California: Task Force Recommends Against Imposition of Per Se Traffic Safety Limits for THC

Sacramento, CA: State lawmakers should reject legislative proposals to impose per se limits prohibiting motorists to operate a vehicle with trace quantities of THC in their blood, according to the recommendations of a state-appointed task force on impaired driving. Such laws criminalize driving a vehicle with trace amounts of THC or other related compounds in one’s system, even absent any evidence of impaired driving performance.

In a report to the legislature, the task force stated: “Drugs affect people differently depending on many variables. A per se limit for drugs, other than ethanol, should not be enacted at this time as current scientific research does not support it.”

The task force included participants from various agencies and organizations, including the National Highway Traffic Safety Administration (NHTSA), the California Highway Patrol, the California Office of Traffic Safety, the American Automobile Association (AAA), and California NORML. Both NHTSA and AAA have previously recommended against the imposition of per se limits for THC – acknowledging that the presence of THC in blood is not a consistent predictor of either recent cannabis exposure or psychomotor impairment. 

NORML has consistently opposed the imposition of THC per se limits, opining that such thresholds are not evidence-based and that they may lead to the criminal prosecution of people who consumed cannabis several days previously but are no longer under its influence.

Six states — Illinois, Montana, Nevada, Ohio, Pennsylvania, and Washington — impose various per se limits for the detection of specific amounts of THC in blood while ten states (Arizona, Delaware, Georgia, Indiana, Iowa, Michigan, Oklahoma, Rhode Island, Utah, and Wisconsin) impose zero tolerant per se standards. In those states, it is a criminal violation of the traffic safety laws to operate a motor vehicle with detectable levels of THC in blood. Colorado law infers driver impairment in instances where THC is detected in blood at levels of 5ng/ml or higher.

Full text of the task force’s report is available online. Additional information about cannabis and psychomotor performance is available from NORML’s fact sheet, “Marijuana and Psychomotor Performance”.