The California Legislature has yet to establish limits concerning cannabis consumption, following voters’ approval in November 2016 of Proposition 64, which allows recreational marijuana use.

Unlike alcohol, measuring marijuana intoxication in a reliable way that can lead to admissible evidence in court has proven difficult. Although tetrahydrocannabinol (THC) − the chemical component of marijuana that causes a “high” − can be detected in a person’s blood or urine for up to 30 days after use, the inebriating effects last only a few hours. Numerous variables may distort the results, such as the user’s age, gender and race; method of consumption; frequency of use; and even the strain of the drug.

Police who respond to suspected drugged driving incidents primarily rely on field sobriety tests, which check physical coordination, plus a screening to look for cognitive changes. For example, drivers may be told to tip back their heads and estimate when 30 seconds has passed, as certain drugs cause the user to perceive time as either accelerated or slowed down. However, a professor at Washington State University conducted research on officers specially trained as drug recognition experts that indicated significant disparity in the quality of the training and results obtained by these officers. Over the course of five years, a false positive rate for marijuana intoxication ranged from 38 percent to 68 percent.

Legislative Efforts

To address these issues, Assembly Bill 6, introduced by California State Assemblyman Tom Lackey (R-Palmdale), proposes to establish a drugged driving task force comprising law enforcement and members of the public to develop practices and procedures to ensure fairness in the policing of drugged driving. Under Assembly Bill 6, a California Highway Patrol task force would be formed to examine various roadside technologies to detect drug impairment.

Officers in Sacramento, Kern and Los Angeles counties have already begun using one such device, which uses mouth swab test kits that detect the presence of six legal and illegal drugs, including marijuana. Unlike blood tests that check for the long-term markers of marijuana, the swab kits test for Delta-9 THC, which diminishes quickly after ingestion. This test theoretically provides law enforcement with an objective measure to demonstrate intoxication. The DS®2 Mobile Test System, manufactured by California-based Alere Toxicology, uses a cheek swab to collect saliva from a suspect. The swab then fits into a hand-held computerized device that shows within five minutes whether any of the six drugs are present in the saliva. The device is reported to have an accuracy rate of 95 percent.

“I believe that the best path forward to deal with marijuana-impaired driving is to develop new field sobriety tests that are specifically designed to recognize when someone is too impaired to drive,” Assemblyman Lackey said. “I also believe we need to use new technology that focuses on detecting recent use in a driver’s breath or saliva. Both of these things need to work in conjunction so drivers who are not impaired are not falsely accused.”

Additional legislation has been introduced by California State Senator Jerry Hill (D-San Mateo) to establish limits and penalties for drugged driving. Senate Bill 698 sets a limit of 5 nanograms of Delta-9 THC per milliliter of blood when a person also registers between .004 and .007 percent of alcohol by weight. Violators would receive an infraction for their first offense, followed by a misdemeanor for each additional violation. Senate Bill 65 would make smoking marijuana while driving a punishable offense.

Testing Technology in the Courts

A Kern County judge ruled last week that results from a swab test are admissible as evidence, a first for prosecutors seeking a drugged-driving conviction. Still, for the time being, drivers asked for a cheek swab are free to refuse to take the drug test.

Rapidly changing marijuana policy has created a challenge for law enforcement and state prosecutors. The development of new technology that provides an objective measurement of cannabis intoxication is a critical step needed to ensure public safety and instill confidence in the legalized marijuana industry.