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Marijuana plus Alcohol a Perplexing Synergy

February 13, 2008

One of the more interesting features of Vehicle and Traffic Law section 1192 is the neat and orderly way in which subdivisions one through four walk through the various prohibited states: impairment, intoxication, intoxication per se, and impairment as a result of drugs. In large part this orderly presentation is a result of continually engrafting upon a model that has been in place since 1917. While one cannot question the effectiveness of describing either alcohol or drug induced disabilities in this fashion, when drugs and alcohol are combined, problems begin to emerge. In this issue, we will examine marijuana, its effect upon driving and the perplexing problems that arise when the two are used in tandem.

Without question, marijuana is the most popular illegal drug of choice. According to the 1999 National Household Survey on Drug Abuse, an estimated 2.3 million people tried marijuana for the first time during 1998, which amounts to about 6,400 new marijuana smokers a day. The annual report also indicated that marijuana use increased for adults ages 18-25 from 13.8 percent in 1998 to 16.4 percent in 1999. Perhaps more telling is that in 1996, this study indicated that approximately twenty-five percent of the 166 million drivers aged 16 and older occasionally drive under the influence of alcohol, marijuana or both.

The active compound in the smoke which is inhaled from marijuana is delta‑9‑tetrahydrocannabinol. Since Public Health Law Section 3306 Schedule I(a)(17) lists tetrahydrocannabinol as a controlled substance, operation of a motor vehicle while under the influence of marijuana is placed squarely within the interdiction created within the Vehicle and Traffic Law.

Generally speaking, marijuana acts upon the cardiovascular and central nervous systems with effects that are largely sedative and hallucinogenic. In low doses, it has been reported as producing a sense of well‑being, relaxation, and sleepiness, while higher doses seem to cause mild sensory distortions, altered time sense, loss of short‑term memory, difficulty in balance, and disruption in thought processes. Higher doses still have been reported to precipitate feelings of depersonalization, severe anxiety and panic, toxic psychosis, hallucinations, loss of insight, delusions, and paranoia. Marijuana has been shown to manifest itself in heart rate increases, dilation of the blood vessels of the eye, tightness in the chest and, of extreme importance to our discussion, a lack of muscular coordination.

From a traffic safety standpoint, marijuana is dangerous, perhaps just as dangerous as alcohol. In Incidence and Toxicological Aspects of Cannabis and Ethanol Detected in 1394 Fatally Injured Drivers and Pedestrians in Ontario, Cimbura, Lucas, Bennett and Donelson examined data from the Canadian province of Ontario. During a 29‑month period commencing March 1, 1982 and terminating July 31, 1984, 2,655 fatal motor vehicle accidents were reported. These crashes resulted in the deaths of 2,114 persons 14 years or older. Out of the 1,169 motorist and 225 pedestrian accidents analyzed, 560 (47.9%) motorists and 107 (47.7%) pedestrians were positive solely for the presence of alcohol. Cannabis use alone was detected in 20 (1.7%) of the drivers and 4 (1.8%) of the pedestrians. Cross use, that is to say, alcohol and marijuana used concurrently, was noted in 107 (9.2%) of the motorists and 13 (5.8%) of the pedestrians. When summarized, THC was identified as being used by 10.3% of those fatally injured motorists and pedestrians falling within the parameters of this study.[1]

Although alcohol is by far the drug most commonly linked to fatal crashes, the National Highway Traffic Safety Administration (NHTSA) links marijuana as number two and is frequently used in conjunction with alcohol. Cimbura, et ano.,[2] found that in 18.7% of those fatalities where THC was found, motorists had a blood alcohol content of .009% to .079%. It is this last aspect which we will review today.

One of the major difficulties in prosecuting charges brought under Vehicle and Traffic Law ' 1192(4) DWAI - Drugs, is that there exists no per se standard upon which to base impairment. By and large, this is due to the unique manner in which the drug interacts. In 1983, the National Institute on Drug Abuse sponsored a conference on drugs and driving in Durham, North Carolina. The objective was to reach a consensus opinion on the relationship between drugs and body fluid concentrations, as well as to ascertain whether sufficient data exists to form opinions as to a relevant standard for impairment. Noting that ethanol concentrations have been measured and correlated for more than a century and that they can be easily measured noninvasively, the panel concluded that other differences, including relatively low toxicity, the lack of long lived active metabolites, even distribution in body water and its rapid equilibration between blood and brain, forced the conclusion that generalizations unique to alcohol cannot be transposed to marijuana and other known drugs that might impair driving skills.

Although Lukas, et al.,[3] and Benowitz, et ano.,[4] noted that THC ingestion appears to attenuate the rise in blood alcohol levels, until recently, relatively little has been written on the subject of marijuana used in conjunction with alcohol and traffic safety.

The April 2000 issue of Annuals of Emergency Medicine reports that the Institute for Human Psychopharmacology at Maastricht University in the Netherlands performed a series of studies for NHTSA in an effort to explore the suspected synergistic effect of alcohol and marijuana upon the ability to operate a motor vehicle. One study was conducted upon motorists between the ages of 20 and 28 who reported that they smoked marijuana and drank alcohol at least once a month. All were licensed drivers and were evenly divided between males and females. Each participant was administered marijuana, alcohol, marijuana and alcohol or placebos. Additionally, two levels of marijuana were given. One group received a dose of 100mg/kg body weight while a second received a dose equivalent of 200mg/kg body weight. A third group also received a placebo consisting of marijuana leaf from which THC, the active ingredient in marijuana had been removed. Alcohol was also administered at two levels. One sufficient to achieve an initial level of .07 which was sustained at a level of .04 and a placebo. Following administration of the marijuana, marijuana and alcohol and/or the placebos, the participants were asked to engage in two roadway situations. The first, lateral tracking, required the motorist to maintain a speed of 100 km or 62 miles per hour in the right hand lane. Paramount in this test was tracking the car evenly between the pavement markings. The second test, entitled the Car Following Test required the motorist to maintain a distance of 50 meters or 164 feet behind a test vehicle that accelerated and decelerated according to plan. The tests were conducted on successive evenings 30 minutes after administration of the marijuana, alcohol or placebo. Each event consisted of driving 25 mile segments on two occasions. Although the tests were conducted upon public highways, in real traffic, the vehicles utilized had multiple controls and each participant was accompanied by a driving instructor who was prepared to take over in the event of an emergency.

As might be expected, participants who were administered the marijuana or alcohol alone showed significantly impaired performance on both road tests compared with the baseline (no alcohol or no marijuana). However, those participants who combined marijuana with alcohol demonstrated Aseverely impaired performance, leading decrements in performance as great as for driving with BACs at 0.09 and 0.14, respectively. For instance, beginning with a mean reaction time of 4.65 seconds to initiate a response, the marijuana plus alcohol group showed an increase of 36%, or 6.33 seconds. At 59 miles per hour, this translates into an additional 139 feet before a response.

Of further significance, was the aspect of the test described as visual search frequency. Participants were fitted with a device to measure the eye movements of the driver. Such movements are essential to safe driving and the ability to avoid unexpected situations. Although the frequency of these movements did not change for participants given moderate doses of alcohol or THC, a marked decrease was found when moderate doses of both drugs were taken in combination. Thus the report concluded that although the effects of singular low doses were minimal, the effects were potentially dangerous for driving when taken in combination.

Given the research of Cimbura, et ano.,[5] that in 18.7% of those fatalities where THC was found, motorists had a blood alcohol content of .009% to .079 %, this conclusion is cause for great concern. The difficulty is that the neat well-ordered scheme established by Vehicle and Traffic Law ' 1192 assumes that the motorist is under the influence of alcohol or drugs, but not both. This can be of great difficulty for prosecutors faced with a Vehicular Manslaughter or Vehicular Assault charge. Both charges require a violation of Vehicle and Traffic Law ' 1192 subdivisions two, three or four. A BAC of .09 or lower will fall beneath the statutory limitation of subdivision two and arguably subdivision three as well. Nor, in the absence of a blood test for THC, would a charge lie under subdivision four.

In light of the foregoing, two points should emerge. First, given the statistical occurrence of THC in low BAC accident cases, a blood test should always be taken when it appears that the BAC falls beneath the statutory .10 threshold. In the event that blood is ordered to determine BAC, it should likewise be tested to determine the presence of THC. Second, legislative correction is sorely needed. At the present time, there is no statute to charge a motorist who is impaired not by alcohol or marijuana but by a combination of both. Indeed, such a change would be minimal. It would merely require that Vehicle and Traffic Law ' 1192(4) be amended to include not only impairment by drugs but by drugs and alcohol taken in combination. Such would prevent the defense from arguing that the level of alcohol or THC was too low to impair operation of a motor vehicle while permitting the prosecution to argue that the impairment was caused by the synergistic effect of both drugs taken at or about the same time.

[1]The study, of course, did not undertake an examination of causation. Therefore, one should not assume that THC was identified as a causative factor in an equal number of accidents.

[2]Cimbura, Lucas, Bennett and Donelson, Incidence and Toxicological Aspects of Cannabis and Ethanol Detected in 1394 Fatally Injured Drivers and Pedestrians in Ontario, Journal of Forensic Sciences (Sept. 1990), pp. 1035‑1041.

[3]Scott E. Lukas, Richard Benedikt, M.D., Jack H. Mendelson, M.D., Elena Kouri, M.S., Michelle Sholar and Amass, Ph.D, Marihuana Attenuates the Rise in Plasma Ethanol Levels in Human Subjects, Neuropsychopharmacology 1992, vol. 7, no. 1, August, 1992, pp. 77‑81.

[4]Neal L. Benowitz, M.D., Reese T. Jones, M.D, Effects of Delta‑9‑tetrahydrocannabinol on Drug Distribution and Metabolism, Clinical Pharmacology and Therapeutics, vol. 22, no. 3, Sept. 1977, pp. 259‑268.

[5]Cimbura, Lucas, Bennett and Donelson, Incidence and Toxicological Aspects of Cannabis and Ethanol Detected in 1394 Fatally Injured Drivers and Pedestrians in Ontario, Journal of Forensic Sciences (Sept. 1990), pp. 1035‑1041.

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