Frankfort, KY: House lawmakers failed to advance Senate-backed legislation, Senate Bill 228, that sought to impose new criminal penalties for any motorist who operates a vehicle with the presence of THC in their blood above 5ng/ml.
Senators passed the measure in March, but House members failed to move it out of committee before the session’s adjournment.
Numerous scientific studies have concluded that the presence of THC in blood is an unreliable predictor of either recent cannabis exposure or impairment of performance. A report by the Congressional Research Service similarly concludes: “Research studies have been unable to consistently correlate levels of marijuana consumption, or THC in a person’s body, and levels of impairment. Thus, some researchers, and the National Highway Traffic Safety Administration, have observed that using a measure of THC as evidence of a driver’s impairment is not supported by scientific evidence to date.”
NORML has long opposed the imposition of THC per se thresholds for cannabinoids in traffic safety legislation, opining: “The sole presence of THC and/or its metabolites in blood, particularly at low levels, is an inconsistent and largely inappropriate indicator of psychomotor impairment in cannabis consuming subjects. … Lawmakers would be advised to consider alternative legislative approaches to address concerns over DUI cannabis behavior that do not rely solely on the presence of THC or its metabolites in blood or urine as determinants of guilt in a court of law. Otherwise, the imposition of traffic safety laws may inadvertently become a criminal mechanism for law enforcement and prosecutors to punish those who have engaged in legally protected behavior and who have not posed any actionable traffic safety threat.”
Six states – Illinois, Montana, Nevada, Ohio, Pennsylvania, and Washington – impose various per se limits for the presence of specific amounts of THC in blood while 11 states (Arizona, Delaware, Georgia, Illinois, Iowa, Michigan, Oklahoma, Rhode Island, South Dakota 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 any 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.
Additional information on cannabis, driving performance, and traffic safety is available from the NORML Fact Sheets on Driving and Marijuana.