MARIJUANA LAW UPDATES BY JUDGE MARY CELESTE (RET.)


Cannabis and Driving Update: Part 1


seems to be a consensus in the scientific community that with increasing levels of THC comes an increase of impaired driving performance, the exact amount of the THC concentration level that equates to marijuana-impaired driving has been an ongoing issue. National associations, organizations, national and international scientific studies, and reports have all continued to weigh in on this topic. Scientific studies have addressed marijuana


T


use and its effects on driving performance. One study demonstrated that the THC dose contained in cannabis was linearly related to cognitive and psychomotor performance. “Response times slowed down and motor control became worse with increasing THC doses.”1


Another major study that is oſten


cited used experimental control groups and a driving simulator to conclude that with the increasing inhalation of marijuana came an increase in driving impairment with respect to standard deviation of lateral control (SDLC) (failure to stay in lane).2


However, there are


also studies that find the contrary—that is, there is no significant difference observed for SDLP with THC impairment.3 A new study from McGill University in


Canada that also used a driving simulator found that the marijuana impairment may last longer than originally believed with respect to more complex driving maneuvers. “Researchers recruited people aged 18 to 24 who were already recreational cannabis users. Tey were tested on a driving simulator at four stages: before inhaling a regular dose of cannabis, then one, three and five hours aſterward. Under the effect of cannabis, participants were able to perform simple driving tasks such as4


braking and steering. Tey even showed increased vigilance one hour aſter 52 datia focus


he last few years have seen new developments in marijuana- impaired driving. Although there


consumption. But when confronted with slightly more complicated scenarios— parking between two cars at a shopping centre, passing through an intersection, or avoiding pedestrians and cyclists—they had trouble.”5 What is the exact amount of the


THC concentration level that equates to marijuana driving impairment? Three major subject-matter experts in the area of traffic safety do not support the setting of a defined or per se THC blood concentration level automatically equating to marijuana driving impairment. The AAA Foundation for Traffic Research (AAA) Study stated that “…a quantitative threshold for per se laws for THC following cannabis use cannot be scientifically supported.” “Drivers can have a low level of THC, the active ingredient in marijuana, in their blood and be unsafe behind the wheel, while others with relatively high levels may not be a hazard.”6


The National


Highway Traffic Safety Administration (NHTSA) agrees. NHTSA’s Report to Congress stated that “the level of THC in the blood and the degree of impairment do not appear to be closely related. Someone can show little or no impairment at a THC level at which someone else may show a greater degree of impairment.”7


They also


stated that there is a poor correlation of THC concentrations in the blood with impairment and that setting per se levels is not meaningful.8


The International


Association of Chiefs of Police (IACP) in their most recent Resolution states that “numerous scientific studies fail to identify a threshold level of THC in blood as a basis for per se legislation . . . all law-enforcement officials, highway- safety officials, and Drug Evaluation and Classification (DEC) Program


coordinators should take the position with their legislative and governing bodies that there is no scientific basis for the adoption of THC per se legislation.”9 The National Sheriff ’s Association supported this IACP Resolution.10 Some scientific studies have also


addressed this “per se” issue. A 2018 Journal of Drug Policy Analysis stated that “{A} per se rule, even if carefully draſted and based on technology capable of distinguishing between active [agents] and inert metabolites, carries a substantial risk of criminally punishing someone for impaired driving who was not, in fact, impaired.”11


“’Measuring a person’s THC


is actually a poor indicator of intoxication. Unlike alcohol, THC gets stored in your fat cells, and isn’t water-soluble like alcohol,’ says Tomas Marcote, co-director of Te Center for Medicinal Cannabis Research at the University of California, San Diego.”12 Te issue of THC’s impact on driving


performance becomes even more compounded when you question whether it makes any difference if the driver is a chronic, heavy, or frequent user of marijuana. A chronic, heavy, or frequent user has been defined from four or more times a week up to everyday use. 13


It is


here that the studies begin to divert, with one position supporting that chronic users develop a tolerance to cannabis impairing their driving and are able to compensate their driving performance, while the other position supports the notion that chronic users have longer periods of impaired driving performance. In the first instance, one study found that


experienced users tend to become tolerant to many of cannabis’ performance-impairing effects. “[F]requent marijuana users may show fewer behavioral signs of disruption during intoxication than infrequent users,


spring 2019


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