The importance of basing marijuana impaired driving laws on sound science

WILLOW GROVE, Pa.-- May 11, 2016--Dr. Barry Logan, a leading figure in drug impaired driving research, spoke up today about his findings on the science of marijuana impaired driving laws, published this week by AAA.

Logan, Chief of Forensic Toxicology at NMS Labs, and Executive Director of the Center for Forensic Science Research and Education, was the lead author on a study commissioned by AAA to look at whether there is a scientific basis for the laws many states are rushing to pass–outlawing driving with a certain amount of THC, the active chemical in marijuana, in a person’s bloodstream.

Several states have moved to set limits for THC in the blood of drivers at which the person is “per se” guilty of impaired driving.

The research team looked at whether subjects arrested for impaired driving and testing positive for THC showed greater evidence of impairment in the standard roadside sobriety tests used by police officers.

“Subjects testing positive for THC showed more evidence of impairment in balance, coordination, and cognitive skills than their drug-free counterparts,” said Logan. “However, when we looked at drivers above and below the 5ng/mL threshold set in Washington, Colorado and Montana, the drivers with lower THC were no less impaired than their high THC counterparts.”

This finding was explained by the researchers on two important effects. The first is that individuals’ tolerance to THC is highly variable and unrelated to their degree of impairment, and also that the roadside tests, known to be effective for detecting alcohol use, are less sensitive to the effects of THC, meaning that many impaired individuals may be missed.

The second crucial finding is that by the time a police officer pulls over a vehicle, talks with the driver, administers sobriety tests, places them under arrest, and takes them for a blood draw, their blood THC concentration is only a fraction of what it was when they were driving, and in most cases falling below the 5ng/mL level.

“Only a third to a half of impaired, arrested drivers had THC concentrations above the 5ng/mL limit,” said Logan, calling into question the effectiveness of laws that give a free pass to the majority of THC impaired drivers based on the level in their blood.

Logan supports the AAA recommendation that drug impaired driving arrests should be made based on a trained police officer’s observations of signs of impairment including effects on speech, balance, coordination, and ability to follow instructions, as well as indicators like pulse and blood pressure. A positive lab test of the person’s blood or saliva for the presence of drugs can then be used to support or refute the officer’s opinion, regardless of the level.

About NMS Labs:

Since 1970, NMS Labs has been a leader in professional laboratory testing with an impeccable reputation in science and service. NMS Labs is best known for its innovation and ability for introducing new tests to meet the needs of the industries it serves. The state-of-the-art headquarters includes clinical, forensic and research facilities, a dedicated and secure crime laboratory, and is staffed by more than 200 highly trained professionals. NMS Labs is passionate about promoting public health and safety. For more information on NMS Labs, please visit www.nmslabs.com.

Copyright Business Wire 2016. The Gayly - 5/16/2016 @ 11:46 a.m. CDT