartphones do not contemplate that
these devices will be used to enable covert surveillance of their movements. To the contrary, subscribers of one such service
greeted a similar suggestion with anger. Quain, Changes to OnStar’s Privacy Terms Rile Some Users, N.Y. Times (Sept. 22, 2011),
online at http://wheels.blogs.nytimes.com/2011/09/22/changes-to-onstars-privacy-terms-rile-some-users (as visited Jan. 19, 2012,
and available in Clerk of Court’s case file). In addition, the bugged container in Karo lacked the close relationship with the target
that a car shares with its owner. The bugged container in Karo was stationary for much of the Government’s surveillance. See 468
U.S., at 708–710, 104 S.Ct. 3296. A car’s movements, by contrast, are its owner’s movements.
1 Although the record does not reveal the size or weight of the device used in this case, there is now a device in use that weighs two
ounces and is the size of a credit card. Tr. of Oral Arg. 27.
2 At common law, a suit for trespass to chattels could be maintained if there was a violation of “the dignitary interest in the
inviolability of chattels,” but today there must be “some actual damage to the chattel before the action can be maintained.” W.
Keeton, D. Dobbs, R. Keeton, & D. Owen, Prosser & Keeton on Law of Torts 87 (5th ed.1984) (hereinafter Prosser & Keeton).
Here, there was no actual damage to the vehicle to which the GPS device was attached.
3 The Court suggests that something like this might have occurred in 1791, but this would have required either a gigantic coach, a
very tiny constable, or both—not to mention a constable with incredible fortitude and patience.
4 See, e.g., Cal. Family Code Ann. § 760 (West 2004).
5 See Uniform Marital Property Act § 4, 9A U.L.A. 116 (1998).
6 See, e.g., NPR, The End of Privacy http://www.npr. org/series/114250076/the-end-of-privacy (all Internet materials as visited Jan.
20, 2012, and available in Clerk of Court’s case file); Time Magazine, Everything About You Is Being Tracked—Get Over It, Joel
Stein, Mar. 21, 2011, Vol. 177, No. 11.
7 See Kerr, The Fourth Amendment and New Technologies: Constitutional Myths and the Case for Caution, 102 Mich. L.Rev. 801,
850–851 (2004) (hereinafter Kerr).
8 See CTIA Consumer Info, 50 Wireless Quick Facts, http://www. ctia.org/consumer_info/index.cfm/AID/10323.
9 See, e.g., The bright side of sitting in traffic: Crowdsourcing road congestion data, Google Blog, http://googleblog.blogspot.
com/2009/08/bright-side-of-sitting-in-traffic.html.
129

10 Even with a radio transmitter like those used in United States v. Knotts, 460 U.S. 276, 103 S.Ct. 1081, 75 L.Ed.2d 55 (1983), or
United States v. Karo, 468 U.S. 705, 104 S.Ct. 3296, 82 L.Ed.2d 530 (1984), such long-term surveillance would have been
exceptionally demanding. The beepers used in those cases merely “emit[ted] periodic signals that [could] be picked up by a radio
receiver.” Knotts, 460 U.S., at 277, 103 S.Ct. 1081. The signal had a limited range and could be lost if the police did not stay close
enough. Indeed, in Knotts itself, officers lost the signal from the beeper, and only “with the assistance of a monitoring device
located in a helicopter [was] the approximate location of the signal ... picked up again about one hour later.” Id., at 278, 103 S.Ct.
1081.
11 In this case, the agents obtained a warrant, but they did not comply with two of the warrant’s restrictions: They did not install the
GPS device within the 10–day period required by the terms of the warrant and by Fed. Rule Crim. Proc. 41(e)(2)(B)(i), and they
did not install the GPS device within the District of Columbia, as required by the terms of the warrant and by 18 U.S.C. § 3117(a)
and Rule 41(b)(4). In the courts below the Government did not argue, and has not argued here, that the Fourth Amendment does
not impose these precise restrictions and that the violation of these restrictions does not demand the suppression of evidence
obtained using the tracking device. See, e.g., United States v. Gerber, 994 F.2d 1556, 1559–1560 (C.A.11 1993); United States v.
Burke, 517 F.2d 377, 386–387 (C.A.2 1975). Because it was not raised, that question is not before us.
* * *
End of Document
© 2012 Thomson Reuters. No claim to original U.S. Government Works.
130

88 Or. L. Rev. 829
Oregon Law Review
2009
Article
HAS THE FOURTH AMENDMENT GONE TO THE DOGS: UNREASONABLE EXPANSION OF CANINE
SNIFF DOCTRINE TO INCLUDE SNIFFS OF THE HOME
Leslie A. Lunneya1
Copyright (c) 2010 University of Oregon; Leslie A. Lunney
*830 The Fourth Amendment, and the personal rights which it secures, have a long history. At the very core stands the right
of a man to retreat into his own home and there be free from unreasonable governmental intrusion.1
Police employ drug-detection dogs in public locations, such as airports, as a quick means of determining whether luggage
contains contraband.2 In United States v. Place, the U.S. Supreme Court explained that the use of drug-detection dogs to sniff
luggage in a public location was not a “search” under the Fourth Amendment because of the accuracy and limited
intrusiveness of the canine sniff technique.3 The Place Court likely reached this conclusion because *831 the background
understanding of the day was that detection dogs were the ideal sensing tool because, in the rare case of a mistake, the dog’s
error was actually a false negative.4 Therefore, any mistake by a drug-detection dog worked to the benefit of the luggage
owner.
Despite recent evidence that drug-detection dogs are inaccurate a surprising percentage of the time, the Court in Illinois v.
Caballes extended the warrantless use of the canine sniff technique to a lawfully stopped vehicle.5 The impact of the Caballes
decision has been felt far beyond vehicle sniffs, however. Lower courts have taken the Place and Caballes decisions as a
signal that canine sniffs are per se nonsearches and that it is therefore permissible to conduct suspicionless canine sniffs of
homes. Without a warrant requirement, or even a suspicion requirement, police are thereby granted unfettered discretion to
conduct dragnet investigations at housing projects or other multidwelling locations, such as apartment complexes, or to
arbitrarily select sniff locations.6 A positive canine alert may then be used to obtain a warrant to enter the home and
physically search for drugs or to target a home for consent-based entry.
Despite the visceral offensiveness of potential dragnet or selective police investigations involving the home, all lower federal
courts that have considered the issue, aside from the U.S. Court of Appeals for the Second Circuit, have concluded that a
canine sniff of a private home is not a “search” under the Fourth Amendment. Therefore, no warrant, or even suspicion, is
required to perform the canine sniff.7 *832 This Article challenges the legitimacy of that conclusion and argues that a canine
sniff of a private residence--a location that is afforded stringent Fourth Amendment protection-- is a “search” within the
meaning of the Fourth Amendment.
The canine home-sniff issue is emblematic of a more generalized Fourth Amendment crossroads that the Court must surely
face. If the legitimacy of our expectations of privacy is determined primarily by the legality or illegality of the item
possessed, then the circumstances of that possession become irrelevant. To precondition Fourth Amendment protection on
the contraband/noncontraband nature of the object of the search without consideration of the privacy interests compromised
by the investigation itself represents a worrisome reorientation of the Fourth Amendment. This shorthand Fourth Amendment
analysis could, for all intents and purposes, consume the Fourth Amendment, except in situations where the Court has
expressly provided protection from intrusive police practices. Accordingly, resolution of the canine home-sniff question has
far-reaching Fourth Amendment implications.
131

To explore the canine home-sniff issue, Part II of this Article considers two competing lines of U.S. Supreme Court caselaw
that have split the lower courts’ analysis in this area.8 Three critical issues *833 generated from the doctrinal analysis are
then considered in Part III. In Part III.A, this Article argues that Place’s justifications, namely accuracy and limited
intrusiveness, do not support extending the canine sniff investigative technique to the home, and that such an unsupported
extension of Place is inconsistent with the Court’s recent demand for logical consistency between doctrinal extensions and
the justifications offered to support the original rule.9 Unfortunately, meaningful legal analysis of Place’s underlying
justifications has been stifled by the Place Court’s use of the term “sui generis”10 in describing canine sniffs. Part III.A
examines the Court’s use of the sui generis descriptor in other Fourth Amendment cases and argues that lower courts are
mistakenly attributing substantive heft to a term that is, in fact, intended to narrow the circumstances under which a doctrine
may be used.
Part III.B considers the heightened expectations of privacy associated with the home and whether the introduction of
potentially dangerous, and clearly intimidating, drug-detection dogs into the protected curtilage areas of a private home is
intrusive such that the practice should be viewed as a “search” under the Fourth Amendment. The analysis in Part III.B builds
on the discussion in Part I, which describes the routine cross-training of drug-detection dogs for criminal apprehension, or socalled
“bite dog,” purposes. Large and aggressive dogs are typically selected for drug-detection training. In analyzing the
reasonableness of privacy expectations, the Supreme Court has instructed that societal understandings are an appropriate
consideration.11 Therefore, this Article argues that our country’s long history of using dogs to intimidate racial minorities and
the offensiveness of dogs to followers of some religions must be *834 considered when examining the intrusiveness resulting
from introduction of a police dog into the protected curtilage area of a private home.
Part III.C argues that trained drug-detection dogs are “natural” technology and that, when used to sniff a private residence,
Kyllo should control. The government itself labels detection dogs as “technology” in its project literature. Further, canine
detection capabilities have been strengthened and enhanced through scientific research, innovative training tactics, geneticsbased
breeding programs, and even cloning technology. As such, this Article argues that drug-detection dogs are “natural”
technology that implicate the same concerns as those voiced in Kyllo: (1) “advancing technology,” in view of the potential
for technology-based enhancement of the canine sniff technique, and (2) the likely disclosure of noncontraband
information.12 Therefore, this Article argues that canine sniffs of the home are “searches” within the meaning of the Fourth
Amendment and, similar to the thermal imager warrants required after Kyllo, must be supported by a dog sniff warrant.
I
Training and Certification of Drug-Detection Dogs and the Science of the Canine Sniff
Dress yonder Marquis [who had stolen the banner of England] in what peacock-robes you will--disguise his appearance--alter
his complexion with drugs and washes--hide him amidst an hundred men--I will yet pawn my sceptre that the hound detects
him . . . .13
As the above quotation suggests, dogs have been used as an adjunct to law enforcement for hundreds of years to assist in the
location of fugitives.14 In modern times, canines are trained for a variety of purposes including drug detection,
apprehension,15 *835 explosives detection,16 cadaver detection,17 and agriculture detection.18 While not trained to be “allpurpose
sniffers,”19 it is not unusual for drug-detection dogs to be cross-trained as apprehension, or so-called “bite dogs.”20
Therefore, larger breeds, such as German shepherds or Belgian malinois,21 are often selected for drug detection purposes.22
While explosives-detection dogs are trained and certified through a federal program and under a federal certification
standard,23 drug-detection dogs are generally trained and certified by private vendors without the benefit of regulatory
standards for training and certification. For example, private vendors such as the U.S. Police *836 Canine Association
(USPCA),24 the National Narcotic Detector Dog Association (NNDDA),25 and the American Working Dog Association
(AWDA)26 offer training classes for canine handlers, as well as certification of drug-detection dogs, based on each
association’s own internally generated certification standards.27
In comparing these certification programs, certain similarities and therefore, perhaps, “minimum” requirements for drug
detection canines emerge. All programs train drug-detection dogs to search for marijuana and cocaine; certification for
additional substances, such as heroin, methamphetamines, and opium, as well as certified derivatives of these drugs, may be
available.28 Significant to the home-sniff issue, detection dogs are trained and certified based on interior walk-throughs and
sniffs of buildings, not perimeter sniffs.29 This is not to say that the certification process entirely excludes outside areas.
Some agencies offer certification for “open areas,” but *837 this certification appears to involve investigations for drugs
132

hidden in open locations, such as fields.30
For purposes of the canine sniff of a private home, the critical issues raised by unregulated drug-detection dog training and
certification standards are significant.31 No private agency specifically trains or certifies detection dogs to investigate for
contraband hidden within a building unless the dog is also permitted to walk through the interior of the structure for detection
purposes. Additionally, there is no reported data concerning the accuracy of drug-detection dogs when the dog is limited to a
perimeter sniff of a home. Without data, training, or certification, evaluating the accuracy of drug-detection dogs in the
home-sniff context amounts to little more than guesswork.
With respect to the science of the canine sniff, the U.S. Department of Justice describes detector dogs as a type of “trace
detector” capable of detecting vapors or particulates of specific items, including drugs or explosives.32 Courts that permit
suspicionless canine sniffs of the home operate on the assumption that drug-detection dogs alert solely *838 to contraband,
and in doing so, reveal no noncontraband information about the contents of the home.33 Nothing could be further from the
truth. Studies show that drug-detection dogs alert not to the illegal drug itself, but instead to a contaminant or by-product in
the drug.34 In fact, detection dogs may not be able to detect the so-called ultrapure forms of drugs, such as cocaine and
heroin, because of the extremely low vapor pressure of the unadulterated drug.35 With cocaine, for example, it appears that
detection dogs do not actually alert to the cocaine itself because the drug is a topical anesthetic that “deadens olfactory
senses.”36 Instead, the detection dog likely alerts to methyl benzoate, a high vapor pressure by-product of cocaine that can
occur naturally or as a result of processing.37 Significantly, although methyl benzoate is a cocaine by-product, the molecule is
also commonly found in everyday consumer products likely to be *839 stored in a home, such as “solvents, insecticides,
[and] perfumes.”38 In other words, drug-detection dogs likely alert to an entirely legal substance, methyl benzoate, which
allows the human police officer to infer that contraband is also present. For example, in Horton v. Goose Creek Independent
School District, although it was not discussed by the court, the drug-detection dog in question appears to have alerted to an
entirely lawful source of methyl benzoate--a bottle of perfume in the student’s purse.39 Because methyl benzoate is
commonly found in the home, further scientific clarification concerning the reliability of canine home-sniffs is essential.
Additionally, it is far from clear that civil forfeiture cases, proceedings in which the government seeks to seize currency
based on its connection to criminal drug trafficking, should be mechanically applied to cases involving canine sniffs of the
home.40 Central to *840 civil forfeiture proceedings is the fact that methyl benzoate is a volatile molecule that dissipates
quickly, meaning that a detection dog will alert to currency that has only recently been contaminated with street drugs, not
currency that contains the trace amounts of drugs routinely detected in American money.41 Therefore, in the civil forfeiture
context, methyl benzoate’s high evaporation rate, or volatility, provides assurance that the currency contamination is fresh.
“Freshness” of contamination cannot be presumed from a positive canine alert in the home-sniff context, however, since most
homes contain entirely lawful sources of methyl benzoate. Additionally, no data exist that consider the evaporation rate of
methyl benzoate on home surfaces or whether conditions exist in the home that might reduce the molecule’s volatility.42
Finally, lack of proximity to the scent source may be a further problem in canine home-sniffs. Scientific studies analyzing the
aerodynamics of canine olfaction indicate that “[c]lose nostril proximity to a scent source is important.”43 The canine nose is
dependent on scent concentration, and “the detailed spatial distribution of a scent source can only be discerned when the
nostril is brought into very close proximity with it.”44 This “close proximity” requirement45 is an inherent limitation to the
canine’s nose that, researchers explain, is compensated for by the dog’s natural agility *841 and mobility.46 When a drugdetection
dog engages in a close proximity sniff, researchers have documented a process, described as “scanning,” by which
the detection canine discovers or hones in on a scent source.47 During the scanning process, the detection dog sniffs close to
the ground until reaching the scent source.48 The dog then moves its nose horizontally to the scent source, pausing when
directly on top of it.49 The dog scans past the scent source but then returns to the scent once the scanning process has ceased,
allowing the canine to take a survey of the distribution of the scent.50
If it is optimal for a drug-detection canine to be in close proximity to the scent source, then a canine home-sniff may be
compromised by situational impediments (i.e., lack of proximity) in using the “scanning” process on which detection and
tracking dogs typically rely.51 The proximity consideration becomes even hazier when considering external factors, such as
weather and crosswinds,52 which can also interfere with the range of a canine sniff. Additionally, the ease of particulate
contamination on locations accessible to the public, *842 such as door handles,53 may render a positive sniff meaningless in
the home-sniff context since the home’s occupants have little, and sometimes no, control over who accesses this open
curtilage area.
133

The canine sniff technique’s reliance on the detection of methyl benzoate raises two separate issues in the home-sniff context:
(1) factual questions involving the detection dog’s accuracy or reliability because the home is a common repository for
substances that contain the entirely legal methyl benzoate molecule, and no data exist that consider whether situational
impediments in the home-sniff context may compromise an otherwise “reliable” canine’s detection capabilities; and (2) legal
questions, since Kyllo prohibits technology-enhanced inferencing about the interior of a home that discloses noncontraband
information.54 Too many uncertainties and gaps in scientific proof presently exist to assume that a positive canine home-sniff
is an appropriate basis on which to issue a search warrant.
II
Competing Lines of U.S. Supreme Court Caselaw: Which Line Controls Canine Sniffs of the Home
Power is a heady thing; and history shows that the police acting on their own cannot be trusted. And so the Constitution
requires a magistrate to pass on the desires of the police before they violate the privacy of the home.55
The Fourth Amendment guarantees “[t]he right of the people to be secure in their persons, houses, papers, and effects, against
unreasonable searches and seizures.”56 The touchstone of the modern Fourth Amendment analysis turns on whether the
person has a *843 “constitutionally protected reasonable expectation of privacy.”57 In Katz, the Court rejected the
government’s argument that a “search” occurs only when there has been a “physical intrusion” into a “constitutionally
protected area,” and reoriented the Fourth Amendment inquiry through the Court’s now-familiar observation that the Fourth
Amendment “protects people, not places.”58
A. Focus on the Item: No Legitimate Expectation of Privacy in Possession of Unlawful Contraband
Prior to Place, the Court signaled in Florida v. Royer the likely favorable treatment that canine sniffs would receive, at least
where the sniff involved luggage located at an airport.59 The Royer Court’s reference to the canine sniff technique was
dicta,60 however, because the detectives never actually subjected Royer’s bags to a drug-detection sniff. As a way of
avoiding lengthy and intrusive detentions, the Royer Court seemed to invite the use of canine sniffs as an investigative tool,
noting that the brevity of the detention associated with a canine sniff would likely ensure that the boundaries of Terry v.
Ohio61 would not be exceeded.62 The Royer dicta was clear foreshadowing of both the favorable treatment that canine sniffs
would receive and the Court’s eagerness to consider the canine sniff issue itself, not just the reasonableness of the detention
that made the sniff possible.
*844 Just three months later, the Court again went out of its way to discuss canine sniffs in United States v. Place.63 There,
detectives seized Place’s luggage on the basis of reasonable suspicion and subjected the luggage to a drug-detection dog. The
issue before the Court was whether Terry supported the limited detention of personal property on the basis of reasonable
suspicion. The Court concluded that Terry would permit such a limited detention, but the detectives’ ninety-minute detention
of the luggage was too lengthy to be supported under Terry.64
Although Place did not challenge the validity of the canine sniff to which his luggage was eventually subjected and the U.S.
Court of Appeals for the Second Circuit did not consider the sniff issue, the Court went beyond the issues presented to
consider the canine sniff question without the benefit of briefs or argument on this issue.65 Writing for the majority, Justice
O’Connor discussed the canine sniff issue in a conclusory, two-paragraph, citationless statement:
A “canine sniff” by a well-trained narcotics detection dog, however, does not require opening the luggage. It does not expose
noncontraband items that otherwise would remain hidden from public view, as does, for example, an officer’s rummaging
through the contents of the luggage. Thus, the manner in which information is obtained through this investigative technique is
much less intrusive than a typical search. Moreover, the sniff discloses only the presence or absence of narcotics, a
contraband item. Thus, despite the fact that the sniff tells the authorities something about the contents of the luggage, the
information obtained is limited. This limited disclosure also ensures that the owner of the property is not subjected to the
embarrassment and inconvenience entailed in less discriminate and more intrusive investigative methods.
*845 In these respects, the canine sniff is sui generis. We are aware of no other investigative procedure that is so limited both
in the manner in which the information is obtained and in the content of the information revealed by the procedure.
Therefore, we conclude that the particular course of investigation that the agents intended to pursue here--exposure of
respondent’s luggage, which was located in a public place, to a trained canine--did not constitute a “search” within the
meaning of the Fourth Amendment.66
134

While the Place Court’s failure to request briefs and argument concerning the canine sniff issue is certainly surprising, the
Court’s refusal to consider the debate that had percolated through the lower courts prior to Place is perplexing.67 The Court
cited not a single case, transforming its pronouncement that a canine sniff is “sui generis,” and therefore not a “search,” into
an unassailable judicial *846 monolith.68 After Place, it appeared that if the original seizure of the individual or the
individual’s personal property was supported by reasonable suspicion, then the ensuing canine sniff was permissible because
the sniff, by definition, was not a search.
Soon after Place, the Court considered another case that would have important implications in the canine sniff area. In United
States v. Jacobsen, the Court considered whether warrantless field testing of a white powder to determine whether it was
cocaine violated the Fourth Amendment when that powder was discovered by Federal Express employees and then turned
over to the U.S. Drug Enforcement Administration (DEA).69 Significant to the canine sniff question, the field test was able to
identify the powder as cocaine but was unable to determine whether the powder was any other substance.70
The Court granted certiorari to consider two separate issues: (1) the scope of the private search doctrine,71 and (2) the
warrantless field testing of suspected contraband. In an opinion authored by Justice Stevens, the Court agreed that field
testing of the white powder was not a search under the Fourth Amendment because it compromised no legitimate interest in
privacy.72 The Court explained that government conduct that established only whether a substance was cocaine and revealed
“no other arguably ‘private’ fact” compromised no legitimate privacy interest.73 The Court’s conclusion was “dictated” by
Place because field testing, like a canine sniff, revealed nothing about noncontraband items.74
*847 In an observation that may have important modern implications, the Jacobsen Court also noted that “[h]ere, as in Place,
the likelihood that official conduct of the kind disclosed by the record will actually compromise any legitimate interest in
privacy seems much too remote to characterize the testing as a search subject to the Fourth Amendment.”75 This
“remoteness” consideration from Jacobsen is potentially significant in analyzing canine sniffs in general, and the home sniff,
in particular. This issue is considered in Part III.A, which discusses our modern understanding of error rates associated with
canine sniffs and whether, in view of these acknowledged error rates, the risk of uncovering private, noncontraband
information during the ensuing search can truly be characterized as “remote.”
Although Place’s conclusions regarding the unique diagnostic capabilities of canine sniffs have been criticized as
inaccurate,76 the Court recently ensured the ongoing legal vitality of the canine sniff technique in Illinois v. Caballes.77
Caballes involved a routine traffic stop for speeding.78 Although there was no suspicion that Caballes was transporting drugs,
a drug interdiction team member, who had arrived at the traffic stop while the ticket was being written, walked a drugdetection
dog around Caballes’s vehicle. The dog alerted on the trunk, which the officers opened and discovered the
marijuana for which Caballes was arrested.79
Important to the Caballes Court in upholding the validity of the canine sniff was both the legality of the initial traffic stop80
and the fact that the canine sniff process had not extended the length of *848 Caballes’s detention beyond the time necessary
to write the ticket.81 In upholding the legality of the canine sniff, the Court relied on Jacobsen’s premise that a person lacks a
legitimate expectation of privacy in contraband.82 Through some arguably loose language, the Court may have expanded the
Jacobsen premise in a manner that could have a real impact on the home-sniff issue. The Caballes Court first quoted Jacobsen
for the proposition that “[o]fficial conduct that does not ‘compromise any legitimate interest in privacy’ is not a search
subject to the Fourth Amendment.”83 The Caballes Court then, in an apparent expansion of Jacobsen, stated that “any interest
in possessing contraband cannot be deemed ‘legitimate.”’84
Returning for a moment to the Jacobsen opinion, the focus there was on the distinction between contraband and
noncontraband information.85 As the Jacobsen Court explained, “[a] chemical test that merely discloses whether or not a
particular substance is cocaine does not compromise any legitimate interest in privacy.”86 The circumstances that made the
field testing possible (the private search issue) were treated separately by the Jacobsen Court.87 Therefore, the focus in this
portion of the Jacobsen opinion was on the accuracy of the information to be gained by the field testing, not the
circumstances under which this investigative tool might be used.88 The Caballes Court, on the other hand, focused on more
than just the contraband/noncontraband nature of the information revealed. By observing that “any interest in possessing
contraband [is not] *849 legitimate,” the Caballes Court may be suggesting that the circumstances of contraband possession
are irrelevant.89 Further support for this reorientation can be found in the Caballes majority’s explanation that the opinion
was “entirely consistent” with Kyllo v. United States in that “[c]ritical to [the Kyllo] decision was the fact that the [thermalimaging]
device was capable of detecting lawful activity--in that case, intimate details in a home, such as ‘at what hour each
night the lady of the house takes her daily sauna and bath.”’90 The key question after Caballes is whether the majority’s
reference to Kyllo was simply illustrative of the special legal significance attributed to an investigative technique that reveals
135

only contraband, but no noncontraband information, or instead, if Caballes is intended to signal the Court’s willingness to
exclude any consideration of the circumstances of the contraband’s discovery. This would mean that a person lacks any
expectation of privacy in contraband, even contraband that is secreted in the person’s private residence.
As a final point, the Caballes Court again used the sui generis terminology to describe the canine sniff and cited to both Place
and Indianapolis v. Edmond, a case involving the canine sniff of a vehicle’s exterior at a drug interdiction checkpoint.91 In
Edmond, although the checkpoint seizure itself was found to violate the Fourth Amendment,92 the Court refused to view the
canine sniff of the vehicle as a “search.”93 While the canine sniff was not “transformed” into a search simply because the
seizure of Edmond’s vehicle at the checkpoint was unreasonable, the Edmond Court did not suggest that the search and the
seizure issues should be analytically severed from one another.94 In fact, the Edmond Court’s holding is to the contrary.
Because the narcotics interdiction checkpoint did not meet the Court’s requirements for suspicionless, administrative-type
seizures, police were required to establish individualized suspicion to stop a vehicle *850 for investigation.95 The effect,
therefore, is that no canine sniff of a moving vehicle would be permissible without first showing the appropriate quantum of
suspicion to stop the vehicle.
Left unanswered after Caballes and Edmond is whether, at least in the vehicle context, the seizure and the search issues could
be analytically severed. The practical effect of disconnecting the seizure from the search would be to make it possible for
police to run drug-detection dogs through public parking lots to conduct suspicionless sniffs of parked vehicles.96 Since no
seizure would be necessary to investigate a parked vehicle and a canine sniff of a vehicle is not a “search,” suspicionless,
dragnet searches would therefore become possible.97 Further, if the Court permits the disconnection of the seizure and search
issues in the vehicle context, it sets the stage for arguing that a home sniff would also be permissible. Since it could be argued
that no seizure occurs when a detection dog performs a sniff from the front-door curtilage area of a private home, the Place
opinion would make most canine sniffs of the home judicially unreachable.
Several points bear emphasis when examining the Place, Jacobsen, and Caballes decisions and their potential applicability to
canine sniffs conducted outside of a home. These cases were implicitly, and in some cases explicitly, based on three essential,
and interrelated, legal and factual observations that will be discussed below: (1) the lawfulness of the antecedent seizure that
made the canine sniff possible, (2) the sniffs occurred under circumstances involving lesser expectations of privacy, and (3)
the sniffed item had been disconnected from the person of the suspect at the time of the sniff.
1. Lawful Antecedent Seizure
First, in each of the above-referenced cases, the legality of the police investigative tactic (i.e., canine sniff and field testing)
implicitly turned on the lawfulness of the initial seizure of the item or *851 person.98 While the Court implicitly tied its
approval of the police investigative tool at issue to the lawfulness of the seizure, the Court failed to expressly precondition
the tool’s use on the lawfulness of the first step, the “seizure.” By making the antecedent justification requirement only an
implicit precondition in these decisions, the Court has made it possible for lower courts to disconnect the seizure from the
sniff altogether.99 The resulting softening and attenuation between these interrelated legal issues100 has important
implications for the home-sniff question. As a factual matter, no control over the residence, in other words, no “seizure,”
need be taken in order to conduct the sniff. By oversimplifying Place and Jacobsen and focusing exclusively on the police
investigative technique, courts have sidestepped the antecedent justification requirement essential to a lawful seizure, in other
words, the context in which the investigative tactic is used. In his Jacobsen dissent, Justice Brennan warned of the danger that
results from this sort of oversimplification.101 He cautioned that exempting any “class of surveillance technique” as
categorically outside the definition of “search” or “seizure” without consideration of the “context” in which the tactic was
used could lead *852 to dragnet-style, or even selective, applications of the surveillance tactic.102
2. Reduced Expectation of Privacy
Second, police investigation of the suspicious items in the above-referenced cases took place at locations, or under
circumstances, where the suspects had lesser expectations of privacy.103 Lower courts have seized on what they view as the
“public location” of canine home-sniffs as a primary justification for allowing them.104 As these courts have explained, the
canine sniff of a home is also conducted from a public location, such as a common hallway in front of an apartment or the
front porch area of a freestanding residence. Therefore, they argue, the public location from which the sniff is conducted
makes it essentially identical to the canine sniff performed in Place. This deceptively plausible argument misses the point. In
both Place and Caballes, the canine sniff was performed under circumstances in which the suspect had a lesser expectation of
privacy; these cases did not turn on the lawfulness of the location of the officer’s feet (or the dog’s paws). While public
136

location may be important in evaluating expectations of privacy, location alone cannot be understood as the sole
circumstance-driven requirement from these Supreme Court decisions. When the analysis is refocused onto the reduced
expectation of privacy involved in the circumstances under which the investigative tactic was used, these decisions stand in
sharp contrast to the heightened privacy interests associated with the home.105
*853 3. Disconnection from the Suspect
Third, as a further observation, in each of the above-referenced cases the suspicious item was not on the person of the suspect
at the time the police investigative technique was used.106 Disconnection therefore reinforces the first and second organizing
principles. In other words, disconnection from the owner could be reflective of the fact that the initial police access to the
item that made the surveillance tactic possible (the “seizure”) was supported by an appropriate quantum of suspicion.
Additionally, when the item is disconnected from the person of the suspect, as was the case in both Place and Caballes,
further investigation, in the form of a canine sniff, may be less invasive and offensive and therefore less intrusive.107 The
disconnection becomes part of the circumstances of the sniff, a fact that suggests that the canine sniff was not so intrusive
that it violated the suspect’s Fourth Amendment interests.108 With a canine home-sniff, no disconnection of the person from
the person’s home is necessary. Therefore, potentially intimidating or offensive encounters between a home’s occupants and
an investigating canine team is increasingly likely.109
B. Focus on Privacy: Sense-Enhancing Technology Directed at the Home
While the extent to which drug-detection dogs will or should be viewed as “technology” remains unresolved, a canine sniff
certainly *854 represents sense enhancement of the human sense of smell.110 Accordingly, courts faced with a warrantless
sniff of a residence must either rely on Kyllo v. United States111 or reject the decision’s applicability.112 Therefore, careful
analysis of Kyllo is essential.
In Kyllo, the defendant moved to suppress evidence obtained pursuant to a search warrant issued in reliance on the results of
a thermal-imaging scan113 of his home. The scan, conducted from the lawful vantage point of a public street, revealed
temperature gradients that were consistent with high-intensity lights used in an indoor marijuana growing operation.114 In
finding that the warrantless use of the thermal imager violated Kyllo’s reasonable expectation of privacy, the Court’s central
legal premise was that “the Fourth Amendment draws ‘a firm line at the entrance to the house”’ that “must be not only firm
but also bright.”115 Justice Scalia, writing for the majority, acknowledged that expectations of privacy had been impacted by
technological advances,116 and framed the issue as “what limits there are upon this power of technology to shrink the realm
of *855 guaranteed privacy.”117 The Court concluded that “obtaining by sense-enhancing technology any information
regarding the interior of the home that could not otherwise have been obtained without physical ‘intrusion into a
constitutionally protected area’ . . . constitutes a search--at least where (as here) the technology in question is not in general
public use.”118 While the technology at issue in Kyllo was “relatively crude,” the majority underscored the danger that
“advancing technology” would pose to privacy interests.119
Kyllo sparked a vigorous dissent, authored by Justice Stevens and joined in by three other Justices. The dissent viewed the
thermal-imaging device as purely passive technology that did no more than measure radiant heat emanating from Kyllo’s
home--not a more sophisticated device that could peer through walls. The dissenting Justices argued that there was a
meaningful constitutional distinction between technology that gave the listener “direct access” to information about the
interior of the home and technology that permitted police officers to draw “inferences” based upon “information in the public
domain.”120 In response, the majority explained that while inferencing alone was not a search, the thermal-imaging device
provided information that allowed police to infer that contraband was present.121 In other words, the thermal scan was a
“search” because it made technology-assisted inferencing about the interior of a home possible.
Two interpretations concerning the scope of Kyllo’s prohibition on technology-assisted inferencing are generated: (1) the
decision applies to all nonroutine technology-assisted surveillance of the home *856 because “any information” regarding the
interior of the home is protected,122 or (2) the decision limits only technology-assisted inferencing that might reveal both
contraband and noncontraband information about the home’s interior.123 In his Kyllo dissent, Justice Stevens expressed
concern that the Court had intended the first interpretation rather than the second. He argued that the majority’s proposed rule
would bar mechanical devices that could detect only the presence of an illegal substance or activity, but would reveal no
noncontraband information,124 a clear reference to the Court’s favorable treatment of detection dogs in Place.
Justice Stevens’s Kyllo dissent certainly foretells the inevitable intersection of the canine home-sniff question and the scope
137

of Kyllo’s limitations on sense-enhancing technology directed at the home. Interestingly enough, it may be Justice Stevens’s
Kyllo interpretation that the Court ultimately embraces. In 2005, Justice Stevens authored the Caballes opinion, which
permitted the suspicionless canine sniff of a lawfully stopped vehicle.125 In dicta, Justice Stevens explained that the
suspicionless use of a canine sniff to investigate the exterior of Caballes’s vehicle was entirely consistent with Kyllo because
the sniff revealed no lawful activities or information.126 By pressing Kyllo’s second explanation concerning the
contraband/noncontraband nature of the information discovered, the Court appears ready to reorient Kyllo to bar only
warrantless use of sense-enhancing technology that might also reveal noncontraband information.
*857 Additionally, the Court has considered the warrantless use of other sense-enhancing technology directed at the home
prior to Kyllo, cases that should prove helpful in analyzing canine home-sniffs. One case in particular, United States v.
Karo,127 which was cited favorably in Kyllo, provides insight into the home-sniff issue. Karo involved the use of beeper
technology128 to track the movement of cans filled with chemicals used in the manufacture or refinement of illegal street
drugs after the cans had been hidden inside a private home.129 The Karo Court concluded that warrantless monitoring of the
beeper violated the Fourth Amendment because the beeper provided “information” about the interior of the home that could
not have been obtained through observation from outside the home’s curtilage.130 The Court analogized the warrantless
monitoring to surreptitious physical entry by DEA agents to search the home to determine whether the can of ether was still
present, a clearly impermissible surveillance technique.131
Karo is potentially significant because it is a post-Jacobsen case, yet the decision uses expansive language to describe the
protection from police discovery afforded to property hidden in a private residence, language that is arguably inconsistent
with the Jacobsen premise. Karo states that the Fourth Amendment protects a person from police discovery of “information”
about the interior of the home,132 “a critical fact” about the interior of the premises,133 whether a “particular article” is
located within the home,134 and concerns about monitoring “property” that has been withdrawn from *858 public view into a
home.135 While some of these references were simply descriptive of Karo’s facts concerning monitoring of the home to
determine whether the can of ether was still present,136 other language in Karo appears to have broad applicability and may
be relevant to the canine home-sniff analysis. In particular, the Karo Court noted:
We cannot accept the Government’s contention that it should be completely free from the constraints of the Fourth
Amendment to determine by means of an electronic device, without a warrant and without probable cause or
reasonable suspicion, whether a particular article--or a person, for that matter--is in an individual’s home at a
particular time. Indiscriminate monitoring of property that has been withdrawn from public view would present far
too serious a threat to privacy interests in the home to escape entirely some sort of Fourth Amendment oversight.137
This language is expansive enough to bar monitoring for any type of item, including contraband. The question then is
whether this is a supportable interpretation of Karo’s reasoning. Perhaps it is. Certainly, there is nothing in Karo’s expansive
discussion to suggest that contraband hidden in the home should be excluded from the Court’s treatment of property
“withdrawn from public view,” and when the Court has intended to limit its holding to certain types of property, it has
certainly made its intentions known.138
As an additional point, the Karo Court referenced the use of technology to locate whether a particular person is in a home at a
particular time.139 While knowing a person’s location is obviously helpful in an ongoing criminal investigation, the location
of a person who has an outstanding arrest warrant is of critical importance to the police. In a sense, the fugitive is like
contraband: (1) with an arrest warrant, police can enter the suspect’s home to arrest (“seize”) him,140 and (2) with a search
warrant, police are authorized to enter a *859 third person’s home in order to make the arrest.141 Karo suggests that
technology-based monitoring of a home to determine the location of a person, apparently even someone who could be
lawfully seized upon discovery, would be impermissible. If police are barred from using technology directed at a home to
locate such a person, then “information” about the home should also be interpreted to include contraband.
Interestingly enough, technology that would enable police to determine an individual’s exact location already exists.142 A
locational scanning device that would allow police to detect an individual’s presence143 by identification of a computer chip
embedded into the individual’s driver’s license is in the development stage.144 While it could be argued that this proposed
technology would detect only the driver’s license rather than the actual fugitive individual, this is an artificial distinction
because, similar to a cell phone, people ordinarily keep their driver’s license on their person or close at hand.145 An
analogous inference arises when a drug- *860 detection dog alerts to a methyl benzoate source inside a private home. Like
the inference that a fugitive is physically present when the fugitive’s driver’s license or cell phone is detected inside a private
home, detection of methyl benzoate by a drug-detection dog enables police to infer that contraband is also present.
138

III
Framing the Canine Home-Sniff Debate
A. Should Place’s Accuracy and Limited Intrusiveness Justifications Be Extended to Support Canine Sniffs of the
Home
This Court is forever adding new stories to the temples of constitutional law, and the temples have a way of collapsing when
one story too many is added.146
While permitting canine sniffs of the home is simply a newer application of the rule set out in United States v. Place,147
extending Place to this newer, residential factual setting requires courts to engage in an analogous sort of “construction”
process to the one warned about above by Justice Jackson in his Douglas v. City of Jeannette concurrence. Courts, at times,
extend a constitutional rule too far to be supported by the rule’s doctrinal underpinnings, and when that happens, sometimes
that floor, too, crashes in. The Court has shown a recent willingness to examine critically a constitutional rule that has been
extended in a way that was incompatible with the rule’s justifications.148 As discussed below, like the rule extension recently
rejected in Arizona v. Gant, Place’s accuracy and limited-intrusiveness justifications do not support extending Place to
include canine sniffs of the home.149
*861 1. Sui Generis:150 A Limiting Descriptor now Used Expansively for Canine Sniffs
Prior to Place, it was believed that detection dogs did not make mistakes that resulted in invasions of privacy. In other words,
when mistakes were made, they inured to the benefit of the suspect not the police.151 In view of that era’s background
assumption concerning detection-dog accuracy, it is not surprising that the Place Court expressed complete confidence in the
canine sniff technique; the Court’s view was simply a reflection of what was accepted as true at the time.152 Both Place and
Jacobsen were premised, in large part, on the fact that the testing at issue--the canine sniff and the field testing of the white
powder--was accurate.153 In language that has had important substantive ramifications for canine home-sniffs, the Place
Court explained that the canine sniff is “sui generis” because the sniff was less intrusive than the traditional rummaging
associated with a physical search and the sniff disclosed only limited information (the presence or absence of contraband).154
Therefore, accuracy and *862 the harmlessness of any potential canine sniff miscue was the background understanding of the
Place era.
In reality, however, error rates for drug-detection dogs undermine the Court’s accuracy justification for treating the canine
sniff as a sui generis practice. As Justice Souter’s Caballes dissent reflects, drug-detection dogs are wrong a surprising
amount of the time.155 Additionally, courts have accepted as “reliable” detection dogs with even higher error rates than the
cases referenced in Justice Souter’s Caballes dissent156 Evaluating Place’s justifications and determining whether time has
borne them out is made more difficult by the Court’s use of sui generis language, however. In practice, lower courts have
seized on the sui generis label but have forgotten the justifications that led the Court to use the label.157 By giving substantive
weight to the sui generis descriptor, lower courts effectively ignore the accuracy justifications of Place and Jacobson by
injecting probably cause-based language into their analyses of whether a given drug-detection dog is sufficiently reliable.158
For these courts, the question then boils down to whether there is simply a *863 “fair probability” that a given drug-detection
dog will be correct, making the accuracy justification essentially disappear.159
While the accuracy of the information revealed was arguably only an implicit basis for approving the canine sniff procedure
in Place,160 the Court expressly endorsed the canine sniff technique based on its accuracy in United States v. Jacobsen.161
Perhaps that should be the end of the sui generis discussion. The Place Court’s accuracy assumption has not withstood the
test of time, and that alone, at a minimum, should be enough to limit the technique’s applicability to the circumstances
previously articulated in Place162 and Caballes.163 In fact, as Justice Souter argued in his Caballes dissent, the canine sniff
accuracy questions that have emerged since Place provide sufficient grounds to reconsider the Place decision itself.164
Analysis of Place’s justifications has been made unnecessarily slippery, however, because of the Court’s use of the sui
generis descriptor.165 It is difficult to meaningfully criticize, or even critique, a doctrine when an ambiguous label has been
used to describe it.166 Therefore, *864 it may prove helpful to gain a better understanding of the Court’s use of the sui
generis label in other cases, particularly in the Fourth Amendment context, to determine whether the label should imply any
meaning other than a descriptive one.
The term “sui generis” appears in 105 U.S. Supreme Court opinions, most of which are simply descriptive of the unique
factual circumstances at issue that warranted one-of-a-kind treatment by the Court.167 In fact, the term “sui generis” often
139

appears in dissenting opinions as a pejorative--used to suggest that the majority had sidestepped the real issue in the case and,
therefore, created a rule of almost no value in future decision making.168 Although some lower courts have used Place’s sui
generis label as an “open sesame,”169 sui generis terminology is actually intended to convey both a narrowly defined rule and
the narrow circumstances under which the rule is applicable. For example, in Dunaway v. New York, also a Fourth
Amendment case, the Court refused to interpret Terry170 expansively to allow custodial interrogation of a suspect at the
station house on the basis of reasonable suspicion, rather than probable cause.171 As the Dunaway Court explained, Terry
created a “special category” of Fourth Amendment seizures that were substantially less intrusive than a traditional arrest
because the detention involved a “brief, on-the-spot stop on the street,” which the Court viewed as reasonable under its
balancing test.172 Although Terry did not use the term sui generis, the Court in Dunaway used the label to describe Terry,
explaining that “[i]nstead [because the intrusion was less than that associated with a traditional arrest], the Court treated the
stop-and-frisk intrusion as a sui generis rubric of police conduct.”173 The Dunaway Court was *865 careful to emphasize,
however, the narrow circumstances that made Terry reasonable.174
The Dunaway Court therefore required a close connection between a one-of-a-kind police practice (stop and frisk) and the
justifications for departing from traditional Fourth Amendment requirements, and in doing so, concluded that custodial
interrogation of a suspect at the station house on the basis of reasonable suspicion was not sufficiently close to Terry’s
justifications. In the canine sniff context, one-of-a-kind treatment of the canine sniff technique means that this practice, too,
must be closely tied to the justifications that led the Court to conclude that a sniff was not a “search.” Otherwise, the sui
generis label would not simply be descriptive; it would convey substantive meaning on its own. The Court would likely reject
such a view since it has disapproved of lower courts’ attempts to “rope off” a legal issue through the use of the sui generis
label in lieu of meaningful legal analysis.175 Therefore, it is crucial to determine whether canine sniffs of the home are
consistent with the narrow circumstances that the sui generis label is meant to describe.176
2. Frozen in Time: Sui Generis Label Shields Drug-Detection Sniffs from Advances in Scientific Understanding
Courts that apply the Place/Jacobsen analysis describe their legal analysis as a “binary” inquiry. As Judge Moylan, on the
Maryland Court of Special Appeals, writing for the majority explained:
*866 The raison d’etre for treating a dog sniff as a non-search is that the binary nature of its inquiry, “contraband
‘yea’ or ‘nay’,” precludes the possibility of infringing any expectation of privacy that society objectively considers
to be legitimate. If the possession of narcotics in an automobile or a suitcase is illegitimate, so too is the possession of
narcotics in a home. It is the criminal nature of the possession itself that takes the activity out from under the
protection of the Fourth Amendment, not the place where the possession occurs.177
These courts focus exclusively on the unlawfulness of contraband possession without any consideration of the circumstances
under which the contraband is possessed. For example, in Fitzgerald v. State, the court distinguished Karo178 and Kyllo179
from a canine home-sniff because both Karo and Kyllo involved the tracking of noncontraband items (ether in Karo and
excessive heat in Kyllo) once the item became a “detail of the home.”180 The Fitzgerald court pointed out that ether, for
example, was “a non-contraband item with many legitimate, as well as illegitimate, uses.”181 The comparison to detection of
methyl benzoate molecules in the canine sniff context is unavoidable. As discussed in Part I, scientific research has shown
that detection dogs likely alert to the volatile methyl benzoate molecule, not to cocaine itself.182 Methyl benzoate, like ether,
has many legitimate uses and, unlike ether, is probably present in the ordinary household.183 This scientific research
therefore undermines these courts’ reliance on the lawful/unlawful character of the substance or item being tracked as a
distinguishing basis to support canine home-sniffs. Similar to the thermal imager’s detection of excessive heat in Kyllo,
detection of methyl benzoate allows police to infer that illegal contraband is also present. As Kyllo instructs, police
inferencing about the contents of a home that is made possible by *867 sense-enhancing technology is a “search” under the
Fourth Amendment.
The potential detection of noncontraband information was crucial to one federal court asked to consider a suspicionless
canine sniff by an explosives-detection dog at a traffic stop.184 Although the facts in United States v. Esparza are clearly
analogous to those of Caballes, the judge distinguished the two sniffs on the fact that explosives-detection dogs are “trained
to detect ammonium nitrate, a chemical found in [ordinary] household items such as fertilizer and printer cartridges.”185
Therefore, similar to the thermal imager at issue in Kyllo, the sniff by an explosives-detection dog was capable of detecting
lawful activity and thereby violated the Fourth Amendment.186 For purposes of drug-detection sniffs, on the other hand, the
Court’s use of the sui generis descriptor has crystallized understanding of such sniffs to the assumptions of the day in 1983,
140

seemingly making impermissible what would otherwise be a clear analogy to Kyllo’s ban on sense enhancement that might
reveal noncontraband information.
As a further thought, reliance on the contraband/noncontraband character of the item being tracked is too simplistic from a
legal perspective as well. As four members of the Court recently reminded, “[t]he Fourth Amendment does not seek to
protect contraband, yet we have required suppression of contraband seized in an unlawful search.”187 Therefore, courts that
focus exclusively on the illegality of the item are missing the point. The Supreme Court requires *868 determinations of
whether an unlawful search has occurred and whether it is appropriate to apply an exclusionary remedy under the
circumstances.188 By categorizing all canine sniffs as permissible, and focusing exclusively on the object of the sniff, these
lower courts never analyze the lawfulness of the circumstances of the underlying sniff. Courts have never accepted such a
simplistic model. For example, where a canine sniff of a person is contemplated, courts have routinely required suspicion, at
least in nonborder situations.189 While the courts in the schoolchild sniff cases focused on the fact that a person, rather than
an unattended item, was being sniffed,190 the key point is that these courts analyzed the circumstances under which the
canine sniff was performed. In other words, these courts recognized that canine sniffs were not per se outside the boundaries
of Fourth Amendment protections. By focusing on the context of the sniff, these courts concluded that the sniff of a
schoolchild was too intrusive to be performed without individualized suspicion.191 The school sniff cases demonstrate that
considering the circumstances of a canine sniff is nothing new, and serve as a clear indicator that evaluating the intrusiveness
of a canine sniff is appropriate in other privacy-sensitive circumstances as well. Refusing to consider the context of the
canine sniff, in favor of focusing on the contraband for which the dog is sniffing, is therefore wrong.
*869 3. “Remoteness” as a Justification for Excluding Canine Sniffs from Fourth Amendment Requirements: Possible
Semantic and Temporal Interpretations and Their Impact on Canine Sniff Jurisprudence
To determine whether a canine home-sniff is tied closely enough to the justifications for treating the technique as a
nonsearch, it is important to examine the Court’s expectations and assumptions concerning the canine sniff technique. As the
Jacobsen Court observed, “[h]ere, as in Place, the likelihood that official conduct of the kind disclosed by the record will
actually compromise any legitimate interest in privacy seems much too remote to characterize the testing as a search subject
to the Fourth Amendment.”192
On the one hand, this discussion provides clear substantiation of an accuracy-based justification for the police investigative
tool at issue. In other words, the Jacobsen Court, in its “remoteness” discussion, could be characterizing the testing involved,
both the field testing and the canine sniff described in Place, as being so accurate that the odds of not finding contraband, and
therefore instead finding private, noncontraband information in the ensuing search, are “much too remote” to view the police
investigative tool as a “search.” This semantic interpretation of “remoteness” is consistent with Place in that Place’s
description of detection dogs as sui generis appeared to be based on both the dog’s accuracy and the limited intrusiveness of
the sniff itself.193 Additionally, lower courts have explained remoteness in semantic terms as well. For example, in Fitzgerald
v. State, the court viewed the likelihood that a drug-detection dog would alert on medically prescribed marijuana as too
remote to be meaningful for purposes of Place.194
On the other hand, “remoteness” could also be interpreted in a temporal sense. The idea here would be that the eventual
search of the person’s now-suspicious item should be severed analytically from *870 the original sniff or field test that
produced the suspicion toward the item. A temporal interpretation of remoteness would therefore allow the Court to
disconnect the use of the police investigative tool from the inevitable consequences of that use--the search. By looking at
these steps in isolation, the Court could ignore the consequences of a false-positive triggering event. In other words, the
exposure of private, noncontraband information as a result of a false-positive canine alert would be “too remote” to reflect
back, in some constitutional sense, on the search-triggering investigative tool.
The answer to the “remoteness” question has important implications for the ongoing vitality of the Jacobsen premise. If the
semantic interpretation for “remoteness” is the proper one, then changes in our understanding of both the accuracy of drugsniffing
dogs, in general, and societal views on what is “contraband” take center stage. In other words, if drug-detection dogs
are not as accurate as once assumed or if lawful citizens increasingly store prescription medications in their homes that
detection dogs would interpret to be contraband, then the likelihood that legitimate interests in noncontraband information
remaining undisturbed is, in fact, not “remote.”
The Supreme Court may be pressing the temporal, rather than the semantic, view of remoteness, however. As the Caballes
Court explained:
141

Although respondent argues that the error rates, particularly the existence of false positives, call into question the
premise that drug-detection dogs alert only to contraband, the record contains no evidence or findings that support his
argument. Moreover, respondent does not suggest that an erroneous alert, in and of itself, reveals any legitimate
private information, and, in this case, the trial judge found that the dog sniff was sufficiently reliable to establish
probable cause to conduct a full-blown search of the trunk.195 It is not clear from this statement whether the majority
concluded, in some definitional sense, that a false positive from a reliable detection dog, by itself, was incapable of
revealing legitimate private information or, instead, that Caballes had simply failed to make this argument.
Significantly, however, the context of the Court’s discussion suggests the former and not the latter. Perhaps, the Court
recognizes that an accuracy-based foundation for permissive use of canine sniffs is becoming increasingly shaky. To
address the problem of false alerts and how such alerts undermine the canine sniff *871 technique’s justifications, the
Court may be willing to sever the connection between the canine sniff and the ensuing search.
Surgically separating the false-positive sniff (which Caballes claims reveals no “legitimate private information”) from the
eventual police rummaging in response to the erroneous alert (which apparently is also not a “search” so long as the dog that
gave the false alert was “sufficiently reliable”)196 represents a genuine drift beyond the now-suspect accuracy and limited
intrusiveness justifications expressed in Place. Further, it is inconsistent with the Court’s earlier express refusal to sever the
search and seizure issues in a case involving contraband drugs.197 The Caballes Court’s surprising statement concerning false
positives represents an implicit acknowledgment that it needs to patch the hole in canine sniff jurisprudence that has become
evident in the years following Place. “Reliable” drug-detection dogs make plenty of mistakes.198 To suggest that a falsepositive
alert reveals no private information is an artificial conclusion, if ever there was one, because the alert leads directly
and inevitably to police rummaging during which private, noncontraband items are uncovered.199
This Caballes dicta may have a real impact on the home-sniff question. There is no data on the accuracy of drug-detection
dogs asked to sniff the exterior of a person’s home.200 The data presently available concern the accuracy of detection dogs
that are asked to scent in close proximity to the container suspected of secreting contraband (e.g., luggage, a vehicle, or an
interior room).201 It is far from clear that existing data concerning luggage and vehicle searches should be unquestioningly
extended to establish “reliability” for canine sniffs of the home. First, the detection dog is not able to gain the same proximity
to the contraband item as is typically the case *872 during vehicle or luggage sniffs.202 A dog that is “reliable” for purposes
of sniffing luggage in close proximity at an airport may not be as effective in a residential setting.203 Significantly, however,
no data exist to allow meaningful review of canine reliability in these newer factual situations.204
Second, home occupants have less control over the people who access their front door and associated curtilage areas.
Although there are exceptions,205 the front door is an open curtilage location where homeowners typically anticipate
interacting with nonfamily members and others. The overall lack of control over who comes and goes from these curtilage
areas creates the risk that a drug-detection dog could alert to contraband waste molecules206 left behind by others -- *873
even a marijuana seed dropped from a visitor’s pocket onto the doormat.207 This lack of control over the location combined
with the dog’s inability to gain proximity to the supposed contraband suggests that, at the very least, scientific data is needed
to support the conclusion that dogs are sufficiently reliable when sniffing homes.
Additionally, Caballes’s dicta concerning canine sniff error rates may generate other problems in the home-sniff context. The
scope of the search generated by a false positive is far more expansive in the residential context.208 While any search based
on a false-positive canine sniff reveals private, noncontraband information, this is especially troubling when the sniffed
location is a private residence.209 The search of luggage based on a positive canine sniff is confined to the luggage, and the
same is true of a vehicle. While the probable cause-based search of an item or vehicle might well be probing,210 the scope of
the search is defined by the size of the container to which the detection dog has alerted. An alert on a private residence
creates suspicion toward a very sizeable container indeed.211 A search warrant, issued in reliance on a positive canine sniff,
would permit a search that is significantly more intrusive than the searches in Place or Caballes because of both the size of
the suspected contraband container and the fact that any search for drugs would likely involve a top-to-bottom perusal of the
home’s every *874 nook and cranny.212 The intrusion on privacy from a false-positive alert would be vast, turning Place’s
justification about limitations on the information revealed on its head.213 In view of the size of the private residence
“container,” unblinking expansion of the Caballes dicta to canine home-sniffs does not make sense.
Additionally, drug-detection dogs have been known to alert on a wide variety of items, including: controlled, nonnarcotic
medications;214 noncontraband medications;215 and various substances.216 In the school-sniff cases, while the issue generally
*875 turned on the lawfulness of a canine sniff of a schoolchild217 and the resulting searches in some of those cases were
extremely troubling,218 the scope of the search was limited to the person of the sniffed student and the student’s on-campus
142

possessions. Without minimizing the intrusiveness of a canine sniff of a person or the ensuing search that results from an
alert, the search of a home on the basis of a positive canine sniff would be both probing and expansive. Therefore, because
detection dogs have been known to alert on such ubiquitous substances as beer, asthma medication, and over-the-counter
medications, a search on the basis of a positive canine sniff may result in a significant invasion of privacy when the sniffed
location is a private home.219
As a final observation, states are adopting, in increasing numbers, statutes related to medical marijuana, most of which allow
possession of between one to eight ounces of marijuana by a qualified patient.220 For obvious reasons, it is preferable to have
such patients store and use this medication in their homes rather than storing it in their vehicles, thus creating the temptation
to use this medication while driving. Medical marijuana is in the unusual position of being a legal medication in these states,
assuming the qualified patient satisfies the state’s applicable laws, but it nevertheless remains a crime to manufacture or
possess marijuana under the federal Controlled Substance Act (CSA).221 This unfortunate dual treatment of medical *876
marijuana creates real risks in the home-sniff context.222 Even if the investigating officers, out of deference to a state’s
decision to decriminalize medical marijuana, wished to avoid home searches on the basis of a positive canine alert for
marijuana, the drug-detection dog has no way to signal that it was “just” marijuana detected in the home.223
B. Should the Context of a Canine Sniff Be Determinative when the Sniffed Location Is a Private Residence
As the Court’s opinion states, “the Fourth Amendment protects people, not places.” The question, however, is what
protection it affords to those people. Generally, as here, the answer to that question requires reference to a “place.”224
Absent exigent circumstances, police cannot cross the threshold of a home to arrest a person inside or to search the
location.225 With the canine sniff technique, however, police do not physically cross the threshold of a home but can
nevertheless deduce information about the interior of the home that could not otherwise be verified by visual surveillance.
Under the Fourth Amendment, the home is “ordinarily afforded the most stringent Fourth Amendment protection.”226
Significant to the home-sniff question, the area immediately *877 surrounding and associated with a private home, the
curtilage, is also afforded Fourth Amendment protection.227 While the Court has clearly extended Fourth Amendment
protection to the curtilage,228 the Court has yet to clarify the degree of protection afforded to the curtilage as compared to the
home itself.229 Further, the front door area, where most canine sniffs are performed, is usually accessible to the public and
therefore enjoys some degree of traffic from nonoccupants of the home. So, while the front door area is likely encompassed
within a home’s curtilage,230 the home’s occupants have little expectation of privacy in items that the public could observe
while standing at the front door.231 With that said, in cases involving surveillance of a private home’s curtilage, the Court has
been careful to emphasize that the information gained about the curtilage was limited to visual observation.232 As the Court
has explained, visual observation is simply less intrusive than an inspection that requires a physical invasion.233
The Supreme Court’s emphasis in earlier cases on the fact that police curtilage observations were made with the naked eye
suggests *878 that other, unenhanced sensory determinations would likely also be permissible, assuming that the officer was
in a curtilage location, like the front door, that the home’s occupant would reasonably anticipate the public to access. The
Court’s focus in its curtilage discussions has been on the lack of sense enhancement, however. Therefore, it is a stretch to
conclude that because an officer, during a lawfully conducted “knock and talk” encounter234 with a home’s occupant, can use
the officer’s own nose to detect contraband,235 that the officer could instead use a detection dog, whose sense of smell is
more than eight times sharper than a human’s,236 to do the sniff work.237
Because the front door is a location that lower courts have generally permitted human police officers to access in order to
engage in consent-based “knock and talk” interaction with a home’s occupants, to distinguish the introduction of a police dog
from that of the human police officer courts must examine: (1) whether there are additional intrusions associated with
introducing a police dog into the curtilage area of a private home that would make the practice unreasonable under the Fourth
Amendment, and (2) whether the heightened expectations of privacy associated with the home would make the warrantless
use of a natural form of technology, such as a canine sniff, to deduce information about the interior of a home unreasonable
under the Fourth Amendment.
*879 Of central importance to courts that conclude that a canine home-sniff is not a “search” is the fact that the sniff is
performed while the detection dog is standing on a location that is accessible to the public.238 While public location may be
important, it should not be presumed to be determinative. After all, prior to Kyllo, the public location from which thermalimaging
scans were conducted was essential to courts in concluding that thermal scans were insulated from the Fourth
Amendment’s warrant requirement.239 Kyllo informed us differently.240 Therefore, as a threshold matter, it is important to
143

consider whether the location of the dog’s paws makes a constitutional difference in the canine sniff analysis or, instead,
whether the focus should be on the intrusiveness of introducing a potentially dangerous and, to some, unclean animal into the
curtilage area of a private home.
The intrusiveness of police behavior cannot be considered in the abstract, since this would amount to nothing more than a
subjective “vote” about whether the practice “felt” unreasonable. As the Rakas v. Illinois Court explained: “[l]egitimation of
expectations of privacy by law must have a source outside of the Fourth Amendment, either by reference to concepts of real
or personal property law or to understandings that are recognized and permitted by society.”241 Toward that end, the Court
has looked to a number of factors in *880 examining the intrusiveness of police behavior to determine whether a warrant is
required.242 The Court has “given weight to such factors as the intention of the Framers of the Fourth Amendment,”243 “the
uses to which the [person] has put a location,”244 “and our societal understanding that certain areas deserve the most
scrupulous protection from government invasion.”245
1. Intrusiveness Based on Intimidation
Although we might prefer to visualize a drug-detection dog as being a member of the U.S. Agricultural Department’s
“Beagle Brigade”246 or a Labrador retriever, like most explosives-detection dogs,247 such is not the case. Drug-detection
dogs are often selected for the intimidation factor that they produce.248 The intimidation is, therefore, intentional.249 When
asked, and sometimes when not asked, these dogs can be dangerous. Unlike an ordinary weapon, which obviously lacks a
mind of its own, the potential exists for a dog, even a well-trained dog, to be disobedient.250 Courts that refuse *881 to apply
Kyllo in the home-sniff context on the basis that dogs are not technological devices cannot also avoid consideration of the
intrusiveness that arises because dogs are not mechanical devices. Simply stated, drug-detection dogs produce fear,
intentionally so, in the ordinary person.251 There is a societal cost associated with introducing intimidating dogs into the
curtilage of a private home, and the Court has instructed that societal “understandings” are an appropriate consideration in
determining reasonableness under the Fourth Amendment.252
2. Intrusiveness Based on Historical Oppression
While the courts that refuse to apply Kyllo emphasize our societal recognition that dogs are familiar and have been used by
law enforcement for tracking purposes for centuries,253 these courts ignore the fact that dogs have also been used as tools of
institutional oppression for perhaps even longer. Although dogs have long been used by military forces,254 as early as 2500
BC, Egyptians used dogs on civilians for purposes of crowd control to protect the pyramids.255 The Spanish conquistadors
used dogs to kill and subdue the native *882 populations upon their arrival in America.256 Dogs were used to attack Native
Americans257 and to chase down runaway slaves.258 During the Civil War, dogs were used to intimidate and injure African-
American soldiers fighting for the North.259 Following Pearl Harbor, dogs were used to intimidate Japanese Americans
residing in Hawaii.260
In more modern times, police dogs have been used for crowd control, even on nonviolent civil rights demonstrators.261 The
passage of time may not have healed these wounds.262 Recent events *883 have again brought intimidating dogs to the
forefront of our national consciousness.263 While the German shepherds used at Abu Ghraib prison were military trained, the
fact remains that our country has an unfortunate history of using dogs to target people of color for oppression by both
military forces and civilian police agencies. This sad legacy cannot be ignored in assessing the intrusiveness of introducing a
police dog into the curtilage of a private home or using a dog for suspicionless screening of multidwelling residential
complexes.
3. Intrusiveness Based on Religious Objections
Americans love dogs. It may therefore be hard for the ordinary American to fathom that many Muslims view dogs as unclean
and that contact with dogs, especially canine saliva, is so offensive that it necessitates a purification ritual.264 Our
increasingly multicultural *884 society requires societal recognition that contact with dogs is offensive to many Muslims,
however, and perhaps to followers of other religions as well.265 In other parts of the world, these objections are taken
seriously. In the United Kingdom, for example, guidelines are being considered that would require detection dogs to wear
rubber-soled “bootees” when searching a Muslim’s home or a mosque.266 The point of this discussion is not to suggest that
special rules should apply to any particular group, but rather to illustrate that contact with dogs, or contamination from dogs,
is highly objectionable to some. Therefore, suspicionless entry of dogs into the curtilage of a home, or dragnet use of
detection canines, must be carefully reconsidered.
144

4. Even Surreptitious Canine Sniffs of the Home Violate the Fourth Amendment
At present, there are few cases that document face-to-face encounters between the occupant of a home and a drug-detection
dog.267 For now, it seems that police officers are trained to avoid introducing a drug-detection dog while making initial
contact in a “knock and talk” encounter, in order to avoid creating a coercive atmosphere that would render the occupant’s
consent to talk or search involuntary.268 In a sense then, law enforcement’s own apparent practice of eschewing dogs during
the initial stages of a “knock and talk” is an implicit acknowledgment that dogs are intimidating and offensive and, therefore,
intrusive.
*885 On the other hand, drug-detection dogs are often used surreptitiously as a means to establish probable cause to obtain a
search warrant or, on a dragnet basis, to isolate homes or apartments for the officers to target for “knock and talks.” While it
could be argued that surreptitious use of drug-detection dogs is not intimidating or offensive because the home’s occupants
are unaware that their home has been sniffed, this is, in reality, beside the point. First, the home’s occupants may have been
aware of the sniff, but chose to avoid direct confrontation with the law enforcement team. Second, for some such canine
contact would likely be offensive on religious grounds, regardless of whether it was discovered at the time the contact was
originally made.269 Third, the potential for discovery,270 and therefore intimidation, offense, and even embarrassment,271
exists and cannot be predicted in advance. Fourth, unrestricted police discretion allows for arbitrary selection of sniff
locations; in other words, police targeting of individuals or neighborhoods for canine sniff screening without objective
antecedent justification.272
As a further thought, there is presently no information about property damage to the home of the sort that detection dogs have
been known to produce in other contexts.273 Property damage of even the most de minimis sort has not gone unnoticed by the
Court, at least in the seizure context. For example, even such de minimis intrusions as the destruction of a minute amount of
white powder by the field *886 testing in Jacobsen274 or the paint scrapings taken from the exterior of the vehicle in
Cardwell v. Lewis275 required justification under the Court’s reasonableness analysis.276 Important to the Court was the fact
that the property at issue, the white powder in Jacobsen and the automobile in Cardwell, had already been lawfully seized at
the time these additional de minimis intrusions occurred.277 For canine home-sniffs, on the other hand, no lawful seizure of
the home is required. Therefore, even relatively minor property damage to the home may be viewed as unreasonable.278
Since it is impossible to know in advance whether doors will be scratched, cats will be chased,279 or occupants will be
frightened or bitten, all canine sniffs of the home should be supported by, at a minimum, reasonable suspicion.280
While the drug-detection dogs presently in service are often of the intimidating sort,281 the intrusiveness that arises from a
dangerous *887 dog’s presence in a home’s curtilage could be mitigated by reliance on more “people-friendly” dogs, like the
members of the U.S. Department of Agriculture’s Beagle Brigade.282 Therefore, this Article does not propose that reliance on
any particular type of drug-sniffing dog, by itself, justifies treating canine home-sniffs as a “search.”283 With that said, it is
nevertheless important to emphasize that the drug-detection dogs presently in service are intimidating and that this fact must
not be ignored by courts asked to consider the home-sniff question. When the practice of introducing threatening, and
potentially offensive, police dogs into the protected curtilage of a private home is viewed in conjunction with the heightened
expectation of privacy associated with the home, then the canine sniff issue comes into sharper focus.
5. Heightened Expectation of Privacy Associated with the Home
The conclusion that a canine sniff of the home is a “search” within the meaning of the Fourth Amendment can be traced to
United States v. Thomas.284 Thomas involved the criminal trial of multiple defendants for their operation of a large
“narcotics ring run by a governing body called the ‘Council.”’285 In Thomas, the U.S. Court of Appeals for the Second
Circuit concluded that the warrantless sniff under the apartment door of one of the defendants violated the Fourth
Amendment:
[A] practice that is not intrusive in a public airport may be intrusive when employed at a person’s home. Although
using a dog sniff for narcotics may be discriminating and unoffensive relative to other detection methods, and will
disclose only the presence or absence of narcotics, . . . it remains a way of detecting the contents of a private, enclosed
space. With a trained dog police may obtain information about what is inside a dwelling that they could not derive
from the *888 use of their own senses. Consequently, the officers’ use of a dog is not a mere improvement of their
sense of smell, as ordinary eyeglasses improve vision, but is a significant enhancement accomplished by a different,
and far superior, sensory instrument. Here the defendant had a legitimate expectation that the contents of his closed
apartment would remain private, that they could not be “sensed” from outside his door. Use of the trained dog
145

impermissibly intruded on that legitimate expectation.286
The Second Circuit’s conclusions on this issue were viewed as unsound, however, and have been rejected by all federal
circuits and district courts that have considered the canine home-sniff issue.287 Only one court has followed Thomas’s
privacy-based analysis and found that a canine home-sniff is a “search” under the Federal Constitution.288 The State v. Rabb
court, in reliance on Thomas and Kyllo’s concerns about protecting the privacy of the home from government intrusions,
explained:
Likewise, it is of no importance that a dog sniff provides limited information regarding only the presence or absence
of contraband, because as in Kyllo, the quality or quantity of information obtained through the search is not the feared
injury. Rather, it is the fact that law enforcement endeavored to obtain the information from inside the house at all, or
in this case, the fact that a dog’s sense of smell crossed the “firm line” of Fourth Amendment protections at the door
of [the] house.289
While federal courts, other than the Second Circuit, have refused to extend Fourth Amendment protection to canine homesniffs,
a number of states have interpreted their own constitutions to provide *889 protection under a variety of canine sniff
circumstances.290 Although not determinative of the Fourth Amendment search issue,291 these cases are strong evidence that
states routinely consider the circumstances of a canine sniff, and when privacy concerns are implicated, states provide
protection. In a sense, the sheer number of states that consider the circumstances of a canine sniff in determining whether it is
a “search” suggests that “time has set its face against” a categorical rule that sniffs are per se nonsearches.292 Further, these
states’ practice is evidence that the canine sniff technique can be viewed as a “search” when used in privacy-sensitive
circumstances without burdensome disruption of police investigative efforts. In view of the heightened expectation of privacy
associated with the home and the intrusiveness of bringing a drug-detection dog into the protected curtilage area of a private
residence, it is appropriate to characterize a canine home-sniff as a “search” under the Fourth Amendment.
*890 6. Reasonable Suspicion or Probable Cause
If the Court were to conclude that a canine home-sniff is, in fact, a “search” under the Fourth Amendment, as this Article
proposes, the essential remaining question would be what quantum of suspicion is required to support the practice: reasonable
suspicion or probable cause293 Certainly, the suspicion standard is an issue over which reasonable minds could disagree.
New York, Arizona, and Indiana, for example, have concluded that a canine home-sniff is a “search” under their state
constitutions but that reasonable suspicion is sufficient to support the sniff-search.294 On the other hand, Washington and
Ohio have interpreted their state constitutions to require a search warrant supported by probable cause.295 The Rabb court
also found the canine home-sniff to be a search but based its conclusion on the Fourth Amendment, which Rabb also
interpreted to require a warrant supported by probable cause.296 In view of the divergent approaches on the suspicion
standard, a few observations seem appropriate.
Absent exigent circumstances, a warrant is required to search a person’s home or person.297 While the Court has refused to
allow increased law enforcement efficiency to serve as a basis for bypassing *891 the warrant requirement,298 the Court does
consider the real-world pressures of law enforcement when police are asked to make split-second decisions involving
unfolding events in the field.299 In most cases involving canine home-sniffs, however, the police decision to perform the sniff
does not involve the sort of split-second calculation that was present in Terry. Similar to the use of a thermal imager, in most
cases there is time for police to resort to the warrant process.300 Some courts faced with the home-sniff question have
suggested that probable cause would be an illogical requirement because a showing of probable cause would allow officers to
obtain a search warrant to conduct a physical search of the premises in any event.301 While this argument may seem
intuitively plausible, it is incorrect. In fact, the same argument could be made for the thermal-imaging device at issue in
Kyllo: if police have probable cause to perform a thermal scan on a private home, then, the argument goes, police would also
have probable cause to physically search the home for contraband, thereby rendering the need for the thermal scan irrelevant.
The years since Kyllo have disproved this argument, however. The focus of post-Kyllo thermal-imaging warrant applications
has been on whether there is probable cause to conduct the scan, not on whether there is probable cause to physically search
the premises.302
*892 Similar to the thermal-imaging warrants required after Kyllo, a canine sniff of a private home should be supported by a
warrant issued on the basis of probable cause to perform the sniff, not probable cause to physically search the premises. The
requirement of a dog-sniff warrant would thereby ensure that canine sniffs of private residences would be limited to
circumstances in which police had conducted an investigation and established an objectively reasonable basis for performing
146

the sniff--to the satisfaction of a neutral and detached magistrate. Examination of the facts by a magistrate would provide the
steadying balance that is essential to ensure that canine sniffs of the home are conducted only under appropriate
circumstances.303
C. Are There Limitations in Kyllo that Argue Against Its Applicability to the Canine Home-Sniff Issue
tech•nol•o•gy . . . 1a: the practical application of knowledge esp. in a particular area . . . b: a capability given by the practical
application of knowledge 2: a manner of accomplishing a task esp. using technical processes,
methods, or knowledge . . . 3: the specialized aspects of a particular field of endeavor[.]304
As the Kyllo oral argument reflects, the Court clearly anticipates the eventual intersection of the canine home-sniff question
and Kyllo’s limitations on sense-enhancing technology directed at the home.305 Kyllo’s relevancy to this question may turn
on whether a detection dog is sense-enhancing “technology” and, if so, whether that technology could be considered
“advancing” technology, to which Kyllo would apparently be applicable, or instead “routine” technology, to which Kyllo
would apparently be inapplicable.
*893 1. Dogs as Natural Technology
Dogs are familiar fixtures in American society. Many of us have one sleeping on our sofa, guilt-free, at any given time. It is
important not to allow our fondness for personal pets color the legal analysis of whether a trained detection dog, when used to
discover information about the interior of a home, should be viewed as “technology” for purposes of Kyllo.306 Lower courts
that refuse to apply Kyllo to canine home-sniffs do so, in part, based on our overall familiarity with dogs and their superior
sense of smell307 and, as they argue, because the canine sense of smell is not a “rapidly advancing technology” of the sort
warned about in Kyllo.308
Interestingly enough, the White House’s Office of National Drug Control Policy discusses detection dogs and lists them as
“Non-Intrusive Technology,”309 and as is discussed below, the government describes detection dogs as “technology” in other
project materials as well. Therefore, the government may find itself in the uncomfortable position of both defining and
treating drug-detection dogs as “technology” in its own project literature and also arguing to courts that such dogs are not
sense-enhancing “technology” for purposes of criminal suppression hearings. Understanding why the government treats drugdetection
dogs as technology is therefore essential in determining whether these dogs are “advancing technology” for Kyllo
purposes.
As a threshold matter, it is helpful to consider more thoroughly the government’s treatment of drug-detection dogs in its own
project literature. For example, a program is presently in place that is intended to enhance the drug-detection dog gene pool.
In its “Nonintrusive Inspection” discussion, the White House’s Office of National Drug Control Policy described the
program’s intended goal of creating a “worldwide gene pool” for substance-detection canines:
*894 In conjunction with the U.S. Customs Service, the graduates of a breeding strategy for substance detecting
canines are now working at U.S. ports of entry. Based on quantitative genetic principles proven by the Australian
Customs Service, initial results indicate the potential to establish a worldwide gene pool for substance detection
canines. . . . Scientists at Auburn University are analyzing functional olfaction characteristics to improve our
understanding of the biological and behavioral processes in substance detection with canines. A dynamic threedimensional
model has been constructed of the olfactory laminar flow, recovery, and adaptation. Further study will
verify the mechanisms of the particle filtration process. Findings are being disseminated to all substance detection
canine training agencies.310
Additionally, the 2002 Counterdrug Research and Development Blueprint Update (Blueprint) includes “substance detection
canines” in the “Technology” section of its brief. Even the placement of the detection-dog technology discussion in the
Blueprint is revealing. There, the discussion of the “worldwide gene pool” is flanked by a neutron-based probe that can be
used to “provide a characterization of the [searched and] imaged object based on its elemental composition,” and a handheld
device that can be used “to identify drugs in solid mixtures (e.g., pills) and aqueous solutions” through a “near infrared
Raman spectroscopy method.”311
While a drug-detection dog is obviously not a gadget, these dogs are the object of meaningful scientific study and
development; study both for the purpose of improved training and to scientifically enhance the dog’s capabilities. The canine
sniff technique is being *895 enhanced (and, therefore, advanced) through scientific research,312 breeding programs,313
147

scientifically validated training programs,314 and cloning technology.315 Just because a dog is not a gadget is not
determinative of whether detection dogs have been trained and developed such that they represent a form of sense-enhancing
technology. As the definition of “technology” suggests, the term describes “practical application of knowledge especially in a
particular area.” Because detection dogs receive careful training using “technical processes, methods, or knowledge,”316 and
are the subject of scientific study that is intended to enhance their capabilities,317 these dogs satisfy the definition of
“technology.” Certainly, the government’s own treatment of drug-detection dogs is a clear indication that, true to the label the
government has attached to them, these specially trained canines are a form of technology, and *896 that substantial scientific
attention has been directed toward “advancing” this technology.
Additionally, from a practical perspective, it makes sense to treat a canine home-sniff as “technology,” and therefore subject
to Kyllo. If dogs are permitted to sniff homes for drug-detection purposes, there would be no principled way to distinguish
between canines and mechanical devices that revealed only the presence or absence of controlled or other illegal
substances.318 The only distinguishing differences between these two varieties of “sniffers” would be that a dog is animate
and perhaps less accurate than any mechanical sniffer that might ultimately be used in the field.319 While some might argue
that the lack of precise accuracy of the canine sniff, as compared to a mechanical sniffer, makes the canine sniff less
intrusive, this argument makes little sense in the home-sniff context because the ensuing search on the basis of a falsepositive
alert would be so extraordinarily intrusive.320 Furthermore, basing any distinction on Kyllo’s expressed concerns
about “advancing technology” seems premature in the canine sniff context because genetics-based breeding programs with
the intended goal of enhancing drug-detection dog capabilities are in place,321 and a so-called “super sniffer” dog has *897
been produced by crossbreeding Siberian huskies with jackals.322 Therefore, the only remaining distinction is that dogs are
animate sensing devices and mechanical sniffers are not. While this is admittedly a way to distinguish the two varieties of
“sniffers,” the distinction appears to be the only way to distinguish them in a principled manner. As the Rabb court observed:
At the end of the analysis, the Fourth Amendment remains decidedly about “place,” and when the place at issue is a
home, a firm line remains at its entrance blocking the noses of dogs from sniffing government’s way into the intimate
details of an individual’s life. If that line should crumble, one can only fear where future lines will be drawn and
where sniffing dogs, or even more intrusive and disturbing sensory-enhancing methods, will be seen next.323
Accordingly, drug-detection dogs represent a “natural” technological aid to law enforcement and should therefore be subject
to Kyllo.324 Similar to the thermal imager in Kyllo, detection dogs do not actually detect contraband in most cases; their alert
to the methyl benzoate molecule instead allows police to infer that contraband is also present. Therefore, drug-detection dogs
are a sense-enhancing technology that implicate the same concerns expressed in Kyllo: (1) “advancing technology,” in view
of the potential for technology-based enhancement of the canine sniff technique (through science-based breeding programs,
cloning technology, and innovative training tactics), and (2) the disclosure of noncontraband information.
2. “Routineness” of Technology Directed at the Home
As Kyllo clearly indicated, not all sense-enhancing technology is barred from use in gathering information about the interior
of the home. The Kyllo Court specified that whether technology was in “general public use,” which Kyllo explained to mean
“routine,” may be a factor in determining whether the police surveillance tactic at *898 issue amounts to a “search.”325
Therefore, it is worthwhile to consider whether dogs could be viewed as sufficiently “routine” to merit treatment as
technology that is in “general public use.” In other words, even if dogs are viewed as sense-enhancing technology within the
meaning of Kyllo, the canine sniff might be sufficiently “routine” that society would lack a reasonable expectation of privacy
in the information revealed by the sniff.
While the Kyllo Court did not specify how “routineness” was to be determined,326 guidance on this issue can be found in
Kyllo’s treatment of earlier cases in which technology was used to gain information about the home or its uncovered
curtilage areas. Kyllo expressly endorsed earlier Supreme Court decisions that permitted the use of technology to facilitate
the ordinary perceptions of police officers.327 In the aerial surveillance cases, Florida v. Riley328 and California v.
Ciraolo,329 the technology of air flight enabled the officers to observe marijuana plants growing in uncovered curtilage areas
of private residences. Neither case involved optical magnification of a human’s ordinary eyesight, however. The Riley and
Ciraolo cases focused on the lawfulness of air flight at the elevations involved and the fact that no intimate details concerning
the home were discovered during the aerial surveillance.330 Although Kyllo clearly accepted the validity of the Riley and
Ciraolo *899 decisions,331 it reoriented their justification to make those decisions consistent with Kyllo’s reasoning. The
Kyllo Court deemphasized the earlier decisions’ reliance on the nonintimacy of the information discovered and instead
148

focused on the routineness of the air flight technology that made the naked-eye observations possible.332
After Kyllo, all “details” concerning the home are private, regardless of the intimacy of that information.333 Significantly,
however, while intending protectiveness, Kyllo may have injected a more damaging categorization issue into the technology
discussion. By characterizing air flight as “routine” and therefore available for gathering information about the home, Kyllo
completely severed the technology, in a definitional sense, from the context in which it was used. As Justice O’Connor
pointed out in her Riley concurrence, the circumstances under which technology is used should determine whether
expectations of privacy are reasonable.334
After Riley, the Court seemed to embrace Justice O’Connor’s more situation-sensitive analysis in Bond v. United States.335
Bond is a pre-Kyllo decision that considered the reasonable societal expectations of bus passengers concerning how their
luggage would be manipulated by other passengers on a bus. Rather than follow a more categorical *900 approach, like the
one used by the Riley plurality,336 the Bond Court instead found that the Fourth Amendment had been violated based on a
context-sensitive analysis: while any passenger could have squeezed Bond’s luggage in attempting to place their own luggage
in the overhead bin, the Court concluded that passengers do not reasonably anticipate that other passengers will manipulate
their luggage in the probing manner used by the officer.337 The Kyllo Court’s shorthand reference to air flight as “routine”
without any reference to the context of the air flight suggests that “routineness” may be analyzed under the categorical
approach of the Riley plurality, rather than the context-sensitive approach articulated in Bond. If this is the case, then once a
given technology is deemed to be “routine,” courts might no longer consider the way in which the technology was used.
For canine home-sniffs, Kyllo’s apparent blueprint for analyzing “routineness” creates risks beyond the obvious ones338:
where a category of excluded surveillance tactics (i.e., one excluded from Fourth Amendment scrutiny because it is
“routine”) collides with another category of excluded surveillance tactics (i.e., a canine sniff), the risk of unreasonably
narrowing Katz’s privacy-based Fourth Amendment analysis becomes real. In allowing canine sniffs of the home, lower
courts have emphasized our overall familiarity with dogs and our societal recognition that dogs have an excellent sense of
smell that has long benefited law enforcement.339 In other words, dogs are “routine,” which sets the stage for the conclusion
that, even if *901 detection dogs are viewed as “technology” for Kyllo purposes, they should be viewed as routine
technology.
The convergence between two categorical exclusions from Katz’s privacy analysis simply goes too far. After Place and
Caballes, unless the context of the canine sniff (here, the home) is viewed as being too intrusive for Fourth Amendment
purposes, the validity of the warrantless canine sniff must be upheld. If routineness is also a factor (assuming for now, as
some lower courts have, that a detection dog could be viewed as “routine”), then no meaningful examination of the context of
the sniff would be available even under Kyllo. Such a model makes no sense. Even assuming the ongoing vitality of the
canine sniff doctrine, adding another layer of insulation from review in the form of “routineness” would render judicial
evaluation of canine sniffs of the home unreachable.340
In addition to the “routineness” factor for Kyllo’s applicability, Riley and Ciraolo are important for another reason. In fact,
these cases are important for what they do not say. Riley and Ciraolo turned on society’s acceptance of modern air travel and
the assumption that items may be viewable by air travelers when looking out airplane windows. The Court in both cases
noted, and perhaps even emphasized, that the observations had been made with the naked eye.341 To be clear, the issue of
optical magnification was not before the Court in either Riley or Ciraolo, only the warrantless use of technology (air flight) to
gain a better vantage point.342 The Riley and Ciraolo Courts’ analysis was based on a generalized lack of privacy in
observations made during the course of air travel, not on the more specific assertion that individuals lack an expectation of
privacy in contraband--even when that contraband is located in their homes or uncovered curtilage areas. Significantly,
however, if the more specific assertion, the Jacobsen premise, controlled the legal question, then the fact that the observations
in Riley and Ciraolo were made with the naked eye would have been irrelevant. If Jacobsen *902 controlled, use of optical
magnification would be permissible since the observations would not be physically intrusive and society has come to accept
that the vantage point for the observation (air flight) is routine. The Riley and Ciraolo Courts did not so much as hint that the
use of optics would have been permissible, however. Instructive to the canine home-sniff question is the fact that nowhere in
Riley and Ciraolo does the Court rely on the Jacobsen premise.
IV
The Path Ahead
149

[W]e cannot forgive the requirements of the Fourth Amendment in the name of law enforcement. This is no formality that we
require today but a fundamental rule that has long been recognized in . . . America. While “[t]he requirements of the Fourth
Amendment are not inflexible, or obtusely unyielding to the legitimate needs of law enforcement,” . . . it is not asking too
much that officers be required to comply with the basic command of the Fourth Amendment before the innermost secrets of
one’s home or office are invaded.343
It is reasonable and appropriate to consider the context in which a police investigative tool is used to determine whether it is a
“search” for Fourth Amendment purposes. Canine sniffs are not per se beyond the reach of the Fourth Amendment when the
sniff is performed under intrusive circumstances or in a location that implicates stringent Fourth Amendment privacy
concerns. A canine sniff of the home is problematic both because of its intrusiveness and because it implicates the privacy
concerns expressed in Kyllo. Therefore, a canine home-sniff is a “search” under the Fourth Amendment and must be treated
accordingly.
Moreover, treatment of canine sniffs as searches would not unduly hamper law enforcement efforts. While dragnet use of
canine sniffs would be prohibited under the Federal Constitution, this practice is already impermissible under a number of
state constitutions, seemingly without adverse law enforcement consequences. Resort to the warrant process appropriately
places a neutral magistrate in the decision-making role for determining whether this privacy-sensitive surveillance tactic
should be used. Similar to the thermal-imaging warrants required after Kyllo, a dog sniff warrant application would consider
whether there was probable cause to conduct the sniff, not whether there was probable cause to physically search the
premises. *903 When viewed in this light, a dog-sniff warrant would not involve an unreasonably burdensome showing and
would provide the objectivity of a magistrate in considering whether this potentially intrusive police technique was
appropriate.
As a final thought, the Court’s recent reminder in Arizona v. Gant344 that extensions of constitutional rules must be supported
by the rule’s underlying justifications has clear applicability to the canine home-sniff issue. Extending Place to include canine
sniffs of the home cannot be justified by Place’s accuracy and limited-intrusiveness justifications. A canine sniff of a home is
not the minimally intrusive law enforcement tool that a sniff of luggage at an airport or a lawfully stopped vehicle at the
roadside would represent. Therefore, mechanically concluding that canine sniffs are per se nonsearches on the basis of Place
and Caballes is unreasonable.
Footnotes
a1
Associate Professor of Law, Loyola University New Orleans College of Law; LL.M., Tulane University School of Law; J.D.,
University of Houston Law Center; B.S.N., University of Texas Medical Branch. I would like to thank my research assistant, Janet
Whitters Nowakowski, for her research skills and excellent contribution to this Article.
1 Silverman v. United States, 365 U.S. 505, 511 (1961).
2 See, e.g., Florida v. Royer, 460 U.S. 491, 506 (1983) (recommending use of the canine sniff technique because “[a] negative result
[from a canine sniff] would have freed Royer in short order; a positive result would have resulted in his justifiable arrest on
probable cause”).
3 United States v. Place, 462 U.S. 696, 707 (1983) (observing that a canine sniff of luggage located in a “public place” was not a
search, explaining that “[w]e are aware of no other investigative procedure that is so limited both in the manner in which the
information is obtained and in the content of the information revealed by the procedure”).
4 See infra notes 151-52 (discussing Place’s apparent assumptions concerning the accuracy of detection dogs). Because Place’s
canine sniff discussion was only two paragraphs in length, referenced no legal or scientific authority, and the canine sniff issue was
neither briefed nor argued to the Court, discussion of the Place Court’s assumptions is necessarily speculative. See Place, 462 U.S.
at 719 (Brennan, J., concurring).
5 Illinois v. Caballes, 543 U.S. 405, 409 (2005).
150

6 See People v. Dunn, 564 N.E.2d 1054, 1058 (N.Y. 1990) (finding that the canine sniff of a home was a “search” under the New
York Constitution). “To hold otherwise, we believe would raise the specter of the police roaming indiscriminately through the
corridors of public housing projects with trained dogs in search of drugs.... Such an Orwellian notion would be repugnant ....” Id.
(citations omitted); see also Hoop v. State, 909 N.E.2d 463, 469 (Ind. Ct. App. 2009) (observing that “[a]llowing random searches,
or searches of those individuals whom the officers hope to find in possession of incriminating evidence gives excessive discretion
to engage in fishing expeditions” (quoting Litchfield v. State, 824 N.E.2d 356, 364 (Ind. 2005))).
7 Compare United States v. Thomas, 757 F.2d 1359, 1367 (2d Cir. 1985) (finding a warrantless canine sniff under an apartment door
to be a “search”), with United States v. Reed, 141 F.3d 644, 650 (6th Cir. 1998) (finding the location of a canine sniff “irrelevant”
and, thus, not a “search”), United States v. Roby, 122 F.3d 1120, 1125 (8th Cir. 1997) (finding that a canine sniff of a common
hotel corridor was not a “search”), United States v. Lingenfelter, 997 F.2d 632, 638 (9th Cir. 1993) (disagreeing with Thomas),
United States v. Colyer, 878 F.2d 469, 475-76 (D.C. Cir. 1989) (same), and United States v. Sklar, 721 F. Supp. 7, 14 (D. Mass.
1989) (finding no expectation of privacy for contraband hidden in the home). Virtually every state court that has considered the
home-sniff issue under the Federal Constitution is in accord that a canine sniff is not a “search.” See, e.g., Fitzgerald v. State, 837
A.2d 989, 1030 (Md. Ct. Spec. App. 2003) (finding no “search” based upon “the binary nature of [the canine sniff] inquiry,
contraband yea or nay, precludes the possibility of infringing any [legitimate] expectation of privacy” (internal quotation marks
omitted)), aff’d, 864 A.2d 1006 (Md. 2004) (declining to decide the “search” issue because reasonable suspicion to conduct the
canine home-sniff was present); Dunn, 564 N.E.2d at 1056-57 (holding that a canine home-sniff was not a “search” under the
Federal Constitution, but finding a “search” under the New York Constitution); State v. Smith, 963 P.2d 642, 647 (Or. 1998)
(questioning Thomas); Rodriguez v. State, 106 S.W.3d 224, 230 (Tex. App. 2003) (holding that a sniff was not a “search” under
the Federal Constitution). In contrast, State v. Rabb, 920 So. 2d 1175 (Fla. 4 th Dist. Ct. App.), cert. denied, 549 U.S. 1052 (2006),
stands alone in finding that a sniff of a private residence was a “search” under the Federal Constitution. Cf. United States v.
Jackson, No. IP 03-79-CR-1H/F, 2004 WL 1784756, at *4 (S.D. Ind. Feb. 2, 2004) (applying Kyllo-based privacy analysis, but the
decision is distinguishable because the detection dog alerted on the back door of the residence, which the court did not view as a
“public place”).
8 Place along with United States v. Jacobsen, 466 U.S. 109 (1984), a case cited for the proposition that a person has no legitimate
expectation of privacy in contraband, have formed the basis for the majority’s conclusion that canine sniffs of the home are not
“searches.” The competing line of cases is based primarily on Kyllo v. United States, 533 U.S. 27 (2001), a case that bars the
warrantless use of nonroutine sense-enhancing technology directed at the home.
9 See Arizona v. Gant, 129 S. Ct. 1710, 1714 (2009) (refusing to extend Belton, explaining that in the search-incident-to-arrest
context, “[t]he safety and evidentiary justifications underlying Chimel’s reaching-distance rule determine Belton’s scope,” and
further finding that the justifications are not satisfied when a recent occupant of a vehicle had been secured after an arrest and
could not access the interior of the vehicle).
10 United States v. Place, 462 U.S. 696, 707 (1983) (“[T]he canine sniff is sui generis.”).
11 See, e.g., Rakas v. Illinois, 439 U.S. 128, 143 n.12 (1978) (observing that “[l]egitimation of expectations of privacy by law must
have a source outside of the Fourth Amendment, either by reference to concepts of real or personal property law or to
understandings that are recognized and permitted by society”).
12 Kyllo, 533 U.S. at 35-38.
13 Sir Walter Scott, The Talisman 256 (Ernest Rhys ed., E.P. Dutton & Co. 1914) (1825).
14 Bloodhounds, as well as other breeds of dogs, are used in trailing fugitives, missing persons, and criminals. See Debruler v.
Commonwealth, 231 S.W.3d 752, 758 (Ky. 2007).
151

15 Apprehension dogs are canines that are trained to locate and immobilize a suspect under circumstances during which it would be
difficult or dangerous for a human officer to locate the suspect or secure him. Apprehension dogs that have been trained in the
“bite and hold” technique are trained to find a hiding human and immobilize him, typically by biting and holding onto the suspect’s
arm. See Jarrett v. Town of Yarmouth, 331 F.3d 140, 143 (1st Cir. 2003) (discussing training and practices of apprehension dogs in
the context of qualified immunity).
16 Explosives-detection dogs are trained to sniff out “explosives, radiological materials, chemical, nuclear or biological weapons.” 6
U.S.C. § 1116(a) (2006).
17 See generally Andrew Rebmann et al., Cadaver Dog Handbook: Forensic Training and Tactics for the Recovery of Human
Remains (2000).
18 See, e.g., Animal & Plant Health Inspection Serv., U.S. Dep’t of Agric., USDA’s Detector Dogs: Protecting American Agriculture
1 (1996), available at http://permanent.access.gpo.gov/lps19118/usdabbb.pdf (describing the Beagle Brigade as “a group of
nonaggressive detector dogs and their human partners” that “search travelers’ luggage for prohibited fruits, plants, and meat that
could harbor harmful plant and animal pests and diseases”).
19 Illinois v. Caballes, 543 U.S. 405, 423 (2005) (Ginsburg, J., dissenting) (“A dog sniff for explosives ... would be an entirely
different matter [from the drug-detection dog at issue in Caballes]. Detector dogs are ordinarily trained not as all-purpose sniffers,
but for discrete purposes.”).
20 See, e.g., Deborah Palman, U.S. Police Canine Ass’n, K9 Options for Law Enforcement,
http://www.uspcak9.com/training/enforcement.cfm (last visited Apr. 29, 2010) (observing that many “find and bite” dogs “are also
cross trained to be detector dogs which locate drugs or other contraband”).
21 See, e.g., Tracy L. English, Office of History, Lackland Air Force Base, The Quiet Americans: A History of Military Working
Dogs 23 (2000), available at http://www.lackland.af.mil/shared/media/document/AFD-061212-027.pdf. The U.S. Department of
Defense Military Working Dog program prefers the Belgian malinois breed because it “share[s] many of the positive traits with the
German Shepherd,” including easy adaptation and “very good prey/kill instincts.” Id. “While some referred to these dogs as ‘living
weapons,’ the main purpose of the animals was deterrence.” Id.
22 In contrast, the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) exclusively uses Labrador retrievers as explosivedetection
canines. Sniffing Out Terrorism: The Use of Dogs in Homeland Security: Hearing Before the Subcomm. on Prevention
of Management, Integration, and Oversight of the H. Comm. on Homeland Security, 109th Cong. 18 (2005) (statement of Special
Agent Terry Bohan, Chief, National Canine Training and Operations Support Branch). Although “other breeds” could detect
explosives, ATF uses only Labrador retrievers because they are a “hearty, intelligent breed ... [and] possess a gentle disposition,”
which allows for them to be used “in crowds and around children.” Id.
23 See 6 U.S.C. § 532(a), (b)(3) (2006) (authorizing the use of the Explosives Training and Research Facility to “train canines on
explosive detection”).
24 U.S. Police Canine Ass’n, USPCA Rulebook 2009 (2009), http:// www.uspcak9.com/certification/USPCARulebook2009.pdf
[hereinafter USPCA Rulebook 2009].
25 Nat’l Narcotic Detector Dog Ass’n, http://www.nndda.org (last visited Apr. 27, 2010).
26 Am. Working Dog Ass’n, http://www.americanworkingdog.com (last visited Apr. 27, 2010).
152

27 See Robert C. Bird, An Examination of the Training and Reliability of the Narcotics Detection Dog, 85 Ky. L.J. 405, 410-15
(1996) (addressing the training of these dogs by federal and state law enforcement agencies).
28 See, e.g., Am. Working Dog Ass’n, Certification Standards: Narcotic Detection Standards,
http://www.americanworkingdog.com/certification_ standards.htm#Narcotic_Detection Standards (last visited Apr. 27, 2010)
[hereinafter AWDA Certification] (displaying the certifications available for narcotics-detection dogs). The NNDDA’s Narcotic
Detection Standard includes, at a minimum, the detection of cocaine and marijuana, with the option of obtaining additional
certification for the detection of heroin, methamphetamines, and opium. See Nat’l Narcotic Detector Dog Ass’n, Narcotic
Detection Standards, http://www.nndda.org/official-docs/doc_download/2-narcotics-detection-standard (last visited Apr. 27, 2010)
[hereinafter NNDDA Certification]; see also USPCA Rulebook 2009, supra note 24, at 18.
29 For building searches under the AWDA standards, the canine must search the interior of a building consisting of no less than two
rooms and having at least one thousand square feet. AWDA Certification, supra note 28. The NNDDA tests detection dogs on their
ability to find two stashes of each narcotic hidden in a given area, which is “of [an] indoor nature (building)” that is “no larger than
one thousand ... square feet.” See NNDDA Certification, supra note 28. The USPCA uses slightly different certification
requirements. The location of the canine testing is limited to a vehicle and indoor, interior rooms. See USPCA Rulebook 2009,
supra note 24, at 18. For the indoor test, the canine must search three furnished rooms, each measuring a minimum of two hundred
square feet. Id.
30 See generally supra notes 24, 28-29 (discussing certification standards for various private vendors).
31 For example, even fundamental issues remain unresolved within the industry, such as whether detection dogs should be trained and
certified using street drugs or, instead, “pseudo-controlled substances,” which are “legal chemicals with the same smell as illegal
narcotics.” See United States v. Broadway, 580 F. Supp. 2d 1179, 1192 (D. Colo. 2008) (defining pseudoscents). Although the use
of pseudoscents may be preferable because they prevent the detection dog from becoming distracted by cutting agents routinely
found in street drugs, most certifying agencies tout the fact that they train and certify detection dogs using only “real” drugs.
Compare Jessica Snyder Sachs, The Fake Smell of Death, Discover, Mar. 1996, at 89, available at http://
discovermagazine.com/1996/mar/thefakesmellofde714 (interviewing sensory biologist Dr. Larry Myers at Auburn University)
(“Myers tells of a narcotics officer who had trained his dog on drugs kept in plastic storage bags. ‘I’ll be damned if that dog didn’t
start alerting to the scent of Ziploc bags,’ says Myers. A dog trained on street drugs can likewise get distracted by cutting agents,
homing in on baking powder in the fridge and ignoring uncut cocaine in the pantry.”), with S. Hills Kennels, Inc., Drug Detection
Dogs, http:// www.southernhillskennels.com/drug-dogs (last visited Apr. 29, 2010) (private vendor advertising that it “only use[s]
real drugs, not pseudo drug scents”), and Nat’l Law Enforcement Canine Org., Certification Standards: Narcotics,
http://www.nleco.org/cert_narc.html (last visited Apr. 29, 2010) (stating that no pseudodrugs are used for certification).
32 Nat’l Inst. of Justice, U.S. Dep’t of Justice, Guide for the Selection of Drug Detectors for Law Enforcement Applications: NIJ
Guide 601-00, at 21-23 (2000) [hereinafter Selection of Drug Detectors]. The report defines a “trace drug detection system” as
“any drug detection system that detects drugs by collecting and identifying traces from the material [which] may be in the form of
either vapor or particulate.” Id. at 50.
33 See, e.g., Fitzgerald v. State, 837 A.2d 989 (Md. Ct. Spec. App. 2003), aff’d, 864 A.2d 1006 (Md. 2004).
34 See generally Gary S. Settles, Sniffers: Fluid-Dynamic Sampling for Olfactory Trace Detection in Nature and Homeland Security--
The 2004 Freeman Scholar Lecture, 127 J. Fluids Engineering 189 (2005) [hereinafter Sniffers]. Dogs may not be detecting drug
molecules, “but rather one or more other chemicals that are contaminants in the [drug] and that have considerably high vapor
pressures.” See also Selection of Drug Detectors, supra note 32, at 21.
35 A canine may not be able to detect drugs “manufactured in ultrapure form.” Selection of Drug Detectors, supra note 32, at 21.
Some drugs, such as heroin, are extremely difficult, if not impossible, to detect from their vapor when conducting a trace detection
search at room temperature and normal atmospheric pressure because the vapor concentration at room temperature is exceptionally
low: one part per trillion. Id. at 43.
153

36 United States v. Funds in the Amount of Thirty Thousand Six Hundred Seventy Dollars ($30,670.00), 403 F.3d 448, 458 (7th Cir.
2005) (“In addition, the research indicates that dogs do not alert to byproducts other than methyl benzoate and would not alert to
synthetic ‘pure’ cocaine unless methyl benzoate was added.”).
37 See L. Paul Waggoner et al., Canine Olfactory Sensitivity to Cocaine Hydrochloride and Methyl Benzoate, 2937 SPIE 216, 216-
217 (1997). The authors explain that “[t]his evidence suggests that when dogs are trained to detect cocaine in the field, their
discriminations probably depend on one or more constituents in the vapor sample in addition to cocaine [hydrochloride].” Id. at
223. The authors also describe that an “odor signature” is the “constituent or multiple constituents of a substance that controls the
olfactory detection responses of a dog,” id. at 224, and note that the study’s results “suggest that methyl benzoate may be one of
the constituents of the illicit cocaine odor signature for dogs.” Id. The authors found that “a combination of methyl benzoate plus
other constituents (e.g. benzoic and acetic acid or ecogine ...) may be required to define the odor signature.” Id. (footnote omitted).
In other words, canines may be alerting not to pure cocaine, but instead, at least in part, to methyl benzoate and other constituents
found in the drug whether present naturally or as a result of the chemical decomposition of the cocaine. Id.
38 See Jacobson v. $55,900 in U.S. Currency, 728 N.W.2d 510, 534-35 (Minn. 2007) (Hanson, J., concurring). In his concurrence,
Justice Hanson noted:
The cases that appear to adopt the methyl benzoate theory of dog sniff drug detection do not discuss the fact that methyl benzoate
is a common chemical used in multiple consumer products--solvents, insecticides, perfumes, etc. Perhaps the underlying studies
eliminate the possibility that a dog may alert to the innocent presence of methyl benzoate from the use of those products, but the
court decisions that discuss the studies do not so indicate. The majority opinion here must rely solely on the broad, untested
conclusions of other courts because we have no scientific evidence in the record before us.
Id. In addition, the U.S. Food and Drug Administration has approved methyl benzoate for use in foods as a synthetic flavoring
substance. 21 C.F.R. § 172.515 (2009); see also Lewis R. Katz & Aaron P. Golembiewski, Curbing the Dog: Extending the
Protection of the Fourth Amendment to Police Drug Dogs, 85 Neb. L. Rev. 735, 754-57 (2007) (observing both that a detection
dog alerts to noncontraband items, such as methyl benzoate in cocaine, and that a detection dog cannot distinguish between similar
contraband and noncontraband scents, such as heroin and acetic acid used in glues, marijuana and products made from hemp,
methyl benzoate and cocaine, and ingredients contained in legal pharmaceutical drugs); Richard E. Myers II, Detector Dogs and
Probable Cause, 14 Geo. Mason L. Rev. 1, 4 (2006) (noting that detection dogs “can also learn to associate certain smells with the
items on which it is trained, for example air freshener or plastic baggies, and thus alert to non-contraband items”).
39 690 F.2d 470, 474 (5th Cir. 1982); see also supra note 38 (discussing the common use of methyl benzoate in consumer products,
including perfume).
40 Courts have been called on to address the argument that most currency is contaminated with trace amounts of cocaine residue and,
therefore, a positive canine alert is meaningless. To address the currency contamination argument, the Ninth Circuit requires a
“sophisticated dog alert,” meaning that the government “must present evidence that the drug detection dog ‘would not alert to
cocaine residue found on currency in general circulation [and that] the dog was trained to, and would only, alert to the odor of a
chemical by-product of cocaine called methyl benzoate.”’ Sumareh v. Doe (In re $80,045.00 in U.S. Currency), 161 F. App’x 670,
671-72 (9th Cir. 2006) (alteration in original) (quoting United States v. $22,474.00 in U.S. Currency, 246 F.3d 1212, 1216 (9th Cir.
2001)).
41 An example of “tenacious” particulate contamination can be found in twenty-dollar bills, which “in the United States are
contaminated with enough cocaine residue to yield positive detections with certain types of trace detectors.” Selection of Drug
Detectors, supra note 32, at 6-7.
42 Cf. United States v. Funds in the Amount of Thirty Thousand Six Hundred Seventy Dollars ($30,670.00), 403 F.3d 448, 458 (7th
Cir. 2005) (observing that “[t]he more closed the environment, the slower the rate of evaporation and the longer the smell [of
methyl benzoate] remains” and that stacked bills “lose the [methyl benzoate] odor more slowly [than unstacked] bills”).
43 Gary S. Settles et al., The External Aerodynamics of Canine Olfaction, in Sensors and Sensing in Biology and Engineering 323,
154

323 (Friedrich G. Barth et al. eds., 2003) [hereinafter Aerodynamics of Canine Olfaction]. The purpose of this study was to
determine how an electronic trace detector could be designed to mimic the capabilities of a dog’s nose. Id.
44 Id. at 325.
45 See Sniffers, supra note 34, at 199 (observing that a detection dog’s ability to “‘read’ detailed olfactory ‘messages”’ is directly tied
to proximity sniffing and, therefore, “in order to properly interrogate chemical traces it really is necessary for a dog to poke its nose
into everyone’s business”).
46 See Aerodynamics of Canine Olfaction, supra note 43, at 334 (explaining that “evolution has ... given the canine an agile platform
with which to bring its aerodynamic sampler into close proximity with a scent source”).
47 Id. at 327-28; see also Sniffers, supra note 34, at 199.
48 See Aerodynamics of Canine Olfaction, supra note 43, at 327; see also Sniffers, supra note 34, at 203.
49 See Aerodynamics of Canine Olfaction, supra note 43, at 327-28.
50 Id. The mucous lining in a canine’s nose serves an important purpose in canine olfaction. Specifically, it can trap contraband
particulates, resulting in “the natural way of sampling and chemosensing aerosol-borne trace substances.” Id. at 331; see also
Sniffers, supra note 34, at 196 (observing that a dry nose or “[e]xtreme aridity” can compromise quality of sniff by inhibiting
olfaction).
51 Even in situations involving more traditional uses of drug-detection dogs, such as luggage or vehicle sniffs, there is little data
concerning the dog’s accuracy. As discussed in Part III.A, almost all of our understanding of detection-dog reliability arises from
anecdotal discussions in judicial opinions concerning the individual detection dog at issue in the case. See R v. Kang-Brown,
[2008] 1 S.C.R. 456, 2008 SCC 18 P 15 (Can.) (observing that “courts are ill-equipped to develop an adequate legal framework for
use of police dogs [because] ... little is known about investigative techniques using sniffer dogs. Indeed, the record remains
singularly bereft of useful information about sniffer dogs.”). The data that does exist suggest real questions about reliability,
however. See infra note 204 (discussing, among other things, studies of drug-detection dog field accuracy as reported by the
Privacy Ombudsman of New South Wales to the Australian Parliament, which revealed that about seventy-three percent of those
searched on the basis of a positive canine sniff were found not to be in possession of illegal drugs).
52 See Sniffers, supra note 34, at 205 (explaining that “[i]n the animal world, the only remedy for [breezes interrupting the sniff
process] is proximity: If your nostrils are touching the sampled surface, then the wind is not an issue”).
53 As the U.S. Department of Justice has explained:
[P]articulate contamination is easily transferred from one surface to another, so a person who has handled cocaine will transfer
cocaine particles to anything else he or she touches, including skin, clothing, door handles, furniture, and personal belongings.
Completely removing particulate contamination from an object requires rigorous cleaning, and, in the case of bare hands, a single
thorough washing may not be sufficient to remove all particles.
Selection of Drug Detectors, supra note 32, at 6 (emphasis added).
54 See generally Kyllo v. United States, 533 U.S. 27 (2001). For a discussion of the police inferencing issue, see infra Part II.B.
55 McDonald v. United States, 335 U.S. 451, 456 (1948).
155

56 U.S. Const. amend. IV.
57 Katz v. United States, 389 U.S. 347, 360 (1967) (Harlan, J., concurring). Katz overruled the “trespass” doctrine of Goldman v.
United States, 316 U.S. 129 (1942), and Olmstead v. United States, 277 U.S. 438 (1928). Later Courts have described the Katz test
as the “touchstone,” California v. Ciraolo, 476 U.S. 207, 211 (1986), and the “lodestar,” Smith v. Maryland, 442 U.S. 735, 739
(1979), in determining whether a surveillance technique is a “search” within the Fourth Amendment.
58 Katz, 389 U.S. at 350-51.
59 460 U.S. 491, 505-06 (1983).
60 In his concurrence, Justice Brennan pointed out that the question of using drug-detection dogs to detect contraband in luggage “is
clearly not before us.” Id. at 511 n.* (Brennan, J., concurring).
61 See generally Terry v. Ohio, 392 U.S. 1 (1968) (upholding the stop and subsequent frisk of an individual based on the officer’s
observation of suspicious behavior and reasonable suspicion that the suspect was armed).
62 Royer, 460 U.S. at 505 (observing that “the State has not touched on the question whether it would have been feasible to
investigate the contents of Royer’s bags in a more expeditious way. The courts are not strangers to the use of trained dogs to detect
the presence of controlled substances in luggage.”).
63 462 U.S. 696, 719 (1983) (Brennan, J., concurring) (observing that the canine sniff issue had not been argued or briefed to the
Court and that consideration of the canine sniff was unnecessary because the Court had concluded that detention of Place’s luggage
had exceeded permissible guidelines under Terry).
64 Id. at 709-10 (majority opinion). In addition, the detectives’ failure to provide Place with clear directions about the storage and
return of his bags exacerbated the intrusiveness of the seizure. Id. at 710.
65 Id. at 719 (Brennan, J., concurring) (observing that Place “did not contest the validity of sniff searches per se” at trial, “[t]he Court
of Appeals did not reach or discuss the [sniff] issue,” and that the question of canine sniffs had not been briefed or argued to the
Court (internal quotation marks omitted)); see also id. at 723 (Blackmun, J., concurring) (“Neither party has had an opportunity to
brief the issue, and the Court grasps for the appropriate analysis of the problem. Although it is not essential that the Court ever
adopt the views of one of the parties, it should not decide an issue on which neither party has expressed any opinion at all.”).
66 Id. at 707 (majority opinion).
67 As the Royer plurality observed, the various Courts of Appeals had disagreed about whether a canine sniff of luggage was a
“search.” Royer, 460 U.S. at 505 n.10. The pre-Place lower courts divided into two camps: (1) those that required reasonable
suspicion to support a canine sniff, see United States v. Beale, 674 F.2d 1327, 1335 (9th Cir. 1982), vacated, 463 U.S. 1202 (1983)
(vacating the judgment and remanding for further consideration in light of United States v. Place), and (2) those that concluded a
canine sniff was not a search, therefore no suspicion was required. See, e.g., United States v. Sullivan, 625 F.2d 9, 13 (4th Cir.
1980). The Second Circuit even coined the amusing phrase “canine cannabis connoisseur” to describe drug-detection dogs. United
States v. Bronstein, 521 F.2d 459, 460 (2d Cir. 1975). The military was also dealing with canine sniff issues involving even clearer
privacy concerns, such as the canine sniff of barracks, lockers, and on-base residences. The Military Rule of Evidence 313(b)
required reasonable suspicion to conduct unscheduled “shakedown” inspections, which could include “any reasonable or natural
technological aid,” such as a canine sniff, of individual living areas and lockers. See Mil. R. Evid. 313(b) (“Inspections may utilize
any reasonable natural or technological aid and may be conducted with or without notice to those inspected.”); see also James P.
Pottorff, Jr., Canine Narcotics Detection in the Military: A Continuing Bone of Contention, Army Law., July 1984, at 73, 77. Two
156

pre-Place decisions issued by the U.S. Air Force Court of Military Review reflect the tension between the military tribunal
decisions on this issue. In United States v. Peters, a canine sniff of the defendant’s car was performed by a drug-detection dog as a
part of a random gate inspection. 11 M.J. 901, 902 (A.F. Ct. Crim. App. 1981). After a suspected bag of marijuana and unknown
pills were found, the handler and canine went to the accused’s on-base residence, where the dog alerted at a front window. Id. At
the time of the alert, the dog’s “hind feet were on the ground in the yard and [its] front paws were on the window sill.” Id. The
court determined that the canine sniff was a search, despite the fact that the window was slightly open. Id. at 904. In contrast, in
United States v. Guillen, the court determined that a canine sniff conducted at the only door of the accused’s residence was not a
search. 14 M.J. 518, 519, 521 (A.F. Ct. Crim. App. 1982). In view of the split on the canine sniff issue and the clear indications
that drug-detection sniffs could be used in ways that implicate more serious privacy concerns, the Place Court’s failure to cite even
a single case and, instead, issue a global pronouncement on this important legal question is therefore perplexing.
68 See Katz & Golembiewski, supra note 38, at 741 (arguing that in Place “[t]here was no authority offered for the broad conclusions
which have controlled the law for the past twenty-three years; moreover, the unsolicited decision of the issue has served to
preclude it from ever being considered fully”).
69 United States v. Jacobsen, 466 U.S. 109, 111 (1984).
70 Id. at 122.
71 The Court explained that, under circumstances where the authorities simply “reexamine” the materials discovered by a private
actor, id. at 119, the government has not intruded on any expectation of privacy that “has not already been frustrated.” Id. at 117.
72 Id. at 123 (explaining that Congress had criminalized the “private” possession of cocaine, making its possession illegitimate).
73 Id. The Court expressly limited its discussion to contraband. Id. at 123 n.23.
74 Id. at 123-24. As Justice Stevens explained, “[t]he field test at issue could disclose only one fact previously unknown to the agentwhether
or not a suspicious white powder was cocaine. It could tell him nothing more, not even whether the substance was sugar or
talcum powder.” Id. at 122.
75 Id. at 124 (emphasis added).
76 See George M. Dery III, Who Let the Dogs Out The Supreme Court Did in Illinois v. Caballes by Placing Absolute Faith in
Canine Sniffs, 58 Rutgers L. Rev. 377, 403-06 (2006) (addressing the various factors affecting the accuracy of drug-detector dogs);
see also Illinois v. Caballes, 543 U.S. 405, 411 (2005) (Souter, J., dissenting) (observing that “[t]he infallible dog, however, is a
creature of legal fiction”). Justice Souter cataloged lower court cases in which surprisingly high error rates failed to result in a
finding of unreliability. See id. at 412.
77 543 U.S. 405, 409 (2005). The Caballes majority opinion was authored by Justice Stevens, who also wrote the majority opinion in
United States v. Jacobsen, 466 U.S. 109 (1984). Caballes was a six-to-two decision in which Chief Justice Rehnquist did not
participate.
78 Caballes, 543 U.S. at 406.
79 Id.
80 Id. at 407 (observing that “[h]ere, the initial seizure of respondent when he was stopped on the highway was based on probable
157

cause and was concededly lawful”).
81 Id. at 407 (“A seizure that is justified solely by the interest in issuing a warning ticket to the driver can become unlawful if it is
prolonged beyond the time reasonably required to complete that mission.”).
82 See Jacobsen, 466 U.S. at 122 (observing that “[t]he concept of an interest in privacy that society is prepared to recognize as
reasonable is, by its very nature, critically different from the mere expectation, however well justified, that certain facts will not
come to the attention of the authorities”).
83 Caballes, 543 U.S. at 408 (quoting Jacobsen, 466 U.S. at 123).
84 Id. (emphasis added).
85 Jacobsen, 466 U.S. at 122.
86 Id. at 123.
87 Id. at 118 (finding that the DEA agents’ invasions of privacy involved “two steps”: (1) the removal of ziplock bags from a
damaged package and a duct-taped tube within the package, both having been previously opened by Federal Express employees,
and the removal of “a trace of powder” from one of the ziplock bags, and (2) the chemical field test of the powder).
88 See id. at 123 (observing that “even if the results are negative-merely disclosing that the substance is something other than cocaine-
-such a result reveals nothing of special interest”).
89 See Caballes, 543 U.S. at 408 (emphasis added) (internal quotation marks omitted).
90 Id. at 409-10 (quoting Kyllo v. United States, 533 U.S. 27, 38 (2001)).
91 531 U.S. 32, 35 (2000).
92 Id. at 47 (observing that “[w]hen law enforcement authorities pursue primarily general crime control purposes at checkpoints such
as here, ... stops can only be justified by some quantum of individualized suspicion”).
93 Id. at 40 (“The fact that officers walk a narcotics-detection dog around the exterior of each car at the Indianapolis checkpoints does
not transform the seizure into a search.... Just as in Place, an exterior sniff of an automobile does not require entry into the car and
is not designed to disclose any information other than the presence or absence of narcotics.”).
94 Id.
95 See id. at 47.
96 Cf. Nina Paul & Will Trachman, Fidos and Fi-dont’s: Why the Supreme Court Should Have Found a Search in Illinois v. Caballes,
9 Boalt J. Crim. L. 1, 20 (2005) (observing that “[g]iven the perhaps overzealous use of dog sniffs currently, the government could
easily fall down the slippery slope of using dog sniffs regularly and anywhere”).
158

97 See Illinois v. Caballes, 543 U.S. 405, 422 (2005) (Ginsburg, J., dissenting) (warning that “[t]oday’s decision ... clears the way for
suspicionless, dog-accompanied drug sweeps of parked cars along sidewalks and in parking lots”).
98 Caballes, 543 U.S. at 409 (finding that a canine sniff during an otherwise lawful traffic stop was permissible even without any
suspicion that driver was transporting drugs in vehicle); United States v. Jacobsen, 466 U.S. 109, 120-21 (1984) (“While the
agents’ assertion of dominion and control over the package and its contents did constitute a ‘seizure,’ ... that seizure was not
unreasonable” (footnote omitted)); United States v. Place, 462 U.S. 696, 710 (1983) (“In short, we hold that the detention of
respondent’s luggage in this case went beyond the narrow authority possessed by police to detain briefly luggage reasonably
suspected to contain narcotics.”).
99 See, e.g., People v. Jones, 755 N.W.2d 224, 229 (Mich. Ct. App. 2008) (“The high court’s fleeting reference to a ‘public place’ in
Place simply indicated, at most, that the luggage containing contraband was in an area in which the police and the canine were
lawfully present.” (emphasis added)).
100 Cf. United States v. Jeffers, 342 U.S. 48, 52 (1951). In Jeffers, the government argued that search and seizure were severable legal
issues in a drug prosecution. Id. The Court disagreed, explaining that “[w]e do not believe the events are so easily isolable. Rather
they are bound together by one sole purpose--to locate and seize the narcotics of respondent. The search and seizure are, therefore,
incapable of being untied.” Id.
101 Jacobsen, 466 U.S. at 137 (Brennan, J., dissenting). As Justice Brennan cautioned:
What is most startling about the Court’s interpretation of the term “search,” both in this case and in Place, is its exclusive focus on
the nature of the information or item sought and revealed through the use of a surveillance technique, rather than on the context in
which the information or item is concealed.... [T]he Court adopts a general rule that a surveillance technique does not constitute a
search if it reveals only whether or not an individual possesses contraband.
Id.
102 See id.
103 See Place, 462 U.S. at 707 (concluding that “the particular course of investigation that the agents intended to pursue here--exposure
of respondent’s luggage, which was located in a public place, to a trained canine--did not constitute a ‘search”’ (emphasis added));
see also Florida v. Royer, 460 U.S. 491, 493-94 (1983) (applying this standard to an airport).
104 See, e.g., Stabler v. State, 990 So. 2d 1258, 1259 (Fla. Dist. Ct. App. 2008) (allowing a canine sniff at the front door of the
defendant’s apartment because the front door was “open to public access and to a common area”); Jones, 755 N.W.2d at 229
(explaining that where the canine sniff was conducted at the front door of the defendant’s private home, there is “no reasonable
expectation of privacy at the entrance to property that is open to the public, including the front porch”).
105 See Kyllo v. United States, 533 U.S. 27, 34 (2001) (observing that the search of the interior of a home represents “the prototypical
and hence most commonly litigated area of protected privacy”).
106 Illinois v. Caballes, 543 U.S. 405, 406 (2005) (considering a drug-detection sniff conducted while Caballes was seated in a police
vehicle); Jacobsen, 466 U.S. at 120 n.18 (stating that “respondents had entrusted possession of the items to Federal Express”);
Place, 462 U.S. at 696 (explaining that after Place identified luggage as his, DEA agents took the luggage from LaGuardia Airport
to Kennedy Airport in order to subject the bags to a “‘sniff test’ by a trained narcotics detection dog”).
107 Cf. Doe v. Renfrow, 631 F.2d 91, 94 (7th Cir. 1980) (Swygert, J., dissenting) (arguing that a canine sniff of a person is more
intrusive than a sniff of “inanimate and unattended objects”).
159

108 See, e.g., Horton v. Goose Creek Indep. Sch. Dist., 690 F.2d 470, 477 (5th Cir. 1982) (contrasting the sniff of a schoolchild’s
person with a luggage sniff at an airport and observing that “[o]ther circuits have emphasized the minimal humiliation entailed in
dogs sniffing unattended luggage”).
109 See, e.g., Langley v. State, 735 So. 2d 606, 607 (Fla. Dist. Ct. App. 1999) (detailing that a suspect encountered six officers and a
police dog while sitting on the steps of her mobile home, and “she was afraid of the dog”).
110 In Place, Justice Brennan pointed out that “[a] dog adds a new and previously unobtainable dimension to human perception” and
therefore represents an additional intrusion into privacy. Place, 462 U.S. at 719-20 (Brennan, J., concurring).
111 533 U.S. 27 (2001). In fact, the only post-Kyllo case that concludes that a canine home-sniff is a “search” under the Federal
Constitution is State v. Rabb, 920 So. 2d 1175 (Fla. 4 th Dist. Ct. App.), cert. denied, 549 U.S. 1052 (2006). United States v. Thomas
is a pre-Kyllo case, but its reasoning is consistent with Kyllo’s concerns about gaining information about the interior of a home.
United States v. Thomas, 757 F.2d 1359, 1367 (2d Cir. 1985) (observing that “[w]ith a trained dog police may obtain information
about what is inside a dwelling that they could not derive from the use of their own senses”).
112 See supra note 7 (listing courts that find a canine sniff of a private residence is not a “search” under the Federal Constitution); see
also Rabb, 920 So. 2d at 1190 (describing the reliance on the Place/Jacobsen binary search approach as representing a
“fundamental philosophical divide” from the privacy-based analysis of the Rabb majority).
113 A thermal imager is a handheld device, similar to a video camera, that detects infrared radiation. Kyllo, 533 U.S. at 29. The device
detects only heat emanating from the exterior of the home, however, and is not able to penetrate walls or windows. Id. at 41 n.1
(Stevens, J., dissenting).
114 Id. at 30 (majority opinion). “The scan showed that the roof over [Kyllo’s] garage and a side wall of [his] home were relatively hot
compared to the rest of [his] home and substantially warmer than [his neighbors’ residences].” Id.
115 Id. at 40.
116 Id. at 33-34 (observing that “[i]t would be foolish to contend that the degree of privacy secured to citizens by the Fourth
Amendment has been entirely unaffected by the advance of technology”). The majority pointed to the aerial surveillance cases as
examples of technology (human flight) that had enabled police to view uncovered areas of the home or curtilage that had
historically gone unobserved. Id. at 34.
117 Id.
118 Id. (citation omitted) (quoting Silverman v. United States, 365 U.S. 505, 512 (1961)).
119 Id. at 35-36 (observing that “[r]eversing [Katz’s] approach would leave the homeowner at the mercy of advancing technologyincluding
imaging technology that could discern all human activity in the home”).
120 Id. at 41 (Stevens, J., dissenting) (arguing that “[t]here is, in my judgment, a distinction of constitutional magnitude between
‘through-the-wall surveillance’ that gives the observer or listener direct access to information in a private area, on the one hand,
and the thought processes used to draw inferences from information in the public domain, on the other hand”). Justice Stevens also
described the inferences as “indirect deductions,” id., and the “mental process of analyzing data obtained from external sources.”
Id. at 49.
160

121 Id. at 37 n.4 (majority opinion) (“We say such measurement is a search; the dissent says it is not, because an inference is not a
search. We took that to mean that, since the technologically enhanced emanations had to be the basis of inferences before anything
inside the house could be known, the use of the emanations could not be a search.”).
122 Id. at 34 (observing that “[w]e think that obtaining by sense-enhancing technology any information regarding the interior of the
home ... constitutes a search” (citation omitted)). For discussion of so-called “routine” technology, see infra notes 325-42 and
accompanying text.
123 Id. at 38 (observing that the thermal-imaging scan “might disclose, for example, at what hour each night the lady of the house takes
her daily sauna and bath-a detail that many would consider ‘intimate”’).
124 Id. at 47 (Stevens, J., dissenting) (arguing that the majority’s rule was “far too broad” because it would embrace “mechanical
substitutes” for detection dogs, a view that would be inconsistent with Place’s conclusion that, because a canine sniff discloses
only the presence of narcotics, it is not a “search”). The dissent pointed out the seeming inconsistency between Kyllo and Place’s
holding and argued that this inconsistency must mean that “sense-enhancing equipment that identifies nothing but illegal activity is
not a search either.” Id. at 47-48.
125 Illinois v. Caballes, 543 U.S. 405, 409 (2005).
126 See Caballes, 543 U.S. at 410 (“The legitimate expectation that information about perfectly lawful activity will remain private is
categorically distinguishable from respondent’s hopes or expectations concerning the nondetection of contraband in the trunk of his
car.”); see also supra note 90 and accompanying text.
127 468 U.S. 705 (1984).
128 “A beeper is a radio transmitter, usually battery operated, which emits periodic signals that can be picked up by a radio receiver.”
United States v. Knotts, 460 U.S. 276, 277 (1983).
129 Karo, 468 U.S. at 708-10.
130 Karo, 468 U.S. at 715. Although the government obtained a warrant authorizing the installment and monitoring of the beeper, the
warrant was later invalidated, and the government did not appeal that ruling. Id. at 710. Therefore, the Court was asked to consider
whether a warrant was required either to install or monitor the beeper. Id. at 711. On the installation issue, Justice White, speaking
for five other Justices, including Chief Justice Burger, concluded that no warrant was required because the installation created no
more than the “potential for an invasion of privacy.” Id. at 712. The presence of the beeper created “at most” a “technical trespass,”
the existence of which would not be determinative on the Fourth Amendment question. Id.
131 Id. at 715.
132 Id. at 710.
133 Id. at 715.
134 Id. at 716.
161

135 Id.
136 Id. at 710.
137 Id. at 716 (emphasis added).
138 See United States v. Jacobsen, 466 U.S. 109, 123 n.23 (1984) (expressly limiting the Court’s discussion to “possession of
contraband”).
139 See Karo, 468 U.S. at 716 (arguing against the use of police technology to determine, among other things, whether a particular
person “is in an individual’s home at a particular time”).
140 Payton v. New York, 445 U.S. 573, 603 (1980) (holding that “an arrest warrant founded on probable cause implicitly carries with it
the limited authority to enter a dwelling in which the suspect lives when there is reason to believe the suspect is within”).
141 See Steagald v. United States, 451 U.S. 204, 205 (1981). The search warrant required in Steagald was necessary to protect the
privacy interests of a third person whose home was entered by police in order to arrest a fugitive, not the privacy interests of the
fugitive. Id. at 222.
142 Radio Frequency Identification (RFID) technology uses radio frequencies to identify people or objects by reading a microchip in a
wireless device from a distance, without making any physical contact or requiring a line of sight. Data Privacy & Integrity
Advisory Comm., U.S. Dep’t of Homeland Sec., No. 2006-02, The Use of RFID for Human Identity Verification 2, 5 (2006),
available at http://www.dhs.gov/xlibrary/assets/privacy/privacy_advcom_ 12-2006_rpt_RFID.pdf; see also U.S. Dep’t of
Homeland Sec., Radio Frequency Identification (RFID): What Is It, http://
www.dhs.gov/files/crossingborders/gc_1197652575426.shtm (last visited May 19, 2010). When in the presence of an appropriate
radio frequency, a microchip embedded in an object responds to the signal by sending information to a device capable of
interpreting the microchip’s signal. Data Privacy & Integrity Advisory Comm., supra, at 2. Differing RFID chips can be read from
different distances: “[s]ome can only operate over a very short distance of a few centimeters or less, while others may operate at
longer distances of several meters or more.” Id.
143 U.S. Dep’t of Homeland Sec., Privacy Impact Assessment for the Use of Radio Frequency Identification (RFID) Technology for
Border Crossings 8 (2008) available at http://www.dhs.gov/xlibrary/assets/privacy/privacy_pia_cbp_ rfid.pdf (identifying
“tracking” as “a form of secondary use that exploits the uniqueness of the RFID number to associate a specific individual with
specific places over time”).
144 The “Enhanced Driver’s License (EDL)” is embedded with an RFID chip and capable of submitting information, including
personal information documents. Id. at 2. Some states have already passed legislation addressing EDLs. See, e.g., Mich. Comp.
Laws Ann. § 28.301-.308 (LexisNexis 2010).
145 See In re Application of U.S. for an Order Authorizing (1) Use of Pen Register and Trap and a Trace Device with Prospective Cell-
Site Information, No. MISC. 09-104, 2009 WL 1530195, at *4 (E.D.N.Y. Feb. 12, 2009) (finding that in the trap and trace context,
cell phone locational technology--commonly known as “pinging” of a suspect’s cell phone--was more precise than a global
positioning system device and, therefore, required a showing of probable cause to obtain a court order because the suspect’s
movements inside the home could be tracked).
146 Douglas v. City of Jeannette, 319 U.S. 157, 181 (1943) (Jackson, J., concurring).
162

147 462 U.S. 696 (1983).
148 See infra note 344 and accompanying text.
149 See Arizona v. Gant, 129 S. Ct. 1710, 1714 (2009); cf. Illinois v. Caballes, 543 U.S. 405, 410 (2005) (Souter, J., dissenting)
(observing that “[w]hat we have learned about the fallibility of dogs in the years since Place was decided would itself be reason to
call for reconsidering Place’s decision”).
150 The term, “sui generis,” is defined as: “Of its own kind or class; unique or peculiar.” Black’s Law Dictionary 1572 (9th ed. 2009).
151 Interestingly, several pre-Place lower courts specifically mentioned errors made by detection dogs, but viewed such mistakes as
harmless since the mistakes were actually false negatives rather than false positives. See, e.g., United States v. Beale, 674 F. 2d
1327, 1334 (9th Cir. 1982) (observing that “any mistake is one of omission, favoring the suspect”), vacated, 463 U.S. 1202 (1983)
(vacating the judgment and remanding for further consideration in light of United States v. Place); see also United States v. Jodoin,
672 F.2d 232, 236 (1st Cir. 1982) (quoting dog handlers as saying “dogs are not foolproof, they are less accurate on hot muggy
days, and drug traffickers have found ways to mask the odors of contraband to fool detection efforts” (internal quotation marks
omitted)); United States v. Bronstein, 521 F.2d 459, 463 (2d Cir. 1975) (observing that while a detection dog “may be in error[,]
her mistake favors the suspect”).
152 See Thomas H. Peebles, The Uninvited Canine Nose and the Right to Privacy: Some Thoughts on Katz and Dogs, 11 Ga. L. Rev.
75, 100 (1976) (describing the fact that “mistakes work in favor of the suspect” as the key difference between canine sniffs and
other forms of surveillance); Max A. Hansen, Comment, United States v. Solis: Have the Government’s Supersniffers Come Down
with a Case of Constitutional Nasal Congestion, 13 San Diego L. Rev. 410, 417 (1976) (observing that “[w]here the use of drug
detection dogs is concerned, the first objection [regarding canine reliability] is lessened because a detector dog’s mistake usually
benefits the criminal”).
153 United States v. Jacobsen, 466 U.S. 109, 123 (1984) (observing that “[i]t is probably safe to assume that virtually all of the tests
conducted under circumstances comparable to those disclosed by this record would result in a positive finding; in such cases, no
legitimate interest has been compromised”); see also United States v. Place, 462 U.S. 696, 707 (1983) (observing that such a sniff
discloses only “limited” information because it “discloses only the presence or absence of narcotics, a contraband item”).
154 See Place, 462 U.S. at 707.
155 See Illinois v. Caballes, 543 U.S. 405, 411 (2005) (Souter, J., dissenting) (“The infallible dog, however, is a creature of legal
fiction.”). Justice Souter documented cases in which dogs were accepted by a court as reliable with an accuracy rate of 71%, see
United States v. Kennedy, 131 F.3d 1371, 1378 (10th Cir. 1997), an error rate of 8% over a dog’s entire career, see United States v.
Scarborough, 128 F.3d 1373, 1378 n.3 (10th Cir. 1997), and an error rate of between 7% and 38%, see United States v. Limares,
269 F.3d 794, 797 (7th Cir. 2001). Caballes, 543 U.S. at 411-12.
156 See, e.g., United States v. Koon Chung Wu, 217 F. App’x 240, 246 (4th Cir.) (accepting as “reliable” a drug-detection dog with
demonstrated field accuracy of 67% and observing that “[b]ecause the probable cause-standard does not require that the officer’s
belief be more likely true than false, ... an accuracy rate of sixty percent is more than reliable enough for Cody’s alert to have
established probable cause” (internal quotation marks omitted) (citation omitted)), cert. denied, 551 U.S. 1110 (2007); United
States v. Cantrall, 762 F. Supp. 875, 882 (D. Kan. 1991) (accepting as reliable any detection percentage over fifty percent, along
with dog training and certification in narcotics detection).
157 See, e.g., State v. Jardines, 9 So. 3d 1, 5 (Fla. 3d Dist. Ct. App. 2008) (“Dogs have been used to detect scents for centuries all
without modification or ‘improvement’ to their noses. That, perhaps, is why the Supreme Court describes them as ‘sui generis’ in
Place.”), review granted, 3 So. 3d 1246 (Fla. 2009); People v. Jones, 755 N.W.2d 224, 228 (Mich. Ct. App. 2008) (describing
163

Place’s holding as a “general categorization of canine sniffs as nonsearches”).
158 See Koon Chung Wu, 217 F. App’x at 246 (4th Cir.) (“Probable cause only requires a ‘fair probability’ that contraband will be
found in a certain place, ... and Cody’s positive alerts to the packages in both searches clearly established a fair probability that the
packages contained controlled substances, given his training and certification as a drug-detection dog” (internal citation omitted)).
159 See id. It is enough for some courts that the detection dog has been trained and certified, without any consideration of the dog’s
track record in the field. See United States v. Sundby, 186 F.3d 873, 876 (8th Cir. 1999) (observing that “a search warrant based on
a drug dog’s alert is facially sufficient if the affidavit states the dog is trained and certified to detect drugs”).
160 See United States v. Place, 462 U.S. 696, 707 (1983) (observing that because the sniff revealed “only the presence or absence of
narcotics ... [t]his limited disclosure also ensures that the owner of the property is not subjected to the embarrassment and
inconvenience entailed in less discriminate and more intrusive investigative methods”).
161 See supra note 75 and accompanying text (comparing field testing at issue to a canine sniff).
162 See Place, 462 U.S. at 707 (applying the canine sniff technique to luggage located in a public place).
163 See Illinois v. Caballes, 543 U.S. 405, 410 (2005) (applying the canine sniff technique to a lawfully stopped vehicle).
164 See id. at 410 (Souter, J., dissenting).
165 An analogous sort of confusion has been generated by the Latin phrase, “res ipsa loquitur.” Creekmore v. United States, 905 F.2d
1508, 1510 (11th Cir. 1990) (quoting Professor Prosser as stating that res ipsa loquitur “has been the source of so much trouble to
the courts that the use of the phrase itself has become a definite obstacle to any clear thought, and it might better be discarded
entirely” (internal quotation marks omitted)); see also Ballard v. N. British Ry. Co., 1923 S.L.T. 219, 226 (Scot. 1923) (observing
that “[i]f this phrase had not been in Latin, no one would have called it a principle”).
166 Cf. State v. Wiegand, 645 N.W.2d 125, 138-39 (Minn. 2002) (Page, J., concurring) (“The U.S. Supreme Court dismisses the
intrusiveness of a dog search by labeling it ‘sui generis.’ ... This is convenient, but lacks any persuasive force given that the dog is
used to detect the very thing the officers would look for themselves if the Fourth Amendment did not limit their ability to do so.”
(citation omitted)).
167 See, e.g., Rice v. Cayetano, 528 U.S. 495, 520 (2000) (Bureau of Indian Affairs); Grove City Coll. v. Bell, 465 U.S. 555, 573
(1984) (student financial aid programs); Robertson v. Rosenthal, 132 U.S. 460, 464 (1889) (steel hair pins).
168 See United States v. Santana, 427 U.S. 38, 47 (1976) (Marshall, J., dissenting). In Santana, the defendant was seen standing in the
doorway of a house and retreated into the vestibule upon announcement of police. Id. at 40. Justice Marshall protested the Court’s
failure to consider the then-unresolved question of entry into a home to make a warrantless arrest, and instead, reached a decision
that “appears sui generis, [in that it is] useful only in arresting persons who are ‘as exposed to public view, speech, hearing, and
touch’ ... as though in the unprotected outdoors.” Id. (citation omitted).
169 See supra note 157.
170 392 U.S. 1 (1968); see also supra note 61.
164

171 Dunaway v. New York, 442 U.S. 200, 212-13 (1979).
172 See Dunaway, 442 U.S. at 209-10 (stressing that Terry was “narrowly defined”).
173 See id. at 209 (internal quotation marks omitted) (quoting Terry, 392 U.S. at 20).
174 See id. at 210 (observing that “[b]ecause Terry involved an exception to the general rule requiring probable cause, this Court has
been careful to maintain its narrow scope”). In the only other Fourth Amendment case that uses the term sui generis as a discussion
point, the dissent used the label to argue for a more narrow interpretation of an earlier case than the one used by the plurality. See
United States v. Harris, 403 U.S. 573, 597 (1971) (Harlan, J., dissenting) (protesting the Court’s relaxation of the probable cause
standard by its expansive interpretation of Brinegar v. United States, 338 U.S. 160 (1949), and explaining that an expansive
reading was not proper because “Brinegar itself was very carefully limited to situations involving the arrest of those driving
moving vehicles, ... a problem that has typically been treated as sui generis by this Court” (internal citation omitted)).
175 See Gateway Coal Co. v. United Mine Workers, 414 U.S. 368, 376 (1974) (disagreeing with the Third Circuit’s assumption
regarding the existence of a “public policy disfavoring compulsory arbitration of safety disputes,” which the Third Circuit had
viewed as “sui generis”); see also White v. Regester, 412 U.S. 755, 761-62 (1973) (disagreeing with the district court’s suggestion
that Abate v. Mundt, 403 U.S. 182 (1971), “in accepting total deviations of 11.9% in a county reapportionment[,] was sui
generis”).
176 Cf. Dunaway, 442 U.S. at 209 n.11, 210 (requiring that the “intrusion must be carefully tailored to the rationale justifying it” and
observing that the Court had been “careful to maintain [Terry’s] narrow scope”).
177 Fitzgerald v. State, 837 A.2d 989, 1030 (Md. Ct. Spec. App. 2003), aff’d, 864 A.2d 1006 (Md. 2004).
178 United States v. Karo, 468 U.S. 705 (1984).
179 Kyllo v. United States, 533 U.S. 27 (2001).
180 Fitzgerald, 837 A.2d at 1036 (quoting Kyllo, 533 U.S. at 38).
181 Id. (observing that “[e]ther is not contraband and its mere possession is entirely lawful.... Thus, Karo is factually distinct from both
Place and Jacobsen, where the procedure disclosed only the presence or absence of a contraband item” (quoting United States v.
Colyer, 878 F.2d 469, 474 n.5 (D.C. Cir. 1989)) (emphasis omitted) (omission in original)).
182 See supra notes 32-38 and accompanying text.
183 See supra note 38 and accompanying text (discussing methyl benzoate as being present in insecticides, solvents, and perfumes).
184 United States v. Esparza, No. CR-07-14-S-BLW, 2007 U.S. Dist. LEXIS 66455, at *6 (D. Idaho Sept. 7, 2007) (finding a
suspicionless sniff of a vehicle by an explosives-detection dog was a “search” because the dog detected both contraband and
noncontraband items and because the facts did not raise any “special need” to sniff for explosives based on any imminent danger to
national security).
185 Id. at *6. Although not discussed in the case, the judge’s findings on this issue appear to be borne out by the scientific literature
concerning explosives-detection sniffs. Explosives-detection dogs “respond to the most-volatile compounds present in an
165

explosive, not necessarily to the explosive species itself.” See Sniffers, supra note 34, at 207 (explaining that when detecting
plastic explosives, the dog is not responding to the explosive component RDX, “which has a very low vapor pressure,” but instead
“to compounds like cyclohexanone, a solvent used in RDX production”).
186 Esparza, 2007 U.S. Dist. LEXIS 66455, at *7.
187 See Hudson v. Michigan, 547 U.S. 586, 621 (2006) (citing Kyllo v. United States, 533 U.S. 27, 40 (2001) (Breyer, J., dissenting));
see also United States v. Jeffers, 342 U.S. 48, 53-54 (1951) (explaining that “Congress, in abrogating property rights in
[contraband drugs], merely intended to aid in their forfeiture and thereby prevent the spread of the traffic in drugs rather than to
abolish the exclusionary rule formulated by the courts in furtherance of the high purposes of the Fourth Amendment”).
188 See Hudson, 547 U.S. at 599 (finding “knock-and-announce” violation but refusing to suppress evidence seized in a search
pursuant to a search warrant because imposition of an exclusionary remedy was “unjustified”).
189 The Courts of Appeals for the Fifth and Ninth Circuits have concluded that a canine sniff of a schoolchild is a “search” that
required a showing of individualized suspicion. See B.C. v. Plumas Unified Sch. Dist., 192 F.3d 1260, 1267-68 (9th Cir. 1999);
Horton v. Goose Creek Indep. Sch. Dist., 690 F.2d 470 (5th Cir. 1982). But see Doe v. Renfrow, 631 F.2d 91 (7th Cir. 1980)
(finding close contact sniff was not a search). For a further discussion of the issue, United States v. Kelly, 302 F.3d 291, 295 (5th
Cir. 2002) (permitting the suspicionless canine sniff of a person at an international border).
190 See Plumas Unified Sch. Dist., 192 F.3d at 1266 (distinguishing between the canine sniff of a person and unattended luggage);
Horton, 690 F.2d at 478 (recognizing that “the interest in the integrity of one’s person, and the fourth amendment applies with its
fullest vigor against any intrusion on the human body”).
191 See Plumas Unified Sch. Dist., 192 F.3d at 1266 (agreeing with the Fifth Circuit’s analysis); Horton, 690 F.2d at 479 (observing
that “[i]ntentional close proximity sniffing of the person is offensive whether the sniffer be canine or human”).
192 United States v. Jacobsen, 466 U.S. 109, 124 (1984) (emphasis added).
193 See United States v. Place, 462 U.S. 696, 707 (1983) (observing that determining whether contraband is present through a canine
sniff does not require opening the suitcase and implicitly assuming the accuracy of the technique); see also Illinois v. Caballes, 543
U.S. 405, 410 (2005) (Souter, J., dissenting) (observing that classification of the canine sniff technique as “sui generis” was based
on the limited intrusiveness of the sniff and its accuracy).
194 See Fitzgerald v. State, 837 A.2d 989, 1028 (Md. Ct. Spec. App. 2003) (observing that “[t]he marijuana in the Place case, for
instance, might conceivably have been medically prescribed in a state such as California. The critical holding of the Court,
however, was not to be foreclosed by a mere ‘remote’ possibility.”), aff’d, 864 A.2d 1006 (Md. 2004).
195 Caballes, 543 U.S. at 409 (emphasis added).
196 Id.
197 See United States v. Jeffers, 342 U.S. 48, 52 (1951); see also supra note 100.
198 See supra notes 151-52, 155-56 and accompanying text.
166

199 As Justice Souter explained, “[n]or is it significant that Kyllo’s imaging device would disclose personal details immediately,
whereas they would be revealed only in the further step of opening the enclosed space following the dog’s alert reaction; in
practical terms the same values protected by the Fourth Amendment are at stake in each case.” Caballes, 543 U.S. at 413 n.3
(Souter, J., dissenting).
200 For a discussion of the fact that canine certification for drug detection is limited to testing for drugs hidden in vehicles or indoor,
interior rooms, rather than perimeter searches of buildings, see supra notes 29-30 and accompanying text.
201 See supra notes 29-30 and accompanying text.
202 For a discussion of the “scanning” process that drug-detection canines use to locate the scent source of narcotics, see supra notes
43-50 and accompanying text. See also Fredric I. Lederer & Calvin M. Lederer, Admissibility of Evidence Found by Marijuana
Detection Dogs, Army Law., Apr. 1973, at 12, 12 (describing a pattern of properly conducted canine-assisted barracks searches).
“While the dog may detect airborne scent and follow it to its source, more likely the dog will have to smell the immediate
proximity of an area to detect marijuana within it.” Id. (second emphasis added).
203 In fact, the scientific literature, discussed in Part I, reveals that proximity is an important consideration in both detecting the drug
and properly identifying the scent source. See supra notes 43-50 and accompanying text.
204 See R v. Kang-Brown, [2008] 1 S.C.R. 456, 2008 1 S.C.C. 18 P 15 (Can.); see also supra note 51. As the Canadian Supreme Court
observed, little empirical research on the accuracy of detection dogs exists. Kang-Brown, 2008 1 S.C.C. P 15. One study,
conducted in Australia, was reported by the Privacy Ombudsman of New South Wales in 2004. The research revealed that seventythree
percent of those searched on the basis of a positive alert from a drug-detection dog were found not to be in possession of
illegal drugs. New South Wales Ombudsman, Discussion Paper: Review of the Police Powers (Drug Detection Dogs) Act 16 fig.3
(2004) [hereinafter NSW Ombudsman 2004]. While sixty-one percent of the false positives were attributable to the “residual
odour” thought to be related to the individual’s admission of use or contact with others who had used drugs; thirty-nine percent of
the false positives could not be explained. Id. at 23-24. In 2006, the Privacy Ombudsman issued a new report concerning the use of
detection dogs. New South Wales Ombudsman, Review of the Police Powers (Drug Detection Dogs) Act (2006) [hereinafter NSW
Ombudsman 2006]. Therein, it was determined that seventy-four percent of those searched did not possess illegal drugs. Id. at 53.
205 Many, if not most, homes and apartments lack gates, signage that forbids entry, locked vestibules (for apartments), or ironically,
dogs that could be thought of as restricting public access to the front door. The issue of impeded access to the front door is an
important consideration to lower courts asked to consider the home-sniff issue. See, e.g., People v. Jones, 755 N.W.2d 224, 229
(Mich. Ct. App. 2008).
206 See United States v. Brooks, 589 F. Supp. 2d 618, 630-31 (E.D. Va. 2008) (observing that “drug dogs alert in the presence of an
odor--even if the controlled substance is no longer present at the site of the alert”); State v. Cabral, 859 A.2d 285, 289 (Md. Ct.
Spec. App. 2004) (detailing a canine handler’s testimony that, based upon training, “residual odor of a drug can last up to 72
hours”).
207 Cf. Fla. Dep’t of Highway Safety & Motor Vehicles v. Jones, 780 So. 2d 949, 950 (Fla. Dist. Ct. App. 2001) (discussing a drugdetection
dog’s alert to marijuana “residue” consisting of stems and seeds of an estimated weight of less than one gram, which the
Florida State Trooper testified was too small in amount to recover because “[i]t was embedded in the carpet and would have taken
tweezers to recover”) (internal quotation marks omitted).
208 Of course, absent exigent circumstances, a warrant is required to enter a home. See Payton v. New York, 445 U.S. 573, 587-88
(1980).
209 It is widely accepted that a positive canine alert can produce probable cause to support the ensuing search for contraband. See, e.g.,
167

Jones, 755 N.W.2d at 226 n.2 (observing that “[t]here is no dispute that a positive reaction by a properly trained narcotics dog can
establish probable cause to believe that contraband is present”). But see United States v. Olivas, No. 3:09-CR-1402-KC, 2009 U.S.
Dist. LEXIS 62270, at *12 n.5 (W.D. Tex. July 17, 2009) (finding “merit to the argument that an alert from a detector dog, even
when that dog is well-trained, cannot by itself constitute probable cause to search under any circumstances”).
210 See generally Carroll v. United States, 267 U.S. 132 (1925) (permitting police to slash upholstery of a vehicle in a search for illegal
alcohol supported by probable cause).
211 See State v. Rabb, 920 So. 2d 1175, 1190 (Fla. 4 th Dist. Ct. App.) (observing that “[v]ehicles on public roadways and luggage in
airports are simply different because the privacy to be invaded by government’s prying eyes is necessarily limited by the size of the
vehicle or bag, plus only the effects of one’s traveling life chosen to appear outside the home and in public are at risk of
exhibition”), cert. denied, 549 U.S. 1052 (2006).
212 See United States v. Jackson, No. IP 03-79-CR-1H/F, 2004 WL 1784576, at *5 (S.D. Ind. Feb. 2, 2004) (stating that a search
warrant issued on the basis of a positive canine sniff of a residence would allow “of course, a top-to-bottom search of a home for
controlled substances, which can be concealed almost anywhere, can be an extremely thorough intrusion into a home”).
213 United States v. Place, 462 U.S. 696, 707 (1983) (observing that the canine sniff revealed “limited” information about the contents
of luggage, which “ensures that the owner of the property is not subjected to the embarrassment and inconvenience entailed in less
discriminate and more intrusive investigative methods”).
214 Cf. Fitzgerald v. State, 864 A.2d 1006, 1018 (Md. 2004) (refusing to consider the defendant’s argument that a drug-detection dog
was trained to alert on diazepam, the generic for Valium, because the issue was not raised at trial). For further discussion, see NSW
Ombudsman 2004, supra note 204, at 26, which documents a false-positive alert on a woman in Australia that was attributed to the
fact that she was carrying her son’s ADD medication in her purse, and NSW Ombudsman 2006, supra note 204, at 52-53, which
documents alerts on various prescription medicines, including flu medication, Valium, and methadone, and notes that “[a]lthough
drug detection dogs are not trained to detect methadone or prescription drugs, we are not aware of any training performed to
eliminate possible false positives with these drugs.” Cf. John M. Dunn, Illinois v. Caballes: The Day the Supreme Court Lost Its
Dog Kyllo, 76 Okla. Bar J. 1791, 1794 (2005).
[I]t is important to note that there are several prescription drugs that contain an amphetamine as the active ingredient. Drug dogs
are trained to smell amphetamines in order to detect methamphetamines. However, Ritalin, Dexedrine and Adderall are drugs
commonly used to treat Attention Deficit Disorder/Attention Deficit Hyperactive Disorder which contain amphetamines as their
active ingredient.... Since the prescription medications are not contraband, their owner should enjoy a legitimate expectation of
privacy.
Id. (footnote omitted).
215 See Jennings v. Joshua Indep. Sch. Dist., 877 F.2d 313, 317 (5th Cir. 1989); Horton v. Goose Creek Indep. Sch. Dist., 690 F.2d
470, 474 (5th Cir. 1982) (observing that the drug-detection dogs involved were “trained to alert their handlers to the presence of
any one of approximately sixty different substances, including alcohol and drugs, both over-the-counter and controlled”). The
plaintiff in Jennings argued that the detection canine was “capable of reacting to some nonprescription drugs and to residual scents
lingering for up to four to six weeks.” Jennings, 877 F.2d at 317. The dog alerted to, among other things, asthma medication and a
Primatene inhaler. Id. at 318.
216 See, e.g., Jennings, 877 F.2d at 318 (discussing the detection dog’s alert to beer caps, empty beer bottles and cans, and the scent of
previously vomited beer); Horton, 690 F.2d at 474 (discussing alcohol).
217 Horton, 690 F.2d at 473.
218 See Doe v. Renfrow, 475 F. Supp. 1012, 1017 (N.D. Ind. 1979) (noting that the thirteen-year-old junior high school student, who
was strip searched to look for drugs after a drug-detection dog alerted, had been playing with her own dog, which was in heat, prior
168

to school).
219 Cf. Katz & Golembiewski, supra note 38, at 754-55 (discussing the inability of a detection dog to distinguish between illicit
substances and pharmaceutical substances and noting that pharmaceutical substances may release the same odor as illicit
substances).
220 Thirteen States have legalized medical marijuana. See Alaska Stat. §§ 11.71.090, 17.37.010 to 17.37.080 (2010); Cal. Health &
Safety Code § 11362.5 (Deering 2010); Colo. Const. art. XVIII, § 14; Haw. Rev. Stat. Ann. §§ 329-121 to 329-128 (LexisNexis
2010); Me. Rev. Stat. Ann. tit. 22, § 2383-B(5) (2009); Mich. Comp. Laws Ann. § 333.26421 (LexisNexis 2010); Mont. Code
Ann. §§ 50-46-101 to -210 (2010); Nev. Const. art. 4, § 38; N.M. Stat. Ann. §§ 26-2B-1 to -7 (West 2009); Or. Rev. Stat. §§
475.300 to 475.346 (2009); R.I. Gen. Laws §§ 21-28.6-1 to - 11 (2010); Vt. Stat. Ann. tit. 18, §§ 4472-4474d (2009); Wash. Rev.
Code Ann. §§ 69.51A.005 to 69.51A.080 (LexisNexis 2010).
221 Pub. L. No. 91-513, 84 Stat. 1242 (codified as amended 21 U.S.C. §§ 801-971 (2006)). The Court held that the CSA’s categorical
prohibition of the manufacture and possession of marijuana would include even locally grown marijuana that was used for medical
purposes, and that the CSA did not exceed Congress’s authority under the Commerce Clause. See Gonzales v. Raich, 545 U.S. 1,
15, 28 (2005).
222 Even the U.S. Department of Justice’s recent clear signal to federal prosecutors, in states that have enacted medical marijuana
laws, to avoid investigation and prosecution of medical users, does not in any way eliminate the risk that a detection dog will alert
on medical marijuana and that a broad search of the home may result. Memorandum from David W. Ogden, Deputy Att’y Gen.,
U.S. Dep’t of Justice, to Selected United States Attorneys (Oct. 19, 2009), http://www.justice.gov/opa/documents/medicalmarijuana.pdf.
223 But see Fitzgerald v. State, 837 A.2d 989, 1028 (Md. Ct. Spec. App. 2003) (dismissing concerns that a canine sniff of a home
might reveal medically prescribed marijuana as a “mere ‘remote’ possibility,” and observing that the marijuana in Place could
“conceivably have been medically prescribed in a state such as California” (internal quotation marks omitted)), aff’d, 846 A.2d
1006 (Md. 2004). In reality, the idea that the Place Court predicted the future and factored medically prescribed marijuana into its
two-paragraph canine sniff discussion, as the Fitzgerald court asserts, is the true “remote possibility.”
224 Katz v. United States, 389 U.S. 347, 361 (1967) (Harlan, J., concurring).
225 See Payton v. New York, 445 U.S. 573, 586 (1980) (“It is a basic principle of Fourth Amendment law that searches and seizures
inside a home without a warrant are presumptively unreasonable.” (internal quotation marks omitted)).
226 See United States v. Martinez-Fuerte, 428 U.S. 543, 561 (1976); Payton, 445 U.S. at 590 (observing that “the Fourth Amendment
has drawn a firm line at the entrance to the house”).
227 Oliver v. United States, 466 U.S. 170, 180 (1984) (observing that “[a]t common law, the curtilage is the area to which extends the
intimate activity associated with the ‘sanctity of a man’s home and the privacies of life”’ (quoting Boyd v. United States, 116 U.S.
616, 630 (1886))).
228 Id. (discussing that curtilage “has been considered part of the home itself for Fourth Amendment purposes”).
229 Id. at 180 n.11 (observing that it was unnecessary under Oliver’s facts “to consider the scope of the curtilage exception to the open
fields doctrine or the degree of Fourth Amendment protection afforded the curtilage, as opposed to the home itself”).
169

230 For example, in Ciraolo, the Court noted that the small, fenced-in backyard at issue “would appear to encompass this small area
within the curtilage.” California v. Ciraolo, 476 U.S. 207, 213 (1986).
231 Cf. United States v. Titemore, 437 F.3d 251, 258-59 (2d Cir. 2006) (finding that a homeowner had no reasonable expectation of
privacy in a patch of front lawn visible from the road). The court observed that “it is possible that an area might fall within the
curtilage of the home, as that concept was defined at common law, but the owner or resident may fail to manifest a subjective
expectation of privacy in that area.” Id. at 258.
232 See United States v. Dunn, 480 U.S. 294, 304 (1987) (explaining that in California v. Ciraolo, “we held that warrantless naked-eye
aerial observation of a home’s curtilage did not violate the Fourth Amendment. We based our holding on the premise that the
Fourth Amendment has never been extended to require law enforcement officers to shield their eyes when passing by a home or
public thoroughfares.” (internal quotation marks omitted)).
233 Bond v. United States, 529 U.S. 334, 337 (2000) (distinguishing California v. Ciraolo and Florida v. Riley from a probing
palpation of a suspect’s luggage because the aerial surveillance cases “involved only visual, as opposed to tactile, observation.
Physically invasive inspection is simply more intrusive than purely visual inspection.”).
234 Consent-based police/resident encounters arise when a police officer approaches a private home, knocks on the door, and attempts
to engage the resident in a consensual discussion or a consent-based search of the premises. See, e.g., United States v. Ray, 199 F.
Supp. 2d 1104, 1110-12 (D. Kan. 2002) (observing that a “knock and talk” encounter is normally consensual unless coercive
circumstances, such as unreasonable persistence, a display of weapons, multiple police officers questioning the occupant, or
questioning conducted in unusual places or at unusual times, transform the encounter into a “seizure” under the Fourth
Amendment).
235 See, e.g., Duhig v. State, 171 S.W.3d 631, 636 (Tex. App. 2005) (allowing officers to proceed to an unfenced backyard after
receiving no answer to a knock at the front door but hearing movement inside the home; officers smelled marijuana coming from
an air conditioning vent); see also United States v. Charles, 29 F. App’x 892 (3d Cir. 2002) (discussing an officer who smelled
“growing” marijuana); Traylor v. State, 817 N.E.2d 611, 614 (Ind. Ct. App. 2004) (finding that during “knock and talk” at a mobile
home, officers smelled the strong odor of ether, a chemical commonly used in the manufacture of methamphetamine).
236 See, e.g., United States v. Beale, 674 F.2d 1327, 1333 (9th Cir. 1982) (observing that “[a] trained canine’s sense of smell is more
than eight times as sensitive as a human’s”), vacated, 463 U.S. 1202 (1983) (remanding for further consideration in light of United
States v. Place).
237 Cf. State v. Guillen, 213 P.3d 230, 240 n.11 (Ariz. Ct. App. 2009) (questioning whether an implied invitation of public access to
curtilage would include implicit consent for a visitor to use intrusive equipment to probe the residence).
238 See, e.g., Stabler v. State, 990 So. 2d 1258, 1259 (Fla. Dist. Ct. App. 2008) (allowing a canine sniff at the front door of the
defendant’s apartment because the front door was “open to public access and to a common area”); Nelson v. State, 867 So. 2d 534,
535 (Fla. Dist. Ct. App. 2004) (“Areas outside of a hotel room, such as hallways, which are open to use by others may not be
reasonably considered as private.”); supra note 99. The front door has not always been required as the permissible sniff location,
however. See United States v. Tarazon-Silva, 960 F. Supp. 1152, 1163 (W.D. Tex. 1997) (permitting the canine sniff of a dryer
vent because the vent was accessible by standing on a paved driveway and the area both was not enclosed and “appears to be
readily accessible to neighbors, visitors, repairmen, salesmen, utility workers, and/or members of the public”), aff’d, 166 F.3d 341
(5th Cir. 1998).
239 Brief for the United States at 15 n.4, Kyllo v. United States, 533 U.S. 27 (2001) (No. 99-8508) (observing that the Courts of
Appeals had “uniformly held” that the use of a thermal imager from a public location to observe the exterior of a dwelling was not
a “search” within the meaning of the Fourth Amendment, and listing applicable cases).
170

240 See Kyllo v. United States, 533 U.S. 27, 33 (2001) (requiring a search warrant to perform a thermal-imaging scan of a private
home and observing that “[t]he present case involves officers on a public street engaged in more than naked-eye surveillance of a
home”).
241 Rakas v. Illinois, 439 U.S. 128, 143 n.12 (1978); see also Georgia v. Randolph, 547 U.S. 103, 111 (2006) (emphasizing “the great
significance given to widely shared social expectations” in assessing reasonableness under the Fourth Amendment in consent
cases).
242 See Oliver v. United States, 466 U.S. 170, 177 (1984) (observing that “[n]o single factor determines whether an individual
legitimately may claim under the Fourth Amendment that a place should be free of government intrusion not authorized by
warrant”).
243 Id. at 178 (citing United States v. Chadwick, 433 U.S. 1, 7-8 (1977)).
244 Id. (citing Jones v. United States, 362 U.S. 257, 265 (1960)).
245 Id. (citing Payton v. New York, 445 U.S. 573 (1980)).
246 See supra note 18 (discussing the U.S. Agricultural Department’s choice of beagles for detection purposes, in part, because they
are “nonaggressive” dogs).
247 See supra note 22 (discussing the ATF’s choice of Labrador retrievers, in part, because they “possess a gentle disposition” that
allows them to be used in crowds and around children).
248 See, e.g., Danelle Aboud, Dog Lends City Police a Paw, Detroit Free Press, Apr. 10, 2003, at 6 (observing that police dogs have
the “intimidation factor,” causing “‘[p]eople [to] react differently when they are stopped and see or hear the barking dog in the
back of the police car”’ (quoting Madison Heights Police Officer David Koehler)); Matt Lait, Role Over for Veteran Police Dog,
L.A. Times, Jan. 5, 1991, at B3 (noting that although fear is “the handler’s first line of defense,” the genesis of that defense is that
“[t]he dogs are used more frequently for mere presence and intimidation and searching than they are for biting” (internal quotation
marks omitted)).
249 See, e.g., Horton v. Goose Creek Indep. Sch. Dist., 690 F.2d 470, 479 (5th Cir. 1982) (observing that a representative from the
security services firm hired to conduct campus sniffs testified that “Doberman pinschers and German shepherds were used
precisely because of the image maintained by the large dogs”). Those breeds of dog were selected “to maintain an image of
strength and ferocity,” id. at 482, although the security firm actually chose individual animals on the basis of their docility. Id.
250 See Merrett v. Moore, 58 F.3d 1547, 1549 (11th Cir. 1995) (noting that during a roadblock for narcotics detection, “one person was
bitten by a dog”); Doe v. Renfrow, 475 F. Supp. 1012, 1017 (N.D. Ind. 1979) (noting that the thirteen-year-old female schoolchild,
who was strip searched to look for drugs after a drug-detection dog alerted, had been playing with her own dog, which was in heat,
prior to school); see also Matthew Pleasant, Police Dog Suspended During Attack Investigation, DailyComet.com, July 23, 2009,
http:// www.dailycomet.com/article/20090723/ARTICLES/907239926/1212Title=Police-dog-suspended-during-attackinvestigation
(reporting that the detection dog, a Belgian malinois, was taken out of service following allegations that the dog
escaped its kennel and attacked a woman and noting that one of the handler’s previous dogs, also a Belgian malinois, mauled a
seventy-seven-year-old bicyclist in 2007 after the dog was unleashed).
251 As Justice Ginsburg noted in her Caballes dissent, “[a] drug-detection dog is an intimidating animal.” Illinois v. Caballes, 543 U.S.
405, 421 (2005) (Ginsburg, J., dissenting); see also id. at 411 n.2 (Souter, J., dissenting) (agreeing with Justice Ginsburg in finding
that the introduction of a narcotics-detection dog into routine stop “can in fact be quite intrusive”).
171

252 See Rakas v. Illinois, 439 U.S. 128, 143 n.12 (1978).
253 See, e.g., Fitzgerald v. State, 837 A.2d 989, 1037 (Md. Ct. Spec. App. 2003) (“The use of the sense of smell generally is a familiar
tool of perception much older than the common law or the Bill of Rights. Indeed, [the Kentucky Supreme Court] stated that
bloodhound evidence ‘was looked upon with favor as early as the twelfth century ....”’ (internal citation omitted)), aff’d, 864 A.2d
1006 (Md. 2004).
254 The ancient Romans used war dogs, training Mastiffs to attack the legs of their enemies, who would then “lower their shields.”
U.S. War Dogs Ass’n, War Dogs in the Marine Corps in World War II, http:// www.uswardogs.org/id187.html (last visited May 4,
2010).
255 James W. Golden & Jeffery T. Walker, That Dog Will Hunt: Canine-Assisted Search and Seizure, in Policing and the Law 71, 71
(Jeffery T. Walker ed., 2002).
256 In 1513, Bartolomé de Las Casas, a missionary and conquistador, described Spanish tactics in the conquest for gold and land. The
Conquistadors slaughtered native peoples, and even “taught their Hounds, fierce Dogs, to teare [natives] in peeces at the first
view.” Bartolomé de Las Casas, Spanish Atrocities in the West Indies (1513), reprinted in Eyewitness to History 82, 83 (John
Carey ed., Harvard Univ. Press 1987) (1987).
257 As Benjamin Franklin wrote to James Read:
In Case of meeting a Party of the Enemy, the Dogs are then to be all turn’d loose and set on. They will be fresher and fiercer for
having been previously confin’d, and will confound the Enemy a good deal, and be very serviceable. This was the Spanish Method.
Letter from Benjamin Franklin to James Read (Nov. 2, 1755) (on file with the Historical Society of Pennsylvania), available at
http:// franklinpapers.org/franklin/framedVolumes.jspvol=6&page=234a (last visited Nov. 7, 2009); see also J. Robert Lilly &
Michael B. Puckett, Social Control and Dogs: A Sociohistorical Analysis, 43 Crime & Delinq. 123, 135 (1997).
258 See, e.g., Brister v. State, 26 Ala. 107, 118 (1855) (observing that “[t]he defendants are slaves ... [and] were taken into custody by
sixteen or seventeen white men, who went on the place armed with double-barreled guns, negro whips and sticks, and accompanied
by a pack of negro dogs, known to be such by defendants”); Benjamin v. Davis, 6 La. Ann. 472 (1851). The court in Benjamin
observed that “the defendants came to the house of witness early in the morning with their negro dogs, and said they were going to
hunt runaway negroes.” Benjamin, 6 La. Ann. at 472. The overseer “had a right to use the dogs in his attempt to make such
capture, such means being customary among the planters of the parish.” Id. at 474.
259 Lilly & Puckett, supra note 257, at 129.
260 Id. at 130.
261 See David Benjamin Oppenheimer, Kennedy, King, Shuttlesworth and Walker: The Events Leading to the Introduction of the Civil
Rights Act of 1964, 29 U.S.F. L. Rev. 645, 646 (1995) (observing that in Birmingham, Alabama, in 1963, television cameras
captured “black children kneeling in prayer or singing spirituals” who were attacked by “vicious police dogs”).
262 See Carlos Campos, Alpharetta Putting 2 Canine Cops on the Beat, Atlanta J. Const., Nov. 24, 1994, at G34 (observing that despite
the passage of time, “some people may associate police-trained German shepherds with the black-and-white news footage of
vicious dogs cut loose on civil rights activists during the 1960s”). As a further illustration, prior to his confirmation hearings,
Justice Thomas described the “bitterness and nostalgia” of his childhood in Savannah, Georgia: “I remember being excluded from
certain parks, stadiums and movie theaters. I saw the Klan marches, the riots, the police dogs and water hoses.” Timothy M.
Phelps, Nominee a Puzzle: A Look at the Pieces on Eve of Hearings on Confirmation, Newsday, Sept. 9, 1991, at 7.
172

263 In 2004, photographs emerged that depicted military-trained German shepherds that were used to intimidate prisoners at Abu
Ghraib prison in Afghanistan as an interrogation strategy. See Bob Deans & Mike Williams, ‘Disgust and Disbelief’: Bush Views
Prison Abuse Photos, Atlanta J. Const. May 11, 2004, at 1A (“The Washington Post, which last week first published photos of a
female U.S. soldier holding a leash attached to the neck of a naked Iraqi prisoner, printed a picture in Monday’s editions of a naked
detainee pinned against cell bars as a pair of guard dogs stood threatening him from both sides.”).
264 Islamic law, known as Shari’a, is derived primarily from the Qur’an and various collections of oral tradition of the Prophet
Muhammad documented in the hadith. See generally Richard C. Martin, Islamic Studies: A History of Religions Approach (2d ed.
1996). While there are no statements concerning dogs in the Qur’an, numerous references to dogs appear in the hadith. Various of
the hadith report that Allah’s messenger, the prophet Muhammad, commanded that dogs were to be killed, except for those used
for hunting and protecting herds and farmland. See, e.g., Sahih Bukhari, Vol. 4, Book 54, Nos. 531, 539-42; Sahih Muslim, Book
10, Nos. 3814-24. Due to their uncleanliness, the hadith warn that angels will not enter a home where a dog is kept, see, e.g., Sahih
Bukhari, Vol. 4, Book 54, No. 448, that the proximity of a dog to a praying person annuls the person’s prayers, see, e.g., Sahih
Bukhari, Vol. 1, Book 9, No. 490, and that keeping a dog as a pet results in a reduction of the keeper’s heavenly rewards, see, e.g.,
Sahih Bukhari, Vol. 3, Book 39, No. 516. For more discussion, see M. Muhsin Khan’s translation of Sahih Bukhari at http://
www.usc.edu/schools/college/crcc/engagement/resources/texts/muslim/hadith/bukhari/, and Abdul Hamid Siddiqui’s translation of
Sahih Muslim at http:// www.usc.edu/schools/college/crcc/engagement/resources/texts/muslim/hadith/muslim/. Important to the
canine home-sniff issue, an item that has become impure due to contact with a dog must be purified by washing the item seven
times, and then by rubbing it with earth the eighth time. See, e.g., Sahih Muslim, Book 2, No. 0551; Evan Thomas, Into Thin Air,
Newsweek, Sept. 3, 2007, at 24 (observing that American soldiers “continually make cultural blunders, like using canine units to
search people’s homes [in view of the fact that] dogs are considered unclean in Muslim culture”).
265 See, e.g., Sniffer Dogs Unclean, N.Z. Herald (Mar. 6, 2006) (“Hindu priests cleansed a shrine to Indian independence leader
Mahatma Gandhi after a visit by [President George W.] Bush, the Hindustan Times reported yesterday. It wasn’t the US leader
who offended them, but the sniffer-dogs that scoured the area ahead of his visit.”).
266 See Stuart MacDonald, Sniffer Dogs to Wear ‘Muslim’ Bootees, Sunday Times (London), July 6, 2008, at 1. The use of such
“bootees,” of course, fails to address the primary concern to many Muslims, which is the canine’s saliva. Cf. Richard Peppiatt, It’s
P.C. Madness; Muslim Raid Dog Bootees, Daily Star (U.K.), July 7, 2008, at 25.
267 Cf. Langley v. State, 735 So. 2d 606, 607 (Fla. Dist. Ct. App. 1999) (finding that a reasonable person would not feel free to leave a
“knock-and-talk” encounter when confronted by six officers and a “K-9 dog”).
268 See, e.g., George S. Steffen & Samuel M. Candelaria, Drug Interdiction: Partnerships, Legal Principles, and Investigative
Methodologies for Law Enforcement 67 (2003) (“The knock and talk team should not take the dog with them to the door when
making contact with the suspect. This creates an intimidating and coercive environment. If a drug canine is available, it should be
kept out of sight while the consent is obtained by the officers.”).
269 For discussion of the purification necessary under Islamic law to cleanse an item or area that has been contaminated by contact
with a dog, see supra note 264.
270 This “potential for discovery” is distinguishable from the reference to a “potential for an invasion of privacy” made by the Karo
Court in discussing whether the installation of a beeper constituted a seizure. See United States v. Karo, 468 U.S. 705, 712 (1984)
(emphasis omitted). In Karo, the “potential” privacy invasion was entirely within the discretion of the police because the police
could decide to turn the beeper on, or not. Here, the intrusiveness that arises either from religious offense or discovery of the
canine-sniff police unit involves circumstances beyond the officer’s control.
271 See, e.g., State v. Guillen, 213 P.3d 230, 238 (Ariz. Ct. App. 2009) (finding that a canine home-sniff violated the Arizona
Constitution and describing canine sniffs of the exterior of a home as “intimidating, embarrassing, distressing, and worrisome
173

encounters”).
272 See supra note 6.
273 See Merrett v. Moore, 58 F.3d 1547, 1549 (11th Cir. 1995) (noting that “the dogs scratched several cars” at a roadblock set up to
detect narcotics); see also United States v. Cota-Lopez, 358 F. Supp. 2d 579, 584 (W.D. Tex. 2002) (stating that a drug-detection
dog alerted “by barking and scratching at the door”).
274 United States v. Jacobsen, 466 U.S. 109, 124 (1984). The Court observed that, even though the amount of tested powder was so
minute that its loss was undetectable, id. at 125 n.27, the field testing “did affect [Jacobsen’s] possessory interests protected by the
[Fourth] Amendment, since by destroying a quantity of the powder it converted what had been only a temporary deprivation of
possessory interests into a permanent one.” Id. at 124-25.
275 417 U.S. 583, 591-92 (1974).
276 See Jacobsen, 466 U.S. at 125 (observing that “[t]o assess the reasonableness of [the field testing], [we] must balance the nature
and quality of the intrusion on the individual’s Fourth Amendment interests against the importance of the governmental interests
alleged to justify the intrusion” (internal quotation marks omitted) (third alteration in original)).
277 See, e.g., id. (observing that “since the property had already been lawfully detained, the ‘seizure’ could, at most, have only a de
minimis impact on any protected property interest”).
278 Id. at 125 n.28 (cautioning that although the destruction of the white powder in Jacobsen was reasonable, “[w]e do not suggest,
however, that any seizure of a small amount of material is necessarily reasonable”).
279 While the idea of cats being chased is introduced, in part, to provide a bit of levity to the discussion, it should be noted that even
inconveniences with respect to property must be supported by a lawful initial seizure. For example, the Jacobsen Court observed
that the seizure of the luggage in Place became unreasonable because the bags were kept too long. Id. at 124 n.25. Again, the key
point with respect to these additional investigative activities (field testing in Jacobsen and the canine sniff in Place) is the fact that
both were supported by a lawful initial seizure of the item involved. No such lawful initial seizure of a private home is required to
conduct a canine home-sniff that would otherwise support inconveniences, such as runaway pets or trodden landscaping.
280 Cf. id. at 125 n.28 (noting that “where more substantial invasions of constitutionally protected interests are involved, a warrantless
search or seizure is unreasonable in the absence of exigent circumstances”).
281 See supra notes 15, 20-21 and accompanying text (discussing the fact that potentially dangerous breeds are generally selected as
drug-detection dogs both for an “intimidation” factor and because these dogs are often cross-trained for apprehension, or “bite,”
capabilities).
282 See supra note 18.
283 Significantly, however, even people-friendly dogs would remain offensive to those who objected to dogs on religious grounds. See
supra notes 264-66 and accompanying text. Further, dogs may produce property damage, like scratched doors or other
inconveniences.
284 757 F.2d 1359 (2d Cir. 1985).
174

285 Id. at 1362. The story of this vast and highly organized drug operation is depicted in “American Gangster,” a movie starring Denzel
Washington as drug kingpin Frank Lucas and Cuba Gooding, Jr., as Leroy “Nicky” Barnes. American Gangster (Universal Studios
2007). Barnes is described as a “co-conspirator” to the defendants in the Thomas opinion. See Thomas, 757 F.2d at 1362.
286 Thomas, 757 F.2d at 1366-67 (citation omitted).
287 See supra note 7 (listing courts that found a canine home-sniff is not a “search” under the Federal Constitution); see also Fitzgerald
v. State, 837 A.2d 989, 1031 (Md. Ct. Spec. App. 2003) (observing that Thomas had met with “universal disapprobation”), aff’d,
864 A.2d 1006 (Md. 2004). The Second Circuit recently distinguished Thomas, but did not reject it or signal that it would reject
Thomas if given the opportunity on appropriate facts. See United States v. Hayes, 551 F.3d 138, 145 (2d Cir. 2008) (finding
Thomas “clearly distinguishable” because the detection dog sniffed a brushy area approximately sixty-five feet from the back door
of the residence, not inside the home itself).
288 See generally State v. Rabb, 920 So. 2d 1175 (Fla. 4 th Dist. Ct. App.), cert. denied, 549 U.S. 1052 (2006). One district court clearly
accepted Thomas’s reasoning, but its holding appears distinguishable because the canine sniff at issue was performed at the back
door of the private home, a location that the court concluded was not a “public place.” See United States v. Jackson, No. IP 03-79-
CR-1H/F, 2004 WL 1784756, at *4 (S.D. Ind. Feb. 2, 2004).
289 Rabb, 920 So. 2d at 1184.
290 See McGahan v. State, 807 P.2d 506, 509-11 (Alaska Ct. App. 1991) (finding that a canine sniff of the exterior of a warehouse was
a “search” under the Alaska Constitution); State v. Guillen, 213 P.3d 230, 239 (Ariz. Ct. App. 2009) (finding that a canine sniff of
the exterior of a home violated the Arizona Constitution); People v. Haley, 41 P.3d 666, 672 (Colo. 2001) (finding that canine
sniffs are “searches” requiring reasonable suspicion under the Colorado Constitution); Hoop v. State, 909 N.E.2d 463, 470 (Ind. Ct.
App. 2009) (finding that a canine sniff of a front door of a residence required reasonable suspicion under the Indiana Constitution);
State v. Baumann, 759 N.W.2d 237, 239 (Minn. Ct. App. 2009) (finding that a canine sniff of a common hallway of an apartment
building was a “search” under the Minnesota Constitution, which must be supported by reasonable suspicion); State v. Tackitt, 67
P.3d 295, 302-03 (Mont. 2003) (requiring “particularized suspicion” under the Montana Constitution); State v. Ortiz, 600 N.W.2d
805, 811 (Neb. 1999) (finding a legitimate expectation of privacy under the Fourth Amendment and the Nebraska Constitution,
which required “reasonable, articulable suspicion” to conduct a canine sniff, although the Nebraska Supreme Court never expressly
stated that a canine sniff of the threshold of the apartment was a “search”); State v. Pellicci, 580 A.2d 710, 716-17 (N.H. 1990)
(finding that a canine sniff of a vehicle was a “search” requiring reasonable suspicion under the New Hampshire Constitution);
People v. Dunn, 564 N.E.2d 1054, 1058 (N.Y. 1990) (holding that a sniff outside an apartment door was a “search” under the New
York Constitution); State v. Woljevach, 828 N.E.2d 1015, 1018 (Ohio Ct. App. 2005) (finding that a canine sniff was a “search”
under the Ohio Constitution); Commonwealth v. Martin, 626 A.2d 556, 560 (Pa. 1993) (finding that a canine sniff of a person was
a “search” under the Pennsylvania Constitution requiring probable cause); State v. Dearman, 962 P.2d 850, 854 (Wash. Ct. App.
1998) (finding that a canine sniff of a garage was a “search” under the Washington Constitution).
291 Cf. Mapp v. Ohio, 367 U.S. 643, 652-53, 660 (1961) (discussing the states’ decision to adopt the exclusionary rule despite the fact
that the Court had not required them to do so and observing that “the experience of the states is impressive ... [and] [t]he movement
towards the rule of exclusion has been halting but seemingly inexorable”).
292 Cf. id. at 653 (discussing, among other things, the states’ voluntary movement toward adopting the exclusionary rule).
293 As the New York Court of Appeals observed, “[o]ur conclusion that there was a search, however, does not end the inquiry.” Dunn,
564 N.E.2d at 1058.
294 Id. (deciding that a canine sniff “may be used without a warrant or probable cause, provided that the police have a reasonable
suspicion that a residence contains ... contraband”); Guillen, 213 P.3d at 239 (finding that a canine sniff of the “seams of a
residence” was a “search” under the Arizona Constitution, which must be supported by reasonable suspicion); Hoop, 909 N.E.2d at
175

470 (finding that a canine sniff of the front door of a residence required reasonable suspicion under the Indiana Constitution); see
also Ortiz, 600 N.W.2d at 811 (requiring “reasonable, articulable suspicion” to conduct a canine sniff without expressly finding
that the canine sniff of the threshold of the apartment was a “search”).
295 Dearman, 962 P.2d 850, 854 (Wash. Ct. App. 1998) (concluding that a canine sniff of a garage was a “search” under the
Washington Constitution and that a search warrant based upon probable cause was required); Woljevach, 828 N.E.2d 1015, 1018
(Ohio Ct. App. 2005) (interpreting the Ohio Constitution to require same); cf. Martin, 626 A.2d 556, 560 (Pa. 1993) (concluding
that a canine sniff of a person was a “search” under the Pennsylvania Constitution, which required a showing of probable cause).
296 State v. Rabb, 920 So. 2d 1175, 1192 (Fla. 4 th Dist. Ct. App.), cert. denied, 549 U.S. 1052 (2006). In fact, Florida’s district courts of
appeal are presently split on the home-sniff issue, with the Fourth District Court of Appeal finding a “search” under the Fourth
Amendment and the Third District Court of Appeal finding that it was not a search. Compare Rabb, 920 So. 2d 1175, with State v.
Jardines, 9 So. 3d 1 (Fla. 3d Dist. Ct. App.), review granted, 3 So. 3d 1246 (Fla. 2009).
297 McDonald v. United States, 335 U.S. 451, 456 (1948).
298 Mincey v. Arizona, 437 U.S. 385, 393 (1978) (“The investigation of crime would always be simplified if warrants were
unnecessary. But the Fourth Amendment reflects the view of those who wrote the Bill of Rights that the privacy of a person’s
home and property may not be totally sacrificed in the name of maximum simplicity in enforcement of the criminal law.”).
299 Terry v. Ohio, 392 U.S. 1, 20 (1968) (observing that “we deal here with an entire rubric of police conduct--necessarily swift action
predicated upon the on-the-spot observations of the officer on the beat--which historically has not been, and as a practical matter
could not be, subjected to the warrant procedure”).
300 See Brigham City v. Stuart, 547 U.S. 398, 402 (2006) (discussing warrantless entry by law enforcement in an emergency).
301 See, e.g., Fitzgerald v. State, 837 A.2d 989, 1039 n.6 (Md. Ct. Spec. App. 2003) (“A requirement for either a probable-cause-based
warrant or even probable cause without a warrant as justification for a dog sniff would be an exercise in redundancy. The probable
cause to conduct a dog sniff would ipso facto make the dog sniff unnecessary. The probable cause would in and of itself justify the
issuance of the search warrant and the dog sniff would be superfluous.”), aff’d, 864 A.2d 1006 (Md. 2004).
302 See, e.g., United States v. Kattaria, 553 F.3d 1171, 1175 (8th Cir. 2009) (finding probable cause to issue a thermal-imaging
warrant, therefore the results of the thermal scan were properly used to obtain a warrant to physically search the premises); United
States v. Henry, 538 F.3d 300, 301 (4th Cir. 2008) (observing that police first obtained a search warrant to perform a thermal scan,
then used the results of the thermal scan as well as other information to obtain a “conventional search warrant” to physically search
the property).
303 See, e.g., Johnson v. United States, 333 U.S. 10, 14 (1948).
The point of the Fourth Amendment, which often is not grasped by zealous officers, is not that it denies law enforcement the
support of the usual inferences which reasonable men draw from evidence. Its protection consists in requiring that those inferences
be drawn by a neutral and detached magistrate instead of being judged by the officer engaged in the often competitive enterprise of
ferreting out crime.
Id. at 13-14.
304 Merriam-Webster’s Collegiate Dictionary 1283 (11th ed. 2007).
305 Transcript of Oral Argument at 19-20, 22, 33, Kyllo v. United States, 533 U.S. 27 (2001) (No. 99-8508), available at http://
www.supremecourtus.gov/oral_arguments/argument_transcripts/99-8508.pdf.
176

306 But cf. Fitzgerald v. State, 864 A.2d 1006, 1015 (Md. 2004) (“[A] dog is not technology--he or she is a dog. A dog is known
commonly as ‘man’s best friend.’ Across America, people consider dogs as members of their family.”).
307 See supra note 253.
308 See Fitzgerald v. State, 837 A.2d 989, 1037 (Md. Ct. Spec. App. 2003) (observing that “[t]he investigative use of the animal sense
of smell, human or canine, cannot even be defined as a technology. It is, a fortiori, not an unfamiliar or rapidly advancing
technology that ‘is not in general use.”’), aff’d, 864 A.2d 1006 (Md. 2004); see also State v. Bergmann, 633 N.W.2d 328, 334
(Iowa 2001) (observing that, in a vehicle-sniff context, “a drug sniffing dog is not technology of the type addressed in Kyllo”).
309 See infra notes 310-11 and accompanying text.
310 The White House, National Drug Control Strategy: Counterdrug Research and Development Blueprint Update, at C-1 (2002)
[hereinafter Counterdrug Research], available at http:// www.whitehousedrugpolicy.gov/ctac/ctac02/blueprint2002.pdf.
Genetics research is also being conducted by the U.S. Transportation Security Administration (TSA) to enhance the capabilities of
explosives-detection dogs. See Zack Phillips, The Sniff Test, Gov’t Executive, Dec. 1, 2006 (quoting Scott Thomas, breeder for
TSA program), http://www.govexec.com/features/1206-01/1206-01s2.htm (“‘We’ll be custom-designing dogs for purposes of
detection .... We call them Labrador retrievers; there may come a day we call them Labrador detectors.”’). The TSA breeding
program has produced “a new custom breed,” the Vinzslador, in the hope of producing detection dogs with the best qualities of
both Labrador retrievers and vizslas. Id. (“‘Let’s not think of a dog as an old tool that can’t be improved on .... It can, with current
technology.”’).
311 Counterdrug Research, supra note 310, at 6 & app. at C-1. Appendix C classifies canines as a “nonintrusive inspection
technolog[y],” see id. app. at C-1, while Appendix D includes the canine breeding program as a type of “narcotics detection
technolog[y].” See id. app. at D-1, D-3.
312 Russia, for example, has created a new breed of “super sniffer” dogs by crossbreeding Siberian huskies with jackals. See Ben Aris,
Russians Breed Superdog with a Jackal’s Nose for Bombs and Drugs, Telegraph.co.uk, Dec. 15, 2002, http://
www.telegraph.co.uk/news/worldnews/europe/russia/1416227/Russians-breed-superdog-with-a-jackals-nose-for-bombs-anddrugs.html.
The “super sniffer dog” has an “enhanced sense of smell” and was the product of a scientific research project that
lasted twenty-seven years. Id.
313 See supra note 310 and accompanying text.
314 For example, in the civil forfeiture context, concerns about currency contamination have led some courts to require a “sophisticated
dog alert” on money that the government seeks to seize because of its connection to drug trafficking. See Sumareh v. Doe (In re
$80,045.00 in U.S. Currency), 161 F. App’x 670, 671 (9th Cir. 2006); see also supra note 40.
315 See supra note 310 and accompanying text (discussing the creation of a “worldwide gene pool” for substance-detection canines).
Additionally, South Korea has used cloning technology to create “the world’s first cloned drug-sniffing dogs.” South Korea to Use
Cloned Sniffer Dogs, Associated Press, Apr. 24, 2008, available at http://www.msnbc.msn.com/id/24296334/ (“‘We came up with
the idea of dog cloning after thinking about how we can possess a superior breed at a cheaper cost.”’ (quoting Hur Yong-suk, head
of the Korean Customs Service)). These cloned dogs are touted as possessing superior drug-detection capabilities. See Clone
Ranger Sniffs Out Airport Drugs, PhysOrg.com, Aug. 12, 2009, http://www.physorg.com/news169283100.html (stating that the
cloned drug detector’s “achievement [in locating three grams of narcotics in a tightly zipped bag] shows cloned dogs are much
better than ordinary dogs at detecting narcotics”).
177

316 See supra note 304.
317 See, e.g., Waggoner et al., supra note 37, at 216 (observing that “[t]he following laboratory study of dogs’ detection of cocaine
hydrochloride and its degradation product methyl benzoate were conducted as part of the ongoing efforts of Auburn University’s
Institute for Biological Detection Systems to enhance canine detection technology” (emphasis added)); see also supra note 315
(discussing the development of a “super sniffer” dog).
318 Cf. Kyllo v. United States, 533 U.S. 27, 47-48 (2001) (Stevens, J., dissenting) (arguing that the Kyllo majority’s analysis would
apparently be applicable to “mechanical substitutes” for detection dogs, even if the device was similarly limited to the type of
information revealed by a canine sniff-- “illegal activity”--and that therefore the majority’s opinion would necessarily bar the use
of such devices).
319 The Georgia Institute of Technology has developed a mechanical sniffer, which has been referred to as an electronic “dog-on-achip.”
The vapor sensor, also known as an “electronic nose,” is said to be more sensitive than a drug-detection dog; dogs can detect
molecules in the part-per-billion range, while the dog-on-a-chip at “a few trillionths of a gram.” Press Release, Ga. Inst. of Tech.,
“Dog-on-a-Chip” Could Replace Drug-Sniffing Canines (Nov. 7, 2003) (reporting results from D.D. Stubbs et al., Investigation of
Cocaine Plumes Using Surface Acoustic Wave Immunoassay Sensors, 75 Analytical Chemistry 6231 (2003)); see also Paige
Bowers, How to Put a Police Dog on a Chip, Time, Jan. 4, 2004, available at http://
www.time.com/time/magazine/article/0,9171,570268,00.html. As discussed in Part I, canine detectors have a natural advantage
over electronic detectors based on the dog’s mobility and agility, which allows the dog to get close to the suspected contraband
source. See supra note 46 and accompanying text. The canine’s natural ability to get close to the scent source was not a
consideration in this scientific research, however. The need for proximity to the suspected contraband source for detection
purposes, while obviously desirable, remains unstudied in the canine home-sniff context.
320 See supra notes 208-18 and accompanying text (discussing the intrusiveness of a search of the home both because of the size of the
home in comparison to other containers and because police would be permitted to examine any container or location capable of
secreting drugs).
321 See supra notes 310, 312, 315.
322 See supra note 312.
323 State v. Rabb, 920 So. 2d 1175, 1192 (Fla. 4th Dist. Ct. App.), cert. denied, 549 U.S. 1052 (2006).
324 While the Kyllo Court also referenced “hi-tech measurement of emanations from a house,” the opinion does not suggest that this
comment was intended to exclude from Kyllo’s reach natural technological aids that implicate Kyllo’s concerns about advancing
technologies in general. See Kyllo v. United States, 533 U.S. 27, 37 n.4 (2001) (responding to the dissent’s argument that the
thermal imager at issue simply allowed police to infer what was going on inside Kyllo’s house).
325 Id. at 39 n.6.
326 In fact, Justice Stevens, in his Kyllo dissent, protested the majority’s failure both to analyze the “general public use” factor and to
remand for an evidentiary hearing on this issue. See id. at 47 n.5 (Stevens, J., dissenting) (arguing that there are thousands of
thermal imagers presently in use and that they are “readily available to the public”).
327 See id. at 33. The majority noted that the Court had concluded on two different occasions that aerial surveillance of private homes
and their surrounding areas was not a “search.” See Florida v. Riley, 488 U.S. 445, 450-51 (1989); California v. Ciraolo, 476 U.S.
207, 213-14 (1986) (majority opinion).
178

328 Riley, 488 U.S. at 448 (observing that “[w]ith his naked eye, [the officer] was able to see through the openings in the roof ... to
identify what he thought was marijuana growing in the structure”).
329 Ciraolo, 476 U.S. at 215 (observing that “[t]he Fourth Amendment simply does not require the police traveling in the public
airways at this altitude to obtain a warrant in order to observe what is visible to the naked eye”).
330 Riley, 488 U.S. at 451 (observing that “it is of obvious importance that the helicopter in this case was not violating the law”);
Ciraolo, 476 U.S. at 213 (noting that “[t]he observations by [the officers] in this case took place within public navigable airspace”).
Also important to the Riley Court was the fact that “no intimate details” about the home or curtilage were observed and the fact
that “there was no undue noise ... and no wind, dust, or threat of injury.” Riley, 488 U.S. at 452.
331 Kyllo cites these cases favorably, in part, because of our long history of permitting nontrespassory visual surveillance. See Kyllo,
533 U.S. at 31-33 (observing that “[v]isual surveillance was unquestionably lawful because ‘the eye cannot by the laws of England
be guilty of a trespass”’ (quoting Boyd v. United States, 116 U.S. 616 (1886) (quoting Entick v. Carrington, 19 How. St. Tr. 1029
(K.B. 1765)))).
332 Id. at 38 n.5 (“We think the [Ciraolo] Court’s focus in this second-hand dictum [from the California Supreme Court] was not upon
intimacy but upon otherwise-imperceptibility, which is precisely the principle we vindicate today.”). The majority explained that
limiting “searches” to those that revealed only intimate details “would not only be wrong in principle; it would be impractical in
application.” Id. at 38.
333 Id. at 40 (observing that “[w]here, as here, the Government uses a device that is not in general public use, to explore details of the
home that would previously have been unknowable without physical intrusion, the surveillance is a ‘search’ and is presumptively
unreasonable without a warrant”).
334 See Riley, 488 U.S. at 455 (O’Connor, J., concurring) (disagreeing with the plurality’s focus on the fact that the helicopter
remained within navigable air space and, alternatively, arguing that “we must ask whether the helicopter was in the public airways
at an altitude at which members of the public travel with sufficient regularity that Riley’s expectation of privacy from aerial
observation was not one that society is prepared to recognize as reasonable” (internal quotation marks omitted)).
335 See Bond v. United States, 529 U.S. 334, 338-39 (2000) (finding that an officer’s probing palpation of Bond’s soft-side luggage
located in a bus’s overhead bin violated the Fourth Amendment).
336 If the Riley plurality approach had been applied, then police would have been permitted to conduct a probing palpation because
any passenger could have probed Bond’s luggage while placing a bag in the overhead bin.
337 See Bond, 529 U.S. at 338-39 (observing that while “a bus passenger clearly expects that his bag may be handled ... [h]e does not
expect that other passengers or bus employees will, as a matter of course, feel the bag in an exploratory manner”).
338 The obvious hazard that Kyllo’s exception for routine technology creates was described by Justice Stevens in his dissent:
“[P]utting aside its lack of clarity, this criterion is somewhat perverse because it seems likely that the threat to privacy will grow,
rather than recede, as the use of intrusive equipment becomes more readily available.” Kyllo, 533 U.S. at 47 (Stevens, J.,
dissenting).
339 See, e.g., Fitzgerald v. State, 837 A.2d 989, 1037 (Md. Ct. Spec. App. 2003), aff’d, 864 A.2d 1006 (Md. 2004). As the Maryland
Court of Special Appeals observed in Fitzgerald:
The investigative use of the animal sense of smell, human or canine, cannot even be defined as a technology. It is, a fortiori, not an
179

unfamiliar or rapidly advancing technology that “is not in general use.” Bloodhounds have been chasing escaping prisoners and
other fugitives through the swamps for hundreds of years ....
Id.
340 Cf. Peebles, supra note 152, at 86 (“[F]ailure to reach the question of reasonableness of a search has meant that many types of
governmental intrusions are taken out of the domain of judicial control altogether. To hold that no reasonable expectation of
privacy existed and that no search occurred permits the judiciary, in effect, to wash its hands of its normal supervisory role over a
given type of governmental investigative activity.”).
341 See supra notes 328-29.
342 However, the lack of optical magnification was an important fact, even to the Kyllo Court. See Kyllo, 533 U.S. at 33 (observing
that, unlike Riley and Ciraolo, “[t]he present case involves officers on a public street engaged in more than naked-eye surveillance
of a home”).
343 Berger v. New York, 388 U.S. 41, 62-63 (1967) (citation omitted).
344 129 S. Ct. 1710, 1723-24 (2009) (refusing to extend Belton to allow for the search of a vehicle after an arrestee had been secured
and therefore could not access the interior of the vehicle because Belton’s safety rationale was not satisfied).
End of Document
© 2012 Thomson Reuters. No claim to original U.S. Government Works.
180

1 Search & Seizure § 2.3 (4th ed.)
Search And Seizure: A Treatise On The Fourth Amendment
Current through the 2011 Update
Wayne R. LaFavea0
Chapter 2. Protected Areas and Interests
§ 2.3. Residential premises
Introduction
Prior to the decision in Katz v. United States,1 the Supreme Court often used the concept of “a constitutionally protected
area”2 to define the reach of the Fourth Amendment’s protections. One such area, specifically enumerated in the Amendment,
is a person’s house. Indeed, one’s dwelling has generally been viewed as the area most resolutely protected by the Fourth
Amendment.3 “At the very core,” the Court cautioned in Silverman v. United States,4 “stands the right of a man to retreat
into his own home and there be free from unreasonable governmental intrusion.” This constitutional protection of houses has
been extended to other residential premises as well, including apartments,5 hotel and motel rooms,6 and rooms in rooming
houses7 or hospitals.8
Katz teaches that the Amendment “protects people, not places,” and that the “constitutionally protected area” concept cannot
“serve as a talismanic solution to every Fourth Amendment problem.” But even under the Katz justified-expectation-ofprivacy
approach, it is still useful to view residential premises as a place especially protected against unreasonable police
intrusion. As Justice Harlan noted in his concurring opinion in Katz, “reference to a ‘place’ ” is ordinarily necessary in
deciding what protection the Fourth Amendment affords to people. And it is still true, he added, that “a man’s home is, for
most purposes, a place where he expects privacy.”8.1 The concern herein is with what police investigative practices, when
directed at residential premises, do not intrude upon a protected privacy expectation as to those premises.
(a) Abandoned premises. It has often been held that if a defendant has in fact abandoned the place where he formerly
resided, then he may not have suppressed from evidence what the police find on those premises after the time of
abandonment. Sometimes such a holding is premised on the conclusion that by abandonment the defendant lost standing to
object,9 sometimes on the notion that the landlord was in a position to give effective consent after the abandonment
occurred,10 and sometimes upon the general proposition that the abandonment terminated any justified expectation of privacy
which the defendant previously had with respect to those premises.11 The concern here is with what constitutes such an
abandonment that it may be fairly said the one-time occupant no longer has a protected expectation of privacy in the
residence.12
One question which arises with some frequency is what it takes to terminate a tenant’s justified expectation of privacy as to a
house or apartment he had been renting. May it be said, for example, that this expectation ends merely by virtue of
nonpayment of rent by the tenant, or must the landlord pursue established legal procedures for eviction Instructive on this
question is United States v. Botelho,13 where the oral lease of a cottage was from period to period with payments of rent to be
prepaid every two weeks. After the tenants were delinquent in the rental payments and also failed to pay electricity and
telephone bills, the landlady informed them they would be evicted on July 15 unless all bills were paid by July 14. No money
was received, so she entered on the 15th, observed a sawed-off shotgun, and then summoned the police, who searched the
cottage. The landlady later instituted summary eviction proceedings, but before they could be carried to their completion the
tenants vacated the premises about the end of July. No rental payments were ever received for the period following June 30.
In holding that the tenants had a justified expectation of privacy in the cottage at the time of the search, the court reasoned:
Rephrased in the terms of Justice Harlan’s test, it is the government’s argument that the notice to vacate
terminated defendant’s tenancy and therefore any expectation of privacy he may have had was unreasonable.
It seems to me that this argument would be sound except for the fact that the notice given by Mrs. MacIsaac
on July 10th was clearly inadequate under Hawaii law. … The requirement of written notice is not a paper
formality because statutes providing for possessory or summary remedies of a landlord against a tenant must
be strictly construed. … Accordingly, the tenancy of the premises was not terminated by Mrs. MacIsaac’s
181

verbal notice of eviction.
Nor do I believe that the non-payment of rent would, without more, make the defendant’s expectation of
privacy unreasonable. … Moreover, in view of the mandatory and exclusive nature of [the aforementioned
statute], the fact that the landlady reserved a right to re-enter on the failure to pay rent is immaterial. It is the
better and more modern rule that a landlord entitled to possession by right of re-entry or otherwise must, on
the refusal of the tenant to surrender the leased premises, resort to the remedy given by law to secure it. Any
other rule is prejudicial to the public peace and order. …
The government argues alternatively that property law should not be controlling in determining the scope of Fourth
Amendment protections. It reasons that despite the invalidity of the notice of eviction the defendant could not have
had a reasonable expectation of privacy in any part of the cottage when the rent, electricity and telephone bills were
unpaid, and the landlady had informed him to be out of the premises by July 15. While persuasive in some respects, I
cannot agree with the government’s contention. Although the Supreme Court has stated that it is “unnecessary and illadvised”
to import property law concepts into the law surrounding Fourth Amendment rights, … it is obvious that this
was intended to broaden the protection afforded against unreasonable searches and seizures, not narrow it.
Furthermore, I am not prepared to hold that a defendant with a perfectly legal right to possession or occupancy of
leased premises can be found to have an “unreasonable” expectation of privacy.13.1
The reasoning in Botelho is generally sound. Although, as the court concedes, property law concepts are not necessarily
controlling on Fourth Amendment issues, the justified expectation of privacy which one has in his place of residence
certainly includes the expectation that the processes of the law rather than self-help will be utilized to terminate a tenant’s
occupancy.14 (or, for that matter, an owner’s occupancy14.1).
But the language in Botelho should not be taken to mean that no abandonment by the tenant is possible before the rental term
expires, for this is not the case.
The question of abandonment for Fourth Amendment purposes does not turn on strict property concepts but on
whether the accused has relinquished his interest in the property to the extent that he no longer has a reasonable
expectation of privacy in the premises at the time of the search. … This principle has been applied to find
abandonment where a tenant has left residential premises even though he may retain the lawful right to possession.15
This means that if by all appearances the tenant has vacated the premises by the time the lease has ended, then Botelho is
inapplicable, for there would be no occasion for the landlord to seek eviction in such circumstances.16 Thus, in United States
v. Wilson,17 where the tenant was over two weeks overdue with his rent, the landlord learned from neighbors that the tenant
had moved out, and the landlord went to the apartment in question and found the door standing open and the apartment in
disarray, the court quite properly held that the tenant had abandoned the apartment. “The proper test for abandonment,” the
court noted, “is not whether all formal property rights have been relinquished, but whether the complaining party retains a
reasonable expectation of privacy in the articles alleged to be abandoned.”18
It is a fair generalization that abandonment is more readily found as to rooms occupied on a transient basis. Thus, in Botelho
the court cautioned: “Because of the transitory nature of most motel and hotel rental arrangements, non-payment of rent in
that context might well require a different rule.” Illustrative is United States v. Parizo,19 where defendant rented a motel room
for a single night, paid only for one night, and never informed the desk that he wished to stay on beyond that time. After
check-out time the following day, the manager entered the room, saw a weapon, and summoned the police. In upholding the
police entry of that room, the court reasoned:
[W]hen the term of a guest’s occupancy of a room expires, the guest loses his exclusive right to privacy in the room.
The manager of a motel then has the right to enter the room and may consent to a search of the room and the seizure
of the items there found.20 …
Appellant argues that, notwithstanding the expiration of the rental period, his intent to retain possession of the
room remains the decisive factor and that we ordered the trial court to turn its decision upon findings bearing
upon whether he had such an intent. However, intentional abandonment is relevant in different factual
situations from the situation here. Had the search occurred during the rental period, appellant would have
standing to object to an unauthorized search of the premises, unless prior to the search he had abandoned the
premises, thereby forfeiting his right to occupancy and privacy. … Preliminary to the inquiry into intentional
abandonment by the defendant, it must be shown that the defendant had sufficient control over the premises to
182

establish a right to privacy therein.
Thus, if the search in Parizo had been conducted before check-out time, then it would be necessary to establish that the
defendant had abandoned the premises “in the sense of having no apparent intention to return and make further use of
them,”21 unless the defendant’s prior conduct had been such to constitute a waiver of his privacy expectation.22 And
doubtless there are cases in which no abandonment will be deemed to have occurred even after the initially indicated term of
rental, as where the tenant had arranged for credit card payment of all charges and both the motel and tenant treated the
tenant’s nondeparture as extending the term.23 Indeed, an abandonment conclusion may sometimes be inappropriate because
of “the hotel’s generally lax practices in enforcing its checkout time.”24
Another difference between houses and apartments, on the one hand, and transient quarters, on the other, is discernible in
those cases where the defendant has been arrested prior to the time of the search. When a person is regularly residing at
certain premises, “[a]bsence due to arrest and incarceration while awaiting trial is not of itself a sufficient basis upon which to
conclude that the accused has abandoned any reasonable expectation of privacy in his home.”25 By comparison, where a
person occupying a hotel or motel room is arrested under circumstances indicating that his incarceration will be more than
temporary, the arrest may be viewed as terminating the occupancy of the room.26 This is particularly likely if, as in Abel v.
United States,27 the arresting officers see to it that the defendant checks out of the hotel after his arrest. In Abel the Supreme
Court upheld a search of the room defendant had occupied at the time of his arrest, reasoning that because he “had vacated
the room” the hotel “had the exclusive right to its possession” at the time of the search.
At least one commentator has called Abel into question, stating:
It may be argued that the petitioner had not voluntarily relinquished control of the premises, and therefore the theory
of abandonment is most tenuous. Additionally, subsequent movement of Fourth Amendment conceptualization
toward an increased emphasis on constitutionally protected privacy renders the viability of Abel increasingly
dubious.28
But, while it may be true that an intent to abandon cannot be presumed merely from the fact of arrest and incarceration, it
does not follow that a person lawfully arrested cannot be said to have abandoned the room by electing to check out after the
arrest. The problem here, as a practical matter, is that the arrested transient may find himself in a “Catch-22” situation; he
may be confronted with the choice of abandoning the room and certain personal effects there (thus subjecting them to police
scrutiny because of the abandonment) or of taking the effects with him (thus subjecting them to inventory at the station).
Perhaps limits upon the inventory authority would alleviate this situation somewhat.29
Another variation of the problem arises when the defendant has not checked out but, by virtue of being in police custody, is
not in a position to extend his occupancy. Such was the situation in United States v. Croft,30 where the court asserted:
Defendant argues that the expiration of the rental period should not control in this case because his arrest prior
to check-out time prevented him from returning to the motel and perhaps extending the rental period. We are
not persuaded by this argument for it was defendant’s own conduct that prevented his return to the motel.
It may be questioned, however, whether expiration of the rental period-especially under these circumstances-can be said to
terminate fully the guest’s justified expectation of privacy as to personal property he had secured in the privacy of his room.
Certainly the innkeeper must be able to remove those effects from the room so that it can be rented to another, and if in that
process he finds evidence of crime it may well be that the former guest cannot complain if, as in Parizo, that incriminating
evidence is made available to the police. But the innkeeper is not without responsibility as to personalty left behind,31 and
thus it might be doubted whether he can give the police carte blanche to rummage through those effects.32 However, if the
hotel places the guest’s effects in storage and then, upon learning of the guest’s arrest, turns them over to the police, this
provides a basis for police inventory of those effects.33
Yet another situation in which courts have had to decide whether the premises have been abandoned to the extent that the
occupant’s justified expectation of privacy therein has ceased is where those premises have been seriously damaged by fire.
Certainly there will be instances in which it may fairly be concluded that the tenant in those premises has left without any
intention to return,34 but the notion that the owner of the burned premises has abandoned them merely because they are not
inhabitable35 is a highly questionable one. No such abandonment should be found when the owner has boarded up the
premises36 or when it appears that there are salvageable items of personal property in the premises which the owner could be
expected to retrieve.37 However, even absent a fire, it sometimes happens that premises are in such an extreme state of
disrepair and apparently unoccupied as to support the conclusion that those premises apparently have been abandoned.37.1
183

It is also necessary to distinguish abandoned premises from those which are merely unoccupied, for justified privacy
expectations are not totally lacking as to the latter. The point is illustrated by State v. Finnell,38 where the owner of vacant
residential structures challenged city code provisions regarding warrantless inspection of the interior of vacant buildings. The
city argued “that no reasonable expectation of privacy exists in a location without the occurrence of intimate and personal
activities traditionally associated with the home,” but the court responded that “this is not the appropriate test.” Emphasizing
that the defendant “is the owner and maintains both possession and control of the building” and “regulates access to the
building,” the court concluded that he had “a subjective expectation of privacy” in those premises “that is reasonable-albeit
an expectation that is protected to a lesser extent than such expectations where the owner is active and the site was in
productive use.”39
(b) Entry of residence. The home “is accorded the full range of Fourth Amendment protections,”40 for it is quite clearly a
place as to which there exists a justified expectation of privacy against unreasonable intrusion. It is beyond question,
therefore, that an unconsented police entry41 (sometimes involving no more than the opening of a screen door)41.1 into a
residential unit, be it a house or an apartment or a hotel or motel room,42 constitutes a search within the meaning of Katz v.
United States.43 Moreover, this Fourth Amendment protection (and thus this search characterization of an entry) extends even
to “occupants of flimsily constructed dwellings with unobstructed windows or other openings directly on public lands,
streets, or sidewalks, who failed to lock their doors to bar entrance.”44
Sometimes the police or a person acting on their behalf will resort to a subterfuge in order to gain entry into a home.
Illustrative is Lewis v. United States,45 where an undercover narcotics agent falsely identified himself as “Jimmy the
Pollack” and claimed that a mutual friend had told him defendant might be able to supply marijuana, at which the defendant
received the agent into his house and sold him marijuana there. The Court was not sympathetic to the defendant’s contention
that his justified expectation of privacy in his home had been breached:
[W]hen, as here, the home is converted into a commercial center to which outsiders are invited for purposes of
transacting unlawful business, that business is entitled to no greater sanctity than if it were carried on in a
store, a garage, a car, or on the street. A government agent, in the same manner as a private person, may accept
an invitation to do business and may enter upon the premises for the very purposes contemplated by the
occupant.
The breadth of the Lewis exception, especially as to the kinds of deception which are permissible, is considered elsewhere in
this Treatise.46
It is not improper for a police officer to call at a particular house and seek admission for the purpose of investigating a
complaint or conducting other official business. If admission is voluntarily granted by a person who is in a position to give
such effective consent,47 then the policeman may enter and make observations while therein consistent with the scope of the
permission he was given.48 But the mere fact that the door of the house is opened in response to the officer’s knock or ring
does not mean that the officer is entitled to walk past the person so responding into the interior of the residence.49 Nor may
the officer enter the home when there is no response at all.49.1, even if the door is open.49.2 As stated in State v. Crider50:
It is not unreasonable for police officers, in the pursuit of criminal investigations, to seek interviews with
suspects or witnesses at their homes, but their right to call upon them at their homes for such purposes does
not include the right to walk in uninvited merely because there is no response to a knock or a ring.
The court in Crider pointed out that the “mere presence of a hallway in the interior of a single family dwelling, without more,
is not in itself an invitation to the public to enter,” so that police entry only into the hallway “must be viewed as an intrusion
into an area in which the defendant was entitled to a reasonable expectation of privacy.”51
The Crider rule is applicable to a building which contains only one residential unit, and does not carry over in its entirety to
such multiple-occupancy structures as apartment buildings, hotels and motels. As Crider elaborates:
Police officers in the performance of their duties may, without violating the constitution, peaceably enter upon the
common hallway of a multiple dwelling without a warrant or express permission to do so. … There is no invasion of
privacy when a policeman without force enters the common hallway of a multiple-family house in the furtherance of
an investigation.52
This is somewhat of an overstatement. It is correct when the circumstances indicate that the hallway is readily accessible to
the general public,53 but not otherwise. For example, in United States v. Carriger54 the entrances to the apartment building
184

were locked and could only be opened by a key or by someone within activating a buzzer system. A federal agent slipped
into the building by holding the door when several workmen exited the premises; he then went to the third floor via a
stairway, where he observed an exchange of drugs in the hallway. Relying upon Justice Jackson’s concurring opinion in
McDonald v. United States,55 the court in Carriger held that the “officer’s entry into this locked apartment building without
permission56 and without a warrant of any kind was an illegal entry and violated appellant’s Fourth Amendment rights.” The
court reasoned:
We cannot agree with the district court that McDonald may be distinguished upon the basis that it proscribed a
forcible entry into an apartment building while the entry here was peaceable. Whether the officer entered
forcibly through a landlady’s window or by guile through a normally locked entrance door, there can be no
difference in the tenant’s subjective expectation of privacy, and no difference in the degree of privacy that the
Fourth Amendment protects. A tenant expects other tenants and invited guests to enter in the common areas of
the building, but he does not expect trespassers.
Other courts have reached the same conclusion upon similar facts,57 but there are also quite a few cases to the contrary,58
which now represent “the majority position.”58.1 One court distinguished Carriger in answering in the negative the question
“whether tenants in a large, high-rise apartment building, the front door of which has an undependable lock that was
inoperable on the day in question, have a reasonable expectation of privacy in the common areas of their building.”59
We have seen that the absence of a lock on the premises is typically viewed as manifesting that hallways and other common
areas are open to the public when the place is an apartment building, hotel or motel, but not when the place is a one-unit
residence. What then if the place is a rooming house The better view is represented by State v. Titus,60 holding that except
in the case in which it is very obvious from other circumstances that the rooming house is open to the general public,61 a
rooming house is to be treated in this respect as if it were a single-unit dwelling, so that an unlocked or even open outer door
cannot be treated by the police as alone manifesting an invitation to enter.62 As explained in Titus:
This holding does not extend to common hallways in unlocked apartment buildings, which generally serve
only to connect separate, self-contained living units typically complete with all of the traditional living areas
(i.e., bathrooms, dining rooms, living rooms, kitchens, etc.). Interior hallways in rooming houses are protected
only by virtue of linking such traditional rooms within the house—they provide rooming house residents with
the only means of access to those rooms, and are an inseparable feature of their “home.” In other words, it is
not any inherent nature of a hallway that controls, but rather what the hallway links (i.e., individual selfcontained
living units versus shared traditional living areas).
Like analysis is called for when the police have entered other areas of a multiple-occupancy structure, such as an attic,63 a
basement64 or parking facility.65 Observations therein do not constitute a Fourth Amendment search if that area is readily
accessible to the public, but do if the area in question has been sufficiently secured so as to give the tenants a justified
expectation of privacy in that place. In making that determination, it must be kept in mind that not all multiple-occupancy
buildings should be treated in like fashion; there is, for example, a difference between “a two-family dwelling such as a
duplex” and a large apartment building.66 In all such cases, however, it must be remembered that the fact the area is not open
to the general public merely means that the police cannot constitutionally enter that area without express permission. Certain
persons, such as the landlord or his representative,67 may consent to police entry into a common area even when the character
of that area is such that it cannot be said there was an implied invitation to the general public to enter.
Finally, it should be noted that a search-by-entry can occur without the necessity of the officer fully intruding his person
inside the residence. Dinkens v. State68 is such a case. There, an officer who had been advised that defendant had a pistol
under his dwelling went there and, after finding no one home, walked to the rear of the house, reached into a small vent
underneath the house and found the pistol. Characterizing this as “an intrusion into the home itself,”69 the court held the
officer had conducted a search by making that intrusion into the householder’s privacy. Authority in accord with Dinkens is
to be found,70 although one pre-Katz case held that such an area is “not within the protection of the Fourth Amendment.”71
The better view is that such action is a search which, because it is not highly intrusive, would be reasonable in somewhat
broader circumstances than would permit a complete physical entry into a residential unit.72
What then of the situation in United States v. Concepcion,73 where the police arrested the defendant, found keys on his
person, used one of them to unlock an apartment in a nearby apartment house, and then used the information that defendant
had access to this apartment to induce him to consent to a search of it In response to the defendant’s claim that the consent
was the fruit of an illegal search, the court first noted that a “keyhole contains information-information about who has access
185

to the space beyond” and that “the tumbler of a lock is not accessible to strangers,” and then concluded: “Because the agents
obtain information from the inside of the lock,73.1 which is both used frequently by the owner and not open to public view, it
seems irresistible that inserting and turning the key is a ‘search.’ ”74 But the court went on to conclude, quite reasonably, that
the intrusion upon “privacy interests is so small” that neither a search warrant nor full probable cause was necessary as a
prerequisite to such a search.75
(c) Looking in or listening at the residence. Although it is generally true that a person has a justified expectation of privacy
with respect to the interior of his place of residence, it does not follow that it is inevitably a search for a law enforcement
officer to see or hear what is occurring therein. At least when the officer only employs his natural senses,76 the prevailing
rule is that such uses of the senses “made from a place where a police officer has a right to be do not amount to a search in
the constitutional sense.”77 In assessing just what circumstances fall within this rule, it is useful to give separate consideration
to single-unit dwellings and then to such multiple-occupancy premises as apartment houses, hotels and motels.
As for a dwelling house, it certainly is not a search for an officer to see or hear what is occurring inside a dwelling while he is
in an area adjacent to that dwelling’s curtilage which is open to the public. Illustrative is People v. Wright,78 where the
surveilling officer so employed his senses of sight and hearing while standing on the nearby railroad right of way. In response
to the defendant’s argument that Katz had rejected the “trespass” doctrine and that therefore this was a search despite the
absence of a trespass, the court reasoned:
We do not, however, read Katz as indicating any constitutional infirmity in the instant search, for we believe the
seemingly restrictive ruling in Katz is applicable only to those instances where electronic eavesdropping devices or
other artificial means are employed in addition to the natural senses. We read the reaffirmation of the lawful position
aspect of the plain-view doctrine in Harris79 as retaining the viability of the trespass doctrine in those cases where law
enforcement officers gain information concerning crimes by use of their natural senses. Therefore, while the absence
of a trespass is no longer to be an adequate ground to justify the admission of evidence secured through the use of the
natural senses assisted by artificial means, the lack of a trespass is still a highly relevant consideration in sustaining
the admission of evidence which has fallen into the plain view of an officer, i.e., gathered solely by the use of his
natural senses.
This result is fully consistent with the Katz rationale, for the defendant in Wright cannot be said to have justifiably relied
upon the privacy of his residence when his activities could be both seen and heard from a nearby public area.
By like reasoning, it may be concluded that no justified reliance is present when a person’s in-premises activities may be
readily observed or heard by neighbors, so that it is not a search for an officer to see or hear those activities from a neighbor’s
property.80 In Commonwealth v. Busfield,81 for example, the surveilling officer obtained a neighbor’s permission to look
from his residence into the window of the suspect premises across the way. From that vantage point, he could see through the
sheer curtain in the suspect premises to the narcotics activity then occurring. The court correctly concluded that because that
activity was in plain sight of the defendant’s neighbor, he had “exposed his transaction to the public.”
This is not to suggest, however, that in every conceivable instance in which surveillance by the natural senses is conducted
without entering the curtilage, it may be concluded that no Fourth Amendment search has occurred. Wright merely says that
the lack of trespass is a “highly relevant consideration,” not that it is controlling, and certainly there are circumstances in
which it must be concluded that the occupant’s justified expectation of privacy was breached notwithstanding the absence of
a trespass. For example, what if policemen were to climb up a telephone pole and peer beneath a second-story window shade,
thereby observing what could not be seen either from ground level or from nearby buildings In such a case, “[a]lthough they
use no electronic gadgetry, the interests on which their activities intrude appear to be indistinguishable from the interest
protected in Katz.”82 It will not do in such a case to say that the occupant of the premises could have closed off that window
more completely.83 It is one thing to assert that an occupant cannot claim a justified expectation of privacy as to activities
within his dwelling when that conduct is carried out in such a manner as to be readily seen or heard by neighbors or by the
passing public. It is quite another to declare that citizens cannot “feel safe in leaving their windows uncurtained to the
skies”84 or in otherwise failing to seal off each and every aperture in their dwellings. And thus when police surveillance takes
place at a position which cannot be called a “public vantage point,”85 i.e., when the police-though not trespassing upon the
defendant’s curtilage-resort to the extraordinary step of positioning themselves where neither neighbors nor the general
public would ordinarily be expected to be, the observation or overhearing of what is occurring within a dwelling constitutes a
Fourth Amendment search. This is really what Katz is all about.
186

The Wright rule also should not be taken to mean that any viewing or hearing of what is occurring in premises is a search if
the police were within the curtilage86 at the time. “A sidewalk, pathway, common entrance or similar passageway offers an
implied permission to the public to enter which necessarily negates any reasonable expectancy of privacy in regard to
observations made there.”87
Absent express orders from the person in possession against any possible trespass, there is no rule of private or public
conduct which makes it illegal per se, or a condemned invasion of the person’s right of privacy, for anyone openly
and peaceably, at high noon, to walk up the steps and knock on the front door of any man’s “castle” with the honest
intent of asking questions of the occupant thereof—whether the questioner be a pollster, a salesman, or an officer of
the law.88
Thus, courts have held “that police with legitimate business may enter the areas of the curtilage which are impliedly open to
use by the public,” and that in so doing they “are free to keep their eyes open and use their other senses.”89 This means,
therefore, that if police utilize “normal means of access to and egress from the house”90 for some legitimate purpose,91 such
as to make inquiries of the occupant,92 to serve a subpoena,93 or to introduce an undercover agent into the activities occurring
there,94 it is not a Fourth Amendment search for the police to see95 or hear96 or smell97 from that vantage point what is
happening inside the dwelling.98
On the other hand, if the police stray from that path to other parts of the curtilage in order to conduct the surveillance, then
the use of natural sight or hearing or smell to detect what is inside is a search within the meaning of the Fourth
Amendment.99 Illustrative is Lorenzana v. Superior Court,100 where an officer, unable to see into the suspect house from the
street or adjacent driveway, crossed a ten foot strip of land on a side of the house where there were no doors or defined
pathways and took a position beneath a window. Although the window was closed and the shade was drawn down to two
inches of the bottom sill, this officer was able to overhear a telephone conversation about a pending narcotics pickup and to
see heroin. The court quite understandably concluded “that the questioned police procedure too closely resembles the process
of the police state, too dangerously intrudes upon the individual’s reasonable expectancy of privacy, and thus too clearly
transgresses constitutional principle.” As for the contention that the defendant had no justified expectation of privacy because
he had not succeeded in totally concealing his criminal activity from such surveillance by the natural senses, the Lorenzana
court responded:
The fact that apertures existed in the window, so that an unlawfully intruding individual so motivated could spy into
the residence, does not dispel the reasonableness of the occupants’ expectation of privacy. … To the contrary, the
facts of this case demonstrate that by drawing the window shade petitioner Lorenzana exhibited a reasonable
expectation to be free from surveillance conducted from a vantage point in the surrounding property not open to
public or common use.101 Surely our state and federal Constitutions and the cases interpreting them foreclose a
regression into an Orwellian society in which a citizen, in order to preserve a modicum of privacy, would be
compelled to encase himself in a light-tight, air-proof box.102
Turning now to multiple-occupancy dwellings, such as apartment houses, rooming houses, hotels, and motels, it may be
noted at the outset that certain situations are not unlike those previously discussed. If, for example, an officer is able to see or
hear what is occurring within a particular unit without intruding into the building or surrounding curtilage and while stationed
at what may be fairly characterized a public vantage point, then here again there has been no search.103 But what is different
about the multiple-occupancy dwelling cases generally is that an occupant can claim an exclusive privacy interest in only a
portion of the premises, and areas immediately adjacent to that portion will be open to public or common usage, so that
courts are inclined to view those occupying such dwellings as having a reduced privacy expectation.104
Rather typical of this view is Moody v. State,105 holding it was no search for a detective to look through the partially opened
blinds into a motel room:
Our courts have accorded a high degree of judicial sanctity to people in their homes, however, this security
against unreasonable searches of homes should be distinguished from the scope of protection afforded a motel
resident. …
A private home is quite different from a place of business or from a motel cabin. A home owner or tenant has the
exclusive enjoyment of his home, his garage, his barn or other buildings, and also the area under his home. But a
transient occupant of a motel must share corridors, sidewalks, yards, and trees with the other occupants. Granted that
a tenant has standing to protect the room he occupies, there is nevertheless an element of public or shared property in
motel surroundings that is entirely lacking in the enjoyment of one’s home.106
187

In the present case, the detectives observed appellant while they were standing outside the motel in an area
used by guests or persons having business there. As an occupant of the motel, appellant only shared in the
property surrounding the motel whereas if he were a homeowner, he would have exclusive enjoyment of his
property.
The occupants of the motel room had no right to expect any privacy with relation to what they did inside the
window as it was within easy view of those utilizing the motel surroundings. It is not unreasonable to hold
motel residents to the expectation that persons using the motel area might peer into open windows.
Other courts have likewise held that it is not a search for the police to look into a motel room from the parking lot or a similar
area used by the public,107 or for the police to listen with the naked ear from such a vantage point108 or from an adjoining
room.109 By like reasoning, similar conduct in a public area or adjoining room of a hotel110 or rooming house111 is deemed
not to be a search. Apartment dwellers fare no better. It is not a search for an officer to look into an apartment while in a
common passageway112 or other common area113 of the apartment complex, or to listen from an adjoining apartment.114
Moreover, at least when the hallways of the apartment building have not been made inaccessible to the general public,115
listening with the naked ear from the hallway outside a particular apartment is not deemed to intrude upon any justified
expectation of privacy of the apartment’s occupants.116 In United States v. Llanes,117 for example, where a narcotics agent
overheard incriminating comments by standing in the hallway near the imperfectly hung apartment door, the court declared
“that conversations carried on in a tone of voice quite audible to a person standing outside the home are conversations
knowingly exposed to the public.”
Decisions such as Llanes are particularly worrisome, for they leave the unfortunate resident of a multiple-occupancy dwelling
with very little privacy. For the reasons stated so well by Professor Amsterdam, it would appear that this line of authority has
diminished the privacy of such persons “to a compass inconsistent with the aims of a free and open society.”118 After
accurately predicting that Katz would undergo a “rapid transmutation into a rule to the effect that if an officer conducts his
observations from a vantage point accessible to the general public and uses no artificial aids to vision, he is clear of the
amendment,”119 Amsterdam asks:
Is this a satisfactory result It does not seem so to me. The problem began, I think, when the simplification of Katz
began, in terms of categorical concepts such as “privacy.” People who live in single houses or well-insulated
apartments tend to take a rather parochial view of privacy. Because we are accustomed to having something
approaching absolute privacy when we lock our outer doors, we tend to conceive of privacy as an absolute
phenomenon and to denigrate the importance of degrees of privacy. To us it seems intuitively evident that anything a
person does within sight or hearing of his neighbors or the general public is not private—and that, as to such things, it
makes no difference whether they are observed by a neighbor or a policeman—because we retire to our homes when
we want real privacy. But if you live in a cheap hotel or in a ghetto flat, your neighbors can hear you breathing
quietly even in temperate weather when it is possible to keep the windows and the doors closed. For the tenement
dweller, the difference between observation by neighbors and visitors who ordinarily use the common hallways and
observation by policemen who come into the hallways to “check up” or “look around” is the difference between all
the privacy that his condition allows and none. Is that small difference too unimportant to claim fourth amendment
protection120
The argument is a compelling one, and justifies the conclusion that conduct such as that in Llanes should not go entirely
unregulated. And while it may be true that “no court is going to say that policemen may not enter apartment hallways without
a search warrant, it would be quite possible for a court to say that police entries into apartment hallways are ‘searches’
subject to some lesser form of regulation.”121
Even if courts do not go this far (and there is unfortunately no evidence to date that they are inclined to embrace the
Amsterdam approach), the Katz justified-expectation-of-privacy approach should nonetheless be interpreted to give the
resident of a multiple-occupancy structure greater protection than he had under the pre-Katz trespass rule. In particular, as
perhaps the Supreme Court is coming to realize,122 courts should not bestow the nonsearch appellation upon police
surveillance (1) which does not occur at a “public vantage point”123; or (2) which is offensive in its intrusiveness in the sense
that it uncovers that which the resident may fairly be said to have protected from scrutiny by the “curious passerby.”124
With respect to the first point, it is useful to consider the facts of Cohen v. Superior Court.125 After receiving an anonymous
tip that prostitution was occurring in a particular fourth-floor apartment at a certain address, officers went to those premises
188

to investigate. Noting that a metal fire escape was attached to the side of the building, one of the officers went out onto the
fire escape from the fourth-floor hallway and then took a position on that part of the fire escape landing which extended to
the balcony under the window of the suspect apartment. From that vantage point the officer saw a woman inside the
apartment handling what was recognized as marijuana. On the question of whether this constituted a search, the trial court
thought that “the issue resolves itself by whether or not the officer did commit a trespass in going out on the balcony,” and
then answered in the negative because the fire escape was not intended for the exclusive use of the occupants of the surveilled
apartment. Under the pre-Katz trespass doctrine, this would by no means be a remarkable result, but it is disheartening to find
essentially the same analysis sometimes accepted as consistent with the rule of the Katz case,126 for, as the appellate court in
Cohen concluded:
The test to be applied in determining whether observation into a residence violates the Fourth Amendment is
whether there has been an unreasonable invasion of the privacy of the occupants, not the extent of the trespass
which was necessary to reach the observation point. Whether a particular search involves an unconstitutional
intrusion into the privacy of an individual is dependent upon the total facts and circumstances of the case. …
In the instant matter the police made their observations from an outside fire escape which was available to
tenants, guests, and other persons lawfully on the fourth floor in case of fire. It is a tenable argument that
tenants whose apartments had windows on the outside wall four stories above the street could reasonably
expect privacy from any observations from the fire escape except during an emergency evacuation. In such a
crisis, it is unlikely that anyone would pause to look into windows.
The Cohen court thus remanded the case for a determination of the critical facts, such as “the customary use or nonuse of the
fire escape platform for purposes other than emergency escape from a fire, and on the extent of view into the apartment by a
person using the escape ladders and not walking away from the escape route.” Consistent with Cohen, some other decisions
also recognize that the resident of a multiple-occupancy dwelling has a justified expectation of privacy against being heard or
seen from vantage points about the building which are not ordinarily utilized by the public or other residents.127
As for the second point, the 1948 Supreme Court case of McDonald v. United States128 provides a relevant fact situation.
There the police suspected a tenant in a rooming house, McDonald, of being involved in a numbers operation. One of them
climbed through a window leading into the room of Mrs. Terry, the landlady, and then proceeded to the second floor to
McDonald’s room. The door to the room was closed, so the officer stood on a chair and looked through the transom, by
which he was able to see two men handling gambling paraphernalia. This, the government argued, amounted to no search visa-vis
McDonald:
Although it was an invasion of privacy for the officers to enter Mrs. Terry’s room, that was a trespass which
violated her rights under the Fourth Amendment, not McDonald’s. Therefore so far as he was concerned, the
officers were lawfully within the hallway, as much so as if Mrs. Terry had admitted them. Looking over the
transom was not a search, for the eye cannot commit the trespass condemned by the Fourth Amendment.
Justice Douglas, writing the opinion of the Court, did not “stop to examine that syllogism for flaws,” but merely announced:
“we reject the result.”129 Justice Jackson, concurring, thought it desirable to identify the flaw; he concluded that tenant
McDonald had “a personal and constitutionally protected interest in the integrity and security of the entire building against
unlawful breaking and entry.” He thus proceeded to make it clear that had the officers made a lawful entry into the common
area of the premises, they would then have had virtual carte blanche to conduct a surveillance there:
Like any other stranger, they could then spy or eavesdrop on others without being trespassers. If they peeped
through the keyhole or climbed on a chair or on one another’s shoulders to look through the transom, I should
see no grounds on which the defendant could complain.
In the context of the pre-Katz trespass rule which then obtained, there is certainly nothing remarkable about this assertion by
Justice Jackson. But the great virtue of the Katz decision is that it liberates courts from the trespass straightjacket and permits
a reasoned value judgment to be made concerning what types of police surveillance are not to go unregulated by
constitutional restraints. And in making that judgment, it is submitted, there is no necessity to conclude that apartment and
hotel dwellers must be deemed to have no justified expectation of privacy against such highly intrusive snooping merely
because they live under conditions which require that others must be allowed to pass their door. Even if we are prepared to
say that these residents must pay the price, in terms of loss of privacy against police scrutiny, for having the misfortune to
189

eside where the doors are cracked130 or imperfectly hung,131 surely at some point the limit is reached. And certainly that
limit is reached when the conduct in question is keyhole-peeping,132 transom-peeping,133 or looking though minute openings
in covered windows.134 To assert that the tenant in a hotel or apartment building has an expectation of privacy in his place of
residence is to say very little if that tenant is put to the choice of papering over his transom and stuffing his keyhole or else
having a policeman look in.
(d) Entry of related structures. Under the traditional pre-Katz interpretation of the Fourth Amendment, the “right of the
people to be secure in their … houses” extended not merely to a person’s dwelling, but also to other structures located within
the curtilage.
Generally speaking, curtilage has been held to include all buildings in close proximity to a dwelling, which are
continually used for carrying on domestic employment; or such place as is necessary and convenient to a dwelling,
and is habitually used for family purposes.135
Applying the curtilage test to the facts of particular cases, courts held that it was a search within the meaning of the Fourth
Amendment for police to enter a garage,136 a barn,137 a smokehouse,138 a bathhouse,139 or a hen house.140 But this by no
means meant that these and like structures were inevitably within the protection of the Amendment. Other decisions,
sometimes involving different facts and sometimes reflecting a different judicial attitude concerning the scope of the curtilage
(especially as to just how close a “close proximity” is), found the following structures to be outside the curtilage and thus
subject to unrestrained entry at the whim of the police: garages,141 barns,142 hen houses,143 stables,144 lean-tos,145 and
outbuildings.146
As perhaps is apparent from these lists, it is bizarre that the curious concept of curtilage, originally taken to refer to the land
and buildings within the baron’s stone walls, should ever have been deemed to be of controlling significance as to the
constitutional limits upon the powers of the police. The Fourth Amendment also protects a person’s “papers, and effects,”
and it was never satisfactorily explained why these papers and effects were with or without protection from unreasonable
search and seizure depending upon whether they were kept in a building close to or distant from the dwelling. As one federal
judge observed some years ago,
the “curtilage” test … would imply … that buildings outside the curtilage are not within the protection of the Fourth
Amendment, and, while I am aware of cases so holding, I can see no reason why a farmer should be afforded less
protection in the barn where he actually does business, whether located within the curtilage or not, than is accorded a
city dweller in his office.147
The same could be said of structures which do not have a business use. It is difficult to understand, for example, why police
should be required to conform to the restraints of the Fourth Amendment when they enter an urban dweller’s garage attached
to or immediately adjacent to his dwelling, but should be permitted to enter at will a garage some distance from or having no
connection with the dwelling. The absurdity of that distinction led at least one court to conclude that “a garage … is protected
against unreasonable searches without regard to whether or not it is within the curtilage of a private dwelling.”148
One of the virtues of Katz v. United States149 is that it makes it apparent that the curtilage concept should not be employed to
limit arbitrarily the reach of the Fourth Amendment’s protections. Under Katz, it is a search to violate “the privacy upon
which [one] justifiably relied,” and unquestionably a person can have such an expectation of privacy as to garages and barns
and the like even when they are not in “close proximity” to his dwelling.
Some of the post-Katz cases still rely upon the curtilage concept in the process of holding that it is a search to enter a
structure which is located within the curtilage.150 This is not particularly objectionable, for there is no reason to view Katz as
having somehow reduced the protection of in-curtilage structures; surely a justified expectation of privacy exists as to them.
But it will no longer do to declare routinely that any entry of a structure beyond the curtilage is not a Fourth Amendment
search. Rather, Katz dictates the approach taken in People v. Weisenberger,151 where, in the course of holding that the
discovery of three 2-pound bags of marijuana in a chicken house was a search, the court reasoned:
In our view the court’s reliance on the curtilage doctrine was misplaced. Even though the area of the search
might have been outside the curtilage, nevertheless, if it was a place where the owner had a reasonable
expectation of privacy, then it was a constitutionally protected area where warrantless intrusions are forbidden
under the federal and state constitutions. …
The record reflects that the chicken house was in proximity to the Weisenberger home and was being put to an
190

active domestic use. It housed ten to fifteen laying hens and contained necessary feed and water for their
maintenance. There was no public exposure of illicit activity being conducted in or about the chicken house.
…
In light of these circumstances, we think it clear that appellant had a reasonable expectation of privacy in this
outbuilding.
In the more recent case of Oliver v. United States,152 the Supreme Court utilized the curtilage concept for purposes of
distinction in reaffirming the “open fields” rule of Hester v. United States.153 But, despite the Oliver Court’s unwillingness to
recognize that an expectation of privacy could be grounded in one’s use of fences and no trespassing signs around his
property,154 that decision casts no doubt upon the soundness of the Weisenberger reasoning. The Court in Oliver only held
“that an individual may not legitimately demand privacy for activities conducted out of doors in fields,” and acknowledged
that the Fourth Amendment’s protections extend to structures other than homes. Similarly, in applying Oliver in United
States v. Dunn,155 the Court ruled that merely looking into a barn outside the curtilage was no search,156 but did not
challenge the defendant’s assertion “that he possessed an expectation of privacy, independent from his home’s curtilage, in
the barn and its contents, because the barn is an essential part of his business,” meaning “his barn enjoyed Fourth
Amendment protection and could not be entered and its contents seized without a warrant.”157
(e) Looking into or listening at related structures. Even if a certain related structure is protected by the Fourth Amendment
in the sense that a physical intrusion into that place would constitute a search, it does not necessarily follow that it is also a
search for the police simply to look inside that structure. In determining whether the looking was a search, the fundamental
question under Katz is whether the looking intruded upon the justified expectation of privacy of the occupant. This, in turn,
ordinarily requires consideration of two factors: (1) the location of the officer at the time of the viewing; and (2) the precise
manner in which the view was achieved.
As for the location of the officer, the easiest case is that in which the policeman is able to look inside without entering upon
the land of the owner or occupant of the garage or similar structure. It is not objectionable, for example, that the officer made
his observations from a public sidewalk158 or alley.159 As is equally true of multiple-occupancy residences,160 a somewhat
lesser expectation of privacy is likely to exist where the structure in question is divided up into separate units. Thus, where
the defendant’s garage was one of a row of garages rented to separate individuals, no intrusion into his privacy occurred
where an officer was able to look into his garage from “the common area shared by all the users of the rented garages.”161
Similarly, where one garage is partitioned off and separate sections are rented to different individuals, it is no search for an
officer to enter one section with the permission of the person renting that stall and from there to look through an opening into
defendant’s portion of the garage.162
When the view is achieved by entering upon the defendant’s property, a closer examination of the facts of the particular case
is essential. Especially in rural or other rather open areas, the so-called open field doctrine163 may prove significant, in that a
viewing accomplished while in an open field area is not likely to be considered an intrusion upon the defendant’s justified
expectation of privacy.164 Instructive in this regard is Fullbright v. United States,165 where federal investigators came upon
the farm of one Marzett and while there looked through the open door of a shed and saw three persons operating a still
therein. In concluding that this was not a search, the court in Fullbright commented:
When the investigators made their initial observation, the door to the shed was open and its light was sufficient to
reveal what was going on. The extent of the investigators’ action at the time was to look. And the use of binoculars
did not change the character or admissibility of the evidence or information gained.166 It has been consistently held
that open fields are not protected by the Fourth Amendment. The investigator here did not make a “search” of any
papers, houses, persons, or effects in the usual sense but rather made distant observations of a house and shed the
direct search of which we shall assume would have been constitutionally prohibited without a warrant as being within
the “curtilage”. If the investigators had physically breached the curtilage there would be little doubt that any
observations made therein would have been proscribed. But observations from outside the curtilage of activities
within are not generally interdicted by the Constitution. Indeed, to so hold might require passing officers to close their
eyes to the commission of felonies on front doorsteps. … By this we do not mean to say that surveillance from outside
a curtilage under no circumstances could constitute an illegal search in view of the teachings of Katz v. United States
…. It is our opinion, however, that on the record before us in light of Hester167 the observations in question may not
be deemed an unreasonable search if they were made from outside the curtilage of the Marzett farm.
191

Although the open fields-curtilage distinction will often be helpful in this context, Fullbright correctly cautions that this
distinction as to the character of the property on which the officer was positioned will not inevitably be controlling. The
ultimate judgment to be made under Katz is whether, by taking that position, the officer intruded upon a privacy expectation
deserving of Fourth Amendment protection.168 In United States v. Minton,169 for example, officers stationed themselves at
the top of a 12–14 foot embankment about 80–90 feet away and from there, with the aid of binoculars, saw illicit liquor
plainly visible in a truck and through the open doorway of a building. Although it was unclear whether the embankment
belonged to Minton, the court declared that
even if it did, such a location at such a distance is probably not within the curtilage. … More important than
the rubric of realty … there was here, we think, no reasonable expectation of privacy—considering the time of
day and all the surrounding circumstances.
If the officer was in closer proximity to the structure, as commonly is the case when the events occur in an urban setting, it
must be considered just how private the particular vantage point actually was. It is not objectionable for an officer to come
upon that part of the property which “has been opened to public common use.”170 The route which any visitor to a residence
would use is not private in the Fourth Amendment sense, and thus if police take that route “for the purpose of making a
general inquiry”171 or for some other legitimate reason,172 they are “free to keep their eyes open,”173 and thus it is
permissible for them to look into a garage or similar structure from that location.174 On the other hand, if the police depart
from that route and go to other, more private parts of the curtilage in order to look into a structure there,175 this constitutes a
search,176 even if the police might have been able to (but didn’t) make the same observation from outside the curtilage.177
Despite the importance of making these kinds of assessments concerning the position of the officer at the time he makes his
observations, it cannot be asserted dogmatically that the viewing is never a search whenever the police conduct in taking that
position did not itself intrude upon the defendant’s justified privacy expectation. Attention must also be given to the manner
of viewing, for the “ultimate question” put by Katz “is whether, if the particular form of surveillance practiced by the police
is permitted to go unregulated by constitutional restraints, the amount of privacy and freedom remaining to citizens would be
diminished to a compass inconsistent with the aims of a free and open society.”178 Certainly that privacy would be so
diminished if persons were put to the choice of sealing up their premises air tight or else assuming the risk that a policeman
will look in. And even if a garage is not entitled to “the special Fourth Amendment protections afforded a dwelling,”179 it is
still true that “when a citizen does as much as ordinary care requires to shield his sanctuary from strangers his constitutional
right to maintain his privacy should not be made to depend upon the resources of skillful peepers and eavesdroppers who can
always find ways to intrude.”180
When the conduct of the officer in gaining access to the vantage point is itself unobjectionable, privacy interests are not
threatened by allowing the officer so positioned to use his naked eye181 to look into a garage, barn or shed through an open
door182 or an uncovered window.183 In such a case, it cannot be said that the occupant of those premises has done “as much
as ordinary care requires.” But when the premises are more carefully secured and the officer consequently has to resort to
other techniques, there comes a point at which the surveillance deserves to be characterized as a search and thus brought
within the restraints of the Fourth Amendment.184 And this can be so even as to structures not technically within the
curtilage, as is illustrated by United States v. Dunn.185 To look into a barn fifty yards from the curtilage boundary, agents
crossed four fences and then used a flashlight to look through a fishnet covering to determine what was inside. In holding that
notwithstanding the Supreme Court’s generous “open fields” rule of Oliver v. United States186 this was a search, the court
noted it had “found no case … applying the term [open fields] to a building of any consequence.”187 The court in Dunn quite
correctly emphasized that a
barn is as much a part of a rancher’s place of business as a warehouse or outbuilding is part of an urban
merchant’s place of business. It is and ought to be constitutionally protected from warrantless searches if the
owner or occupier takes reasonable steps to effect privacy.
The court of appeals in Dunn later declined to rely on that reasoning and instead claimed the barn was within the curtilage,188
a holding the Supreme Court reversed in United States v. Dunn.189 Examining several “factors” deemed to bear upon the
“open fields”-curtilage distinction, the Court first concluded that the barn in fact was outside the curtilage.190 The importance
of that conclusion, in the majority’s judgment, was that consequently the officers at the time of their viewing were
themselves outside the curtilage and thus could not have been engaging in Fourth Amendment activity. Why Because
“under Oliver and Hester, there is no constitutional difference between police observations conducted while in a public place
and while standing in the open fields.”190.1 Dunn thus was governed by the previous Term’s decision in California v.
192

Ciraolo,191 involving aerial surveillance into a curtilage yard.192
The two dissenters in Dunn concluded that the barn was in the curtilage and that, even if it were not, the police activity
intruded upon the defendant’s reasonable expectation of privacy. They wisely concluded:
The Fourth Amendment prohibits police activity which, if left unrestricted, would jeopardize individuals’
sense of security or would too heavily burden those who wished to guard their privacy. In this case, in order to
look inside respondent’s barn, the DEA agents traveled a half-mile off a public road over respondent’s fencedin
property, crossed over three additional wooden and barbed wire fences, stepped under the eaves of the barn,
and then used a flashlight to peer through otherwise opaque fishnetting. For the police habitually to engage in
such surveillance-without a warrant-is constitutionally intolerable.
Although courts have given less than adequate attention to that point,193 it is useful here to take note of the carefully reasoned
opinion in United States v. Vilhotti.194 In that case, an officer standing in a service alley abutting a garage was able, with the
aid of a flashlight, to peer through a small space between the boards covering a rear window and see stolen goods stored
therein. Finding that these facts presented “a close question under the Fourth Amendment,” the court reasoned that
to ascertain what constitutes an unreasonable search the court must evaluate a person’s efforts to insure the
privacy of an area or activity in view of both contemporary norms of social conduct and the imperatives of a
viable democratic society. …
The two most important variables in deciding whether a visual search contravenes the Fourth Amendment are
accessibility to view and the nature of the premises. Thus, for example, “objects falling within the plain view of an
officer who has a right to be in the position to have that view” are not constitutionally protected. … While Kelly’s
vantage point was a well-travelled public right of way, it would be distorting the “plain view” doctrine to hold that it
encompasses peering through cracks in a boarded window. …
The photographs submitted in evidence by the government show, however, that the gaps between the boards covering
the windows were readily apparent to any passerby. The fact that private citizens have peered through these gaps does
not necessarily permit a government agent to do the same. … But under Katz, an agent is permitted the same license
to intrude as a reasonably respectful citizen would take. Therefore, the nature of the premises inspected—e.g.,
whether residential, commercial, inhabited or abandoned—is decisive; it determines the extent of social inhibition on
natural curiosity and, inversely, the degree of care required to ensure privacy. Here, given that an unattached garage
was the object of search, neither social nor physical barriers were sufficient to protect its interior from intrusion by a
casual observer. Kelly’s flashlight search, therefore, did not encroach upon defendants’ reasonable expectations of
privacy. Indeed, it is not unlikely that police officers would routinely make such inspections as part of their
peacekeeping functions.195
Without suggesting that the result ultimately reached in Vilhotti is beyond dispute,196 the fundamental approach taken
deserves to be emulated by other courts. The court in Vilhotti asks the right kinds of questions-questions which must be
answered in order to keep faith with Katz.
Yet another type of situation which has been addressed by the Supreme Court is that in which the looking into a related
structure occurs from the vantage point of an aircraft. In Florida v. Riley,197 an officer in a helicopter hovering 400 feet
above defendant’s residence looked into a partially covered greenhouse in the backyard and saw marijuana plants. Relying on
California v. Ciraolo,198 the Court held no search had occurred. In Ciraolo, involving a viewing into defendant’s fenced back
yard from a fixed-wing aircraft flying at 1,000 feet, the Court reached the highly questionable199 conclusion that defendant
had no reasonable expectation of privacy because “any member of the public flying in this airspace who glanced down could
have seen everything that these officers observed.” A four-Justice plurality in Riley reached the conclusion, surely no less
vulnerable than that in Ciraolo, that “any member of the public could legally have been flying over Riley’s property in a
helicopter at the altitude of 400 feet and could have observed Riley’s greenhouse.”
Is there any form of aerial surveillance without sense-enhancing devices200 which does constitute a “search” so as to be
subject to Fourth Amendment limitations The Riley plurality appears to assume the answer is yes,201 but is not very helpful
as to what additional facts will push a case across the Fourth Amendment line. Somewhat curiously, they note that there was
no “intimation here that the helicopter interfered with respondent’s normal use of the greenhouse or of other parts of the
curtilage. As far as this record reveals, no intimate details connected with the use of the home or curtilage were observed, and
there was no undue noise, no wind, dust, or threat of injury.”202 Also, all members of the Court seem to agree that flights at
193

some particular altitude could be sufficiently “rare” to make a householder’s expectation of privacy reasonable, but there is
no agreement on just what degree of rarity is required203 or on who has to prove what on the degree-of-rarity issue.204
(f) Entry of adjoining lands. Certain lands adjacent to a dwelling205 called the “curtilage” have always been viewed as
falling within the coverage of the Fourth Amendment.206 This is still the case under the approach to Fourth Amendment
issues adopted by the Supreme Court in Katz v. United States207 As for the extent of the home’s curtilage, the Supreme Court
in United States v. Dunn208 decided
that curtilage questions should be resolved with particular reference to four factors: the proximity of the area claimed
to be curtilage to the home, whether the area is included within an enclosure surrounding the home, the nature of the
uses to which the area is put, and the steps taken by the resident to protect the area from observation by people
passing by.209
But under the Katz approach, certain observations (albeit not into the residence or some other structure) made while the
police are within the curtilage are covered by the Fourth Amendment,210 while some others are not, depending upon whether
there was an intrusion upon a justified expectation of privacy. In making that judgment, perhaps the most important
consideration is precisely where on the adjacent lands the police were positioned. This is because a portion of the curtilage,
being the normal route of access for anyone visiting the premises, is “only a semi-private area.”211 As elaborated in State v.
Corbett212:
People commonly have different expectations, whether considered or not, for the access areas of their
premises than they do for more secluded areas. Thus, we do not place things of a private nature on our front
porches that we may very well entrust to the seclusion of a backyard, patio or deck. In the course of urban life,
we have come to expect various members of the public to enter upon such a driveway, e.g., brush salesmen,
newspaper boys, postmen, Girl Scout cookie sellers, distressed motorists, neighbors, friends. Any one of them
may be reasonably expected to report observations of criminal activity to the police …. If one has a reasonable
expectation that various members of society may enter the property in their personal or business pursuits, he
should find it equally likely that police will do so.
Thus, when the police come on to private property to conduct an investigation213 or for some other legitimate purpose214 and
restrict their movements to places visitors could be expected to go (e.g., walkways,215 driveways,216 porches217),
observations made from such vantage points are not covered by the Fourth Amendment.218 But other portions of the lands
adjoining the residence are protected, and thus if the police go upon these other portions and make observations there, this
amounts to a Fourth Amendment search,219 and this is so even if these other portions are themselves clearly visible from
outside the curtilage.220 (However, legitimate police business may occasionally take officers to parts of the premises not
ordinarily used by visitors.221)as “where knocking at the front door is unsuccessful in spite of indications that someone is in
or around the house.”221.1
Account must also be taken of the nature of the premises. Whether considered from the perspective of the curtilage
concept222 or the more modern justified-expectation-of-privacy approach,223 it is a fair generalization that the lands adjoining
a multiple-occupancy residence are less likely to receive Fourth Amendment protection than the yard of a single-family
residence. Under the Katz test, the privacy expectation as to such an area is often diminished because it is not subject to the
exclusive control of one tenant and is utilized by tenants generally and the numerous visitors attracted to a multipleoccupancy
building. Thus, it has been held that tenants in an apartment building have no justified expectation of privacy as to
“a portion of the home which all residents and visitors must use to enter,”224 “the common yard open to the public”225 or the
parking lot open to all users of the apartment building.226
This is not to say, however, that tenants in multiple-occupancy buildings may never have a protected privacy expectation as
to adjoining lands merely because no one tenant has exclusive control. Just as the tenants in such a building may have a
collective expectation of privacy vis-a-vis the general public in their corridors and hallways because of the manner in which
the building is secured,227 they will sometimes have a protected collective expectation as to certain areas outside. A case in
point is Fixel v. Wainwright,228 where an officer entered a fenced backyard behind a four-unit apartment building and
discovered a bag of heroin there. To the government’s argument that “the multi-unit character of this residence results in a
relinquishment of any right of privacy relating to the backyard,” the court responded:
The backyard of Fixel’s home was not a common passageway normally used by the building’s tenants for gaining
access to the apartments. … Nor is the backyard an area open as a corridor to salesmen or other businessmen who
might approach the tenants in the course of their trade. … This apartment was Fixel’s home, he lived there and the
194

ackyard of the building was completely removed from the street and surrounded by a chain link fence. … While the
enjoyment of his backyard is not as exclusive as the backyard of a purely private residence, this area is not as public
or shared as the corridors, yards or other common areas of a large apartment complex or motel. Contemporary
concepts of living such as multi-unit dwellings must not dilute Fixel’s right to privacy any more than is absolutely
required. We believe that the backyard area of Fixel’s home is sufficiently removed and private in character that he
could reasonably expect privacy.229
Yet another relevant consideration is the precise manner the police observation occurs, especially the degree of scrutiny
which is involved. In those cases saying, in effect, that no justified expectation of privacy was intruded upon because the
police entered as would a tradesman or any other visitor, it is ordinarily the case that the police merely saw from their vantage
point what would have been readily apparent to anyone coming upon the premises. Illustrative is State v. Detlefson,230 where
police came on the front porch and saw marijuana plants there; the court understandably said that defendant had no
“reasonable expectation of privacy in the front porch of his home where, presumably, delivery men and others were free to
observe the plants there.” Delivery men, unlike the police, might not have recognized the plants as marijuana, but that is not
significant, as the critical fact is that the police did not do anything on the porch that any other visitor would be unlikely to
do. When that is not the case, the expectation-of-privacy issue deserves another look.
An excellent example is provided by Wattenburg v. United States,231 where the defendant, who resided at and operated a
certain motel, claimed that federal officers conducted an illegal search when they examined a stockpile of cut trees near the
motel and determined that the trees had been removed from government lands without authority. The stockpile was twenty to
thirty-five feet from the motel, but was only five feet from a parking area used by personnel and patrons of the lodge. The
court first reached the dubious conclusion232 “that the stockpile of Christmas trees here in question was within the curtilage
of Wattenburg’s abode at the Hideaway Lodge, and therefore, at least as to him, protected by the Fourth Amendment,” and
then proceeded to assess the facts under the “more appropriate” Katz test. The court concluded that the conduct of the agents
was also a search under that test, which would seem equally dubious if a mere observation of the Detlefson type had
occurred, for it would not seem that motel grounds so close to the much-used parking area could themselves be characterized
as private. But more than a casual observation was involved, and this made the difference:
Measured by the test we suggest, Wattenburg was, without doubt, protected by the Fourth Amendment from a
warrantless search and seizure of the kind described above. In the daytime and in the dark, from 2:35 p.m. to
9:00 p.m. on November 8, 1965, several law enforcement officials meticulously went through the stockpile of
trees …. It must have been necessary to move most of the trees from one place to another in order to make the
kind of examination which the officers carried on. Lights must have been required as the men moved about
after dark and there was undoubtedly a certain amount of noise. There can be no doubt that Wattenburg, in
placing the stockpile this close to his place of residence, sought to protect it from this kind of governmental
intrusion.
Whether the foregoing analysis can in all respects be squared with the Supreme Court’s more recent decision in Oliver v.
United States233 is not entirely clear. In the course of reaffirming the “open fields” doctrine,234 the Court there seemed to
attach greater significance to the common law “curtilage” concept than had, for example, the lower court in Wattenburg. The
Supreme Court in Oliver asserted that the curtilage, as distinguished from open fields, is “part of the home itself for Fourth
Amendment purposes,” and that “Fourth Amendment protection” extends to the curtilage as “defined [by] the common law.”
But the Court stressed also that this definition necessitates “reference to the factors that determine whether an individual
reasonably may expect that an area immediately adjacent to the home will remain private.” This suggests that it is still quite
proper to take into account the nature of the premises in the manner previously described, but it is less apparent that the
precise manner of the police observation remains as a separate consideration.
(g) Looking into or listening at adjoining lands. If, as concluded above, there are certain parts of the grounds surrounding a
residence which are private in the Katz sense, so that a physical intrusion upon them is covered by the Fourth Amendment, it
remains to be determined whether it is also a search to view objects or activities on those grounds or to overhear
conversations occurring on those grounds while at some other location. In many instances the answer is no,235 but this is not
inevitably so; depending upon the circumstances of the individual case, it may appear that the occupant of the premises in
question had a justified expectation of privacy against such intrusions.
195

Certainly no justified expectation is present when the physical facts are such that the incriminating objects or activities were
readily visible to persons on the public way236 or neighboring lands.237 Illustrative is State v. Pontier,238 where police, after
receiving an anonymous tip that marijuana was growing in the back yard of a certain residence, entered a neighbor’s back
yard with permission and from there looked over a short picket fence and through some overhanging foliage and saw
marijuana plants. Noting that in Katz the Court had stated that “[w]hat a person knowingly exposes to the public, even in his
own home or office, is not a subject of Fourth Amendment protection,” the Pontier court concluded:
The back yard of appellant’s home was enclosed by a waist high picket fence and foliage growing at various
locations along the fence. Planting marijuana plants in a back yard enclosed only by a picket fence and
intermittent vegetation is not an action reasonably calculated to keep the plants from observation since it is
certainly foreseeable that a reasonably curious neighbor, while working in his yard, might look over the picket
fence into appellant’s yard and see the plants, whether or not he knew what they were.
More difficult are those cases in which the yard is much better secured from outside viewing and the police consequently
have to engage in conduct which arguably exceeds that which could be expected of “a reasonably curious neighbor.”
Consider, for example, the facts of United States v. McMillon,239 where the back yard was enclosed by a six-foot high stake
fence overgrown with vines and bushes. The officers managed to pierce this visual barrier by standing on a neighbor’s back
porch, which was separated from defendant’s porch by a partition and was slightly recessed from defendant’s porch. One
officer was able to photograph the plants in the yard by standing on his toes or a box, but the other officer testified that he
was able to videotape the plants by aiming the camera over the fence while holding it at eye level. The court concluded that
no search had occurred:
There is no doubt that the officers had the right to stand on the porch, having been invited to do so by occupants of the
premises.240 Nor are the indications that some of the observations were made by the officers while standing on their
toes, or leaning around the side of the partition, or perhaps standing on a box on the porch sufficient to constitute their
actions a search within the proscriptions of the Fourth Amendment. As stated by Judge Leventhal in James v. United
States241 …: “That the policeman may have to crane his neck, or bend over, or squat, does not render the doctrine
inapplicable, so long as what he saw would have been visible to any curious passerby.”
If it is true that one of the officers was able to make the observations from eye level, then the result reached in McMillon may
be correct. The case comes very close, however, to the limit of non-search surveillance. Although admittedly yards are not as
private as houses, “the amount of privacy and freedom remaining to citizens would be diminished to a compass inconsistent
with the aims of a free society”242 if all such nontrespassory observations were unregulated by constitutional restraints.
Surely there comes a point at which it can be said that the householder has done all that can be reasonably expected of him to
keep his yard private, even though the police by some extraordinary measure have been able to breach that privacy without
physical entry. Thus, if a person has surrounded his property with a solid wooden fence eight feet high,243 it is fair to say that
he has a justified expectation of privacy there even if the police are able to locate some small crack or knothole by which to
peer inside.244 Similarly, if the police can view the incriminating object in defendant’s back yard only by squeezing into a
narrow area between the neighbor’s garage and defendant’s fence, almost blocked off by heavy foliage and weeds, and from
that vantage point using a telescope,245 such viewing deserves to be characterized as a search under the Katz test.246
Sometimes the incriminating object or activity is not observable from a neighbor’s land, but can be (and is) seen from some
other portion of the defendant’s land. In such circumstances, the “open fields” doctrine247 comes into play, so that such
viewing by the police is unobjectionable-even if what is seen is itself within the protected area called the “curtilage”-if the
police vantage point was itself in the “open fields.” Illustrative is State v. Rogers,248 where police came onto defendant’s
tract of wooded property and viewed marijuana plants growing in the garden near his house. Though the garden itself was
deemed to be within the curtilage, the court concluded no search had occurred because, in cases of this genre, “the place of
observation is normally more important than the place observed.”249 In reaching that holding, the court emphasized “the
absence of two factors that could have changed our conclusion: affirmative action by defendants to block observation of the
garden from the surrounding woods and use of technology by the trooper to aid his observation.”
Sometimes the police obtain a view of residential lands from the air by using a helicopter or an airplane.250 Two California
cases illustrate the possibilities. In People v. Sneed251 officers saw marijuana plants growing in defendant’s back yard from a
helicopter which hovered as low as 20 to 25 feet above the property; in People v. Superior Court252 an officer using
binoculars saw stolen auto parts in defendant’s back yard from a plane which flew over the area at an altitude of about 500
196

feet. The viewing from the helicopter was held to be a search, while the observation from the plane was held not to be a
search.
When considered from the perspective of the Katz test, the two decisions are not inconsistent. In Sneed, the court reasoned
that
[w]hile appellant certainly had no reasonable expectation of privacy from … airplanes and helicopters flying
at legal and reasonable heights, we have concluded that he did have a reasonable expectation of privacy to be
free from noisy police observation by helicopter from the air at 20 to 25 feet and that such an invasion was an
unreasonable governmental intrusion into the serenity and privacy of his back yard.
In the other case, by comparison, the court noted:
Patrol by police helicopter has been a part of the protection afforded the citizens of the Los Angeles
metropolitan area for some time. The observations made from the air in this case must be regarded as routine.
An article as conspicuous and readily identifiable as an automobile hood in a residential yard hardly can be
regarded as hidden from such a view.
But these two cases do not suggest that whether the aerial surveillance is or is not a search should be determined merely by
the altitude of the aircraft. The fundamental question is whether this surveillance permitted the police to see that which the
occupant justifiably believed was private. In Superior Court, therefore, it would seem highly relevant that the officers in the
airplane saw a large object which was readily observable by the defendant’s neighbors.253 By contrast, in Sneed it was not
conclusively established that the marijuana plants could have otherwise been observed without intruding onto protected
property.254 But some later lower court cases seemed to proceed as if it was simply a matter of whether the surveilling
aircraft was at a lawful height.255
More and more cases of this genre reached the courts, with the ultimate result of “doctrinal incoherence and conflict among
the court decisions”256 on just how Katz applied to aerial surveillance of the curtilage. As for whether society is prepared to
recognize the dweller’s actual expectation of privacy as reasonable,
courts have taken two sharply conflicting approaches. The first, best described as the “reasonable passerby” approach,
holds that if a dweller has exhibited an expectation of privacy, the reasonableness of the dweller’s expectation must
then be determined by comparing the nature and conduct of the aerial surveillance with the range of normal aerial
behavior of the public in the vicinity. The second approach, best described as the “reasonable per se” approach, holds
that if a dweller has exhibited an expectation of privacy, it is per se one that society will find may not reasonably be
violated from the air.257
Then came California v. Ciraolo,258 where police, proceeding on an anonymous tip that defendant was growing marijuana in
his backyard, surrounded by a 6-foot outer fence and 10-foot inner fence, flew over the property at an altitude of 1,000 feet
and saw marijuana plants 8 to 10 feet in height, which they photographed with a standard 35 mm. camera. The observation,
on which a search warrant was thereafter grounded, was held by the court of appeals to be an illegal search, but the Supreme
Court, in a 5-4 decision, disagreed. Stating the question as “whether naked-eye observation of the curtilage by police from an
aircraft lawfully operating at an altitude of 1,000 feet violates an expectation of privacy259 that is reasonable,” the majority
responded:
The observations by Officers Shutz and Rodriguez in this case took place within public navigable airspace, see 49
U.S.C.App. § 1304, in a physically nonintrusive manner; from this point they were able to observe plants readily
discernable to the naked eye as marijuana. That the observation from aircraft was directed at identifying the plants and
the officers were trained to recognize marijuana is irrelevant. Such observation is precisely what a judicial officer
needs to provide a basis for a warrant. Any member of the public flying in this airspace who glanced down could have
seen everything that these officers observed. On this record, we readily conclude that respondent’s expectation that
his garden was not protected from such observation is unreasonable and is not an expectation that society is prepared
to honor.260
As discussed earlier,261 the most sensible way to apply the Katz justified-expectation-of-privacy test is to characterize police
surveillance as a search unless it occurs from a “public vantage point” and uncovers what the person has not protected from
scrutiny by the “curious passerby.” Under that approach, the Ciraolo case should have come out the other way. The fact that
the aircraft was in “public navigable airspace” does show that the surveillance occurred from a “public vantage point,” but
197

that is all. As the four Ciraolo dissenters correctly observed,
the actual risk to privacy from commercial or pleasure aircraft is virtually nonexistent. Travelers on
commercial flights, as well as private planes used for business or personal reasons, normally obtain at most a
fleeting, anonymous, and nondiscriminating glimpse of the landscape and buildings over which they pass. The
risk that a passenger on such a plane might observe private activities, and might connect those activities with
particular people, is simply too trivial to protect against. …
… The only possible basis for this holding is a judgment that the risk to privacy posed by the remote possibility that a
private airplane passenger will notice outdoor activities is equivalent to the risk of official aerial surveillance. But the
Court fails to acknowledge the qualitative difference between police surveillance and other uses made of the air space.
Members of the public use the air space for travel, business, or pleasure, not for the purpose of observing activities
taking place within residential yards.262
It is important to note, however, that Ciraolo only holds it is no search to make a naked-eye observation into the curtilage
from navigable air space. That result, therefore, is not inconsistent with the decision in Sneed (though, at the same time, it
must be recognized that Ciraolo does not settle that any surveillance from a flight in violation of FAA regulations is by that
fact alone a search263). The Supreme Court’s more recent decision in Florida v. Riley264 supports this conclusion. In the
course of concluding that surveillance by helicopter at 400 feet was no search, the four-Justice plurality cautioned that there
was no “intimation here that the helicopter interfered with respondent’s normal use of the greenhouse or of other parts of the
curtilage. As far as this record reveals, no intimate details connected with the use of the home or curtilage were observed, and
there was no undue noise, no wind, dust, or threat of injury.”265
If it is still correct to say that the conduct in Sneed was a search, then it is certainly arguable that it would still be a search if
the same discovery had been made from a high-altitude aircraft employing sophisticated observation equipment. As noted in
Dean v. Superior Court266:
At a recent but relatively primitive time, an X-2 plane could spy on ground activity from a height of 50,000
feet. Today’s sophisticated technology permits overflights by vehicles orbiting at an altitude of several
hundred miles. Tomorrow’s sophisticated technology will supply optic and photographic devices for minute
observations from extended heights. Judicial implementations of the Fourth Amendment need constant
accommodation to the ever-intensifying technology of surveillance. In analyzing claims of immunity from
aerial surveillance by agents of government, the observer’s altitude is a minor factor. Horizontal extensions of
the occupant’s terrestrial activity form a more realistic and reliable measure of privacy than the vertical
dimension of altitude.
In this regard, it is important to take note of the companion case to Ciraolo, Dow Chemical Company v. United States,267
where the aerial surveillance did involve the use of rather sophisticated equipment-as the dissenters described it, “the finest
precision aerial camera available” which “cost in excess of $22,000.00” and “was capable of taking several photographs in
precise and rapid succession,” thus facilitating “stereoscopic examination, a type of examination that permits depth
perception,” and which produced photographs “capable of enlargement to a scale of 1 inch equals 20 feet or greater, without
significant loss of detail or resolution,” by which “it is possible to discern equipment, pipes, and power lines as small as ½
inch in diameter.” The Dow majority strongly implied that the use of such equipment was no search only because it was
directed at “a 2,000-acre outdoor manufacturing facility,” and further cautioned: “We find it important that this is not an area
immediately adjacent to a private home, where privacy expectations are most heightened.” In addition, the Court asserted
“that surveillance of private property by using highly sophisticated surveillance equipment not generally available to the
public, such as satellite technology, might be constitutionally proscribed absent a warrant.”268 Reading Ciraolo with Dow,
then, by no stretch of the imagination can it be asserted that the Court has manifested its approval of aerial surveillance of the
curtilage which involves use of sophisticated sense-enhancing equipment.
In the not too distant future, the question may be whether police surveillance from an unmanned aircraft system constitutes a
Fourth Amendment search. Such systems, as compared with manned airplanes and helicopters, “bear unique risks to society’s
expectation of privacy,” as they are “practically invisible at altitudes where a manned aircraft could be seen from the
ground,” “operate almost silently, making them significantly harder to detect,” and, especially, have “the ability to hover or
circle in the sky for hours” and thus “present a potential for intrusion far more pervasive than the merely flyover of a plane or
helicopter.”268.1 Given these characteristics, it has understandably been contended that “UAS surveillance of the curtilage of
the home is an unconstitutional search within the meaning of the Fourth Amendment.”268.2 But it is less than certain that such
198

cases as Ciraolo, Riley and Dow mandate such a conclusion,268.3 and thus it remains “speculative at best.”268.4
Instances of aural surveillance which result in the police overhearing conversations occurring outside but near residential
premises must be analyzed in essentially the same fashion. Certainly “one who lives in a built-up city or suburban
neighborhood must expect that his conversations in his home or in his yard may be audible to his neighbors or to
passersby.”269 Thus, if police in such circumstances are able to hear such conversations with the naked ear while in a
neighbor’s yard, this would not constitute a search under Katz. In a rural setting, if the eavesdropping officers were
positioned in an “open field” and did not physically intrude into the curtilage, then it would appear that what they hear with
the unaided ear is no search.270 But the use of electronic eavesdropping equipment brings the police conduct within Katz
even when the conversations are in the open rather than, as in Katz, an enclosed space.271
Westlaw. © 2011 Thomson Reuters. No Claim to Orig. U.S. Govt. Works.
Footnotes
a0 David C. Baum Professor Of Law Emeritus, And Professor Emeritus In The Center For Advanced Study, The University Of
Illinois.
1 Katz v. United States, 389 U.S. 347, 88 S.Ct. 507, 19 L.Ed.2d 576 (1967).
2 E.g., Silverman v. United States, 365 U.S. 505, 81 S.Ct. 679, 5 L.Ed.2d 734 (1961).
3 See Hafetz, “A Man’s Home Is His Castle”: Reflections on the Home, the Family, and Privacy During the Late Nineteenth and
Early Twentieth Centuries, 8 Wm. & Mary J.Women & L. 173 (2002).
4 Silverman v. United States, 365 U.S. 505, 81 S.Ct. 679, 5 L.Ed.2d 734 (1961).
5 E.g., Clinton v. Virginia, 377 U.S. 158, 84 S.Ct. 1186, 12 L.Ed.2d 213 (1964).
6 E.g., Stoner v. California, 376 U.S. 483, 84 S.Ct. 889, 11 L.Ed.2d 856 (1964).
“Private sleeper cars on passenger trains are comparable to hotel rooms in that the occupant enjoys a heightened expectation of
privacy.” United States v. Dimick, 990 F.2d 1164 (10th Cir.1993).
E.g., Commonwealth v. Lopez, 458 Mass. 383, 937 N.E.2d 949 (2010).
7 E.g., McDonald v. United States, 335 U.S. 451, 69 S.Ct. 191, 93 L.Ed. 153 (1948).
Commonwealth v. Porter P., 456 Mass. 254, 923 N.E.2d 36 (2010) (defendant had reasonable expectation of privacy in room he
shared with mother at homeless shelter, even though his use of room was limited and shelter staff had master key and could enter
“for professional business purposes”).
8 Jones v. State, 648 So.2d 669 (Fla.1994); People v. Brown, 88 Cal.App.3d 283, 151 Cal.Rptr. 749 (1979); State v. Stott, 171 N.J.
343, 794 A.2d 120 (2002) (where defendant shared room at state-run psychiatric hospital under circumstances where his “stay
would be of some duration,” and “defendant’s room had many of the attributes of a private living area and … had served as such a
place throughout defendant’s occupancy,” “defendant had a reasonable expectation of privacy in the area searched by the police,”
who looked within hem of curtain, though “case might be different if the police had searched [deceased roommate’s] personal
wardrobe”); Morris v. Commonwealth, 208 Va. 331, 157 S.E.2d 191 (1967).
8.1 One commentator objects that the “Fourth Amendment has disproportionately protected residential privacy rights on the basis of
property law concepts and the rhetoric of the inviolate physical home,” and “advocate[s] replacing housing exceptionalism and
formalistic property approaches with a strong and consistent doctrinal focus on harm to substantive privacy and intimate
association.” Stern, The Inviolate Home: Housing Exceptionalism in the Fourth Amendment, 95 Cornell L.Rev. 905, 955–56
(2010).
9 See § 11.3(a).
When the question is one of standing, the perspective of the inquiry regarding the “abandonment” changes. “The object of
measurement shifts from reasonable appearances to historic reality. What finally matters shifts from what the policeman
reasonably believed out on the street to what the suppression hearing judge ultimately knows in the courtroom.” Faulkner v. State,
317 Md. 441, 564 A.2d 785 (1989). See also Oken v. State, 327 Md. 628, 612 A.2d 258 (1992) (thus all facts presented to court at
time of hearing relevant).
10 See § 8.5(a).
199

11 E.g., United States v. Wilson, 472 F.2d 901 (9th Cir.1972).
12 As for purported abandonment merely by disclaimer of ownership, see § 11.3(a).
13 United States v. Botelho, 360 F.Supp. 620 (D.Hawaii 1973).
13.1 Compare United States v. Bolden, 545 F.3d 609 (8th Cir.2008) (where police, on basis of Jan. 2003 information from defendant’s
accomplice, retrieved gun from bag under gutter on outside of residence defendant had rented, defendant without expectation of
privacy, as landlord had commenced eviction proceedings in Nov. 2002 and retook possession in Dec. 2002; court rejects
defendant’s claim “that the landlord’s history of forgiving his rent deficiencies and the fact that eviction notices were returned
undelivered gave him a reasonable expectation of privacy,” as defendant “knew he was facing eviction …, yet made no attempt to
prevent eviction and asserted no continuing possessory interest in the residence”); Marshall v. State, 232 P.3d 467
(Okla.Crim.App.2010) (where defendant “evicted from the house … approximately one month before” and “[e]verything had been
moved out except for a twin bed, some clothing and trash” and “the front door was ajar,” defendant “did not have an expectation of
privacy in the house”).
14 In People v. Stadtmore, 52 A.D.2d 853, 382 N.Y.S.2d 807 (1976), the landlord instituted a summary proceeding which culminated
in the issuance of a warrant to evict the defendant for nonpayment of rent. As the defendant was finishing packing and moving his
effects into the hallway, two officers entered and searched the apartment. Though the state contended that “the landlord-tenant
relationship terminates upon the issuance of a warrant to evict,” the court held: “Until the moment of his actual eviction defendant,
regardless of his technical status under property law, was lawfully occupying the apartment in question. In our view, respondent
seeks to convert civil process into a warrant for a general search. In short, the single fact of non-payment of rent should not result
in the forfeiture of one’s Fourth Amendment rights.
“Turning to the District Attorney’s remaining contentions, we note that a defendant’s reasonable expectation of privacy has been
considered a factor in determining the reasonableness of a warrantless search …. In terms of reasonable expectations, we do not
believe that a tenant who is about to be evicted should anticipate that police officers will be present to conduct a general search for
contraband on the pretense of insuring the total removal of his belongings ….”
See also United States v. Sanford, 493 F.Supp. 78 (D.D.C.1980) (where marshal executed writ of restitution for nonpayment of
rent, tenant “was entitled to an expectation that his personal effects and property would be not subject to a full-scale exploratory
search even though they would be displaced and removed to the public street”); Boone v. State, 39 Md.App. 20, 383 A.2d 412
(1978) (where landlord pursues statutory procedure for repossession, this terminates tenant’s expectation of privacy in apartment,
but diminished his expectation of privacy as to his effects only to extent necessary for removal of them); State v. McNichols, 106
Nev. 651, 799 P.2d 550 (1990) (where defendant “lost his legal interest in the property when it was foreclosed” and “lost his
possessory interest in the property when he was evicted,” and “new owner changed the locks, and the constable’s office placed
court seals on the entry,” defendant’s “trespassory re-entry did not create an objective expectation of privacy”).
Compare United States v. Buchanan, 633 F.2d 423 (5th Cir.1980) (no expectation of privacy where search was one month after
tenant failed to pay rent, lease said it expired 5 days after nonpayment, and 10 days before search landlord changed the locks).
14.1 Although the law may recognize that certain legal processes may be combined with some degree of self-help, in which case those
processes plus the self-help will likely be deemed sufficient to work an abandonment. See Laney v. State, 379 Md. 522, 842 A.2d
773 (2004) (where defendant purchased improved real property and, to finance purchase acquired loan secured by mortgage on
purchased property, after which defendant failed to make payments according to loan agreement, following which necessary legal
steps to terminate the mortgagor’s interest in and right to possession of the property—notice, foreclosure, sale, and judicial
ratification—were taken, so that the law then recognizes that the purchaser may either obtain a court order to remove holdover
mortgagor or take possession of the property peacefully without court’s assistance and purchaser did latter, that made defendant a
trespasser without any reasonable expectation of privacy in the premises, considering (i) that he “no longer had any right to occupy
the premises,” (ii) that defendant “had been notified that the foreclosure sale would take place,” and (iii) that state law did not
require new owner “to pursue some additional judicial remedy to evict”).
15 Bloodworth v. State, 233 Ga. 589, 212 S.E.2d 774 (1975). See also United States v. Levasseur, 816 F.2d 37 (2d Cir.1987)
(defendants had abandoned the premises notwithstanding their failure to take their weapons, clothing and personal belongings;
“subsequently discovered events may support an inference that appellants had already chosen, and manifested their decision, not to
return,” and such the case here, as all circumstances indicated that when they learned of arrest of confederates elsewhere they fled
to another city to avoid arrest and thus “forfeited their reasonable expectation of privacy”); United States v. De Parias, 805 F.2d
1447 (11th Cir.1986) (defendant had abandoned his apartment when he left for another city and told his girl friend, with whom he
shared apartment, that he was not returning; though he “fled Miami to avoid capture, a lawful police investigation does not
constitute such coercion that the abandonment should be considered involuntary”); People v. Morrison, 196 Colo. 319, 583 P.2d
924 (1978) (though defendant had moved into apartment 1 week ago and paid half of first month’s rent and security deposit,
200

premises were abandoned where all clothing, bedding and personal effects had been removed, the only items found were in trash
pile, and defendant never returned to apartment or paid balance of first month’s rent but instead left the state); State v. Grissom,
251 Kan. 851, 840 P.2d 1142 (1992) (where defendant, who used storage locker with Thibido in painting business, told Thibido
that he going to California and was giving Thibido “complete custody and control of the painting business,” and Thibido later
found the lock securing the locker was gone, and defendant with Thibido’s help loaded most of his personal effects from his
apartment into his car and, before departing, told Thibido he “could have the remaining contents of the apartment,” defendant had
abandoned the locker and apartment even if rental periods had not expired).
Compare People v. Brewer, 690 P.2d 860 (Colo.1984) (where rent on month-to-month tenancy overdue but defendant’s effects
known to still be there and defendant had arranged to move them out the coming weekend without objection from landlord, this
showed a continued expectation of privacy and no abandonment).
United States v. Stevenson, 396 F.3d 538 (4th Cir.2005) (where defendant rented his apartment on week-to-week basis and was
behind in rent but landlord did not attempt to evict him and indicated he could pay rent later, defendant deemed to have abandoned
the apartment after his arrest, as he manifested intention not to return by letter to his girlfriend, giving her ownership of the
personal property in his apartment and referring to himself as the “former renter”).
16 State v. Christian, 95 Wash.2d 655, 628 P.2d 806 (1981).
17 United States v. Wilson, 472 F.2d 901 (9th Cir.1972).
Compare Wilson v. Health & Hospital Corporation of Marion Co., 620 F.2d 1201 (7th Cir.1980) (with respect to owner of the
property, one is not required to “keep his doors closed and locked … to maintain in full effectiveness an expectation of privacy,”
and thus corporation not entitled to summary judgment upon the “fact that the basement and apartment doors were open”).
Compare People v. Pitman, 211 Ill.2d 502, 286 Ill.Dec. 36, 813 N.E.2d 93 (2004) (where, though defendant did not own the farm,
he had possessory interest in entire farm and had ability to exclude others, and owner had conferred on defendant legal authority to
take care of the farm, barn outside the curtilage not abandoned just because doors were unlocked and wide open).
18 See also United States v. Hoey, 983 F.2d 890 (8th Cir.1993) (abandonment where defendant “personally told her landlord that she
was leaving,” she “was six weeks behind on her rent,” “held a moving sale, and her neighbor saw her leaving the apartment”);
United States v. Binder, 794 F.2d 1195 (7th Cir.1986) (business office abandoned where defendant, substantially arrears in rent,
had moved out and taken many business records); United States v. Sellers, 667 F.2d 1123 (4th Cir.1981) (defendant had no
expectation of privacy where he had departed the community, was 5 months delinquent in rental payments, and left a note for his
landlady saying he was sorry he could not pay and that he was leaving his effects behind and that she could have them); United
States v. Sledge, 650 F.2d 1075 (9th Cir.1981) (defendant gave landlord notice of intent to vacate by March 31, rent paid through
March, landlord left note for tenant to call on March 15 but no call received, on March 29 landlord saw apartment door wide open
and premises empty, landlord entered on March 30 when circumstances unchanged; held, premises abandoned); State v. Tucker,
268 Ark. 427, 597 S.W.2d 584 (1980) (defendant had no expectation of privacy where he had not been at apartment he shared with
deceased for a month, he left the state by bus without advising anyone of an intention to return, and he established residence and
obtained employment in another state); Thomas v. State, 274 Ga. 156, 549 S.E.2d 359 (2001) (where defendant not tenant of
landlord and landlord had never given permission to sublet the townhouse and two weeks earlier ordered defendant to vacate the
premises, and “townhouse was abandoned by the time of the search,” defendant “had no expectation of privacy at [that] time of the
searches”); Criss v. State, 512 N.E.2d 858 (Ind.1987) (apartment was abandoned where left empty except for trash and rent past
due); Waters v. State, 275 Ind. 182, 415 N.E.2d 711 (1981) (no expectation of privacy where tenant failed to pay rent in advance as
required by law, he moved and bought home in another town, but left a few items behind); State v. Hunt, 682 A.2d 690 (Me.1996)
(where defendant testified “that he had removed from the apartment everything that he wanted, leaving behind only ‘trash,’ and
that he left the apartment on October 5 intending never to return,” he “voluntarily abandoned his apartment and the items left
therein”); Commonwealth v. Lanigan, 12 Mass.App.Ct. 913, 423 N.E.2d 800 (1981) (where “the defendant immediately on
learning that the police were investigating him, fled from the Commonwealth with the intention of not returning to the apartment
during the short period, if any, which remained of his rental period,” he had abandoned the premises; it irrelevant that police
unaware of this, as a “relinquishment of rights by abandonment does not depend on knowledge by the police that the abandonment
has occurred”); State v. Madera, 206 Mont. 140, 670 P.2d 552 (1983) (apartment abandoned where defendant two days overdue on
rent, his car gone and curtains drawn, and landlord found key inside and personal effects gone and garbage strewn about); State v.
Hodge, 225 Neb. 94, 402 N.W.2d 867 (1987) (where defendants relinquished control of house and vacated premises when lease
ended, they had abandoned the premises and thus had no expectation of privacy as to padlocked attic); Swearingen v. State, 101
S.W.3d 89 (Tex.Crim.App.2003) (where defendant and wife decided to move from trailer to his parent’s home and landlord so
advised on Dec. 24 and both keys returned to landlord by Jan. 1, and landlord cleaned trailer on Jan. 6, defendant had abandoned
pair of pantyhose with leg missing that landlord had taken away with other trash); State v. Christian, 26 Wash.App. 542, 613 P.2d
1199 (1980), judgment aff’d, 95 Wash.2d 655, 628 P.2d 806 (1981) (defendant had no justified expectation of privacy in apartment
on June 1 where he told landlord he would not continue tenancy after May 31, defendant put personal effects in truck and drove off
on May 31, and landlord had advised him of plans to enter and clean on June 1, notwithstanding fact defendant unknownst to
landlord returned and stayed another night; fact possession not terminated per landlord-tenant statute not relevant where, as here,
201

tenant was vacating voluntarily and was not being evicted).
See also Caraballo v. State, 39 So.3d 1234 (Fla.2010) (despite “lack of a final order of eviction” defendant had abandoned
apartment where he served with a 3-day eviction notice for nonpayment of rent and thereafter “the apartment maintenance
supervisor conducted a walk-through of the apartment and determined that it had been abandoned,” following which a vendor’s
lock placed on door to allow access for cleaners and painters).
19 United States v. Parizo, 514 F.2d 52 (2d Cir.1975).
20 See also United States v. Kitchens, 114 F.3d 29 (4th Cir.1997) (“absent a pattern or practice to the contrary, a person’s legitimate
expectation of privacy in a motel room terminates at check-out time”); United States v. Huffhines, 967 F.2d 314 (9th Cir.1992)
(“guest in a motel has no reasonable expectation of privacy in a room after the rental period has expired”); United States v. Rahme,
813 F.2d 31 (2d Cir.1987) (“when a hotel guest’s rental period has expired or been lawfully terminated, the guest does not have a
legitimate expectation of privacy in the hotel room or in any articles therein of which the hotel lawfully takes possession”); United
States v. Larson, 760 F.2d 852 (8th Cir.1985) (defendant’s expectation of privacy in motel room had lapsed where he stayed 7 hrs.
past checkout time and 5 hrs. past time he allowed to stay over without paying next day’s rent in advance); United States v. Diggs,
649 F.2d 731 (9th Cir.1981) (Botelho not applicable in motel context; abandonment existed without formal notice of eviction
where defendant left owing $1,000 and was not seen or heard from thereafter and motel terminated the tenancy upon receiving
room key in the mail); Sumdum v. State, 612 P.2d 1018 (Alaska 1980) (“after the rental period has terminated, a guest’s reasonable
expectations of privacy are greatly diminished,” and thus after checkout hour motel personnel, who had been unable to reach guest
by phone or by knocking, could enter); State v. Ahumada, 125 Ariz. 316, 609 P.2d 586 (App.1980) (abandonment where defendant
failed to check out of motel at room checkout time or to pay for another day in advance, as required by motel policy); State v.
Kirksey, 647 S.W.2d 799 (Mo.1983) (where defendant’s companion paid part of hotel bill and said they had no more money and
party was leaving hotel and defendant, when questioned by police, “gave a name different from that of the room registration and
told the officers that he was not a registered guest of the hotel,” premises were abandoned); Brimage v. State, 918 S.W.2d 466
(Tex.Cr.App.1994) (“logic [of this point in Parizo] is sound and should be applied to the present case”).
United States v. Lanier, 636 F.3d 228 (6th Cir.2011) (“general rule” is that occupant’s expectation of privacy ends when the rental
period has expired or been lawfully terminated).
21 Paty v. State, 276 So.2d 195 (Fla.App.1973). In Paty, when the motel owner smelled marijuana in defendant’s room and told
defendant the police would be summoned, defendant fled to a building across the street carrying a footlocker. When the police
arrived, they saw defendant’s other personal effects in the room, but proceeded to search there and found marijuana. Defendant
returned shortly thereafter and was arrested. The trial court upheld the search on the ground that the police were justified in
assuming defendant had abandoned the premises, but this ruling was overturned on appeal: “While it is true that appellant fled
from the room carrying a footlocker, he left in the room his jacket and motorcycle helmet, and he left parked outside of the room
the motorbike. It was then well before the checkout time for the day, and appellant had already advised the manager that he wished
to have the room for another day. Within a matter of a few minutes after fleeing the scene, appellant was back sans footlocker. He
confirmed that the room was his and there is no evidence to indicate that had he not been arrested he would not have remained in
the room for some additional period of time. It would not seem reasonable, especially at that point in time, for the police officer to
assume that appellant had vacated the premises in the sense of having no apparent intention to return and make further use of them.
It is significant that there is no evidence indicating that the officer himself had assumed or believed that appellant had abandoned
or vacated the room.”
See also Farmer v. State, 759 P.2d 1031 (Okl.Crim.App.1988) (though defendant “had told the clerk to tell anyone who called that
he had checked out,” motel room not abandoned where “motel receipts showed that he had paid for another night, he had retained
his key, and he had left his belongings”).
Compare United States v. Hunter, 647 F.2d 566 (5th Cir.1981) (motel room abandoned before checkout time where defendant paid
bill in full and left motel room with room key locked inside the room); United States v. Akin, 562 F.2d 459 (7th Cir.1977) (hotel
room abandoned where tenant left door wide open and no luggage or suits were in the room); Buttrum v. State, 249 Ga. 652, 293
S.E.2d 334 (1982) (motel room abandoned, even though rent paid in advance for 2 more days, where key left on counter in office
and all personal belongings had been removed from room); State v. Oken, 569 A.2d 1218 (Me.1990) (though defendant had taken
key with him and had left a few effects—jersey, vodka, orange juice, and pair of socks-in room, room abandoned by 8:30 a.m.,
before 11 a.m. checkout; court stresses no luggage there, bed never turned down, defendant paid in advance for one night by credit
card, and defendant on prior day drove to another motel an hour away and checked in there and next day paid for extra day there);
Commonwealth v. Paszko, 391 Mass. 164, 461 N.E.2d 222 (1984) (motel room abandoned though one-week rental period had
another day to run, as defendant had already checked into another motel and had moved all his personal effects there except a few
items he apparently overlooked).
Compare United States v. James, 534 F.3d 868 (8th Cir.2008) (motel room deemed abandoned by defendant, as while motel
management only said defendant “scheduled to leave that day,” assault victim “reported that James fled with all his belongings
after the assault,” and room “contained no personal belongings”).
202

22 Young v. Harrison, 284 F.3d 863 (8th Cir.2002) (hotel eviction of unruly guests effective, so that subsequent police entry of their
room lawful, even though hotel “did not follow the procedures set out in South Dakota’s Forcible Entry and Detainer statute,” as
presumably “South Dakota would join many other jurisdictions in concluding that a hotel guest is not a tenant and is subject to
self-help eviction”); State v. Perkins, 588 N.W.2d 491 (Minn.1999) (where registration card defendant signed gave notice guest
would be “removed” if other guests were disturbed by a guest or his associates, and defendant aware of two earlier complaints and
warnings prior to the time manager asked him to leave, and of fact “the ‘party’ remained excessively loud,” defendant no longer
had a reasonable expectation of privacy in the room).
United States v. Molsbarger, 551 F.3d 809 (8th Cir.2009) (defendant had no reasonable expectation of privacy in hotel room after
manager ordered him and other occupants evicted for continued raucous behavior after prior warnings); Johnson v. State, 285 Ga.
571, 679 S.E.2d 340 (2009) (when police advised hotel manager defendant selling drugs from his room, and manager decided to
evict defendant and followed established protocol of calling room, then going to room and knocking when no answer to phone, and
then opening door when no answer to knock, defendant “lost his expectation of privacy in the hotel room when he was properly
evicted” in that manner).
Compare United States v. Bautista, 362 F.3d 584 (9th Cir.2004) (where motel manager had taken “no affirmative steps to repossess
the room once she learned that it had been reserved with a stolen credit card,” but merely “asked the police to investigate the matter
* * * and would have evicted Bautista only if he later failed to provide either a satisfactory explanation or another form of
payment,” and “manager did not ask the police to evict Bautista,” defendant “was still a lawful occupant who retained a legitimate
expectation of privacy in the room”). The court distinguished People v. Satz, 61 Cal.App.4th 322, 71 Cal.Rptr.2d 433 (1998),
where defendant used a stolen credit card to register and admitted she had no money to pay for the room, and the manager
specifically asked the police to assist her in evicting the defendant.
23 United States v. Mulder, 808 F.2d 1346 (9th Cir.1987) (defendant secured payment of bill with American Express card and
indicated one-day stay, defendant returned seeking his bag 48 hours later and hotel had billed his card for another day; no
abandonment).
24 United States v. Dorais, 241 F.3d 1124 (9th Cir.2001) (where hotel did not strictly enforce noon checkout and defendant indicated
he would stay until 12:30, abandonment occurred only after latter time).
Consider also United States v. Lanier, 636 F.3d 228 (6th Cir.2011) (citing cases in support, court notes exceptions to general rule
where defendant “ask[ed] the hotel to extend his stay” and thus “receive[d] permission from the hotel for a later check-out time,”
or where “the hotel had [a] history of acquiescing in delayed departures by” defendant, not present in this case; also, while hotel,
upon discovery of drugs in defendant’s room allowed police to search the room before one-hour “traditional grace period” had
expired, since defendant “knew nothing about the one-hour grace period” hotel free to retract it in specific cases, as where drugs
seen).
25 Commonwealth v. Strickland, 457 Pa. 631, 326 A.2d 379 (1974).
But, additional facts may show abandonment in such circumstances. See, e.g., Commonwealth v. Jackson, 384 Mass. 572, 428
N.E.2d 289 (1981) (defendant, arrested Dec. 26, had paid rent through Jan. 1, but after arrest he told cotenants to move out and
remove his belongings; this “protection of one’s belongings is not inconsistent with an intent to abandon the premises,” and thus
police entry of empty apartment in mid-January proper).
26 State v. Rhodes, 337 So.2d 207 (La.1976) (where armed robber was arrested in his motel room and at time of arrest locker with his
personal effects was taken to station, it was not “unreasonable on the succeeding day to search the motel room, the occupancy of
which had been terminated by the prior day’s arrest and incarceration of defendant on a fugitive warrant”); Commonwealth v.
Netto, 438 Mass. 686, 783 N.E.2d 439 (2003) (day after motel room occupants arrested on murder warrants, manager asked police
to take items remaining in the room; “even if the motel manager let the police into the room slightly prior to the customary
checkout time,” effects were abandoned due to “the guests’ abandonment of the room … due to their arrest on murder charges,”
and fact that the following day “they had not returned to retrieve their belongings, made any arrangements to have someone else
retrieve their belongings, or taken any steps to extend the rental period”).
27 Abel v. United States, 362 U.S. 217, 80 S.Ct. 683, 4 L.Ed.2d 668 (1960).
28 J. Cook, Constitutional Rights of the Accused—Pretrial Rights 314 (1972).
29 See § 5.5(b).
30 United States v. Croft, 429 F.2d 884 (10th Cir.1970). See also United States v. Huffhines, 967 F.2d 314 (9th Cir.1992)
(defendant’s argument he had continuing expectation of privacy in motel room “because his arrest prevented him from returning to
the motel to renew the rental agreement” rejected, as he “cannot rely on his own misconduct to extend the period of his expectation
of privacy”); United States v. Rahme, 813 F.2d 31 (2d Cir.1987) (“when a defendant has been arrested, it was presumably his ‘own
203

conduct that prevented his return to the [h]otel’ ”); United States v. Ramirez, 810 F.2d 1338 (5th Cir.1987) (makes no difference
abandonment involuntary because of defendant’s arrest); United States v. Lee, 700 F.2d 424 (10th Cir.1983) (following Croft on
similar facts); Gardner v. State, 296 Ark. 41, 754 S.W.2d 518 (1988) (after defendant’s arrest motel employees took possession of
his effects per standard procedures and later turned purse over to police on their request; held, notwithstanding fact defendant’s
“inability to return to his room was not of his own choosing,” no “expectation of privacy in the purse after employees of the Inn
had removed it from Gardner’s former room and had taken it into their possession”); Myers v. State, 454 N.E.2d 861 (Ind.1983)
(after defendant’s arrest his two-day rental of motel room expired, at which point “he no longer had an expectation of privacy” in
it); Obermeyer v. State, 97 Nev. 158, 625 P.2d 95 (1981) (defendant arrested, hotel keys found on his person, so 2 days later officer
went to hotel and searched room with hotel personnel; proper, as defendant’s rent past due, notwithstanding fact defendant’s
effects still in the room).
31 R. Anderson, The Hotelman’s Basic Law § 16:9 (1965).
32 The leading case in point is Commonwealth v. Brundidge, 533 Pa. 167, 620 A.2d 1115 (1993), where the court concluded that
while after the rental period on a motel room has run no justified expectation of privacy “exists in the room or in any item in plain
view to anyone readying the room after checkout time for the next occupant,” “a motel guest has a reasonable expectation of
privacy to the contents of discrete and concealed personal effects in a motel room after checkout time.
“While the motel personnel must have access to and use of the motel room after the rental period expires, this does not extend to
items of personal luggage or other containers which do not reveal the nature of their contents. In this case, the motel management
had no economic or other justification to examine the contents of the closed personal possessions of its guests, especially where
only a relatively short period of time had elapsed since checkout time, appellee’s car remained parked at the motel, the room
remained locked, and petitioner returned shortly thereafter to register for a second night. Therefore, the search of the jacket [found
in the closet with a protective bag over it] should have been accomplished pursuant to a judicial warrant issued upon probable
cause.”
See also United States v. Ramos, 12 F.3d 1019 (11th Cir.1994) (at end of 5-month lease of condo unit, when defendant to check
out by 10 a.m. and another renter due later that day, cleaners entered that afternoon and summoned police, who looked inside
locked briefcase; in holding lower court erred in ruling briefcase abandoned, court stresses testimony that general practice when
cleaner finds effects was “to pack the personal belongings and hold them until the owner of the items-the departing lessee-could be
located”); United States v. Huffhines, 967 F.2d 314 (9th Cir.1992) (“Although the assistant manager lacked the authority to
consent to a search of Huffhines belongings left in the room, it was not clearly erroneous for the court to find that the assistant
manager’s consent to a search of the room included the area under the mattress where the gun was found”).
See also Johnson v. State, 285 Ga. 571, 679 S.E.2d 340 (2009) (eviction from hotel room, resulting in “loss of the expectation of
privacy in the room does not mean that [defendant] had lost his expectation of privacy with regard to personal items in the room,”
but police check on bulge in jacket justified by safety concerns).
33 United States v. Rahme, 813 F.2d 31 (2d Cir.1987).
34 E.g., State v. Felger, 19 Or.App. 39, 526 P.2d 611 (1974); State v. Disbrow, 266 N.W.2d 246 (S.D.1978) (abandonment re May 1
inspection where all personal effects in defendant’s apartment destroyed in April 25 fire, defendant never paid rent for April or
May, and after living with friend for short time defendant moved to another state).
Even if the tenant is deemed to have abandoned the burned premises, it does not inevitably follow that this would cause his
“privacy interest to shift automatically to [the owner] like some reversionary property interest.” State v. Smith, 656 S.W.2d 882
(Tenn.Crim.App.1983) (no expectation of privacy in landlord, as he also made no efforts to secure the premises).
35 E.g., People v. Bailey, 42 Mich.App. 359, 202 N.W.2d 557 (1972).
The condition of the premises may have some bearing, however, upon the question of whether an arson investigation into the
premises would be a reasonable search. See § 10.4.
36 Swan v. Superior Court, 8 Cal.App.3d 392, 87 Cal.Rptr. 280 (1970). See also State v. Zindros, 189 Conn. 228, 456 A.2d 288
(1983) (no abandonment where tenant came to premises after fire several times and on leaving each time secured the premises).
37 People v. Dorney, 17 Ill.App.3d 785, 308 N.E.2d 646 (1974): “On the record before this court we cannot say that the trial court’s
finding of non-abandonment was clearly erroneous. Although the trailer was rendered uninhabitable by the fire, defendant returned
on at least one occasion to pick up salvageable items of personal property. When the defendant returned a second time for similar
reasons, the trailer had been removed by the authorities without his permission and without notice to defendant of its new location.
These facts certainly do not warrant the inference that defendant intended to abandon his trailer.”
See also State v. Hansen, 286 N.W.2d 163 (Iowa 1979) (rejecting the “habitability” standard as inconsistent with Katz and finding
a search had occurred of house not damaged extensively where defendant, temporarily housed with relatives, still had much
personal property therein).
204

37.1 McKenney v. Harrison, 635 F.3d 354 (8th Cir.2011) (reasonable for police to conclude house abandoned where they “found the
house in disrepair, with an unkept yard and a fence that was incomplete and falling apart,” there “no vehicles parked in the
driveway,” no one “responded when the officers knocked on the front door,” “back door was open” and officers “could see into
kitchen, where the cabinets were open and empty, the refrigerator was open and empty,” and “there was no furniture or personal
effects” and “no lights on, sounds from appliances, or other indications that the house had electrical power”).
Compare State v. Carter, 54 So.3d 1093 (La.2011) (no showing officers “reasonably believed that the house was abandoned, as
detective merely stated conclusion that residence was “abandoned” and “did not testify that the house appeared abandoned,” and
“officers on the scene evidently did not report that they viewed a dilapidated structure boarded up and surrounded by overgrown
weeds, or that the officer came by a belief the home had been abandoned from any other reliable basis”).
38 State v. Finnell, 115 Ohio App.3d 583, 685 N.E.2d 1267 (1996). Compare State v. Perry, 124 N.J. 128, 590 A.2d 624 (1991) (no
search for officers to enter house “that appeared vacant and whose front door was not only unlocked but open”).
39 Thus, the court added, defendant’s “privacy interest in his vacant buildings is less than that of home owners in their homes, or
business owners in their business premises.” And if, which was unknown, defendant “uses the buildings for storage,” the court
added, “the city admits that his interest would be greater than if the buildings were completely empty.”
40 Lewis v. United States, 385 U.S. 206, 87 S.Ct. 424, 17 L.Ed.2d 312 (1966).
41 Even if “very limited.” McNairy v. State, 835 S.W.2d 101 (Tex.Crim.App.1991).
See also Martin v. United States, 952 A.2d 181 (D.C.App.2008) (where unconsented police entry of house, after which defendant
retrieved weapon from closet, trial court’s “no search” ruling in error, as “the Fourth Amendment was implicated as soon as the
police entered”).
41.1 As explained in United States v. Arellano-Ochoa, 461 F.3d 1142 (9th Cir.2006), whether “opening a screen door breaches a
reasonable expectation of privacy depends on the circumstances. During winter in a cold climate, people ordinarily keep the solid
door shut. About the only way for mail and package delivery people, solicitors, missionaries, children funding school trips, and
neighbors to knock on the door is to open the screen door and knock on the solid door. People understand that visitors will need to
open the screen door, and have no expectation to the contrary. The reason why people do not feel that their privacy is breached by
opening the screen door to knock is that it isn’t; the solid door protects their privacy.
”In the summer, when people leave their solid doors open for ventilation, the screen door is all that separates the inside from the
outside. People can get a resident’s attention by knocking on the screen door without opening it. Where the solid door is wide
open, the screen door is what protects the privacy of the people inside-not just their visual privacy, which it protects only partially,
but also their privacy from undesired intrusion. Where the solid door is open so that the screen door is all that protects the privacy
of the residents, opening the screen door infringes upon a reasonable and legitimate expectation of privacy.”
42 Or, indeed, even a tent, for though “a tent may not provide the sturdy protection against the winds, the rains, the heat, and the cold
which a customary house provides, the tent-dweller is no less protected from unreasonable government intrusions merely because
his dwelling has walls of canvas rather than walls of stone.” Kelley v. State, 146 Ga.App. 179, 245 S.E.2d 872 (1978). See also
United States v. Sandoval, 200 F.3d 659 (9th Cir.2000) (defendant had expectation of privacy as to tent, closed on all 4 sides and in
area “heavily covered by vegetation and virtually impenetrable,” on Bureau of Land Management land, without regard to whether
he had permission, as “camping on public land, even without permission, is far different from squatting in a private residence,” and
defendant “was never instructed to vacate or risk eviction”); People v. Schafer, 946 P.2d 938 (Colo.1997) (defendant had
reasonable expectation of privacy as to interior of his tent where he “camping on unimproved publicly accessible land which was
neither fenced nor posted”); Alward v. State, 112 Nev. 141, 912 P.2d 243 (1996) (defendants “had an objectively reasonable
expectation of privacy in the tent,” which was “their temporary residence,” notwithstanding fact they “camped on land managed by
the Bureau of Land Management”).
Or, indeed, even a fish house, “erected and equipped to protect its occupants from the elements and often providing eating,
sleeping, and other facilities.” State v. Larsen, 650 N.W.2d 144 (Minn.2002).
Compare United States v. Ruckman, 806 F.2d 1471 (10th Cir.1986) (cave in which defendant residing on land owned by U.S. and
controlled by Bureau of Land Management not within Fourth Amendment’s protection).
For more on the expectation of privacy in tents and other camping shelters, see Note, 26 U.Mem.L.Rev. 293 (1995). For more on
the expectation of privacy of those trespassing on federal lands, as in Sandoval, see Comment, 50 Emory L.J. 1357 (2001).
See also State v. Pruss, 145 Idaho 623, 181 P.3d 1231 (2008) (defendant had reasonable expectation of privacy in his “hooch,” a
camouflaged frame structure in the woods with a backpacking tents erected inside wooden frame).
43 Katz v. United States, 389 U.S. 347, 88 S.Ct. 507, 19 L.Ed.2d 576 (1967).
205

44 United States v. Moss, 963 F.2d 673 (4th Cir.1992).
45 Lewis v. United States, 385 U.S. 206, 87 S.Ct. 424, 17 L.Ed.2d 312 (1966).
46 See § 8.2(m).
47 On who may consent, see §§ 8.4, 8.5. As noted there, some persons who could not give a valid consent to a full search of the
residence (e.g., children residing there) might nonetheless be able to consent to entry of a policeman to that area where visitors are
normally received.
48 See § 8.1(c).
49 United States v. Curran, 498 F.2d 30 (9th Cir.1974); People v. O’Hearn, 931 P.2d 1168 (Colo.1997).
So too, a police officer is not free to enter an open garage door. United States v. Oaxaca, 233 F.3d 1154 (9th Cir.2000).
49.1 Compare United States v. Walker, 474 F.3d 1249 (10th Cir.2007) (where officer knocked several times on the storm door but got
no response, and then opened the storm door and knocked on the inner wooden door, which was about ten inches ajar, that “not a
Fourth Amendment intrusion,” as “most visitors would have done the same”).
49.2 State v. Kochel, 744 N.W.2d 771 (N.D.2008) (“While an open door may ‘invite the gaze of curious passers-by and lessen the
reasonable anticipation of privacy in the home,’ it does not alone justify an officer’s entry”).
50 State v. Crider, 341 A.2d 1 (Me.1975).
51 Similarly, where a residence has a front door and a patio door and also a door leading through the garage to a kitchen door, an
officer wanting to serve civil process may not opt for walking through the garage, which “is an intimate part of a person’s
residence.” State v. Blumler, 458 N.W.2d 300 (N.D.1990).
Compare State v. Breuer, 577 N.W.2d 41 (Iowa 1998) (where house divided into 2 apartments had porch with 2 doors, and officer
desiring to question defendant rang his doorbell but received no response and then opened door and walked up stairs to second
floor apartment and knocked on door at top of stairs and, when defendant opened door, smelled burning marijuana, court holds
defendant had legitimate expectation of privacy as to the stairway and landing because it “was not an area used by other people,”
but that because police “may go onto a person’s private property, approach the residence, and knock on a door to speak with a
person regarding a police investigation,” climbing stairs was a legitimate “minimal intrusion” equivalent to trying a back door
when no response at front door); State v. Kitchen, 572 N.W.2d 106 (N.D.1997) (though area entered by police characterized as an
“enclosed entryway,” defendant’s reliance on Crider unavailing, as court concludes area is “a porch-type entrance,” as inner door
flush with original exterior wall of house and “vestibule-like addition” had an unlocked screen door, so space “was impliedly open
to at least some access by the public”).
See also State v. Kochel, 744 N.W.2d 771 (N.D.2008) (distinguishing Kitchen, infra, improper for police to enter addition to
mobile home, as “the structure is fully enclosed by wooden walls complete with a door and a window”).
52 Assuming circumstances in which this is so, it is another matter whether the officer, while there, may make use of that vantage
point to look into or listen at a particular residential unit. This matter is explored in the immediately following subsection.
As for what other investigative techniques are permissible, consider Harvin v. United States, 228 Ct.Cl. 605, 661 F.2d 885
(Ct.Cl.1981) (where investigator put match sticks between door and door jam of plaintiff’s motel room to keep track of his
comings and goings, this no search; “plaintiff had no reasonable expectation of privacy which was invaded when the match sticks
fell after someone opened the door”); Commonwealth v. Montanez, 410 Mass. 290, 571 N.E.2d 1372 (1991) (no search for officer
to move tile in dropped ceiling directly outside door to defendant’s apartment and thereby discover defendant’s narcotics stash).
53 United States v. Mendoza, 281 F.3d 712 (8th Cir.2002) (duplex, where outer door to vestibule not secured, there were two
mailboxes outside, and “there was no signal to the officers that knocking on the outer door would have been necessary”); United
States v. Cephas, 254 F.3d 488 (4th Cir.2001) (police officer’s movement from door of house containing apartments to door of
defendant’s apartment was with consent of another resident, but in any event was “through an area common to the several separate
apartments in the house, an area where any pollster or salesman could have presented himself”); United States v. Brown, 169 F.3d
89 (1st Cir.1999); United States v. Clark, 67 F.3d 1154 (5th Cir.1995) (apartment building upper level walkway “neither enclosed
nor locked”); United States v. Acosta, 965 F.2d 1248 (3d Cir.1992); United States v. Sewell, 942 F.2d 1209 (7th Cir.1991); United
States v. Penco, 612 F.2d 19 (2d Cir.1979); Brown v. United States, 627 A.2d 499 (D.C.App.1993); Cox v. State, 160 Ga.App.
199, 286 S.E.2d 482 (1981); People v. Smith, 152 Ill.2d 229, 178 Ill.Dec. 335, 604 N.E.2d 858 (1992) (unlocked “common area
shared by other tenants, the landlord, their social guests and other invitees”); Commonwealth v. Acosta, 416 Mass. 279, 627
N.E.2d 466 (1993); State v. Macke, 594 S.W.2d 300 (Mo.App.1980); Commonwealth v. Miley, 314 Pa.Super. 88, 460 A.2d 778
206

(1983); State v. Eddy, 519 A.2d 1137 (R.I.1987).
United States v. Rheault, 561 F.3d 55 (1st Cir.2009) (tenant of apartment on second floor without expectation of privacy in
washing machine on third floor landing, to which third floor tenants and their guests had relatively unfettered access); United
States v. Dillard, 438 F.3d 675 (6th Cir.2006) (“Dillard did not have a reasonable expectation of privacy in the common hallway
and stairway of his duplex that were unlocked and open to the public”; court also stresses door was ajar and that “there was no
visible way for the police or anyone else to alert the duplex tenant of their presence”).
54 United States v. Carriger, 541 F.2d 545 (6th Cir.1976).
55 McDonald v. United States, 335 U.S. 451, 69 S.Ct. 191, 93 L.Ed. 153 (1948), where an officer climbed through a window into the
landlady’s room and then proceeded to the second floor and, by standing on a chair, looked through the transom into defendant’s
room and saw gambling paraphernalia. Justice Jackson asserted “that each tenant of a building, while he has no right to exclude
from the common hallways those who enter lawfully, does have a personal and constitutionally protected interest in the integrity
and security of the entire building against unlawful breaking and entry.”
56 By contrast, entry with permission, even if obtained by a ruse, does not violate the Fourth Amendment. See, e.g., State v.
Anderson, 517 N.W.2d 208 (Iowa 1994) (officers “gained entry to the apartment building by randomly pushing apartment buzzers
until someone let them in the locked building”; despite such “ruse” officers’ presence “was not unlawful until such time as
someone with authority requested them to leave,” and thus overhearing conversation in hallway no search).
As for consent without a ruse, see United States v. Taylor, 248 F.3d 506 (6th Cir.2001) (officers communicated via intercom with
residents “until they found a resident who was willing to let them in, provided that she not be identified as the one giving them
access,” and thus entry of locked common areas lawful under Carriger).
57 United States v. Heath, 259 F.3d 522 (6th Cir.2001) (“the holding of Carriger is applicable here,” as the officers “entered a locked
building without utilizing the proper procedure”; fact they used key lawfully seized from defendant makes no difference, as “the
mere possession of a key will not transform an illegal entry into a valid one,” for it “is the authority to enter, not the manner of
entry, that provides the legality for the officers’ conduct”); Reardon v. Wroan, 811 F.2d 1025 (7th Cir.1987) (expectation of
privacy in hallway of fraternity house; “fraternity members could best be characterized as ‘roommates in the same house,’ not
simply co-tenants sharing certain common areas. Moreover, a fraternity, by definition, is intended to be something of an exclusive
living arrangement with the goal of maximizing the privacy of its affairs”); United States v. Booth, 455 A.2d 1351 (D.C.App.1983)
(police not entitled to enter hallway of rooming house where nothing about the premises suggested strangers free to enter); People
v. Trull, 64 Ill.App.3d 385, 20 Ill.Dec. 960, 380 N.E.2d 1169 (1978) (holding “that the common entries and hallways of a locked
apartment building are protected by the fourth amendment”); State v. Di Bartolo, 276 So.2d 291 (La.1973) (“apparently the
building was kept locked and only tenants who had keys and guests whom they admitted could gain entrance to the building”);
Garrison v. State, 28 Md.App. 257, 345 A.2d 86 (1975) (“the entrance door was kept locked and only tenants and management
personnel had keys to the door,” and the “only way one visiting a tenant could gain entrance was by telephoning a tenant who
‘would come down’ and unlock the door”); People v. Beachman, 98 Mich.App. 544, 296 N.W.2d 305 (1980) (Fourth Amendment
protections extend to lobby of locked residential hotel). See also Note, 101 Mich.L.Rev. 273, 310 (2002) (concluding upon wellreasoned
analysis that “Supreme Court precedent, the history of the Fourth Amendment, the intent of the Framers, and
considerations of sound public policy all necessitate the recognition of a constitutionally protected privacy interest within the
locked common-areas of an apartment building”).
58 United States v. Nohara, 3 F.3d 1239 (9th Cir.1993) (police entry of “high security” apartment building when defendant “buzzed”
in one Nobrega who contacted defendant via intercom and who then cooperating with police in investigation of Nobrega’s drug
supplier; “an apartment dweller has no reasonable expectation of privacy in the common areas of the building whether the officer
trespasses or not”); United States v. Barrios-Moriera, 872 F.2d 12 (2d Cir.1989) (“common hallway” in apartment building is “an
area where there is no legitimate expectation of privacy … even though the area is guarded by a locked door”); United States v.
Holland, 755 F.2d 253 (2d Cir.1985) (arrest within locked common hallway of two-apartment house not within Payton rule
requiring warrant for in-premises arrests; “we never have held that the common areas must be accessible to the public at large”);
United States v. Luschen, 614 F.2d 1164 (8th Cir.1980) (no expectation of privacy in apartment building hallway even though it
within “a security building” which officer only able to enter by getting “security key” from manager); United States v. Eisler, 567
F.2d 814 (8th Cir.1977) (on ground “expectation of privacy necessarily implies an expectation that one will be free of any
intrusion, not merely unwarranted intrusions”); United States v. Moore, 463 F.Supp. 1266 (S.D.N.Y.1979) (holding that the
“common areas of an apartment building, even if they are normally kept locked, are not places in which tenants of the building
have a reasonable expectation of privacy,” and that same is true where “the main entrance … was serviced by a doorman,” as in
“either case, the tenant will find other tenants, visitors to other apartments, workmen and others using the common areas”).
State v. Talley, 307 S.W.3d 723 (Tenn.2010) (collecting federal and state cases in accord with view that there is no “reasonable
expectation of privacy in the common areas of a locked apartment building,” court holds that police entry of locked condominium
building by virtue of assistance from unknown person who opened the door for the officers was lawful, especially in light of fact
207

“that the condominium residents had collectively provided not only the police department but also several others with the entry
code for use in the ordinary course of their duties”).
58.1 State v. Talley, 307 S.W.3d 723 (Tenn.2010).
59 United States v. Miravalles, 280 F.3d 1328 (11th Cir.2002).
60 State v. Titus, 707 So.2d 706 (Fla.1998).
61 And thus the Titus court distinguished City of Evanston v. Hopkins, 330 Ill.App. 337, 71 N.E.2d 209 (1947), upholding police
entry of a rooming house where there was a “Public Telephone” sign at the entrance and the door was open.
62 Accord: People v. Douglas, 2 Cal.App.3d 592, 82 Cal.Rptr. 718 (1969); Bryant v. United States, 599 A.2d 1107 (D.C.App.1991);
United States v. Booth, 455 A.2d 1351 (D.C.App.1983); State v. Berlow, 284 N.J.Super. 356, 665 A.2d 404 (Ct.Law Div.1995).
Contra: United States v. Anderson, 533 F.2d 1210 (D.C.Cir.1976); United States v. Perkins, 286 F.Supp. 259 (D.D.C.1968), aff’d
432 F.2d 612 (D.C.Cir.); State v. Kechrid, 822 S.W.2d 552 (Mo.App.1992).
63 Griffin v. West RS, Inc., 143 Wash.2d 81, 18 P.3d 558 (2001) (in this civil case, it a proper instruction that tenant of apartment
building had reasonable expectation of privacy in attic area accessible only through living space of that tenant).
64 State v. Reddick, 207 Conn. 323, 541 A.2d 1209 (1988) (it a search for police to enter basement of 2-apartment house; “the
basement was secured from the outside and readily accessible only from the two apartments within the dwelling” and thus “is an
area where a tenant might expect other tenants and invited guests but would not expect deliverymen, salesmen, mailmen,
policemen or trespassers”); Bryant v. United States, 599 A.2d 1107 (D.C.App.1991) (was a search for police to enter basement of
rooming house where, as trial judge concluded, there no indication it “open to the general public”); Garrison v. State, 28 Md.App.
257, 345 A.2d 86 (1975) (police made a search when they entered “a basement area closed to the public and to be used only by
tenants of the building”).
But see United States v. Hawkins, 139 F.3d 29 (1st Cir.1998) (where entry of building lawful to execute search warrant for
defendant’s apartment, defendant “had no reasonable expectation of privacy in the basement common area,” and thus police entry
there no search); United States v. McGrane, 746 F.2d 632 (8th Cir.1984) (relying on Eisler, note 58 supra, court holds that visual
inspection of defendant’s storage locker in basement no search, as this a common area accessible to all tenants and the landlord,
though the office gained entry to the basement by trespass); Penny v. United States, 694 A.2d 872 (D.C.App.1997) (where, as here,
front door of apartment building unlocked and immediately inside stairway led down to unlocked basement, police entry of
basement no search, as “the tenant of an apartment in a multi-tenant building has no reasonable expectation of privacy in the
common areas of that building, such as … basements”).
But see Commonwealth v. Williams, 453 Mass. 203, 900 N.E.2d 871 (2009) (defendant without reasonable expectation of privacy
in basement, unlocked and used by various tenants in the building).
65 United States v. Penco, 612 F.2d 19 (2d Cir.1979) (garage of apartment building open to all); United States v. Cruz Pagan, 537
F.2d 554 (1st Cir.1976) (police entered underground parking garage of condominium; held, “a person cannot have a reasonable
expectation of privacy … in such a well travelled common area of an apartment house or condominium”).
66 United States v. King, 227 F.3d 732 (6th Cir.2000), concluding that “the nature of the living arrangements of a duplex, as opposed
to a multi-unit apartment building, affords the tenant of the duplex a greater expectation of privacy in areas the tenant of the multiunit
apartment building would not enjoy, because in the case of a duplex, access to such areas is limited to the duplex’s tenants and
landlord.”
United States v. Fluker, 543 F.2d 709 (9th Cir.1976) (given “particular circumstances” of the case, defendant who occupied one
unit in duplex had a legitimate expectation of privacy in a common hallway of duplex normally locked to outsiders).
Compare United States v. Villegas, 495 F.3d 761 (7th Cir.2007) (defendant had no reasonable expectation of privacy in duplex
common hallway, where outer door open and screen door unlocked, and hallway used not only by residents, but also by customers
of other unit, which advertised business on sign outside building; court distinguished King because there occupants of two units all
related, so that situation there “more closely resembled a single family house,” and distinguished Fluker because there residents of
both units were co-conspirators in drug distribution operations and thus “would maintain the privacy of all occupants of the duplex
to advance their common purpose”).
67 See § 8.5(a). Thus, for example, where the hallway could be entered only through a locked door opened by key or a buzzer
activated by someone in an apartment, but the building’s manager had authorized the police to enter and had given them a key, the
entry was lawful. People v. Howard, 63 Cal.App.3d 249, 133 Cal.Rptr. 689 (1976).
208

68 Dinkens v. State, 291 So.2d 122 (Fla.App.1974).
69 Compare the investigative techniques discussed in note 57 supra.
70 E.g., United States v. Pacheco-Ruiz, 549 F.2d 1204 (9th Cir.1976); People v. Hurst, 325 F.2d 891 (9th Cir.1963).
71 Marullo v. United States, 328 F.2d 361 (5th Cir.1964).
See also United States v. Romano, 388 F.Supp. 101 (E.D.Pa.1975) (officer found cocaine in newspapers concealed in drainpipe
attached to rear wall of townhouse on college campus occupied by defendant and four other students; held, no search, as common
areas of multiple dwellings are “not within the curtilage of the individual tenant,” and defendant had no justified expectation of
privacy because the area was not in his “exclusive control”).
72 As explained in Amsterdam, Perspectives on the Fourth Amendment, 58 Minn.L.Rev. 349, 389–90 (1974), this thinking may
underlie Marullo. The court first declared that this was a reasonable warrantless search, but when the defendant in his petition for
rehearing pointed to authority that a warrantless search of a dwelling is per se unreasonable, the court then asserted that no search
had occurred. As Amsterdam says, id. at 390: “Confronted with the necessity of enforcing the warrant requirement all the way to
the boundary line of the fourth amendment, the court moved the boundary line over a couple of feet.”
73 United States v. Concepcion, 942 F.2d 1170 (7th Cir.1991).
73.1 In Reeves v. Churchich, 484 F.3d 1244 (10th Cir.2007), where a police officer pointed a rifle at an occupant of a duplex from a
noncurtilage space, see note 225 infra, but the end of the rifle intruded into the home’s interior, the court distinguished Concepcion
and held the insertion of the rifle “was not a search because the rifle was incapable of obtaining information and did not obtain any
information,” and was at most “a common law trespass.”
74 The court found “a close parallel” in Arizona v. Hicks, 480 U.S. 321, 107 S.Ct. 1149, 94 L.Ed.2d 347 (1987), holding it is a search
to turn over a phonograph to read its serial number.
Accord: United States v. DeBardeleben, 740 F.2d 440 (6th Cir.1984); United States v. Portillo-Reyes, 529 F.2d 844 (9th Cir.1975),
questioned in United States v. Grandstaff, 813 F.2d 1353 (9th Cir.1987); Cole v. State, 858 S.W.2d 915 (Tenn.Crim.App.1993)
(but “the intrusion requires neither a search warrant nor probable cause, only a founded suspicion”).
But see United States v. Salgado, 250 F.3d 438 (6th Cir.2001) (trying key in lock of defendant’s apartment, “accessible by means
of an unlocked, common hallway,” no search, as “the mere insertion of a key into a lock, by an officer who lawfully possesses the
key and is in a location where he has a right to be, to determine whether this key operates the lock, is not a search”); United States
v. $109,179 in U.S. Currency, 228 F.3d 1080 (9th Cir.2000) (insertion of car key into a nearby parked car “for the sole purpose of
aiding the police in identification of an individual” detained on reasonable suspicion deemed not an unreasonable search, as it was
“a ‘minimally intrusive’ action” serving “the strong governmental interests in investigating drug crimes”; court says Portillo-Reyes
only said insertion of key “constituted the beginning of the search” and thus “is inapplicable here since there was no search that
followed”) United States v. Hawkins, 139 F.3d 29 (1st Cir.1998) (trying key found in defendant’s apartment during execution of
search warrant there in storage locker found in common area of basement no search); United States v. Lyons, 898 F.2d 210 (1st
Cir.1990) (trying key in rented storage compartment no search); People v. Trull, 64 Ill.App.3d 385, 20 Ill.Dec. 960, 380 N.E.2d
1169 (1978) (determining key fit lock no search); Commonwealth v. DeJesus, 439 Mass. 616, 790 N.E.2d 231 (2003) (“Inserting a
key into a lock and turning it to see whether it fits cannot be construed as a warrantless search of a lock tumbler”); State v. Jackson,
268 N.J.Super. 194, 632 A.2d 1285 (1993) (“the ‘testing’ of Jackson’s validly seized keys” in two doors “did not constitute a
search”); State v. Roman, 182 N.J.Super. 297, 440 A.2d 1155 (1982) (using key found in victim’s car to determine whether it fit
lock at defendant’s residence no search).
But see United States v. Moses, 540 F.3d 263 (4th Cir.2008) (“the discrete act of inserting the key into the lock and discovering
whether or not it fit did not offend the Fourth Amendment”); State v. Robinson, 158 N.H. 792, 973 A.2d 277 (2009) (no Fourth
Amendment violation, as “the mere information of ownership obtained from inserting a key into a door is not the type of
information in which a defendant has a reasonable expectation of privacy”).
75 The court noted that Hicks, note 74 supra, said a warrant is unnecessary and that Hicks, requiring probable cause, was
distinguishable because there the privacy interest was more substantial because the officers obtained information “they could not
have come by in any other way.”
See also Commonwealth v. Alvarez, 422 Mass. 198, 661 N.E.2d 1293 (1996) (assuming putting key in lock of apartment a search,
it legal, as “for such an unobtrusive search the police needed only a founded or reasonable suspicion to insert the key”).
76 On the use of various aids to the senses, see § 2.2.
77 Lorenzana v. Superior Court, 9 Cal.3d 626, 108 Cal.Rptr. 585, 511 P.2d 33 (1973).
209

78 People v. Wright, 41 Ill.2d 170, 242 N.E.2d 180 (1968). Though this case involved an apartment house, the reasoning is equally
applicable to a single-family dwelling.
79 The reference is to the post-Katz decision in Harris v. United States, 390 U.S. 234, 88 S.Ct. 992, 19 L.Ed.2d 1067 (1968),
concerning “the plain view of an officer who has a right to be in the position to have that view.”
80 United States v. Whaley, 779 F.2d 585 (11th Cir.1986) (no search to surveil from neighbor’s property and on nearby canal open
only to area landowners; court rejects defendant’s argument it is a search because officer’s vantage point not open to general
public); State v. Texeira, 62 Haw. 44, 609 P.2d 131 (1980) (gambling seen and heard from adjoining property); Turner v. State,
499 S.W.2d 182 (Tex.Crim.App.1973); State v. Vogel, 428 N.W.2d 272 (S.D.1988) (no search to look into defendant’s house from
hilltop outside curtilage; “Anyone on the neighbor’s property could have walked, unobstructed, to the hilltop, and seen the plants”).
81 Commonwealth v. Busfield, 242 Pa.Super. 194, 363 A.2d 1227 (1976).
82 Amsterdam, Perspectives on the Fourth Amendment, 58 Minn.L.Rev. 349, 402 (1974).
83 As in Commonwealth v. Hernley, 216 Pa.Super. 177, 263 A.2d 904 (1970), holding the defendant had no justified expectation of
privacy re the interior of his print shop because he failed “to curtain the windows,” though the windows were well above eye level
and the officer had looked in by standing on a four-foot ladder and using binoculars.
In Commonwealth v. Williams, 494 Pa. 496, 431 A.2d 964 (1981), involving a 9-day surveillance of a third story apartment from
another apartment 30–40 feet away, including use of binoculars and a startron which permitted the police to see into the apartment
even in darkness, the court timidly distinguished Hernley because in the instant case the police observed “two acts of sexual
intercourse not involving the person … for whom the surveillance was established.”
84 Montgomery, J., dissenting in Commonwealth v. Hernley, 216 Pa.Super. 177, 263 A.2d 904 (1970).
85 Pate v. Municipal Court, 11 Cal.App.3d 721, 89 Cal.Rptr. 893 (1970).
86 As the Court stated in Oliver v. United States, 466 U.S. 170, 104 S.Ct. 1735, 80 L.Ed.2d 214 (1984), “the curtilage is the area to
which extends the intimate activity associated with the ‘sanctity of a man’s home and the privacies of life,’ … and therefore has
been considered part of home itself for Fourth Amendment purposes. Thus, courts have extended Fourth Amendment protection to
the curtilage; and they have defined the curtilage, as did the common law, by reference to the factors that determine whether an
individual reasonably may expect that an area immediately adjacent to the home will remain private.” The Court added that “for
most homes, the boundaries of the curtilage will be clearly marked; and the conception defining the curtilage-as the area around the
home to which the activity of home life extends-is a familiar one easily understood from our daily experience.”
87 Lorenzana v. Superior Court, 9 Cal.3d 626, 108 Cal.Rptr. 585, 511 P.2d 33 (1973).
88 United States v. Hersh, 464 F.2d 228 (9th Cir.1972), quoting from Davis v. United States, 327 F.2d 301 (9th Cir.1964).
See also United States v. Cormier, 220 F.3d 1103 (9th Cir.2000) (officer acted properly, as he “knocked on the door for only a
short period spanning seconds,” “there was no police demand to open the door,” and officer “was not unreasonably persistent in
her attempt to obtain access to Cormier’s motel room”); People v. Holmes, 981 P.2d 168 (Colo.1999) (where police officer called
because of loud party knocked hard on door in effort to get attention of occupant over the noise, and door swung open because not
properly latched, allowing officer to observe bong within, no search; “Knocking on the door of a residence for the purpose of
investigating a crime is reasonable police conduct and does not infringe upon the occupant’s right of privacy”); Commonwealth v.
Acosta, 416 Mass. 279, 627 N.E.2d 466 (1993) (officer, in knocking on defendant’s door, “did no more than any citizen could do
by entering a common area” and thus no search). Compare the Jurez case, note 98 infra.
See also People v. Rivera, 41 Cal.4th 304, 59 Cal.Rptr.3d 473, 159 P.3d 60 (2007) (police officer may approach and knock on door
of residence, and such actions “require no articulable suspicion of criminal activity”).
89 State v. Crea, 305 Minn. 342, 233 N.W.2d 736 (1975).
90 Lorenzana v. Superior Court, 9 Cal.3d 626, 108 Cal.Rptr. 585, 511 P.2d 33 (1973). Sometimes a departure from the most direct
route will be permissible. See United States v. Garcia, 997 F.2d 1273 (9th Cir.1993) (looking in back door no search where, as
here, both front and back door “are readily accessible from a public place like the driveway and parking area here,” so that police
went to back door “reasonably believing it is used as a principal entrance to the building”); United States v. Daoust, 916 F.2d 757
(1st Cir.1990) (where front door “is inaccessible there is nothing unlawful or unreasonable about going to the back of the house to
look for another door”); United States v. Anderson, 552 F.2d 1296 (8th Cir.1977) (when officer who wished to question defendant
210

eceived no answer to knock on front door, but lights were on and dog heard barking in back, it reasonable for officer to walk to
the rear of the premises to see if defendant with dog); Miller v. State, 342 Ark. 213, 27 S.W.3d 427 (2000) (where police entered
curtilage during legitimate police investigation and knocked at front door but received no response, and then followed path around
unfenced property to back porch and knocked on rear door, and smelled marijuana from that vantage point, no search); State v.
Glines, 134 Or.App. 21, 894 P.2d 516 (1995) (officer properly went to side door to knock on door where, as here, “side entry is
about eight feet from the front wall of defendant’s house” and “adjacent to a common driveway that defendant shares with his
neighbor, is visible from the public sidewalk and is equipped with a doorbell”).
Also, what are “normal means” may depend somewhat on the circumstances. See United States v. Jackson, 585 F.2d 653 (4th
Cir.1978) (no search for officer to stand on chair under window and look in open window of house with “for rent” sign in front, as
it would be expected that prospective tenants “would inspect the house, look in the windows and view the surrounding premises in
order to determine what interest they might have in renting”).
Compare People v. Camacho, 23 Cal.4th 824, 98 Cal.Rptr.2d 232, 3 P.3d 878 (2000), where police, responding to a complaint of a
loud party at defendant’s home, arrived there at 11 p.m. and heard no excessive noise. The officers walked into a side yard open
area covered with grass without any path or walkway and with no entrance to the home on that side, and looked in a large side
window, visible from the public street or sidewalk though the interior was not, and saw defendant with drugs. In holding this was a
search, the court emphasized that the officers had “proceeded directly into [defendant’s] darkened side yard” “without bothering to
knock on defendant’s front door,” though they arrived there “late in the evening and heard no such noise.” The court added that
“had the officers on their arrival at defendant’s house heard a raucous party, confirming the anonymous complaint that brought
them there in the first place, and had they then banged on the front door to no avail, their entry into the side yard in an attempt to
seek the source of the noise would likely have been justified.”
91 “To come within the implied invitation, a police officer must be on some police business. That does not necessarily mean that the
officer has to have probable cause or even an objectively reasonable suspicion that criminal activity is afoot. The police business
may be administrative as well as investigative, and it may be action based on a suspicion that turns out to be without substantial
basis, provided the suspicion is held in good faith rather than as a pretext for an arbitrary search. Officer Sabin’s burglary
suspicion, based on recent reports of burglaries in the community and the fact that Cloutier’s basement was the only illuminated
room in the house, although tenuous, was held in good faith and was not pretextual.” State v. Cloutier, 544 A.2d 1277 (Me.1988).
92 United States v. Hersh, 464 F.2d 228 (9th Cir.1972); State v. Deary, 753 So.2d 200 (La.2000) (officer was “conducting a legitimate
police investigation” when he came onto porch and knocked on side of house and looked through open door, as purpose was “to
question the occupants about the individual the officer had observed leave the premises in the company of another person known to
[the officer] from prior narcotics arrests”); State v. Crea, 305 Minn. 342, 233 N.W.2d 736 (1975); State v. Perez, 85 S.W.3d 817
(Tex.Crim.App.2002) (knocking on door of apartment to which theft suspect fled, at which defendant opened door, was only an
encounter and thus no reasonable suspicion required).
Jones v. State, 407 Md. 33, 962 A.2d 393 (2008).
93 State v. Poling, 207 W.Va. 299, 531 S.E.2d 678 (2000).
94 Hall v. State, 15 Md.App. 363, 290 A.2d 803 (1972); State v. White, 18 Or.App. 352, 525 P.2d 188 (1974).
95 United States v. Hammett, 236 F.3d 1054 (9th Cir.2001) (no search for officer to look through gap in siding on house while
completing circling of house looking for another door after no one answered front door); United States v. Taylor, 90 F.3d 903 (4th
Cir.1996) (where defendant’s “front entrance was as open to the law enforcement officers as to any delivery person, guest, or other
member of the public,” it no search for officer on front porch to look through picture window); United States v. Evans, 27 F.3d
1219 (7th Cir.1994) (looking into house from driveway no search, as “no evidence that the public had limited access to Glenn’s
driveway”); United States v. Daoust, 916 F.2d 757 (1st Cir.1990) (officer, properly at rear of premises seeking “an accessible main
floor entrance” then “looked up through the window simply to see if someone was at home”); People v. Willard, 238 Cal.App.2d
292, 47 Cal.Rptr. 734 (1965) (while on steps leading up to side door of house, officer observed illegal activity through screen
door); People v. McGahey, 179 Colo. 401, 500 P.2d 977 (1972) (house was located 100–150 yards off street, officer drove into
driveway to within 25 feet of house and then saw marijuana plants in picture window); State v. David, 269 Ga. 533, 501 S.E.2d
494 (1998) (where official accompanied landlord checking on possible unauthorized occupancy, and when landlord knocked on
door it was opened and officer then saw through the open door a marijuana pipe, this no search); State v. Dickerson, 313 N.W.2d
526 (Iowa 1981) (no search to look through window of front door and then photograph what seen); State v. Brisban, 809 So.2d 923
(La.2002) (officer was “on the porch for a legitimate purpose when he looked through the screen door and saw what appeared to be
contraband”); State v. Cloutier, 544 A.2d 1277 (Me.1988) (no search where officer on path from side door looked in basement
window); State v. Gott, 456 S.W.2d 38 (Mo.1970) (while standing at front door, officer looked in window and saw defendant
rolling a marijuana cigarette); State v. Prevette, 43 N.C.App. 450, 259 S.E.2d 595 (1979) (while on front porch, officer saw
marijuana inside); State v. White, 18 Or.App. 352, 525 P.2d 188 (1974) (while on porch approaching front door, officer looked
through window and saw marijuana); State v. Rose, 128 Wash.2d 388, 909 P.2d 280 (1996) (looking through picture window from
211

porch no search, as officer “entitled to walk up onto the porch,” for it “was accessible from a large parking area” nearby and thus
“was impliedly open to the public”); State v. Poling, 207 W.Va. 299, 531 S.E.2d 678 (2000) (no search where officer on front
porch on lawful business saw marijuana plants through uncovered window).
Considering the Lorenzana case in the text following, it may sometimes be argued that the observation was not a search because
the defendant had not made reasonable efforts to maintain privacy. Generally, it would appear that somewhat greater efforts might
be required as to windows at or by an entrance to the premises as compared to the kind of windows involved in Lorenzana. But see
State v. Jordan, 29 Wash.App. 924, 631 P.2d 989 (1981) (where police on porch responding to complaint of noisy party, looking
into 6″ space between drape and window casing a search, as “by drawing the curtains the individuals inside the duplex had clearly
demonstrated a reasonable expectation of privacy”; dissent objects this a valid plain view because it cannot be said “the officers
had to strain and contort so that they might see through a tiny opening”).
Taylor v. Michigan Dept. of Natural Resources, 502 F.3d 452 (6th Cir.2007) (under “conditions consistent with a winter-time
break in of a potentially-seasonal home” that “warranted a brief protective check,” it not objectionable that officer, in “broad
daylight, … spent approximately five minutes looking in open windows”); United States v. Khabeer, 410 F.3d 477 (8th Cir.2005)
(no search for officer to see TV set through front window of home while standing in driveway); Hardister v. State, 849 N.E.2d 563
(Ind.2006) (where officers lawfully went to back yard in reasonable anticipation that suspects within would flee out back door, but
they did not, once officers “lawfully present in the backyard, their looking into the kitchen through the side and rear windows, was
also reasonable as an effort to locate the fleeing suspects”); Commonwealth v. Hatcher, 199 S.W.3d 124 (Ky.2006) (since officer
“authorized to knock on Hatcher’s door to respond to the report of an allegedly abandoned minor,” no Fourth Amendment
violation when he “looked into her house through the open door”).
96 People v. Smith, 152 Ill.2d 229, 178 Ill.Dec. 335, 604 N.E.2d 858 (1992) (defendant’s confession to murder overheard by officers
in unlocked apartment building common-area hallway); Hall v. State, 15 Md.App. 363, 290 A.2d 803 (1972) (officer overheard
words while on front porch).
97 Miller v. State, 342 Ark. 213, 27 S.W.3d 427 (2000) (smelling marijuana within while lawfully at back door no search); People v.
Baker, 813 P.2d 331 (Colo.1991) (officer smelled odor of marijuana from outside open front door); State v. Garcia, 374 So.2d 601
(Fla.App.1979) (officer smelled odor of marijuana from front porch); State v. Prevette, 43 N.C.App. 450, 259 S.E.2d 595 (1979)
(same); State v. Glines, 134 Or.App. 21, 894 P.2d 516 (1995) (while at side door, officer smelled odor of marijuana coming from
basement, interior access to which was located by that door); State v. Perez, 85 S.W.3d 817 (Tex.Crim.App.2002) (smelling of
marijuana inside apartment after defendant answered lawful knock on door).
Sometimes a court will, in the alternative, deem the approach and smelling a search, albeit one justified by exigent circumstances.
See, e.g., Holder v. State, 847 N.E.2d 930 (Ind.2006) (where officers detected odor of ether from as far away as 100 yards from
defendant’s home, which “led them to walk across the private property of several residents in the neighborhood and ultimately to
crouch near the defendant’s basement window to take a sniff,” the “significant degree of the fumes from a known explosive and
flammable chemical in a residential area compelled the officers to find its source for the sake of the safety and health of the nearby
residents”).
98 United States v. Cephas, 254 F.3d 488 (4th Cir.2001) (“A voluntary response to an officer’s knock at the front door of a dwelling
does not generally implicate the Fourth Amendment, and thus an officer generally does not need probable cause or reasonable
suspicion to justify knocking on the door and then making verbal inquiry”); United States v. Tobin, 923 F.2d 1506 (11th Cir.1991);
United States v. Peters, 912 F.2d 208 (8th Cir.1990) (“After Peters opened the door to the hotel room in which he was staying, in
response to the simple knock on the door by the police officers, a search did not occur when the detectives looked into Peters’
room through the open doorway”); People v. Baker, 813 P.2d 331 (Colo.1991); State v. Sanders, 374 So.2d 1186 (La.1979) (“It is
an almost implicit understanding and custom in this country that, in the absence of signs or warning, a residence may be
approached and the occupants summoned to the door by knocking”); Commonwealth v. Acosta, 416 Mass. 279, 627 N.E.2d 466
(1993) (no search where officer viewed defendant when he opened door in response to a knock; officer “did not announce himself
as a police officer” and “did no more than any citizen could do by entering a common area and knocking on the door”).
In trying to summon the occupant to the door, it is not objectionable that the police resorted to a ruse. United States v. Leung, 929
F.2d 1204 (7th Cir.1991). But the result is otherwise if the door is opened in response to a police command. United States v.
Conner, 127 F.3d 663 (8th Cir.1997) (“an unconstitutional search occurs when officers gain visual … access to a motel room after
an occupant opens the door not voluntarily, but in response to a demand under color of authority”). As for the distinction between
an order and a request, see Bailey v. Newland, 263 F.3d 1022 (9th Cir.2001) (when officers approached motel room, Cowans
stepped outside, after which Bailey slammed the door; police put Cowans in police car and then one officer “began knocking on
the door and … identified himself as a police officer”; “he knocked for about one-minute-and-a-half to two minutes while
continuing to identify himself as a police officer but issued no commands or orders”; Bailey then opened the door and stepped out,
permitting police to see gun and drug paraphernalia within; court concludes it has “no basis to conclude that Bailey voluntarily
answered the door”); United States v. Tobin, 923 F.2d 1506 (11th Cir.1991) (where officer knocked 3–4 minutes and called out,
“I’m a police officer, I would like to talk to you, I need for you to come here,” this not an order, as the officer “did not use the
imperative” and “he phrased his words in the form of a request”); Commonwealth v. Hamilton, 24 Mass.App.Ct. 290, 508 N.E.2d
212

870 (1987). In such a case, the fact that “the officers gained visual access to the interior of a dwelling without physically entering it
is irrelevant to the question whether a search was effected.” United States v. Winsor, 846 F.2d 1569 (9th Cir.1988).
Also, note that in some circumstances an insistent effort to get the occupant to come to the door can amount to a seizure of those
within. See United States v. Jerez, 108 F.3d 684 (7th Cir.1997) (where deputies knocked on motel room door at 11:00 p.m. for 3
minutes, made commands and requests to open the door, knocked for 1½ to 2 minutes on outside of window, and shone flashlight
through small opening in window’s drapes into face of one defendant as he lay in bed, collectively manifesting “the law
enforcement officers refusal to take ‘no’ for an answer,” this constituted a seizure).
But, while it is doubtless true that “as a matter of public policy … [l]ate-night intrusions into people’s homes are, and should be,
discouraged and should not be permitted unless necessary,” “courts have declined to find a seizure based on a night-time ‘knock
and talk’ in the absence of other coercive circumstances.” Scott v. State, 366 Md. 121, 782 A.2d 862 (2001) (random knocking on
motel room doors at 11:30 p.m. in hopes occupants would allow police to enter and ultimately consent to search). See also United
States v. Cormier, 220 F.3d 1103 (9th Cir.2000) (after 8:00 p.m.); United States v. Taylor, 90 F.3d 903 (4th Cir.1996) (at 9:15
p.m.). And the “knock and talk” procedure is unquestionably proper when utilized during daylight hours. See, e.g., United States v.
Adeyeye, 359 F.3d 457 (7th Cir.2004); State v. Johnston,—N.H.-, 150 N.H. 448, 839 A.2d 830 (2004).
Re Conner: Accord: United States v. Mowatt, 513 F.3d 395 (4th Cir.2008) (seeing inside through open door a search where, as
here, occupant opened door in response to police command); United States v. Poe, 462 F.3d 997 (8th Cir.2006) (opening door not
consensual when after “over ten minutes of persistent knocks” by one officer and another “had commanded Poe to open the door”).
Likewise if the door is kept open in response to a police threat or command. United States v. Washington, 387 F.3d 1060 (9th
Cir.2004).
Re Scott: See also State v. Warren, 949 So.2d 1215 (La.2007) (at 2:30 a.m., police “detected a strong odor of marijuana smoke
coming from the room”). Re daylight hours: especially where the tactic does not result in police entry of the residence. Jones v.
State, 407 Md. 33, 962 A.2d 393 (2008).
For further discussion of the “knock and talk” procedure, see Note, 41 Suffolk U.L.Rev. 561 (2008); Consider also Bradley,
“Knock and Talk” and the Fourth Amendment, 84 Ind.L.J. 1099 (2009), proposing “possible solutions to the intrusiveness that the
‘knock and talk’ technique imposes on the home,” the most severe of which would be “to ban ‘knock and talk’ entirely when a
particular home or suspect is the focus of police investigation.” This, Bradley contents, would constitute a “return to the principles”
of Johnson v. United States, 333 U.S. 10, 68 S.Ct. 367, 92 L.Ed. 436 (1948), claimed to stand for the proposition that “police
cannot get people to open their doors without a warrant and then use evidence obtained as a result of that opening as the basis for a
valid search or arrest.” Bradley, supra, at 1103. However, in Johnson, where the government attempted to justify search of a hotel
room as incident to the valid arrest of an occupant, the Court never questioned the police conduct that caused the “opening” of the
door in response to their knock, as compared to the subsequent unlawful police “entry … under color of their police authority”: the
Court held that defendant’s arrest was unlawful precisely because based “on the knowledge that she was alone in the room, gained
only after, and wholly by reason of, their entry.”
99 United States v. Blount, 98 F.3d 1489 (5th Cir.1996) (where no walkway to back yard and no indication back door a principal
means of access to that residence, “when a police officer walks into the partially fenced back yard of a residential dwelling, using a
passage not open to the general public, and places his face within inches of a small opening in an almost completely covered rear
window to look into the house and at the inhabitants, that officer has performed a ‘search’ ”); People v. Camacho, 23 Cal.4th 824,
98 Cal.Rptr.2d 232, 3 P.3d 878 (2000) (illegal search where police, responding to a complaint of a loud party at defendant’s home,
arrived there at 11 p.m. and heard no excessive noise. The officers walked into a side yard open area covered with grass without
any path or walkway and with no entrance to the home on that side, and looked in a large side window, visible from the public
street or sidewalk though the interior was not, and saw defendant with drugs); Olivera v. State, 315 So.2d 487 (Fla.App.1975)
(officer overheard incriminating discussions at rear bedroom window; “the implications of sanctioning police surveillance by
standing in a yard at one’s window in the middle of the night are too obvious to require elaboration”); State v. Kaaheena, 59 Haw.
23, 575 P.2d 462 (1978) (officer searched by standing on crates to gain access to 1-inch opening between drapes and blinds); State
v. Ragsdale, 381 So.2d 492 (La.1980) (officer went to rear patio, completely enclosed by tall and solid wooden fence, and looked
through narrow gap in closed curtains; this is a search).
Compare McDougall v. State, 316 So.2d 624 (Fla.App.1975), distinguishing such cases “on the basis that there the law
enforcement officers had no right to be on the premises in the first instance,” and holding there was no search where a police
officer looked in the rear window of a duplex after receiving a call to investigate a possible burglary at that duplex. The court could
just as well have said that it was a search but a reasonable one under the circumstances. Compare also Nordskog v. Wainwright,
546 F.2d 69 (5th Cir.1977), holding that when police have probable cause to arrest and receive no answer to their knock on the
front door, they may look in a side window and rear door to see if defendant is there.
Lundstrom v. Romero, 616 F.3d 1108 (10th Cir.2010) (a search where officer “either scaled a fence or opened a gate to gain access
to Lundstrom’s backyard, taking up a position that allowed him to observe Lundstrom in the rear of the house”); Quintana v.
Commonwealth, 276 S.W.3d 753 (Ky.2008) (when no one answered front door, officer walked to back yard to window where air
conditioner was located and smelled marijuana from air coming out; this a search, as “back yard is not normally an area that the
general public would perceive as public access”); State v. Foster, 347 Or. 1, 217 P.3d 168 (2009) (no “lawful vantage point” here,
as officer “had walked past the front door to look in the window,” but this justified by legitimate safety concerns of police present
213

to serve restraining order at residence where they had encountered many difficulties in the past); State v. Arctic, 327 Wis. 392, 786
N.W.2d 430 (2010) (where police officer walked around house and entered fenced-in back yard and approached rear door, such
“presence within the curtilage was not lawful,” and thus what seen and heard within by officer may not be considered in
determining lawfulness of entry of house).
100 Lorenzana v. Superior Court, 9 Cal.3d 626, 108 Cal.Rptr. 585, 511 P.2d 33 (1973).
101 This is not to suggest that drawing a shade or closing blinds is inevitably necessary. In People v. Camacho, 23 Cal.4th 824, 98
Cal.Rptr.2d 232, 3 P.3d 878 (2000), where the state attempted to distinguish Lorenzana on the ground that in the instant case
“defendant’s rather large (four-by-eight-foot) window was completely uncovered,” the court nonetheless held the 11 p.m. side-yard
windowpeeping was nonetheless a search. That result is correct, given that the “window is visible from the public street or
sidewalk, but the inside of the room is not” (perhaps because “a red bulb dimly lit the room”).
102 Compare United States v. Hammett, 236 F.3d 1054 (9th Cir.2001), where police, receiving no answer to their knock at the front
door, circled the house looking for another entrance. When they had almost completed the trip, they saw drugs within by looking
through a ½ inch to 1 inch wide crack in overlapping pieces of corrugated steel siding forming the walls of the residence. In
holding there was no search, the court emphasized that “the officers were able to view the marijuana plants through the crack from
a distance of approximately five to six feet without making any contortions.”
103 Williamson v. State, 707 A.2d 350 (Del.1998); People v. Wright, 41 Ill.2d 170, 242 N.E.2d 180 (1968).
104 E.g., State v. Benton, 206 Conn. 90, 536 A.2d 572 (1988) (rejecting defendant’s contention “that a different rule should apply to
multiple family dwellings in general and duplex apartments in particular”).
Similarly, when the defendant was a long-time squatter on government property, he may have had a justified expectation of
privacy as to the interior of the dwelling, but had no expectation of privacy in the immediately adjacent property, which any
member of the public might well enter. State v. Dias, 62 Haw. 52, 609 P.2d 637 (1980). And if the defendants choose to engage in
their activity in a vacant house without any curtains, there is again a reduced expectation of privacy, so that police may enter the
back yard. State v. Johnson, 580 S.W.2d 254 (Mo.1979).
105 Moody v. State, 52 Ala.App. 552, 295 So.2d 272 (1974).
106 Quoting from Marullo v. United States, 328 F.2d 361 (5th Cir.1964).
107 Ponce v. Craven, 409 F.2d 621 (9th Cir.1969); People v. Gomez, 632 P.2d 586 (Colo.1981) (no search to look into motel room
from sidewalk); State v. Holtz, 300 N.W.2d 888 (Iowa 1981) (no search to look into motel room window from common walkway);
Commonwealth v. Johnson, 777 S.W.2d 876 (Ky.1989) (“what would be sufficient vigilance to preserve one’s privacy in a home,
apartment or office may be insufficient in a motel room” and thus it no search to look through partially open motel room door and
window); State v. Brown, 9 Wash.App. 937, 515 P.2d 1008 (1973).
Cf. State v. Cardenas, 146 Wash.2d 400, 47 P.3d 127 (2002) (as for looking into motel room window, court says, citing illustrative
cases, that “failure to completely close the curtains is not necessarily determinative” on the lack of a reasonable expectation of
privacy, and says instant case, where “the curtains were partially closed, leaving a three-inch gap,” and “the officers were required
to peer through the opening on bended knees, presents a close question” the court need not answer because justification existed for
looking in even if it a search).
108 United States v. Burns, 624 F.2d 95 (10th Cir.1980) (no search to listen from motel hallway, as if guests “converse in a fashion
insensitive to the public, or semipublic, nature of walkways adjoining such rooms, reasonable expectations of privacy are
correspondingly less”); Ponce v. Craven, 409 F.2d 621 (9th Cir.1969); Satterfield v. State, 127 Ga.App. 528, 194 S.E.2d 295
(1972).
109 United States v. Hessling, 845 F.2d 617 (6th Cir.1988); United States v. Mankani, 738 F.2d 538 (2d Cir.1984) (“the presence of a
visible door, crack or opening in the wall adjacent to another hotel room, as was the case here, should suggest to the average person
that his or her privacy may be limited”); United States v. Jackson, 588 F.2d 1046 (5th Cir.1979); United States v. Sin Nagh Fong,
490 F.2d 527 (9th Cir.1974); United States v. Lopez, 475 F.2d 537 (7th Cir.1973); United States v. Fisch, 474 F.2d 1071 (9th
Cir.1973); State v. Moses, 367 So.2d 800 (La.1979); State v. Gerry, 23 Wash.App. 166, 595 P.2d 49 (1979).
In United States v. Agapito, 620 F.2d 324 (2d Cir.1980), the court rejected defendant’s argument that it is a search to hear with the
naked ear that which can be heard only by pressing the ear to the separating door, relying “upon three critical factors.
“First, appellants’ conversations were heard by the naked human ear. Regardless of whether the tones may be described as loud or
normal, the fact remains that appellants were talking loud enough to be heard by others in an adjoining room. The agents were
unaided by any artificial, mechanical or electronic device.
214

“Second, the agents had a legal right to be in the adjoining room. We decline to restrict their movements in their own room in order
to prevent the overhearing of conversations in an adjoining room. It strikes us as impractical to permit an agent in an adjoining
room to listen while standing immediately next to a wall or connecting door without touching it but to prohibit him from listening
by moving his ear several inches and pressing it against the wall or connecting door. …
“Third, appellants were in a hotel room. True, the occupants of a hotel room are entitled to the protection of the Fourth
Amendment. … But the reasonable privacy expectations in a hotel room differ from those in a residence. …
“In view of the transient nature of hotel guests, moreover, one cannot be sure who his neighbors are in a hotel room. A person in a
residence generally knows who his neighbors are. A person in a hotel room therefore takes a greater risk than one in a residence
that, instead of neighbors, an adjoining room may contain strangers or, as in this case, even persons with interests adverse to his
own.”
Fisch involved the added fact that the agents, with the aid of the motel operator, had the suspects moved to a different room so that
a vacant adjoining room could be made available to the agents, but the court concluded that the “accomplishment of the move of
the defendants’ room to one more accessible for surveillance violated no constitutional right of the appellants. They could, had
they wished, refused the transfer. The officers were in a room open to anyone who might care to rent.”
United States v. Hearn, 563 F.3d 95 (5th Cir.2009).
110 United States v. Leung, 929 F.2d 1204 (7th Cir.1991) (no search where officer looked through motel room door when occupant
opened it, and this so even though police resorted to ruse by having housekeeper knock and ask to clean the room); Borum v.
United States, 318 A.2d 590 (D.C.App.1974) (officer in hallway looked through crack in door and saw use of drugs; no search, as
the hallway “is open to the general public” and the “crack was readily apparent and accessible to anyone walking along that hall”);
Hatcher v. State, 141 Ga.App. 756, 234 S.E.2d 388 (1977) (no search where officers in hallway knocked on door and saw stolen
goods in room when defendant opened door); People v. Miller, 30 Ill.App.3d 643, 332 N.E.2d 440 (1975) (observation from
hallway through open door no search, as “this area was open to the public”).
111 Ray v. United States, 288 A.2d 239 (D.C.App.1972) (listening from adjoining room).
112 United States v. Acevedo, 627 F.2d 68 (7th Cir.1980) (no search to look into apartment window from gangway used by general
public to reach adjoining tavern); Gross v. State, 8 Ark.App. 241, 650 S.W.2d 603 (1983) (conversation overheard from
“residential walkway” of apartment house); People v. Berutko, 71 Cal.2d 84, 77 Cal.Rptr. 217, 453 P.2d 721 (1969) (observation
from common passageway bordering defendant’s apartment); State v. Macke, 594 S.W.2d 300 (Mo.App.1980) (observation
through open door from common area); Commonwealth v. Johnson, 247 Pa.Super. 208, 372 A.2d 11 (1977) (observation from
patio steps used by anyone entering apartment building from the rear).
113 United States v. Fields, 113 F.3d 313 (2d Cir.1997) (no search where police entered fenced side-yard of apartment house and
looked through 6-inch opening into defendant’s illuminated bedroom, as defendants’ activity was in plain view of “a common area
accessible to the other tenants in the multi-family apartment building-in which they had no legitimate expectation of privacy”);
United States v. Lloyd, 36 F.3d 761 (8th Cir.1994) (no search to look through open door of apartment from unlocked hallway);
People v. Becker, 188 Colo. 160, 533 P.2d 494 (1975) (observation was “from a common area in front of the apartment … through
the uncurtained part of a large picture window adjacent to the front door”); Latham v. Sullivan, 295 N.W.2d 472 (Iowa App.1980)
(no search to look in apartment window from ordinary outside route used to reach apartment door); People v. Funches, 89 N.Y.2d
1005, 657 N.Y.S.2d 396, 679 N.E.2d 635 (1997) (no search when officer came down fire escape to landing outside defendant’s
second-story apartment and looked in, given “defendant’s lack of exclusive control over the use of the fire escape”); State v.
Taylor, 61 Ohio App.2d 209, 401 N.E.2d 459, 15 O.O.3d 323 (1978) (no search to look into apartment from “the semi-public
walkway” leading to building); Rodriguez v. State, 653 S.W.2d 305 (Tex.Crim.App.1983) (no search where police in hallway
looked through open door).
114 State v. Benton, 206 Conn. 90, 536 A.2d 572 (1988) (listening with naked ear while “not closer than twelve to eighteen inches to
the common wall” of the duplex).
115 In Commonwealth v. Hall, 366 Mass. 790, 323 N.E.2d 319 (1975), the apartment building in question had double doors; after
passing through the first one into the vestibule, a visitor confronted another door and three doorbells, one for each apartment. This
door could be opened by key or by a buzzer mechanism activated from one of the apartments. The police gained entry twice-once
when the door happened to be unlocked, once by immediately following a person who had rung a doorbell and had been admitted
by buzzer. The court held the hallway was not a public area because “the arrangement made-the lock on the downstairs door and
the buzzer system—was designed to exclude members of the public and to admit none but the defendant’s own guests and invitees.
… A justified expectation of privacy therefore arose. That the lock on the vestibule door could be and was bypassed on the two
occasions when the eavesdropping took place cannot alter the picture, for police do not have carte blanche to pass through doors
that are unlocked or even ajar if the area beyond has a private character.”
See also People v. Killebrew, 76 Mich.App. 215, 256 N.W.2d 581 (1977); State v. Ortiz, 257 Neb. 784, 600 N.W.2d 805 (1999)
215

(“under the case law, the degree of privacy society is willing to accord an apartment hallway may depend on the facts, such as
whether there is an outer door locked to the street which limits access …; the number of residents using the hallway …; the number
of units in the apartment complex …; and the presence or absence of no trespassing signage”).
116 United States v. Moore, 463 F.Supp. 1266 (S.D.N.Y.1979); People v. Foster, 19 Cal.App.3d 649, 97 Cal.Rptr. 94 (1971);
Commonwealth v. Dinnall, 366 Mass. 165, 314 N.E.2d 903 (1974); State v. Kuznitz, 105 N.J.Super. 33, 250 A.2d 802 (1969).
117 United States v. Llanes, 398 F.2d 880 (2d Cir.1968).
118 Amsterdam, supra note 82, at 403.
119 Id. at 404.
120 Ibid.
121 Id. at 405. Some courts have indicated that surveillance into premises, even when a search, is not of the same order as a search
which involves a physical entry of the premises and scrutiny of possessions therein, so that somewhat different Fourth Amendment
standards are applicable in the surveillance cases. See, e.g., Texas v. Gonzales, 388 F.2d 145 (5th Cir.1968); Borum v. United
States, 318 A.2d 590 (D.C.App.1974).
122 See Florida v. Riley, 488 U.S. 445, 109 S.Ct. 693, 102 L.Ed.2d 835 (1989), involving helicopter surveillance. Though a majority of
the Court held on the facts presented that the defendant had not established a search had occurred, Blackmun, J., dissenting,
observed that a majority of the Court accepted the notion that it is a search to so view within defendant’s curtilage if “private
helicopters rarely fly over curtilages” at that altitude, though such flight was “at a lawful altitude under FAA regulations.” That is,
in essence, the “public vantage point” concept. Also, no less than four Justices in Riley discuss the second point of whether the
resident has done all that can be expected of him by way of protecting his property from outside scrutiny.
123 Pate v. Municipal Court, 11 Cal.App.3d 721, 89 Cal.Rptr. 893 (1970).
124 United States v. Wright, 449 F.2d 1355 (D.C.Cir.1971). Consider, in this regard, the bringing of a drug-sniffing dog into the
hallway, discussed in § 2.2(g).
125 Cohen v. Superior Court, 5 Cal.App.3d 429, 85 Cal.Rptr. 354 (1970).
126 In State v. Clarke, 242 So.2d 791 (Fla.App.1970), the court held that because “the fire escape of the apartment complex was a
common escape route for use by any persons,” “the occupants of the apartment in question had no reasonable right to expect any
privacy with relation to what they did inside the window within easy view of any person on that fire escape.”
127 Pate v. Municipal Court, 11 Cal.App.3d 721, 89 Cal.Rptr. 893 (1970) (where occupants of motel room had drawn curtains so that
observations could not be made from adjacent ground area, it a search for officers to climb onto a second-story trellis and there
look into window); Borum v. United States, 318 A.2d 590 (D.C.App.1974) (surveillance from roof atop the lobby into second floor
hotel room is a search); Commonwealth v. Panetti, 406 Mass. 230, 547 N.E.2d 46 (1989) (it a search for police to overhear
defendant’s conversations from crawl space under his first floor apartment, given defendant’s justified expectation “that no one
would be in the crawl space to which neither the public nor tenants had access”); State v. Carter, 569 N.W.2d 169 (Minn.1997)
(police conducted search by looking in apartment window, as even if “the area just outside the apartment window was a common
area, the fact that [the officer] left the sidewalk, walked across the grass, climbed over the bushes, placed his face within 12 to 18
inches of the window … makes it clear that he took extraordinary measures to enable himself to view the inside of a private
building”); State v. Alexander, 170 N.J.Super. 298, 406 A.2d 313 (1979), order aff’d, 173 N.J.Super. 260, 414 A.2d 36 (1980)
(police looked in defendant’s second-story apartment by leaning over fire escape railing to see in window 8 feet from fire escape;
this a search as the window was “well out of the view of anyone engaged in normal use of the fire escape”).
128 McDonald v. United States, 335 U.S. 451, 69 S.Ct. 191, 93 L.Ed. 153 (1948).
129 As Amsterdam, supra note 82, at 389, notes: “Examination of the syllogism would, I think, have stirred some of the fourth
amendment’s deeper difficulties. But the rejection of its result was as foreordained as Zarathustra’s rejection of the gods, and for
much the same reason. If this totally unreasonable conduct were not a search and seizure, how could the Supreme Court condemn
it as an unreasonable search and seizure Therefore, it was a search and seizure.”
130 Borum v. United States, 318 A.2d 590 (D.C.App.1974).
216

131 United States v. Llanes, 398 F.2d 880 (2d Cir.1968).
132 State v. Person, 34 Ohio Misc. 97, 298 N.E.2d 922 (1973) (concluding that even though the landlord’s son could admit the police
to the hallway of the rooming house, the police officer’s actions in “surreptitiously peering through a keyhole” constituted a Fourth
Amendment search). Cf. State v. Morrow, 95 Wis.2d 595, 291 N.W.2d 298 (App.1980) (where officer assumed prone position on
floor of hotel hallway and looked under door into room, this a search, but one made on probable cause and in exigent
circumstances on facts of this case).
133 Cf. State v. Adams, 378 So.2d 72 (Fla.App.1979) (where police looked in defendant’s room in a rooming house by going onto the
porch and then standing on a chair to peer through a window above eye level, this was a search because defendant had a reasonable
expectation of privacy against such surveillance).
134 State v. Carter, note 127 supra (also emphasizing officer “peered through a small gap between the blinds”).
Compare United States v. Fields, 113 F.3d 313 (2d Cir.1997) (distinguishing case in which court held it a search to look through a
very small opening in a sheet of plywood covering a broken window, court concludes looking from common area of apartment
complex into bedroom no search, given “the five-to six-inch opening beneath the blinds in this case” which was “sufficiently large
to be clearly visible from the interior of the room to anyone who cared enough about his privacy to close the blinds”).
135 United States v. Potts, 297 F.2d 68 (6th Cir.1961). The Supreme Court stated in Oliver v. United States, 466 U.S. 170, 104 S.Ct.
1735, 80 L.Ed.2d 214 (1984), that “the curtilage is the area to which extends the intimate activity associated with the ‘sanctity of a
man’s home and the privacies of life, … and therefore has been considered part of home itself for Fourth Amendment purposes.
Thus, courts have extended Fourth Amendment protection to the curtilage; and they have defined the curtilage, as did the common
law, by reference to the factors that determine whether an individual reasonably may expect that an area immediately adjacent to
the home will remain private.” The Court added that “for most homes, the boundaries of the curtilage will be clearly marked; and
the conception defining the curtilage-as the area around the home to which the activity of home life extends-is a familiar one easily
understood from our daily experience.”
The extent of the curtilage depends upon the nature of the premises. As stated in Commonwealth v. Thomas, 358 Mass. 771, 267
N.E.2d 489 (1971): “In a modern urban multifamily apartment house, the area within the ‘curtilage’ is necessarily much more
limited than in the case of a rural dwelling subject to one owner’s control. … In such an apartment house, a tenant’s ‘dwelling’
cannot reasonably be said to extend beyond his own apartment and perhaps any separate areas subject to his exclusive control.”
136 Taylor v. United States, 286 U.S. 1, 52 S.Ct. 466, 76 L.Ed. 951 (1932); Martin v. United States, 183 F.2d 436 (4th Cir.1950); State
v. Brochu, 237 A.2d 418 (Me.1967); State v. Winkler, 552 N.W.2d 347 (N.D.1996).
Distinguishable from those decisions is City of Whitefish v. Large, 318 Mont. 310, 80 P.3d 427 (2003) (where defendant’s carport
was attached to but beneath her condominium unit, police could enter the carport because “it would be comparable to the front
porch” in other cases, as “casual visitors might easily walk through her carport to reach the stairs to her front door”).
State v. Jenkins, 143 Idaho 918, 155 P.3d 1157 (2007).
137 Rosencranz v. United States, 356 F.2d 310 (1st Cir.1966); Walker v. United States, 225 F.2d 447 (5th Cir.1955).
138 Roberson v. United States, 165 F.2d 752 (6th Cir.1948).
139 Wakkuri v. United States, 67 F.2d 844 (6th Cir.1933).
140 People v. Lind, 370 Ill. 131, 18 N.E.2d 189 (1938); Cantu v. State, 557 S.W.2d 107 (Tex.Crim.App.1977).
141 Carney v. United States, 163 F.2d 784 (9th Cir.1947); Guaresimo v. United States, 13 F.2d 848 (6th Cir.1926); People v. Lees, 257
Cal.App.2d 363, 64 Cal.Rptr. 888 (1967); People v. Swanberg, 22 A.D.2d 902, 255 N.Y.S.2d 267 (1964).
142 Schnorenberg v. United States, 23 F.2d 38 (7th Cir.1927); Guaresimo v. United States, 13 F.2d 848 (6th Cir.1926).
143 Hodges v. United States, 243 F.2d 281 (5th Cir.1957); Schnorenberg v. United States, 23 F.2d 38 (7th Cir.1927).
144 United States v. McBride, 287 F. 214 (S.D.Ala.1922).
145 United States v. Mitchell, 12 F.2d 88 (S.D.Tex.1926).
146 Brock v. United States, 256 F.2d 55 (5th Cir.1958) (was 150 to 180 feet from residence).
217

147 Rives, J., dissenting in Walker v. United States, 225 F.2d 447 (5th Cir.1955).
148 United States v. Hayden, 140 F.Supp. 429 (D.Md.1956).
149 Katz v. United States, 389 U.S. 347, 88 S.Ct. 507, 19 L.Ed.2d 576 (1967).
150 E.g., Los Angeles Police Protective League v. Gates, 907 F.2d 879 (9th Cir.1990) (garage connected to home); Kishel v. State, 287
So.2d 414 (Fla.App.1974) (building located 30 feet from residence); McGee v. State, 133 Ga.App. 184, 210 S.E.2d 355 (1974)
(shed within 45 to 69 feet of the house on a country farm); State v. Legg, 633 N.W.2d 763 (Iowa 2001) (garage attached to house);
State v. Winkler, 552 N.W.2d 347 (N.D.1996) (garage near house).
E.g., State v. Trusiani, 854 A.2d 860 (Me.2004) (attached garage used for storage and used as entry by family but not by visitors).
151 People v. Weisenberger, 183 Colo. 353, 516 P.2d 1128 (1973). See also State v. Showalter, 427 N.W.2d 166 (Iowa 1988) (entry of
barn outside curtilage a search, as defendant has expectation of privacy as to it independent from house and curtilage); State v.
Vicars, 207 Neb. 325, 299 N.W.2d 421 (1980) (was a search to enter calf shed 100 feet from residence and on opposite side of
chain link fence surrounding yard, as “shed was clearly used by the defendant’s family in their farming operation in such a manner
that there was certainly a reasonable expectation of privacy in the shed”).
152 Oliver v. United States, 466 U.S. 170, 104 S.Ct. 1735, 80 L.Ed.2d 214 (1984).
153 Hester v. United States, 265 U.S. 57, 44 S.Ct. 445, 68 L.Ed. 898 (1924).
154 See § 2.4(a).
155 United States v. Dunn, 480 U.S. 294, 107 S.Ct. 1134, 94 L.Ed.2d 326 (1987).
156 See § 2.3(e).
157 Thus in State v. Showalter, 427 N.W.2d 166 (Iowa 1988), the court viewed Dunn as no bar to concluding the defendant had an
expectation of privacy as to his barn outside the curtilage; and in Siebert v. Severino, 256 F.3d 648 (7th Cir.2001), the court
reached the same conclusion as to plaintiff in § 1983 action.
Compare State v. Martin, 553 A.2d 1264 (Me.1989) (no search to enter “a shanty for animals to get in out of the weather” located
50 ft. from defendant’s dwelling, as it not within curtilage; because freezer in shed apparently not connected to electrical supply,
the shed not an area which “harbors the intimate activities associated with the sanctity of a home and the privacies of life”).
To the same effect is People v. Pitman, 211 Ill.2d 502, 286 Ill.Dec. 36, 813 N.E.2d 93 (2004).
See other cases in note 51, § 2.4(a).
158 United States v. Hanahan, 442 F.2d 649 (7th Cir.1971).
159 United States v. Wright, 449 F.2d 1355 (D.C.Cir.1971); Bruce v. State, 268 Ind. 180, 375 N.E.2d 1042 (1978).
160 See § 2.3(c).
161 State v. Mack, 21 Or.App. 522, 535 P.2d 766 (1975).
162 United States v. Hufford, 539 F.2d 32 (9th Cir.1976). See also State v. Bobic, 140 Wash.2d 250, 996 P.2d 610 (2000) (relying on
Hufford, court holds there no search where officer looked into defendant’s rented storage unit from unrented adjoining unit by
looking through small hole in the wall without aid of flashlight; no search, considering that “the detective’s observations were
made without extraordinary or invasive means and could be seen by anyone renting the unit”).
163 See § 2.4(a).
164 United States v. Mooring, 137 F.3d 595 (8th Cir.1998); United States v. Brady, 993 F.2d 177 (9th Cir.1993); Whistenant v. State,
50 Ala.App. 182, 278 So.2d 183 (1973).
165 Fullbright v. United States, 392 F.2d 432 (10th Cir.1968).
166 For more on the use of binoculars, see § 2.2(b).
218

167 The reference is to the “open fields” case of Hester v. United States, 265 U.S. 57, 44 S.Ct. 445, 68 L.Ed. 898 (1924).
168 Another way in which the curtilage concept is occasionally used inconsistently with the Katz test, though fully consistent with the
traditional curtilage definition, see text at note 135 supra, is by assuming that a protected privacy expectation in a structure such as
a barn can exist only if the adjacent residence is occupied. See, e.g., Norman v. State, 362 So.2d 444 (Fla.App.1978) (because
house on farm not occupied, the barn “did not have the same protected status” it would otherwise have, and thus police could climb
fence and walk 250 yards to barn and look through windows with flashlight, though they knew a man living elsewhere was
working the farm). As was recognized in overturning that decision, 379 So.2d 643 (Fla.1980), it makes no sense to say that a
farmer has a justified expectation of privacy as to his “business premises” (e.g., a barn) only if he lives immediately adjacent
thereto.
169 United States v. Minton, 488 F.2d 37 (4th Cir.1973).
170 People v. Superior Court, 33 Cal.App.3d 475, 109 Cal.Rptr. 106 (1973). See also United States v. French, 291 F.3d 945 (7th
Cir.2002) (no search where officer looked into shed from gravel walkway, as it a “route which any visitor … would use”); Pistro v.
State, 590 P.2d 884 (Alaska 1979) (officer could see through garage window from driveway, “a normal means of ingress and
egress impliedly open to public use by one desiring to speak to occupants of the garage, or to park off the street while visiting
occupants of the house”); People v. Houze, 425 Mich. 82, 387 N.W.2d 807 (1986) (no search where police “looked into an
unattached garage which abutted a public alley from a common access route”); State v. Winkler, 552 N.W.2d 347 (N.D.1996)
(where officers “entered Winkler’s property on the driveway, which extends over 200 feet from the public road to Winker’s home,
and followed the driveway’s right-hand turn behind the home” to where they could see into the open garage, this no search, as “any
member of the public would have entered upon Winkler’s property in the manner the officers did”).
Compare State v. Christensen, 131 Idaho 143, 953 P.2d 583 (1998) (under state constitution, where officer approached residence
and in doing so saw marijuana in hot hut, this an illegal search, as while property not fenced, officer passed over or by gate clearly
posted with “No Trespassing” sign, as a “reasonable respectful citizen when confronted with a closed gate and a no trespassing
sign does not proceed further”; sign does not create “an absolute barrier to warrantless entry into the curtilage by police,” who
could nonetheless approach the house in a more serious matter than here, where police came upon premises “only to make general
inquiries about nearby residents”).
171 United States v. Knight, 451 F.2d 275 (5th Cir.1971).
172 United States v. French, 291 F.3d 945 (7th Cir.2002) (stressing “that Kelly came to French’s property not to conduct a search, but
for the express purpose of locating an errant probationer” he believed was on that property). Compare State v. Ross, 141 Wash.2d
304, 4 P.3d 130 (2000) (officers here were not “on legitimate police business,” as “the officers’ purpose was not to investigate
criminal activity but to obtain information to prepare the affidavit in order to obtain a search warrant,” for they “entered the
property at 12:10 a.m., an hour when no reasonably respectful citizen would be welcome absent actual invitation or an
emergency,” and they “had no intention of contacting the defendant,” but rather walked up the driveway to the garage, where they
smelled marijuana therein, in an attempt to determine whether that was the smell noticed on an earlier visit).
173 State v. Crea, 305 Minn. 342, 233 N.W.2d 736 (1975).
174 United States v. Knight, 451 F.2d 275 (5th Cir.1971); Bower v. State, 769 S.W.2d 887 (Tex.Crim.App.1989) (officer looked in
garage while approaching “front door by the only means of access-the driveway”); Bies v. State, 76 Wis.2d 457, 251 N.W.2d 461
(1977).
175 However, an officer may have some other legitimate reason for departing from that route, in which case observations made within
structures will still come within the plain view doctrine. See Doe v. State, 131 Idaho 851, 965 P.2d 816 (1998) (where police,
seeking to question defendant, implicated in a burglary, went to dairy farm where he resided with parents and, when no one
answered door of residence, walked to area of a shop 40–50 ft. away and there saw a vehicle and shotgun through open shop doors,
this no search, for “[a]fter finding no one in the home, it was reasonable for the officer to look for Doe in the shop, especially when
the area was well lit,” and it “reasonable to conclude that the occupants could be found working somewhere on the property”);
State v. Krout, 100 N.M. 661, 674 P.2d 1121 (1984) (seeking out a person to be arrested).
See State v. DeWitt, 324 Mont. 39, 101 P.3d 277 (2004) (where defendant did not answer residence door when police knocked, but
his truck was parking in driveway with warm engine and light was on inside garage, police properly knocked on side entry door to
garage, so when door swung open because of the knock police made no search in seeing smoke and smelling exhaust).
176 Daughenbaugh v. City of Tiffin, 150 F.3d 594 (6th Cir.1998) (looking into plaintiff’s open garage from plaintiff’s back yard,
where police not lawfully present, a search); United States v. Morehead, 959 F.2d 1489 (10th Cir.1992) (looking in window of
219

shop building near residence a search, but was lawful because police there with a warrant to arrest defendant and had reason to
believe defendant inside shop building because light on there and no one answered at residence); Ex parte Maddox, 502 So.2d 786
(Ala.1986) (looking into greenhouse from within curtilage is a search; vantage point not on regular route of visitors to farm);
Norman v. State, 379 So.2d 643 (Fla.1980) (it a search for officer to climb fence to which gate locked and then look into barn;
privacy expectation justified because defendant “took overt steps to designate his farm and barn not open to the public”; the “barn,
an integral part of petitioner’s farming business, enjoyed the same Fourth Amendment protection as do other business premises”);
Huffer v. State, 344 So.2d 1332 (Fla.App.1977) (officers walked through side yard to back yard and shined light through small tear
in plastic cover of hothouse and saw marijuana plants inside; held, “[u]nder either the traditional curtilage approach or the more
contemporary reasonable expectation of privacy approach, the appellant’s hothouse was deserving of constitutional protection”);
Gonzalez v. State, 588 S.W.2d 355 (Tex.Crim.App.1979) (it a search when officer deviated from normal route of visitor on
property to peek into outdoor toilet near dwelling); State v. Daugherty, 94 Wash.2d 263, 616 P.2d 649 (1980) (it a search to look
into garage where defendant had backed up 2 trucks to open garage door to block view and officer went between the trucks,
beyond that part of the driveway which was a pathway to the house, to gain view).
177 State v. Christensen, 131 Idaho 143, 953 P.2d 583 (1998).
178 Amsterdam, Perspectives on the Fourth Amendment, 58 Minn.L.Rev. 349, 403 (1974).
179 United States v. Wright, 449 F.2d 1355 (D.C.Cir.1971).
180 Wright, J., dissenting in United States v. Wright, 449 F.2d 1355 (D.C.Cir.1971).
181 As to whether it should be otherwise when aids to the natural senses are employed, see § 2.2.
182 United States v. Minton, 488 F.2d 37 (4th Cir.1973); Fullbright v. United States, 392 F.2d 432 (10th Cir.1968); Bies v. State, 76
Wis.2d 457, 251 N.W.2d 461 (1977).
183 United States v. Hanahan, 442 F.2d 649 (7th Cir.1971); State v. Mack, 21 Or.App. 522, 535 P.2d 766 (1975).
184 This is not to say that all of the restrictions applicable to entry of such a structure should necessarily be imposed as to such a lesser
intrusion. See Amsterdam, supra note 178, at 388–95.
185 United States v. Dunn, 766 F.2d 880 (5th Cir.1985).
186 Oliver v. United States, 466 U.S. 170, 104 S.Ct. 1735, 80 L.Ed.2d 214 (1984).
187 But, the term might be applied to a lesser structure. See, e.g., Rainey v. Hartness, 339 Ark. 293, 5 S.W.3d 410 (1999) (entry of
wooded area no search because it within open field doctrine, and it likewise no search to look into deer stand there, as it “little
more than a metal box, with sides three to four feet high and a roof elevated on poles,” as persons within “were exposed to the
public’s view,” and there no evidence plaintiff “used the stand to engage in private activity, other than eating meals, or that he
attempted to shield his activities from the public”).
188 United States v. Dunn, 782 F.2d 1226 (5th Cir.1986).
189 United States v. Dunn, 480 U.S. 294, 107 S.Ct. 1134, 94 L.Ed.2d 326 (1987), discussed in Note, 18 Golden Gate U.L.Rev. 397
(1988).
190 This aspect of the case is discussed in § 2.4(a).
190.1 See also United States v. Gerard, 362 F.3d 484 (8th Cir.2004) (where garage outside curtilage of farmhouse, officer did not
conduct illegal warrantless search of 2-story garage when he climbed ladder to peer through vent into lighted and locked garage in
attempt to locate or ascertain safety of owner).
191 California v. Ciraolo, 476 U.S. 207, 106 S.Ct. 1809, 90 L.Ed.2d 210 (1986).
192 See § 2.3(g).
193 See, e.g., United States v. Wright, 449 F.2d 1355 (D.C.Cir.1971) (use of flashlight to look through small crack between garage
doors); People v. Superior Court, 33 Cal.App.3d 475, 109 Cal.Rptr. 106 (1973) (looking through cracks in garage door, aided
220

however by fact lights were on inside the garage).
194 United States v. Vilhotti, 323 F.Supp. 425 (S.D.N.Y.1971).
195 See also State v. Bowling, 867 S.W.2d 338 (Tenn.Crim.App.1993) (police viewing of defendant’s truck, parked in his garage, was
a search, as “truck was behind a solid, completely closed garage door,” and while “the only other garage door was open, it had
been raised a mere one and a half feet to allegedly enable the dog to come and go,” so officer’s “actions of getting on his hands and
knees with his head very near to the ground and looking into the garage are not those actions which society would permit of a
reasonably respectful citizen”).
Compare United States v. Pace, 955 F.2d 270 (5th Cir.1992) (declining, on basis of Supreme Court’s Dunn case, supra, to reach
same result where a barn outside the curtilage involved; while “officers could not see inside the barn from any distance, but had to
press their faces close to the opening to see inside,” court concluded controlling fact was that police were still outside curtilage at
time of observation; decision subject to question in that one of the four factors in Dunn was that the defendants there had done little
to prevent someone standing in the open fields from viewing the interior of the barn).
Compare State v. Buzzard, 112 Ohio St.3d 451, 860 N.E.2d 1006 (2007) (where tracks from burglarized business led to driveway
ending at nearby windowless building, but locked double door was “warped and loose fitting” so that quarter-inch gap allowed
police to see stolen goods within, that no search, as “the viewing took place in front of the garage, where there is a diminished
expectation of privacy”).
196 See the dissent by Wright, J., in the rather similar case of United States v. Wright, 449 F.2d 1355 (D.C.Cir.1971). It may be,
however, that Wright is a better case than Vilhotti for finding that a search had occurred. In Vilhotti the gaps were “readily
apparent to any passerby”; In Wright, the majority said there was “a nine-inch gap between the doors,” but the dissent points out
that the “records shows that the ‘nine-inch gap’ was actually an eight-inch slit one half inch wide … and the police may have
pulled on the doors so they could see inside.”
197 Florida v. Riley, 488 U.S. 445, 109 S.Ct. 693, 102 L.Ed.2d 835 (1989), discussed in Foster, Warrantless Aerial Surveillance and
the Right to Privacy: The Flight of the Fourth Amendment, 56 J. Air & Com. 719 (1991); 28 Duq.L.Rev. 327 (1990); 17
Fla.St.U.L.Rev. 157 (1989); 17 Hastings Const.L.Q. 725 (1990); 19 Stetson L.Rev. 273 (1989); 23 Suffolk U.L.Rev. 866 (1989);
62 U.Colo.L.Rev. 407 (1991); 67 U.Detr.L.Rev. 143 (1989); 38 U.Kan.L.Rev. 107 (1990); 1990 Utah L.Rev. 407; 43 Vand.L.Rev.
275 (1990).
198 California v. Ciraolo, 476 U.S. 207, 106 S.Ct. 1809, 90 L.Ed.2d 210 (1986).
199 See the discussion of Ciraolo in § 2.3(g).
200 On use of such devices, see § 2.2(b), (c) and (d).
201 They assert: “This is not to say that an inspection of the curtilage of a house from an aircraft will always pass muster under the
Fourth Amendment simply because the plane is within the navigable airspace specified by law.”
202 See also Henderson v. People, 879 P.2d 383 (Colo.1994) (no search where helicopter overflight, by which marijuana plants in shed
spotted, was between 500 and 700 ft. and notwithstanding five passes there was “little evidence of the noise, wind, dust, threat of
injury, or interference with the use of the curtilage” required by Riley).
Compare Commonwealth v. Oglialoro, 525 Pa. 250, 579 A.2d 1288 (1990) (where police in helicopter “reduced their altitude to 50
feet, where they hovered over the property for 15 seconds and then made 3 passes over the property over a five minute period,” so
the defendant’s wife “experienced sensations caused by the helicopter’s proximity, including loud noise and vibration of the house
and windows,” “such evidence is sufficient to establish that the helicopter’s presence at 50 feet above the barn represented a hazard
to persons and property on the ground and that the conduct of the police in flying at this level was unreasonable”).
203 The plurality ambiguously refers to where flights are “sufficiently rare”; O’Connor, J., concurring, asks whether “members of the
public travel with sufficient regularity” at that altitude; Brennan, J. (joined by two other Justices), dissenting, inquiries whether
“public observation” of Riley’s curtilage was “commonplace”; and Blackmun, J., dissenting, asks whether “private helicopters
rarely fly over curtilages at an altitude of 400 feet.”
204 The 4-Justice plurality assumed nonrarity from the collective facts that there are over 10,000 helicopters in the U.S. and that it is
lawful to operate them at 400 feet. By reference to “the record not suggesting otherwise,” they seemed to assume the defendant had
the burden (unmet here) of showing otherwise. O’Connor, J., concurring, more specifically relied on the fact “the defendant must
bear the burden of proving that his expectation of privacy was a reasonable one,” which included proof of the rarity of helicopters
at 400 feet. Blackmun, J., dissenting, “would impose upon the prosecution the burden of proving contrary facts necessary to show
221

Riley lacked a reasonable expectation of privacy,” and would remand to permit such a showing (i.e., nonrarity of helicopter flights
at 400 feet) “because our prior cases gave the parties little guidance on the burden of proof issue.” The other three dissenters would
simply “take judicial notice that … such flights are a rarity,” but added that in burden-of-proof terms the burden should be on the
prosecution because it “has greater access to information concerning customary flight patterns and because the coercive power of
the State ought not be brought to bear in cases in which it is unclear whether the prosecution is a product of an unconstitutional,
warrantless search.”
205 Compare United States v. Barajas-Avalos, 359 F.3d 1204 (9th Cir.2004) (where 12-foot travel trailer was parked in “natural
clearing” on defendant’s farm land, while interior of such “a ‘non-traditional’ house” protected by Fourth Amendment against
entry, police did not violate defendant’s rights “by viewing the interior of the travel trailer through a window,” as the clearing was
not a “curtilage” because “there is no evidence that the travel trailer was used as a permanent or temporary home since 1993”);
Olson v. State, 166 Ga.App. 104, 303 S.E.2d 309 (1983) (uninhabited house is not a dwelling and thus lacks a protected curtilage).
Compare United States v. Basher, 629 F.3d 1161 (9th Cir.2011) (“classifying the area outside of a tent in a National Park or
National Forest land campsite as curtilage would be very problematic,” as such sites “are open to the public and exposed”).
Re Barajas-Avales: as amended, 377 F.3d 1040 (9th Cir.2004).
206 Care v. United States, 231 F.2d 22 (10th Cir.1956).
207 Katz v. United States, 389 U.S. 347, 88 S.Ct. 507, 19 L.Ed.2d 576 (1967).
Compare Wattenburg v. United States, 388 F.2d 853 (9th Cir.1968) (asserting that after Katz “a more appropriate test in
determining if a search and seizure adjacent to a house is constitutionally forbidden is whether it constitutes an intrusion upon what
the resident seeks to preserve as private even in an area which, although adjacent to his home, is accessible to the public”).
208 United States v. Dunn, 480 U.S. 294, 107 S.Ct. 1134, 94 L.Ed.2d 326 (1987).
209 On the interpretation of these factors by the lower courts, see § 2.4(a).
210 This is not to say, however, that for such a search to be lawful all of the restrictions upon a search into premises must necessarily
be complied with. See, e.g., People v. Doerbecker, 39 N.Y.2d 448, 384 N.Y.S.2d 400, 348 N.E.2d 875 (1976), where an officer
without a warrant came upon land adjoining a residence and found a package containing guns and pills under some leaves. This
surveillance was at the headquarters of one of two motorcycle gangs between which a feud was under way, and members of one of
the gangs had already been apprehended with dynamite. After concluding that the officer had made a Fourth Amendment search
because he had intruded upon a justified expectation of privacy, the court continued: “That expectation, however, was only one of
the elements to be considered in determining the reasonableness of the search. Also relevant was the relatively limited extent of the
intrusion on the privacy when measured against the justification which existed for it. … Here, the intrusion was lesser rather than
greater, not extending into the primary building of the landowner or indeed into any building at all …; at the same time the
justification-the preservation of the public safety-was more than adequate.”
211 United States v. Magana, 512 F.2d 1169 (9th Cir.1975).
212 State v. Corbett, 15 Or.App. 470, 516 P.2d 487 (1973).
213 In Corbett, the court stated: “Criminal investigation is as legitimate a societal purpose as is census taking or mail delivery.” See
also United States v. Hammett, 236 F.3d 1054 (9th Cir.2001) (“officer may encroach upon the curtilage of a home for the purpose
of asking questions of the occupants”); Alvarez v. Montgomery County, 147 F.3d 354 (4th Cir.1998) (police lawfully entered
curtilage to investigate 911 call re underage drinking party); United States v. Daoust, 916 F.2d 757 (1st Cir.1990) (“policeman may
lawfully go to a person’s home to interview him”); Scott v. State, 347 Ark. 767, 67 S.W.3d 567 (2002) (officers who came onto
defendant’s front porch and knocked on his door “were justified in approaching Mr. Scott’s residence to question him about
potential criminal activity”); People v. Shorty, 731 P.2d 679 (Colo.1987) (“In conducting a criminal investigation, a police officer
may enter those residential areas that are expressly or impliedly held open to casual visitors”); Warner v. State, 773 N.E.2d 239
(Ind.2002) (“police were legitimately on the premises to question Warner as part of their initial investigation” of a murder); State v.
Townsend, 571 A.2d 1206 (Me.1990) (proper for officer to come into defendant’s driveway “pursuing his investigation of the
defendant, … even though he chose to disguise his real purpose by engaging the defendant in conversation about another matter”);
State v. Rand, 430 A.2d 808 (Me.1981) (“not unreasonable for the police officers, in the pursuit of criminal investigations, to seek
interviews with suspects or witnesses at their homes”); Doering v. State, 313 Md. 384, 545 A.2d 1281 (1988) (police properly
entered curtilage “in the course of a legitimate investigation of a serious crime”); Commonwealth v. A Juvenile (No. 2), 411 Mass.
157, 580 N.E.2d 1014 (1991) (to investigate possible hit-and-run vehicle in driveway); State v. Alayon, 459 N.W.2d 325
(Minn.1990) (officer “did not need a warrant or probable cause to walk up to defendant’s home, knock on the door and say the
things he said”); Waldrop v. State, 544 So.2d 834 (Miss.1989) (where owner of house trailer consented to search of it, police
222

properly crossed defendant’s land to accomplish their “right of ingress and egress” to the trailer); State v. Johnson, 171 N.J. 192,
793 A.2d 619 (2002) (officers came onto porch “for a legitimate investigative purpose,” i.e., “to investigate a report of drug
activity”); People v. Kozlowski, 69 N.Y.2d 761, 513 N.Y.S.2d 101, 505 N.E.2d 611 (1987) (“Nor were defendant’s constitutional
rights violated when the officer investigating the reported traffic incident entered upon defendant’s property, knocked on the front
door, and asked questions which defendant chose to answer”); State v. Lodermeier, 481 N.W.2d 614 (S.D.1992) (officers there to
question defendant “about a ladder he had reported stolen”); State v. Ryea, 153 Vt. 451, 571 A.2d 674 (1990) (officer properly
approached defendant after he pulled into his driveway to make Terry stop on suspicion defendant had been driving on suspended
license); State v. Byrne, 149 Vt. 224, 542 A.2d 276 (1988) (game warden properly entered curtilage “to conduct an investigation”);
State v. Aydelotte, 35 Wash.App. 125, 665 P.2d 443 (1983) (lower court erred in saying police may not enter curtilage to
investigate suspicious circumstances and that entry proper only if crime in fact occurred); State v. Seagull, 26 Wash.App. 58, 613
P.2d 528 (1980), judgment aff’d, 95 Wash.2d 898, 632 P.2d 44 (1981) (proper for officer to call at houses in vicinity to inquire
about blood-stained abandoned vehicle).
Compare Estate of Smith v. Marasco, 318 F.3d 497 (3d Cir.2003) (rejecting “sweeping proposition” that “officers may proceed to
the back of a home when they do not receive an answer at the front door any time they have a legitimate purpose for approaching
the house in the first place,” court holds officers may so proceed only if it “the only practical way of attempting to contact the
resident,” as “where the front door was inaccessible,” or if the “officers reasonably may believe … that the person they seek to
interview may be located elsewhere on property within the curtilage,” or because of “the presence of an exigency justifying entry
into the curtilage”); Rogers v. Pendleton, 249 F.3d 279 (4th Cir.2001) (right of police is “to knock on a residence’s door or
otherwise approach the residence seeking to speak to the inhabitants, not the right to make a general investigation in the curtilage
based on reasonable suspicion,” and right of police to “approach a home to speak to the inhabitants … clearly fails to encompass a
continued search of the curtilage for people or things after officers have spoken to the owner of a home and been asked to leave”).
See also Nikolas v. City of Omaha, 605 F.3d 539 (8th Cir.2010) (officer “could enter the property through its open gate and
proceed up the driveway to the front door of the main residence to ask for consent to search”); United States v. Lakoskey, 462 F.3d
965 (8th Cir.2006) (postal inspector was “lawfully allowed to approach * * * front door and contact [defendant] for investigative
purposes” re suspicious package); United States v. Taylor, 458 F.3d 1201 (11th Cir.2006) (police came on property on “legitimate
police business” after “911 hangup call” followed by more hangups in response to two call-backs); United States v. Weston, 443
F.3d 661 (8th Cir.2006) (entry “in furtherance of a legitimate law enforcement objective” permissible, and such the case here,
where officers intended “to inquire about stolen vehicles, and to request consent to search the remainder of the property”); Estate
of Smith v. Marasco, 430 F.3d 140 (3d Cir.2005) (upon responding to neighbor’s complaint of bright light on suspect’s property,
when officers did not receive response at front door but believed suspect was at home and knew he sometimes sat on back porch,
entry into backyard lawful, but same not true of subsequent entry after it learned suspect not there); People v. Rivera, 41 Cal.4th
304, 59 Cal.Rptr.3d 473, 159 P.3d 60 (2007) (police officer may approach and knock on door of residence, and such actions
“require no articulable suspicion of criminal activity”); Trimble v. State, 842 N.E.2d 798 (Ind.2006) (“police entry onto private
property and their observations do not violate the Fourth Amendment when the police have a legitimate investigatory purpose for
being on the property and limit their entry to places visitors would be expected to go”); Quintana v. Commonwealth, 276 S.W.3d
753 (Ky.2008) (“the officer who approaches the main entrance of a house has a right to be there, just as any member of the public
might be”); State v. Beane, 770 N.W.2d 283 (N.D.2009) (police on “legitimate business” may enter curtilage, as here, where they
seeking parole violator known to associate with resident); State v. Wright, 391 S.C. 436, 706 S.E.2d 324 (2011) (“A police officer
without a warrant is privileged to enter private property to investigate a complaint or a report of an ongoing crime”); Gompf v.
State, 120 P.3d 980 (Wyo.2005) (“absent a clear expression by the owner to the contrary, police officers are permitted to approach
a dwelling and seek permission to question an occupant in the course of their official business,” and such the case here though
officers arrived at 2 a.m., as the “lights were on in the house and the officers, therefore, assumed people were awake inside”).
Compare Jacob v. Township of West Bloomfield, 531 F.3d 385 (6th Cir.2008) (code enforcement officer’s repeated entry of
defendant’s curtilage and thereby discovering “castoff material” violating land use ordinance was a search); Knott v. Sullivan, 418
F.3d 561 (6th Cir.2005) (inspecting pile of ashes within curtilage was a search).
214 In Corbett, the purpose of the visit was to obtain some descriptive information to be used in applying for a search warrant. See also
United States v. Raines, 243 F.3d 419 (8th Cir.2001) (entry to serve civil process proper); United States v. Morehead, 959 F.2d
1489 (10th Cir.1992) (entry to serve arrest warrant on defendant); Causey v. State, 374 So.2d 406 (Ala.Crim.App.1979) (proper for
officer to go to door of defendant, “to whom it would seem he owed the courtesy of at least reporting to him that one of the stolen
tires had been found in his driveway”); Johnson v. State, 291 Ark. 260, 724 S.W.2d 160 (1987) (entry to arrest defendant for
observed offense, observation of marijuana thereafter a plain view situation); Gilreath v. State, 247 Ga. 814, 279 S.E.2d 650 (1981)
(proper for officer to call at house after woman’s father expressed concern for her safety).
Compare State v. Shepherd, 303 Ark. 447, 798 S.W.2d 45 (1990) (from driveway police looked through partially open garage
door; this not a lawful plain view, as police “were there on the pretext of serving an illegal subpoena”; dissent objects invalidity of
subpoena irrelevant where, as here, “an officer has come upon the land in the same way that any member of the public could be
expected to do”).
See also United States v. Frencher, 503 F.3d 701 (8th Cir.2007) (officers properly came onto property “to serve an eviction
notice,” and properly continued knocking on door when they detected movements within); Widgren v. Maple Grove Township,
223

429 F.3d 575 (6th Cir.2005) (zoning administrator’s intrusion onto owner’s property to post civil infraction notice on front door of
house not a search); State v. Orde, 161 N.H. 260, 13 A.3d 338 (2010) (“police officer has a right to enter a person’s curtilage or
legitimate business,” here “to serve a dog complaint”).
215 United States v. Raines, 243 F.3d 419 (8th Cir.2001) (where no one answered front door, but several cars parked on driveway and
it a summer evening, it proper for officer to walk through 10-foot opening in fence to backyard); United States v. Hammett, 236
F.3d 1054 (9th Cir.2001) (where no one answered front door, officer properly “circled the house with the intent of locating another
door”); United States v. Thomas, 120 F.3d 564 (5th Cir.1997) (police could take walkway to front door notwithstanding privacy
fence 3 feet from front door, as gate was open and there no door bell or knocker at the gate, so it “reasonable for the officers to
believe the front door was readily accessible to the general public”); United States v. James, 40 F.3d 850 (7th Cir.1994) (no search,
as officer “used a paved walkway along the side of the duplex leading to the rear side door,” “passage to the rear side door was not
impeded by a gate or fence,” and both “the paved walkway and the rear side door were accessible to the general public”); United
States v. Morehead, 959 F.2d 1489 (10th Cir.1992) (“walking to the back of the house” proper where police there to arrest
defendant and no answer at front door); United States v. Daoust, 916 F.2d 757 (1st Cir.1990) (where front door “is inaccessible
there is nothing unlawful or unreasonable about going to the back of the house to look for another door”); People v. Bradley, 1
Cal.3d 80, 81 Cal.Rptr. 457, 460 P.2d 129 (1969) (discovery of marijuana plants no search, as “they were located a scant 20 feet
from defendant’s door to which presumably delivery men and others came”); People v. Shorty, 731 P.2d 679 (Colo.1987) (picking
up unsecured 2 ft. square piece of carpeting serving as door mat in front of basement apartment 7 steps below ground level no
search: “While the Supreme Court has held that the curtilage surrounding one’s home may be protected under the Fourth
Amendment, … the fact that a search occurs within the curtilage is not dispositive if the area’s public accessibility dispels any
reasonable expectation of privacy”); State v. Duda, 437 So.2d 794 (Fla.App.1983) (marijuana seen when officer went to rear door,
which proper for him to do, as he sent to investigate domestic disturbance and noise was heard at rear of house); State v. Lyons,
167 Ga.App. 747, 307 S.E.2d 285 (1983) (proper for officer investigating animal complaint to go to back door, from which he saw
marijuana plants, as he “unable to elicit a response at the front door of a residence reasonably believed to be occupied”); Warner v.
State, 773 N.E.2d 239 (Ind.2002) (police who received no answer at front door properly went to side door); State v. Nine, 315
So.2d 667 (La.1975) (officer on a sideyard “used as a passageway”); State v. Hubbel, 286 Mont. 200, 951 P.2d 971 (1997) (police
“well within their authority to proceed on the open walkway to the front door, where they saw yet more evidence in plain view”);
State v. Ramaekers, 257 Neb. 391, 597 N.W.2d 608 (1999) (officer “was lawfully on the front walk when he observed the ongoing
party” in the yard, and thus observation no intrusion on justified expectation of privacy); State v. Byrne, 149 Vt. 224, 542 A.2d 276
(1988) (officer took walkway to steps, where hair and blood observed); State v. Seagull, 26 Wash.App. 58, 613 P.2d 528 (1980),
aff’d, 95 Wash.2d 898, 632 P.2d 44 (1981) (no search for officer to take sideyard path from south porch to north porch upon
recalling being told occupants could not hear knocking on south porch; though officer “strayed slightly from the most absolutely
direct route between the two doors,” it “would be unreasonable to require, in every case, that police officers walk a tight rope while
on private property engaging in legitimate police business”).
United States v. Cousins, 455 F.3d 1116 (10th Cir.2006) (entry of sideyard area lawful, as it was expected path one would take on
paved walkway); People v. Terrazas-Urquidi, 172 P.3d 453 (Colo.2007) (police approach of backyard shed lawful where defendant
“using the shed as living quarters, and the front door contained a peephole and a dead bolt, suggesting that he expected casual
visitors”); Hardister v. State, 849 N.E.2d 563 (Ind.2006) (defendant living at 407 “had no cognizable expectation of privacy
because the backyard and sidewalk were shared with the residents of 405 and were not enclosed by a fence”); Clausell v. State, 326
Mont. 63, 106 P.3d 1175 (2005) (”officers were well within their authority to proceed on the open walkway to the front door,
where they saw evidence in plain view”).
216 United States v. Reyes, 283 F.3d 446 (2d Cir.2002) (“we have found no Fourth Amendment violation based on a law enforcement
officer’s presence on an individual’s driveway where,” as here, “that officer was in pursuit of legitimate law enforcement
business”); United States v. Roberts, 747 F.2d 537 (9th Cir.1984) (police drove up shared unobstructed but private road and then
onto lawn of residence where cars parked, where no driveway as such); United States v. Ventling, 678 F.2d 63 (8th Cir.1982)
(driveway and yard adjacent to front door); McDonald v. State, __ Ark. __, 119 S.W.3d 41 (2003) (defendant “had no reasonable
expectation of privacy in the driveway” and thus officer’s observation of VIN of vehicles while in driveway lawful); People v.
Edelbacher, 47 Cal.3d 983, 254 Cal.Rptr. 586, 766 P.2d 1 (1989) (driveway a “normal route used by visitors approaching the front
doors”); State v. Brighter, 60 Haw. 318, 589 P.2d 527 (1979); State v. Lewis, 675 N.W.2d 516 (Iowa 2004) (“the Fourth
Amendment did not prohibit the police from entering Lewis’s driveway” and thus observation of backyard activities from there
lawful); State v. Townsend, 571 A.2d 1206 (Me.1990) (in entering driveway “the police officer did not exceed the ‘implied
invitation’ to use it when he entered on legitimate police business”); State v. Keniston, 483 A.2d 1240 (Me.1984) (driveway in
front of house onto which car being followed parked); State v. Rand, 430 A.2d 808 (Me.1981) (“a common driveway of a multiple
dwelling”); Commonwealth v. A Juvenile (No. 2), 411 Mass. 157, 580 N.E.2d 1014 (1991) (examination of car in driveway no
search where “the driveway was the normal route by which to approach the front door”); People v. Taormina, 130 Mich.App. 73,
343 N.W.2d 236 (1983) (long and circular driveway without gates); Mitchell v. State, 792 So.2d 192 (Miss.2001) (officer “was in
an area of common use, near the driveway”); State v. Hubbel, 286 Mont. 200, 951 P.2d 971 (1997) (“police were thus well within
their authority when they drove into the driveway and parked in the general parking area where they observed evidence in plain
224

view”); State v. Merrill, 252 Neb. 510, 563 N.W.2d 340 (1997) (given “the accessibility and visibility of the driveway from the
public roadway,” “any member of the public could have entered upon Merrill’s property in the same manner the officers did,” and
thus officers viewing of marihuana plants from driveway no search); State v. Johnston, 150 N.H. 448, 839 A.2d 830 (2004) (police
conduct proper, as “the defendant’s driveway was semi-private in nature, and the officers entered the property for a legitimate
purpose”); State v. Pinkham, 141 N.H. 188, 679 A.2d 589 (1996) (driveway “an access route to the house typically used by
neighbors, mail carriers, salespersons, and other visiting members of the public”); State v. Corbett, 15 Or.App. 470, 516 P.2d 487
(1973) (officer proceeded 150–200 feet up longer driveway through foliage; court stresses “the house number is marked at the
entry and there is no gate”); State v. Lodermeier, 481 N.W.2d 614 (S.D.1992) (officer examined exterior of garden tractor parked
in driveway lawful, as “officer with legitimate business may enter a driveway and, while there, may inspect objects in open view”);
State v. Pike, 143 Vt. 283, 465 A.2d 1348 (1983) (driveway “the normal route of access for anyone visiting the premises”); State v.
Maxfield, 125 Wash.2d 378, 886 P.2d 123 (1994) (no search, as officer “stayed on the pathway, the driveway or the immediate
access routes to the house and garage”).
United States v. Brown, 510 F.3d 57 (1st Cir.2007) (arrest made where officer properly positioned, in driveway next to garage,
especially considering that defendant ran a motor repair business from the garage and allowed customers to enter the driveway and
garage); United States v. Taylor, 458 F.3d 1201 (11th Cir.2006) (proper that officer “proceeded down the driveway that provided
access to the house” and “went to the front door”); United States v. Carter, 360 F.3d 1235 (10th Cir.2004) (officers’ actions in
“walking up the driveway, and shining their flashlight into a car in the driveway * * * do not implicate the Fourth Amendment”);
Tryon v. State, 371 Ark. 25, 263 S.W.3d 475 (2007) (no search as to what police viewed on defendant’s premises from his
driveway); Trimble v. State, 842 N.E.2d 798 (Ind.2006) (police properly on driveway where it “wraps around the back of
[defendant’s] house” to the “back door, the main entryway for visitors”); State v. Wright, 391 S.C. 436, 706 S.E.2d 324 (2011)
(lawful observation where police “could properly drive up the dirt driveway to get to the front door”); Robinson v.
Commonwealth, 273 Va. 26, 639 S.E.2d 217 (2007) (officer could properly drive up driveway, at least to point where it intersected
with path to front door).
217 Bickar v. Gray, 380 F.Supp. 804 (N.D.Ohio 1974) (“There were no signs warning the agents to stay away from the petitioner’s
porch and it was open for the use of tradesmen; thus it cannot be said that the agents were not entitled to go to the door and
knock”); United States v. Grogan, 293 F.Supp. 45 (M.D.Ala.1968) (officer on porch saw illegal liquor in car; this no search, as “it
would scarcely be reasonable to expect that no visitors with legitimate purposes would approach the house”); People v. Edelbacher,
47 Cal.3d 983, 254 Cal.Rptr. 586, 766 P.2d 1 (1989) (no search to observe and photograph shoe tracks on front porch); State v.
Detlefson, 335 So.2d 371 (Fla.App.1976) (“It cannot be said the defendant had a reasonable expectation of privacy in the front
porch of his home where, presumably, delivery men and others were free to observe”); State v. Tye, 276 Ga. 559, 580 S.E.2d 528
(2003) (where police came onto defendant’s porch to question him in connection with murder investigation, they “were in an
authorized location” when they saw defendant’s bloodstained clothing); Gilreath v. State, 247 Ga. 814, 279 S.E.2d 650 (1981)
(where no answer at front door, proper to go to side door and enter screened porch there); State v. Johnson, 171 N.J. 192, 793 A.2d
619 (2002) (officer “did not go beyond the porch, thus restricting his movements to the places that any other visitor could be
expected to go”); State v. Kitchen, 572 N.W.2d 106 (N.D.1997) (though police entered what court at one point refers to as an
“enclosed entryway,” court concludes it a “porch-type entrance,” as officer knocked on inside door flush with original exterior wall
of the house after entering a “vestibule-like addition” with an unlocked screen door, and police entry no search because that space
“was impliedly open to at least some access by the public”); State v. Rose, 128 Wash.2d 388, 909 P.2d 280 (1996).
Cf. State v. Wilbourn, 364 So.2d 995 (La.1978) (proper for police to view evidence of hit-run accident on exterior of car parked in
carport, where carport must be entered by anyone “knocking at the sidedoor to find out if someone was home or to deliver or sell
something”).
Compare State v. Reinier, 628 N.W.2d 460 (Iowa 2001) (“The porch of Reinier’s house was just like any other portion of her
house. It had glass-encased windows covered with blinds. The entrance to the porch had a solid wood door with a deadbolt lock
and a screen door. Reinier stored personal belongings in the porch and kept the wood door locked at night. These circumstances
reveal Reinier maintained an expectation of privacy which society clearly recognizes as reasonable. Thus, entry into the area by
police constituted a search”).
United States v. Titemore, 437 F.3d 251 (2d Cir.2006) (while porch was on side of building, it “was in fact a primary entrance
visible to and used by the public,” as manifested by fact “steps led up to the porch” and there a doorbell “suggest[ing] to visitors
that they could visit the home from the porch”); United States v. Thomas, 430 F.3d 274 (6th Cir.2005) (encounter with defendant
at back deck of residence proper, for “the rear deck was adjacent to the driveway and served as the primary entrance to Hopper’s
home”).
218 But consider Brown v. State, 392 So.2d 280 (Fla.App.1980), where defendant was seen on his back porch by police who had
driven past the gate and all the way up the driveway, and the court concluded this was a search because the events occurred at 1:45
a.m., a time when visitors would not ordinarily call, and thus defendant was entitled to expect privacy within his enclosed yard at
that time.
219 United States v. Van Dyke, 643 F.2d 992 (4th Cir.1981) (it a search for officers to climb fence and watch from honeysuckle patch
225

150 feet from house in rural area; curtilage not limited to nearer mowed area; assuming “that sheer distance could in some
instances lead us to conclude that a particular area was outside the curtilage even though inside a fence surrounding a residence,
this case does not present such a situation”); Griffin v. State, 347 Ark. 788, 67 S.W.3d 582 (2002) (though police obtained consent
to enter after knocking on door, that consent invalid because police had already made stealthy entry of the property after 10 p.m.
and had first “checked out a shed and walked around the premises”); State v. Parker, 399 So.2d 24 (Fla.App.1981) (was a search to
enter fenced back yard), as it “not accessible to the public” and was “more private than the (front”); Norman v. State, 134 Ga.App.
767, 216 S.E.2d 644 (1975) (officer examined car which was in small meadow behind barn on farm, not an access route); People v.
Pakula, 89 Ill.App.3d 789, 44 Ill.Dec. 919, 411 N.E.2d 1385 (1980) (it a search for officer to enter through closed gate to fenced
back yard); State v. Lewis, 675 N.W.2d 516 (Iowa 2004) (where “backyard was located adjacent to the home” and a “fence with a
gate completely enclosed the backyard” and “enclosed rear porch was located in the fenced backyard” and “screens and or
windows with a door fully enclosed the rear porch,” entry of yard and porch a search); State v. Silva, 509 A.2d 659 (Me.1986)
(entry of backyard area within curtilage a search); People v. Doerbecker, 39 N.Y.2d 448, 384 N.Y.S.2d 400, 348 N.E.2d 875
(1976) (see note 210 supra for facts); State v. Johnson, 301 N.W.2d 625 (N.D.1981) (it a search to look behind entry structure to
area not observable from road or nearby driveway to mobile home); Dale v. State, 38 P.3d 910 (Okla.Crim.2002) (agent’s entry of
defendant’s property “by climbing over the locked driveway gate, which was part of a secure perimeter fence, and proceeding
between the two residential structures in order to confront [him] was an unlawful entry onto the curtilage of the home”); State v.
Prier, 725 S.W.2d 667 (Tenn.1987) (entry of garden area within curtilage a search); Gonzalez v. State, 588 S.W.2d 355
(Tex.Crim.App.1979) (it a search where officer deviated from normal route to explore weeded area in back yard); State v. Harris,
671 P.2d 175 (Utah 1983) (a search where officer went to defendant’s garden, at rear of his property behind farm building and well
screened).
United States v. Struckman, 603 F.3d 731 (9th Cir.2010) (defendant’s “backyard—a small, enclosed yard adjacent to a home in a
residential neighborhood—is unquestionably” part of curtilage, and thus police entry without exigent circumstances unreasonable);
State v. Fisher, 283 Kan. 272, 154 P.3d 455 (2007) (search here, as “once [police officer’s] knock and talk was complete, instead
of driving away from the house to the highway, he simply drove deeper into the property on the driveway-according to the
photographs, perhaps as much as 50 yards-directly to the previously observed bag”); State v. Orde, 161 N.H. 260, 13 A.3d 338
(2010) (where police officer walked up onto deck at side of house and saw marijuana plants there, that illegal search, considering
that items on deck not visible from the road, the driveway, or the side door reached by path from driveway, and given officer’s
“departure from the obvious paths on the property”).
220 Hoffman v. People, 780 P.2d 471 (Colo.1989).
221 The cases upholding such police activity do not necessarily make it clear whether such action is deemed to be no search or a
reasonable search. See, e.g., Alvarez v. Montgomery County, 147 F.3d 354 (4th Cir.1998) (where police responding to 911 call re
underage drinking party approached front door to notify residents of complaint but, seeing sign reading “Party In Back,” walked
around house to back yard where party going on and asked to see host, such entry “did not exceed their legitimate purpose for
being there” and thus “satisfied the Fourth Amendment’s reasonableness requirement”); Brenneman v. State, 264 Ark. 460, 573
S.W.2d 47 (1978) (where officer seeking to serve traffic citation on defendant received no answer at door but saw defendant’s car
parked nearby, he properly went to rear of premises to see if defendant “was on the premises, but perhaps outside the house”);
State v. Hider, 649 A.2d 14 (Me.1994) (officer tracking thief from airport with tracking dog lawfully entered rear of defendant’s
curtilage); State v. Curtin, 175 W.Va. 318, 332 S.E.2d 619 (W.Va.1985) (police properly in yard at rear of house to secure
premises while others executed search warrant within).
United States v. Taylor, 458 F.3d 1201 (11th Cir.2006) (”to the extent that the officers moved away from the front door and toward
Taylor” when he walked out from behind the barn, “this small departure from the front door also does not trigger the protections of
the Fourth Amendment”); Tryon v. State, 371 Ark. 25, 263 S.W.3d 475 (2007) (officer “did not violate Tryon’s constitutional
rights by merely walking into the backyard after he saw Tryon take off running”); Vidos v. State, 367 Ark. 296, 239 S.W.3d 467
(2006) (where officer “knocked at the residence and discovered that no one was home,” his “merely walking from the house to the
barn” in search of person he sought lawful); State v. Dunn, 340 Mont. 31, 172 P.3d 110 (2007) (defendant “did not have a
reasonable expectation of privacy in his backyard area” vis-a-vis police entry to investigate neighbors’ complaint of loud party
there, where “noise was coming from the backyard”); State v. Domicz, 188 N.J. 285, 907 A.2d 395 (2006) (not objectionable that
police “passed through the rear gate and entered the curtilage for the purpose of knocking on defendant’s door and speaking with
him,” as “position of the parked cars in defendant’s driveway led the officers to believe that the back door was used by residents
and visitors”); State v. Beane, 770 N.W.2d 283 (N.D.2009) (“The officers’ ‘small departure’ from the front door of the residence to
meet Beane coming from the unattached garage also did not trigger the protections of the Fourth Amendment”).
221.1 Hardesty v. Hamburg Township, 461 F.3d 646 (6th Cir.2006). Accord: Estate of Smith v. Marasco, 318 F.3d 497 (3d Cir.2003);
United States v. Hammett, 236 F.3d 1054 (9th Cir.2001); United States v. Anderson, 552 F.2d 1296 (8th Cir. 1977); United States
v. Bradshaw, 490 F.2d 1097 (4th Cir.1974).
222 As stated in Commonwealth v. Thomas, 358 Mass. 771, 267 N.E.2d 489 (1971): “In a modern urban multifamily apartment house,
226

the area within the ‘curtilage’ is necessarily much more limited than in the case of a rural dwelling subject to one owner’s control.
… In such an apartment house, a tenant’s ‘dwelling’ cannot reasonably be said to extend beyond his own apartment and perhaps
any separate areas subject to his exclusive control.”
Compare United States v. Williams, 581 F.2d 451 (5th Cir.1978) (concluding, as to farm, that where the outbuildings “are not
encompassed by a fence that also includes the house, or perhaps a privacy or exclusionary one around them, the outer limits of the
curtilage are defined by the walls of the remote outbuildings,” so that it was no search to smell illegal liquor while positioned near
a shed but more distant from the main house than the shed); Sanders v. State, 264 Ark. 433, 572 S.W.2d 397 (1978) (garden some
100–200 yards behind house trailer, though separated by fence from trailer, was within curtilage, as police knew given fact they
first tried to justify search of garden as incident to execution of warrant for premises later held invalid).
223 United States v. Acosta, 965 F.2d 1248 (3d Cir.1992) (where “landlord gave the defendants permission to use the backyard” but
“the right to grant permission to others remained with the landlord” and “the landlord used the backyard freely, as did his
employees,” “the fact that defendants had permission to use the yard did not create any legal expectation of privacy in it”).
224 State v. Johnson, 171 N.J. 192, 793 A.2d 619 (2002) (questioning proposition that the “curtilage concept has limited applicability
with respect to multi-occupancy premises because none of the occupants can have a reasonable expectation of privacy in areas that
are also used by other occupants”).
225 State v. Hines, 323 So.2d 449 (La.1975). See also People v. Holt, 91 Ill.2d 480, 64 Ill.Dec. 550, 440 N.E.2d 102 (1982) (area under
porch of apartment building). The same is true of a motel, State v. Berry, 223 Kan. 102, 573 P.2d 584 (1977), a duplex, State v.
Hook, 60 Haw. 197, 587 P.2d 1224 (1978), or when two buildings have a common curtilage, Walley v. State, 353 Ark. 586, 112
S.W.3d 349 (2003) (“a person does not have an objectively reasonable expectation of privacy in the area around a rental residence,
especially where, as here, a second building on the property is rented to another person who shares the curtilage with the accused”).
See also Reeves v. Churchich, 484 F.3d 1244 (10th Cir.2007) (front yard of duplex not part of building’s curtilage, where yard not
enclosed and residents could not exclude others from the yard, which they shared with other residents).
226 United States v. Soliz, 129 F.3d 499 (9th Cir.1997) (no search for officer to enter parking area used by residents and guests, located
between buildings in 2-building apartment complex; court doubts whether “a shared common area in a multi-unit dwelling
compound is sufficiently privacy oriented to constitute curtilage”); State v. Coburne, 10 Wash.App. 298, 518 P.2d 747 (1973). The
same is true of a motel parking lot. United States v. Diaz, 25 F.3d 392 (6th Cir.1994).
227 See § 2.3(b).
228 Fixel v. Wainwright, 492 F.2d 480 (5th Cir.1974).
229 See also Espinoza v. State, 265 Ga. 171, 454 S.E.2d 765 (1995) (where defendant lived in left side of duplex and his apartment
reached by left half of a private driveway shaped like a stethoscope, search which uncovered garbage bag among bushes 7–8’ to
left of his driveway and outside the stethoscope, “a place where visitors to the duplex would not be expected to go,” intruded on
defendant’s justified expectation of privacy).
Compare United States v. Arboleda, 633 F.2d 985 (2d Cir.1980) (where defendant threw package out window of third-floor
apartment and it landed on ledge, officer could examine package, as there was no evidence defendant “exercised any exclusive
control over the ledge,” and “it is doubtful that the curtilage concept has much applicability to multi-family dwellings”); Bunn v.
State, 153 Ga.App. 270, 265 S.E.2d 88 (1980) (where common grassy area had 6-foot privacy fence, but there was an opening
between the fence and building which permitted persons to pass through the area and area was used by all tenants and their
invitees, it no search to enter that area; but this did not justify officer going onto adjoining concrete patio of particular apartment, as
that area qualifies as the curtilage of that apartment).
230 State v. Detlefson, 335 So.2d 371 (Fla.App.1976). See also United States v. Miller, 589 F.2d 1117 (1st Cir.1978) (court concluded
defendant had no justified expectation of privacy as to 40 lb. bale of marijuana on his residential land, though the bale was covered
by a tarpaulin, where nearby marijuana debris would have been apparent to any passerby).
231 Wattenburg v. United States, 388 F.2d 853 (9th Cir.1968). Also illustrative is State v. Goude, 49 Or.App. 721, 620 P.2d 957
(1980), where police examined a car up on blocks in defendant’s driveway. Noting that this was not a casual inspection, but
included looking inside and under the car, the court concluded this was a search because the defendant “could reasonably expect
that people would not be crawling around his car, opening the hood and possibly getting inside to inspect the interior.”
232 See note 223 supra.
233 Oliver v. United States, 466 U.S. 170, 104 S.Ct. 1735, 80 L.Ed.2d 214 (1984).
227

234 See § 2.4(a).
235 Of course, this conclusion merely establishes the lawfulness of the viewing or overhearing, and it does not follow that a warrantless
entry onto the premises to seize evidence would also be lawful. United States v. Whaley, 781 F.2d 417 (5th Cir.1986).
236 Causey v. State, 374 So.2d 406 (Ala.Crim.App.1979) (no search for officer to look into defendant’s property from public road);
Johnson v. State, 291 Ark. 260, 724 S.W.2d 160 (1987) (no search to observe from street defendant carrying stalks of marijuana);
Hoffman v. People, 780 P.2d 471 (Colo.1989) (no search to look into curtilage through wire mesh fence from service alley); State
v. Holbron, 65 Haw. 152, 648 P.2d 194 (1982) (no search to look into defendant’s yard from adjacent public tennis courts); State v.
Lorenz, 622 N.W.2d 243 (S.D.2001) (while on public road, officers observed and photographed marijuana plants growing
alongside defendant’s residence).
United States v. Bucci, 582 F.3d 108 (1st Cir.2009) (no search to view defendant’s driveway and garage interior for 8 months from
video camera on utility pole across the street, where those areas “plainly visible” from the street); United States v. Poole, 407 F.3d
767 (6th Cir.2005) (where “officers here merely looked into Appellant’s backyard from their position in the public alley,” no
search); Tryon v. State, 371 Ark. 25, 263 S.W.3d 475 (2007) (no search where officer saw defendant’s truck with air compressor in
bed, parked on defendant’s property, “from the road,” “a lawful vantage point”); State v. Wright, 391 S.C. 436, 706 S.E.2d 324
(2011) (activities outside adjacent to defendant’s residence “were knowingly exposed to the public” when observed by deputies
“driving by the residence on a public road”).
237 United States v. Campbell, 395 F.2d 848 (4th Cir.1968) (“the viewing by Alcohol and Tobacco Tax Division agents from an
adjacent cornfield of a transaction in illicit whiskey which took place in the back yard of Campbell’s home” was not a search);
People v. Superior Court, 37 Cal.App.3d 836, 112 Cal.Rptr. 764 (1974) (no search, as the “observations made by the officers
looking over the five-foot fence from the neighbor’s yard disclosed no more than what was in plain view of the neighboring
householders and anyone else who might be on their premises with or without an invitation”); People v. Ortega, 175 Colo. 136,
485 P.2d 894 (1971) (no search for police to watch defendant’s actions in back yard of apartment house from adjoining property);
State v. Rickard, 420 So.2d 303 (Fla.1982) (no search to observe marijuana plants in defendant’s yard from nearby citrus grove);
State v. Dupuis, 378 So.2d 934 (La.1979) (no search to look in from neighbor’s field, as “any stranger could have … been in the
field and observed the defendant’s loading activities”); State v. Pease, 520 A.2d 698 (Me.1987) (no search to look into curtilage
from nearby wooded area); State v. Nason, 498 A.2d 252 (Me.1985) (proper for police to observe comings and goings at
defendant’s house from vantage point at which they had a right to be); State v. Peakes, 440 A.2d 350 (Me.1982) (marijuana plants
observable from neighbor’s yard).
Miller v. State, 342 Ark. 213, 27 S.W.3d 427 (2000) (no search to view marijuana plants from neighbor’s property).
Widgren v. Maple Grove Township, 429 F.3d 575 (6th Cir.2005) (no search to observe exterior of owner’s house for tax
assessment purposes from neighbor’s property).
238 State v. Pontier, 95 Idaho 707, 518 P.2d 969 (1974).
239 United States v. McMillon, 350 F.Supp. 593 (D.D.C.1972).
240 This is not to suggest that such an invitation is essential. See, e.g., Sarantopoulos v. State, 629 So.2d 121 (Fla.1993) (where police
looked over fence from neighbor’s back yard, which he entered without obtaining permission, this no search; court relies on United
States v. Dunn, 480 U.S. 294, 107 S.Ct. 1134, 94 L.Ed.2d 326 (1987), holding a trespass even on defendant’s own property not
sufficient to establish that a search occurred).
241 James v. United States, 418 F.2d 1150 (D.C.Cir.1969).
242 Amsterdam, Perspectives on the Fourth Amendment, 58 Minn.L.Rev. 349, 403 (1974).
243 Compare Sarantopoulos v. State, 629 So.2d 121 (Fla.1993) (defendant’s “extraordinary efforts” objection rejected where 6′2″
officer on neighbor’s property was able by standing on his tiptoes to see over 6 ft. high solid board fence; court said defendant
without reasonable expectation of privacy because fence “protected from view only as to those who remained on the ground and
who were unable to see over the six-foot fence unaided”).
244 These were the facts in George v. State, 509 S.W.2d 347 (Tex.Crim.App.1974). The court did not say that no search had occurred;
rather, the court held “that the limited investigation by the officer which resulted in the observation of the marijuana was not
unreasonable under the circumstances.” The surveillance was undertaken on the basis of information from an informant to the
effect that marijuana was growing in that yard, which the court acknowledged “did not constitute probable cause for an arrest or
search within the house or within the fence.” George illustrates the important point that to say looking into the curtilage is a search
228

is not to conclude that a search of that limited nature may be undertaken only upon facts which would justify a much more
intrusive search.
245 On other uses of telescopes and binoculars, see § 2.2(c).
Mere use of binoculars from a more readily accessible vantage point, such as the woods just outside defendant’s curtilage, is no
search. Ex parte Maddox, 502 So.2d 786 (Ala.1986).
246 People v. Fly, 34 Cal.App.3d 665, 110 Cal.Rptr. 158 (1973). See also United States v. Cuevas-Sanchez, 821 F.2d 248 (5th
Cir.1987) (distinguishing Ciraolo, text at note 258 infra, court holds it is a search to look into defendant’s back yard, surrounded by
10 ft. high solid fence, by installing video camera on top of power pole); State v. Kender, 60 Haw. 301, 588 P.2d 447 (1978)
(where officer had to climb three-quarters of way up fence and support himself on fellow officer’s shoulder and then use 60-power
telescope to see marijuana plants in defendant’s back yard, this a search; court says notion it no search for officer to see from
vantage point where he lawfully present applies only when the situation “involved observations by police officers which were
facilitated by the defendant’s failure to take sufficient steps to protect his privacy,” which not so here given fence around and
heavy foliage on defendant’s yard).
247 See § 2.4(a).
248 State v. Rogers, 161 Vt. 236, 638 A.2d 569 (1993).
249 In support, the court quite properly relied upon United States v. Dunn, 480 U.S. 294, 107 S.Ct. 1134, 94 L.Ed.2d 326 (1987),
holding that looking into a barn from outside the curtilage was no search. Dunn says that “there is no constitutional difference
between police observations conducted while in a public place and while standing in the open fields. Similarly, the fact that the
objects observed by the officers lay within an area that we have assumed … was protected by the Fourth Amendment does not
affect our conclusion.”
See also United States v. Hatfield, 333 F.3d 1189 (10th Cir.2003) (“police observation of a defendant’s curtilage from a vantage
point in the defendant’s open field is not a search”).
See also Widgren v. Maple Grove Township, 429 F.3d 575 (6th Cir.2005) (observation for tax purposes of exterior of owner’s
house from owner’s open fields no search).
250 See Granberg, Is Warrantless Aerial Surveillance Constitutional, 55 Cal.St.B.J. 451 (1980); Kaye, Aerial Surveillance: Private
Versus Public Expectations, 56 Cal.St.B.J. 258 (1981); Comments, 15 Ariz.L.Rev. 145 (1973); 18 Gonzaga L.Rev. 307 (1983); 17
J. Marshall L.Rev. 455 (1984); Notes, 50 Fordham L.Rev. 271 (1981); 60 N.Y.U.L.Rev. 725 (1985); 17 Val.U.L.Rev. 309 (1983);
35 Vand.L.Rev. 409 (1982).
251 People v. Sneed, 32 Cal.App.3d 535, 108 Cal.Rptr. 146 (1973).
252 People v. Superior Court, 37 Cal.App.3d 836, 112 Cal.Rptr. 764 (1974). See also People v. Lashmett, 71 Ill.App.3d 429, 27
Ill.Dec. 657, 389 N.E.2d 888 (1979) (no search to see tractor and similar farm machinery from plane at 2400 feet).
253 Indeed, the police later looked at the auto parts again from the neighbor’s yard, which was separated from defendant’s property by
a five-foot fence. See also United States v. Allen, 633 F.2d 1282 (9th Cir.1980) (helicopter surveillance not a search where “the
objects observed were large scale modifications of the Allen Ranch landscape and barn”); Reece v. State, 152 Ga.App. 760, 264
S.E.2d 258 (1979) (no search to discover from airplane stolen vehicles in open field); People v. Lashmett, 71 Ill.App.3d 429, 27
Ill.Dec. 657, 389 N.E.2d 888 (1979) (no search to see large farm machinery from plane at 2400 feet); State v. Ryder, 315 N.W.2d
786 (Iowa 1982) (no search to view farm machinery from airplane); State v. Bridges, 513 A.2d 1365 (Me.1986) (post-Ciraolo case
cautiously notes defendant’s conduct observed from plane also readily observable from passersby on road, so it “immaterial that
their activities happened to be observed from the air”).
254 The court in Sneed was not as careful with respect to this point as it might have been. The court did say that there was no evidence
“that anyone had viewed the plants from the neighbor’s corn field,” but did not declare unequivocally that such a viewing could not
readily have been made. It is significant, however, that in discussing the question of whether there is a reasonable expectation of
privacy in a back yard, the court stated that this depended upon the facts of the individual case and then recited factors which
would be relevant in terms of viewing from adjacent property rather than from the air: “the location of the premises, that is,
whether in an urban or isolated area, the existence or nonexistence and height of natural or artificial structures adjacent to the
premises, the height and sight-proof character of the fencing, the location of public or common private walkways adjacent to the
premises.”
255 Williams v. State, 157 Ga.App. 476, 277 S.E.2d 923 (1981) (no search, as aircraft at lawful height); State v. Layne, 623 S.W.2d
229

629 (Tenn.Crim.App.1981) (no search, as plane in navigable air space).
256 Note, 60 N.Y.U.L.Rev. 725, 749 (1985).
257 Id. at 746.
258 California v. Ciraolo, 476 U.S. 207, 106 S.Ct. 1809, 90 L.Ed.2d 210 (1986), discussed in Junker, The Structure of the Fourth
Amendment: The Scope of the Protection, 79 J.Crim.L. & C. 1105, 1152–55 (1989); Comments, 30 Ariz.L.Rev. 361 (1988); 75
Cal.L.Rev. 1767 (1987); 36 Cath.U.L.Rev. 667 (1987); 22 Gonzaga L.Rev. 393 (1987); Notes, 73 Cornell L.Rev. 97 (1987); 53
J.Air.L. & C. 291 (1987); 47 La.L.Rev. 1365 (1987); 18 Loyola U.L.J. 285 (1986); 52 Mo.L.Rev. 507 (1987); 40 Sw.L.Rev. 1133
(1986); 23 Tulsa L.J. 259 (1987); 66 Wash.U.L.Q. 111 (1988).
259 The Court “assumed” the defendant had an actual expectation of privacy, but nonetheless made some troublesome observations in
that connection. See § 2.1(c).
260 Ciraolo was followed in Florida v. Riley, 488 U.S. 445, 109 S.Ct. 693, 102 L.Ed.2d 835 (1989), upholding police surveillance from
a helicopter at an altitude of 400 feet. The surveillance was of the interior of a greenhouse, and thus the case is further discussed at
note 197 supra.
See also State v. Ainsworth, 310 Or. 613, 801 P.2d 749 (1990) (relying on Ciraolo, court holds no search where naked eye police
observation from helicopter and “they lawfully were in the air above defendants’ land”).
See also United States v. Warford, 439 F.3d 836 (8th Cir.2006) (though helicopter sometimes “dropped to an altitude of 200 or
300” feet, that legally permissible and not shown to be so rare as to violate reasonable expectation of privacy); United States v.
Boyster, 436 F.3d 986 (8th Cir.2006) (even if lands viewed within curtilage and helicopter was “at an altitude of around one
hundred feet,” there no search, as defendant did not claim flight at that level illegal or “so rare as to make aerial surveillance at that
level unreasonable”).
261 E.g., text at note 121 supra.
262 On such analysis, the court in People v. Mayoff, 42 Cal.3d 1302, 233 Cal.Rptr. 2, 729 P.2d 166 (1986), decided to reject Ciraolo
“and thus adhere to the contrary state view.”
On this dissent, see Hancock, Justice Powell’s Garden: The Ciraolo Dissent and Fourth Amendment Protection for Curtilage-Home
Privacy, 44 San Diego L.Rev. 551 (2007).
263 In State v. Davis, 51 Or.App. 827, 627 P.2d 492 (1981), the court rejected the trial court’s position that the viewing by aircraft was
a search solely because the flight at 600–700 feet was lower than permitted by the FAA for fixed-wing aircraft:
The trial court’s application of the FAA regulation is not an appropriate method of analysis in a search and seizure
area for several reasons. It provides a mechanical approach to search and seizure issues-one merely determines
whether an aircraft was above or below the prescribed minimum altitude, and Fourth Amendment protection is or is
not afforded based on this demarcation. …
We also find little attraction in the idea of using FAA regulations because they were not formulated for the purpose
of defining the reasonableness of citizens’ expectation of privacy. They were designed to promote air safety. …
Lastly, we wish to point out that the FAA regulations distinguish between the types of aircraft involved. The
regulation in this case was applied to a fixed-wing aircraft. The regulation allows helicopters to be flown at lower
altitudes. To use the regulation would make ‘a crazy quilt’ out of the Fourth Amendment, with the ‘pattern of
protection’ being dictated by the type of aircraft used for surveillance.
Comment, 24 Cal.W.L.Rev. 379, 380 (1988), concludes “that aerial surveillance by a helicopter at an altitude of 300 to 500 feet
does not offend the fourth amendment and is not unreasonable if the aircraft is (1) being lawfully operated, and (2) not
unreasonably intrusive.”
264 Florida v. Riley, 488 U.S. 445, 109 S.Ct. 693, 102 L.Ed.2d 835 (1989). See also United States v. Breza, 308 F.3d 430 (4th
Cir.2002) (spotting marijuana plants in defendant’s noncurtilage garden from helicopter no search here, where “the helicopter fully
complied with applicable regulations regarding proper altitude” and “such flights were a regular occurrence in the area”); United
States v. Fernandez, 58 F.3d 593 (11th Cir.1995) (under Riley, observation of marijuana plants from helicopter at 500 feet no
search); Commonwealth v. One 1985 Ford Thunderbird Automobile, 416 Mass. 603, 624 N.E.2d 547 (1993) (no Fourth
Amendment violation when helicopter flew over defendant’s home at altitude of 1,500, 800 and 700 ft., so that visible to naked eye
view were hundreds of marijuana plants in empty swimming pool).
230

265 Such analysis was challenged by 3 of the 4 dissenters: “If indeed the purpose of the restraints imposed by the Fourth Amendment is
to ‘safeguard the privacy and security of individuals,’ then it is puzzling why it should be the helicopter’s noise, wind, and dust that
provides the measure of whether this constitutional safeguard has been infringed.”
Consider also Commonwealth v. One 1985 Ford Thunderbird Automobile, 416 Mass. 603, 624 N.E.2d 547 (1993) (cautiously
concluding that under the state constitution such overflight is lawful “when the police have a reasonable suspicion that illegal
activity is occurring in a backyard”).
Consider also State v. Bryant, 183 Vt. 355, 950 A.2d 467 (2008) (helicopter surveillance by circling over defendant’s yard at 100
feet for 15–30 minutes, contrary to law, violated state constitution).
266 Dean v. Superior Court, 35 Cal.App.3d 112, 110 Cal.Rptr. 585 (1973).
267 Ciraolo, Dow Chemical Company v. United States, 476 U.S. 227, 106 S.Ct. 1819, 90 L.Ed.2d 226 (1986).
268 Governments are beginning to use satellite imagery for a variety of enforcement purposes, such as to detect the growing of crops
without an irrigation permit, unreported property improvements, and unreported timber cutting. This practice will doubtless
increase, for, as compared with taking photographs from airplanes, “satellite imagery can be much more cost-effective” and “is
faster as well. … And as sharper-resolution photos become available, … the program could be used to look for objects as small as
backyard porches, to check if homeowners have their construction permits in order.” Kerber, When Is a Satellite Photo an
Unreasonable Search, Wall St.J., Jan. 27, 1998, p. B.1, col. 3–4; p. B4, col. 4–5.
For an updated description and assessment of satellite surveillance, see Note, 65 Ohio St.L.J. 1627 (2004).
268.1 Comment, 51 S.Tex.L.Rev. 173, 201 (2009).
268.2 Comment, 74 J.Air L. & Com. 627, 661 (2009), reasoning: “This conclusion follows from a variety of factors, such as the rarity of
UAS use within the public sector, the ability of technology to perceive details that would otherwise be imperceptible without
physically entering the curtilage of the home, and the invasive nature of UAS surveillance conducted through stealth.”
268.3 See, generally, Comments, 74 J.Air L. & Com. 627 (2009); 49 Jurimetrics J. 491 (2009); 51 S.Tex.L.Rev. 173 (2009).
268.4 Comment, 74 J.Air L. & Com. 627, 661 (2009).
269 United States ex rel. Gedko v. Heer, 406 F.Supp. 609 (W.D.Wis.1975).
270 To the contrary is United States ex rel. Gedko v. Heer, 406 F.Supp. 609 (W.D.Wis.1975), where officers gained entrance to
petitioner’s farm through an adjoining field. The officers climbed a fence at the boundary of petitioner’s farm premises and
proceeded thereupon through open fields and timber to a point about 300 to 400 feet from petitioner’s farm buildings. After a
surveillance plane criss-crossed over the property several times, the officers heard the petitioner and his wife shouting to one
another about the need to dispose of the marijuana. Petitioner’s farm was fenced; the farm yard was six-tenths of a mile from the
public road; and a no trespassing sign was posted at the gate. In holding that the officers had intruded upon petitioner’s justified
expectation of privacy, the court stated: “In this case … there was nothing to indicate that petitioner and his wife should have had
any reason to expect their conversations, even their shouted conversations, to be overheard by anyone. They had taken deliberate
measures to ensure that their activities and conversations would be protected from other persons, official or non-official.”
However, such analysis cannot be squared with the Supreme Court’s more recent Oliver decision, discussed in § 2.4(a).
271 See § 2.2(e).
End of Document
© 2012 Thomson Reuters. No claim to original U.S. Government Works.
231