FORENSIC TOXICOLOGY - Bio Medical Forensics

to fully prosecute the case, negotiations on a plea agreement, assessment or
treatment for drug use, and allocation of law enforcement resources.
The data were also examined to assess relative rates of drug use
among drivers with high BAC’s compared to lower BAC’s, and the data
are presented in table 2.
Table 2. Drug positivity with respect to blood alcohol concentration.
Drug Positive Drug Negative Totals
Alcohol >0.08g/100mL 192 (41.9%) 200 (43.7%) 392 (86.0%)
Alcohol 0.01–0.079g/100mL 43 (9.3%) 23 (5.0%) 66 (14.0%)
Totals 235 (51.3%) 223 (48.7%) 458
Of the alcohol positive cases 392 (86%) had alcohol concentrations of
0.08g/100mL or above. Among these high BAC drivers, 48.9% were
positive for drugs. For the low BAC drivers (0.01 – 0.079g/100mL), 65%
were positive for drugs. The combination of low levels of alcohol with other
drugs having CNS depressant properties such as marijuana, benzodiazepines,
opiates and muscle relaxants, can cause impairment in a synergistic manner.
When circumstances suggest poor or inattentive driving, and the blood
alcohol is less than 0.08g/100mL, further assessment of the drivers sobriety,
and collection of a blood sample should be standard procedure.
The data were examined for evidence of any relationship between the
drug classes detected as a function of BAC, and the data are shown in Table 3.
Table 3. Relative frequency of major drugs/classes identified as a function
of blood alcohol concentration † .
Alcohol Negative Alcohol Alcohol
(n=242) 0.01 -0.079g/ >0.08g/100mL
100mL (n=43) (n=392)
Any impairing drug 47.5% 65.1% 48.9%
Cannabinoids 9.9% 58.0% 26.7%
Amphetamines 14.9% 6.9% 2.0%
Cocaine 2.4% 6.9% 4.8%
Opiates* 8.7% 27.9% 12.8%
Benzodiazepines* 4.1% 20.9% 8.9%
* Note: Opiates and benzodiazepines may be administered during emergency
medical treatment prior to the collection of a forensic blood sample,
therefore opiate and benzodiazepine rates should be interpreted with
caution in this population.
† Columns will not total to 100% since many subjects were positive for
more than one class of drugs.
Overall rates of drug positivity were high in all three groups.
Therapeutic drug use was highest in the alcohol negative group with
muscle relaxants, antiseizure medications, sleep aids and over the counter
drugs being more frequently encountered than in the alcohol positive
groups. These drugs can nevertheless cause driving impairment even when
used according to directions. Rates of combined marijuana and alcohol use
were dramatically higher in the alcohol positive groups, with cannabinoids
being detected in 58% of low BAC drivers and 26.7% of high BAC drivers.
Combined alcohol and marijuana use, particularly in young drivers has
been demonstrated to cause synergistic impairment. Amphetamine use
(principally methamphetamine) was highest among the alcohol negative
drivers. Other studies have demonstrated relatively low rates of concomitant
alcohol use among methamphetamine users.
In conclusion, this study documents the high frequency of combined
drug and alcohol use among drivers suspected of impaired driving leading
to vehicular assault or vehicular homicide. According to current practice,
suspicion of drug use increases when a subject’s low BAC is not consistent
with their observed impairment, and these data validate that practice. In
addition however, the data demonstrate that drug use is a factor throughout
the range of BAC, and that investigators should be alert for indicia of drug
use in any contact with a suspected alcohol impaired driver.
Toxicology, Impaired Driving, Drugs of Abuse
* Presenting Author
K28 She “Lost that Lovin’ Feelin’ “ in the
Arizona Dust: Angry Teen on Alcohol,
Cannabis and Cocaine
Michelle A. Spirk, MS*, Arizona Department of Public Safety, Central
Regional Crime Laboratory, 2323 North 22nd Avenue, Phoenix, AZ 85009
After attending this presentation, attendees will be exposed to a Case
Study involving interpretive toxicology and drug impaired driving. This
case provides valuable discussion material as it lacks many of the factors
that would make for an “ideal” DUID case; thus forcing a discussion of
how real-life drugged driving interpretations may be handled. Drug effects,
DRE evidence, analytical issues, case strengths, weaknesses and summary
statements will be covered.
This presentation will impact the forensic community and/or humanity
by addressing the difficult challenges associated with drugged driving interpretations.
Although many forensic toxicologists are asked to provide these
interpretations and related expert testimony, they are rarely presented to colleagues
in this type of case study format. Utilizing a detailed Case Study
model as presented here, is an excellent way to share knowledge and promote
discussion regarding challenging drugged driving interpretations.
Ideal drug-impaired driving cases include significant driving
behavior, a DRE evaluation, psychoactive parent drug(s) quantitated in
blood obtained close to the time of driving that corroborate the DRE
opinion, and driver admissions supporting impairment. This case was not
ideal as it lacked much of the information allowing an interpretive analysis
of driving impairment; thus, it was a typical DUID case. A 16-year-old
female presented with qualitative blood confirmations of Benzoylecgonine
(BE), Carboxy-THC and a low alcohol concentration (0.015g/100mL),
obtained two hours and 32 minutes after significant driving behavior
resulting in a fatal collision causing the death of a seven-year-old child in a
second vehicle. The collision occurred on the Tohono Oodham Reservation
at approximately 9:41 pm as the teen drove with her boyfriend, and his two
nephews (ages 3 and 7) in the back. An argument ensued resulting in her
holding onto his shirt to restrain him as he tried to exit the moving vehicle;
the 3-year-old was crying to leave. She then ran a stop sign, making a left
turn into the opposing traffic lane and colliding nearly head-on with the
second vehicle. She had the moderate odor of an alcoholic beverage on her
breath, slurred speech and red bloodshot eyes. Confirmatory blood cutoffs
for Cocaine/BE and THC/C-THC were 50ng/mL and 2ng/mL respectively,
thus parent drugs may have gone undetected. Later additional quantitative
analysis of Cocaine and THC was precluded by sample size and consideration
of non-enzymatic hydrolysis of Cocaine during extended refrigerated
storage. Alcohol concentration was too low to provide extrapolation evidence.
No DRE was available. Interpretation: BE is detectable in blood for
~ 48 hours post ingestion; blood BE indicates that Cocaine was present at
the time of, or prior to, the blood draw. Duration of effects for Cocaine is
2-4 hours and is dose dependent. Effects consistent with Cocaine influence
were: self-absorbed; inattentive; decreased divided attention and increased
risk taking. Cocaethylene, although not tested for, is a possible additional
contributor to driving impairment. Carboxy-THC detection in blood is
highly dependent upon dose and frequency of use; blood Carboxy-THC
indicates that THC was present at the time of, or prior to, the blood draw.
Duration of effects for THC is 3-6 hours with some complex divided
attention tasks up to 24 hrs. Effects consistent with THC influence were:
bloodshot eyes; decreased divided attention; difficultly thinking, problemsolving
and processing information; decreased car handling performance;
slow reaction times; decreased perceptual functions and significantly
greater effects when combined with alcohol. The absence of Cocaine and
THC in this case does not rule out their presence at the time of driving or
sampling, or potential dysphoric effects of cocaine. Driver is a minor, with
limited driving experience, thus drug-impaired driving would likely occur
at a reduced threshold than for a more experienced driver. Strengths: inattentive,
inexperienced driving resulting in a fatal collision; admission of
recent prior alcohol use; confirmation of polydrug metabolites in blood that
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