July/August 2004 VOICE FOR THE DEFENSE 1

unless the urine is diluted. Although the creatinine level will
reflect overdilution, the test is not often performed.
• Misinterpretation of results (conversion formula not
applied). Many people mistakenly assume that there is a direct,
one-to-one correlation between ACL in the blood and ACL in
the urine. This is an incorrect assumption, and not scientifically
valid.
In the case described above, both the probation office and
the court incorrectly assumed that, because the subject’s urine
ACL was 0.08 mg percent, his BAC was also. Aside from the fact
that the subject did not void prior to sample collection in the
case noted above, the ACL of urine is between 1.2 and 1.4 times
the ACL of blood; the mean multiplier is 1.3. If an individual
has a BAC of 0.1 mg percent, his urine ACL is between 0.12 mg
percent and 0.14 mg percent.
According to this formula, the man in the case report with
a urine ACL of 0.08 mg percent or higher had an actual BAC
of 0.57 mg percent. Had he arrived at the probation office and
been required to void and then to wait until he had accumulated
enough urine to void again, a more accurate specimen would
have been obtained, and his urine ACL would have been less
than 0.08 mg percent.
Summary
The use of the urine alcohol level test to document an ACL
for legal purposes is increasing, but the test is often misadministered
and misinterpreted. Its accuracy and reliability are
frequently confused with that of urine drug screening, which
measures drug metabolites in the urine. Urine alcohol tests
measure only overflow of alcohol in the urine, not the metabolic
products of alcohol. The result of a urine ACL test is most often not
an accurate measure of BAC, an inaccuracy that is compounded
when the urine specimen is not properly obtained and when
the result is not calculated using the appropriate conversion
formula.
Endnotes
1 R. M. Sissman, Alcohol Consumption as It Pertains to Absorption and
Elimination of Alcohol from the Urine, Art. 88, in Texas Drunk Driving
Law (J. Gary Trichter, Lexis 3 rd ed., 1996).
2 R. M. Sissman, The Use of Urinalysis in DWI Prosecutions in Texas,
Art. 87, in Texas Drunk Driving Law (J. Gary Trichter, Lexis 3 rd ed.,
1996).
3 A. W. Jones, Ethanol Distribution Ratios between Urine and Capillary
Blood in Controlled Experiments and in Apprehended Drinking Drivers,
37(1) J Forensic Sci, 21-34 (1992).
4 A. W. Jones, Lack of Association between Urinary Creatinine and Ethanol
Concentration and Urine/Blood Ratio of Ethanol in Two Successive Voids
from Drinking Drivers, 22(3) J Anal Toxicol, 184-90 (1998).
5 N. Kuroda, K. Williams, and D. J. Pounder, Estimating Blood Alcohol
from Urinary Alcohol at Autopsy, 16(3) Am J Forensic Med Pathol,
219-22 (1995).
6 A. W. Jones and L. Andersson, Influence of Age, Gender, and Blood-Alcohol
Concentration on the Disappearance Rate of Alcohol from Blood
in Drinking Drivers, 41(6) J Forensic Sci, 922-6 (1996).
7 A. W. Jones, Excretion of Alcohol in Urine and Diuresis in Healthy Men
in Relation to Their Age, the Dose Administered and the Time after
Drinking, 45(3) Forensic Sci Int, 217-24 (1990).
8 H. J. Mittmeyer and A. K. Blattert, Urinary Alcohol Content/Blood
Alcohol Content Quotient with Reference to Bladder Filling [article in
German], 49 Beitr Gerichtl Med, 263-7 (1991).
9 E. Keil and R. Werner, Urine Alcohol Determination [article in German],
123(34-35) Dtsch Med Wochenschr, 1022 (1998).
10 Goodman and Gilman’s The Pharmacologic Basis of Therapeutics
386-92 (Louis S. Goodman, Lee E. Limbird, Perry B. Milinoff,
Raymond W. Ruddon, Alfred G. Gilman, and Joel G. Hardman, eds.,
McGraw-Hill 9 th ed., 1996).
11 Drug Abuse HANDBOOK 358-63 (Steven B. Karch, ed., CRC Press,
1997).
George S. Glass, M.D. is a Distinguished Life
Fellow of the American Psychiatric Association,
certified by the American Board of Psychiatry
and Neurology, certified by the American
Medical Society on Alcoholism and other drug
dependencies. Contact information: George S.
Glass, M.D., 4600 Post Oak Place, Suite 307,
Houston, Texas 77027, 713.666.9811 phone and
713.627.3488 fax .
The best way to measure ACL in the body is to sample the
blood. It follows then that the best way to determine the accuracy
and reliability of a urine ACL test result is to draw a
blood specimen simultaneous with the collection of the urine
sample and compare the results. 10,11 Unsurprisingly, such double
testing is neither convenient nor justified since the testing of
blood would obviate the need to test the urine. It seems logical
then that testing for urine alcohol concentration levels will be
abandoned because this test, by itself, does not consistently yield
accurate and reliable results despite the fact that urine alcohol
and drug screens do reveal the presence of alcohol, drugs, and
controlled substances accurately and reliably. In summary, the
convenience of taking a urine specimen is not an excuse for
disregarding principles of science and truth.
16 VOICE FOR THE DEFENSE July/August 2004