On Tuesday, Massachusetts’ Supreme Judicial Court ruled that roadside sobriety tests used for drunk-driving cases cannot be used as evidence that a driver was under the influence of marijuana. The court’s decision is that in DUI marijuana cases, police officers can only testify as non-expert witnesses, and can only share information about how defendants performed during sobriety tests. Officers may not tell juries their own assessments, such as if the defendant was too high to be driving. Neither can officers reveal if defendants passed or failed the tests.
Massachusetts’ court cited that there is no reliable scientific test to detect marijuana impairment like there is for blood alcohol content. The Massachusetts legislature has founded a special commission to research issues relating to driving under the influence of marijuana.
While the concept of marijuana impairment testing is up for debate—cannabis affects everyone slightly differently, making each person’s tolerance limit unique—California is currently using a THC saliva detection test in three counties. In Sacramento, Los Angeles, and Kern counties, California Highway Patrol is using plastic swab sticks to collect drivers’ saliva and detect active THC. This is more accurate than the controversial blood test that measures metabolites, which detects cannabis use in the “recent past” but cannot determine impairment.
The saliva detection test, developed by Alere Toxicology in Santa Rosa, has a 95 percent accuracy rate and is capable of detecting impairment from cannabis, cocaine, methamphetamines, and opiates. The test measures impairment by analyzing the concentration of drugs in the blood. California currently has no set limit for cannabis intoxication while driving, but Washington’s threshold is five nanograms per milliliter of blood, to cite an example.
California’s Proposition 64 provides funding for the development of these new tests and for the CHP to experiment with these technologies. Prop 64 passed in November, designating $3 million annually for four years to the CHP to create protocols for detecting DUI marijuana drivers. Another piece of proposed California legislation, Assembly Bill 6, would start a CHP task force to compare roadside tests and strategies to determine drug impairment. The bill was last amended in Senate on June 19 and is currently in committee.