Medical Expert Witness Forensic Toxicologist | Medical Expert Witness Services & More | Dr. Nachman Brautbar

Driving Under the Influence
- Intoxication Defense -
(Analyzing and Finding the Truth)

Examples on how to analyze DUI and intoxication cases

  1. Worker falls off the roof breaking his spine. In the emergency room, blood test revealed presence of alcohol and urine test was positive for marijuana. The insurance company declined coverage citing impairment secondary to alcohol and drugs (intoxication defense).
  2. A driver gets injured in a car collision. At the hospital, urine is collected and detects cocaine. Coverage by the insurance company is denied under the intoxication defense.
  3. A motorcyclist is killed as a result of a traffic collision. Autopsy analysis of blood from the heart demonstrated elevated levels of alcohol. Samples from the vitreous (eye balls) and femoral vein are not obtained. Based on the heart alcohol content, argument is made that the motorcyclist was impaired (intoxication defense) and insurance coverage is denied.
  4. A pedestrian is hit by a car, injured, and taken to the emergency room where blood analysis indicated presence of prescription medications--opiates (Vicodin), Xanax and soma. At the trial, the argument is made that the pedestrian crossed the street while under the influence of medications and the intoxication defense is argued

These are only a few examples of what happens daily, the risk, and outcomes. In this short educational manuscript Dr. Brautbar (toxicologist) analyzes the scenarios, methods, and provides guidance.

In the case of the worker (case #1) who fell off the roof and was found to have marijuana in his urine, one must understand the toxicology of marijuana. Tetrahydrocannabinol is the main component of marijuana (THC). In one study of 10 volunteers, peak urinary 11-carboxy-THC concentration ranged from 6-129 μg/L with 16 hours of smoking a single 10 mg dose THC (McBurney, 1986). After smoking 27 mg of THC, peak urine of 8 volunteers had measured 22 μg/L THC at 2.0 hours and 78 μg/L 11-carboxy-THC at 3 hours (Kemp, 1995). In frequent users, urine levels of 11-carboxy-TCH have been seen as high as 2705 μg/L (Baselt, 1984). In heavy marijuana smokers, mean urinary elimination half-life of 11-carboxy-THC was 3 days (range, 0.8-9.8 days) (Johansson, 1989). The worker testified under oath that he used marijuana 4 days before the fall while attending a party and was offered “a joint”. The police officer who was at the scene testified that the worker was alert and did not display signs of impairment. Coworkers testified that his behavior before the fall was usual. Based on the absence of clinical signs of impairment and or intoxication, the doctor toxicologist testified marijuana peak effect on the brain is 4-8 hours, and that the scientific literature clearly states that the mere finding of marijuana in the urine without evidence of impairment can not be used to determine intoxication, the marijuana defense is dropped (Chiang, 1984; Hollister, 1981). As far as the blood alcohol the sample was not admissible as the doctor toxicologist demonstrated lack of calibration of the testing equipment and failure to follow chain of custody. The court decided in favor of the worker.

In the case of the driver (case #2) and cocaine in the urine, the driver testified that he did not use cocaine on the day of accident and that he last used cocaine 5 days before the accident when friends offered it to him at a gathering. He states he never used illicit drugs before. The doctor toxicologist examined the urinary data, i.e., cocaine and its metabolites (breakdown products). In urine, cocaine is generally detectable only in the first few hours following the last dose (Ambre, 1985). The relative levels of cocaine and its metabolites (ecgonine methyl ester and benzoylecgonine) may give indication of when the last time cocaine was consumed. The doctor toxicologist provided literature describing the pharmacology and toxicology of cocaine (Baselt, 2000; Ellenhorn, 1997; Hamilton, 1977). Peak effect of cocaine after intravenous and intranasal administration have been found to occur within 5 to 10 minutes and 15 to 20 minutes after intake, respectively (Resnick, 1977). The laboratory methodology and records were standard. If cocaine is detectable in the urine, but the ratios of ecgonine methyl ester/cocaine or benzoylecgonine/cocaine are less than 100, it would suggest that the time of last dose (recent use of cocaine) was less than 10 hours ago (Ambre, 1985). Testimony from other witnesses described the driver angry and changing lanes while driving at high speed. The paramedics testified that the driver was combative and argumentative. Based on all these data the medical toxicologist opined that the driver was impaired and under the influence of cocaine. The court ruled in favor of the insurance company. (An important part of the decision was based on the doctor toxicologist, scientific literature, about the urine test and ratios.)

In the case of the motorcyclist (case #3), the family of the deceased asked the medical toxicologist to review all medical records and testimonies in the case. (See the section on alcohol in this web site: There were no testimonies to suggest that the cyclist was an alcohol drinker, nor were there testimonies of erratic driving. Blood was taken at autopsy from the heart, but the coroner failed to take samples of blood from the femoral vein and or vitreous fluid. The doctor-medical forensic toxicologist provided scientific literature indicating that in autopsy cases especially when major physical trauma occurs, heart blood sample without verification of vitreous fluid or femoral blood is unreliable and therefore determined that there was no evidence to support the intoxication defense. The court decided for the motorcyclist.

In the case of the pedestrian (case #4), the doctor toxicologist examined medical records, testimonies and laboratory toxicology studies. Blood test taken in the emergency room demonstrated very high levels of opiates (from Vicodin) and soma. Medical records demonstrated that the pedestrian suffered from chronic back pain and was prescribed by his doctor Vicodin tablets, 2 tabs every 6 hours for pain as needed and soma 2 tab every 8 hours for muscle spasms as needed. The patient followed the doctors’ instructions and had ingested Vicodin and soma five and one-half hours before the injury. The doctor toxicologist opined that based on these data, high levels of opiates found in blood and the synergistic effects on brain with soma, the pedestrian was impaired. The court found 50% responsibility on the pedestrian, who in turn sued the doctor for not advising him of the side effects of these medications.


  1. Ambre, J. The urinary excretion of cocaine and metabolites in humans: a kinetic analysis of published data. J Anal Toxicol. 1985 Nov-Dec;9(6):241-5.
  2. Baselt, R.C. Disposition of Toxic Drugs and Chemicals in Man, Fifth Edition. Foster City, CA: Chemical Toxicology Institute, 2000.
  3. Baselt, R.C. Unusually high cannabinoid concentrations in urine. J Anal Toxicol. 1984;8:16A.
  4. Chiang CW, Barnett G. Marijuana effect and delta-9-tetrahydrocannabinol plasma level. Clin Pharmacol Ther. 1984 Aug;36(2):234-8.
  5. Ellenhorn, M.J., et al. Chapter 21. Cocaine. In: Ellenhorn's Medical Toxicology: Diagnosis and Treatment of Human Poisoning, Second Edition. Williams & Wilkins. A Waverly Company. January 1997. Pages 356-386.
  6. Hamilton HE, Wallace JE, Shimek EL Jr., et al. Cocaine and benzoylecgonine excretion in humans. J Forensic Sci. 1977 Oct;22(4):697-707.
  7. Hollister LE, Gillespie HK, Ohlsson A, Lindgren JE, et al. Do plasma concentrations of delta 9-tetrahydrocannabinol reflect the degree of intoxication? J Clin Pharmacol. 1981 Aug-Sep;21(8-9 Suppl):171S-177S.
  8. Johansson E, Halldin MM. Urinary excretion half-life of delta 1-tetrahydrocannabinol-7-oic acid in heavy marijuana users after smoking. J Anal Toxicol. 1989 Jul-Aug;13(4):218-23.
  9. Kemp PM, Abukhalaf IK, Manno JE, et al. Cannabinoids in humans. II. The influence of three methods of hydrolysis on the concentration of THC and two metabolites in urine. J Anal Toxicol. 1995 Sep;19(5):292-8.
  10. McBurney LJ, Bobbie BA, Sepp LA. GC/MS and EMIT analyses for delta 9-tetrahydrocannabinol metabolites in plasma and urine of human subjects. J Anal Toxicol. 1986 Mar-Apr;10(2):56-64.
  11. Resnick RB, Kestenbaum RS, Schwartz LK. Acute systemic effects of cocaine in man: a controlled study by intranasal and intravenous routes. Science. 1977 Feb 18;195(4279):696-8.

Dr. Brautbar is a board-certified internist and nephrologist, and certified in forensic medicine. If you are interested in retaining Dr. Brautbar for forensic and expert witness testimony services, please submit the Contact Form.

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