COCAINE URINE SCREEN: DAUBERT/ROBINSON HEARING TO EXCLUDE TESTIMONY
A tanker truck was backing out of a filling station after dark onto a two lane road. A passenger vehicle collided with the trailer after failing to see spotters with flashlights. Road conditions were clear and lighted. The driver of the automobile, at the time of the accident, had a diabetic condition which was out of control and visual acuity of 20/200 with dense bilateral cataracts. Witnesses with close contact with the truck driver during at least 15 minutes prior to the accident testified that his behavior was not unusual and he did not appear impaired. The interviewing officer saw no signs of impairment during a 20 minute interaction. A post accident urine specimen was collected from the truck driver five days after the accident and tested positive for cocaine metabolites. Suit was filed against the truck driver and others.
PLAINTIFF POSITION: The truck driver was impaired as a result of cocaine use. Expert for the plaintiff proposed testimony that the positive urine test proved that impairment existed at the time of the accident.
DEFENSE POSITION: Introduction of testimony that cocaine-related impairment existed at the time of the accident was not supported by the evidence and its introduction at time of trial could only be prejudicial.
DISCUSSION: Widespread practice in industry of pre-employment and random urine screening for drugs of abuse is effective in the pursuit of a drug-free workplace since properly performed urine tests provide indisputable evidence of drug use at some time prior to the urine collection. Performance of post accident urine drug tests for the purpose of identifying impairment as a consequence of the use of cocaine is not based on reliable scientific principles. Urine tests for cocaine detect substances which are inactive derivatives of cocaine formed in the body. There is no established relationship between these tests and impairment. The physiological effects resulting from the use of cocaine persist for minutes to hours depending on the route of administration. By contrast, the inactive derivatives continue to be present in the urine for up to three days. While a positive urine does permit a reasonable medical probability statement that the subject had used cocaine at some time prior to collection of the specimen, it does not permit establishment of the time frame during which the substance was used other than within three days.
In the current case, urine collection occurred five days after the accident. Since derivatives can continue to appear in the urine for up to, but rarely beyond, three days, the positive test represents cocaine use after the accident. The few reports in the literature of derivatives of cocaine persisting in the urine for more than three days are suspect concerning interim drug use or involve circumstances unlikely to have prevailed in this case. As a result, introduction of the test results at time of trial can only be prejudicial, contributing nothing to understanding the competence of the truck driver to operate a vehicle at the time of the accident.
CONCLUSION: During a pre-trial hearing, after presentation of appropriate peer reviewed literature from professional and scientific journals, testimony by the plaintiff expert was excluded as having no scientific merit.
Eric G. Comstock, M.D., expert for the defense. (9390); Richard Harrison, Attorney at
Law, Sherman, TX.
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NOTES AND REFERENCES
The urine specimen tested in this case was processed in accordance with the Code of Federal Regulations, Title 49, Subtitle A, Part 40, "Procedures for Transportation Workplace Drug Testing Programs." 40.29(e) (1) states "The initial test shall be an immunoassay which meets the requirements of the Food and Drug Adminstration for commercial distribution. The following initial cutoff levels will be used when screening specimens to determine whether they are negative for five drugs or classes of drugs (Cocaine metabolites 300 ng/ml)." In this instance, no confirmatory test and no quantitation were performed. The opinions expressed are based upon a qualitative analysis which was positive by EMIT at or above 300 ng/ml. Use of procedures with a lower threshold of detection would result in more positive urines and positives at times more remote than five days from most recent use.
Positive urines at the 300 ng/ml cutoff have, under unusual circumstances, been demonstrated to occur 22 days after prolonged and heavy use. Three examples presented were using eight grams per day intravenously, 10 grams of cocaine freebase daily for several months prior to admission, and smoking up to 30 grams of cocaine a day, respectively. (Weiss, 1988)
Burke, 1990, tested 35 "cocaine dependent men" among which one was positive after eight days, none were positive after seven, five were positive after six, and eleven were positive on the fifth day (31.4%) using a threshold of 300 ng/ml. These patients were reported to have used cocaine regularly with an average dose of 0.5 grams per day.
Use of the 300 ng/ml threshold may reasonably be expected to rule out passive inhalation as a source of a positive urine. (Cone, 1995). The threshold dose for a positive urine screen is approximately one milligram of cocaine.
These observations emphasize the necessity of obtaining information on the method of analysis and the cutoff values being used by the analytical laboratory.
Burke WM. Prolonged Presence of Metabolite in Urine After Compulsive Cocaine Use. J. Clin. Psychiatry 51:145-148, 1990.
Cone EJ, et al. Passive Inhalation of Cocaine. J. Analyt.Toxicol. 19(6):399-411, Oct 1995.
Weiss RD,et al. Protracted Elimination of Cocaine Metabolites in Long Term, High Dose Cocaine Abusers. Amer. J. Med. 85:879-880,1988.
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