In the wake of recent legalization of cannabis sales in California, state law enforcement’s message is clear: Drive high, get a DUI.
But unlike alcohol, which has a .08 percent blood alcohol limit in the state, there is no chemical threshold to mark marijuana impairment for drivers in California.
Instead, prosecution for driving under the influence of weed rests almost entirely on patrol officer-observed signs and symptoms, and exams made by specially trained drug-recognition officers after an arrest.
While the National Highway Traffic Safety Administration reported to Congress in July 2017 that setting THC levels for driving “is not meaningful,” some states have set specific limits for THC, the psychoactive chemical in marijuana. In Colorado and Washington state 5 nanograms (5 billionths of a gram) per milliliter of blood marks impairment. In Nevada it is as low as 2 nanograms.
Without a threshold, cannabis DUI cases can be more difficult to prosecute than a DUI for drinking.
“It would be very helpful to have an established blood-THC limit,” said CHP Officer Allan Zang, one of about six officers in the CHP Santa Rosa unit who has gone through the nearly three-week-long drug recognition course. “It wouldn’t just be helpful for us, but for the District Attorney’s Office as well.”
The Sonoma County District Attorney’s Office declined to comment. A spokesman said it was not appropriate to discuss difficulties convicting people of driving high when the office was actively prosecuting those cases.
The CHP is currently researching the relationship between impairment and THC levels, said Zang, who has been a trained drug recognition expert for 10 years. And while a legal limit would be welcome, for him there’s never much question if a driver is too high to drive or not.
“The effects of marijuana differ from person to person,” he said. “But I don’t think there’s a gray area; someone is either too impaired to drive or not.”
The National Organization for the Reform of Marijuana Laws, which has pushed for the decriminalization and legalization of cannabis since 1970, supports California lawmakers’ decision not to set a THC threshold.
“All the numbers (states have used) are completely arbitrary. They’re pulled out of a hat,” said Paul Armentano, the national deputy director of NORML. “Any proposed threshold for cannabis will inadvertently criminalize individuals who have not broken the law.”
A habitual smoker might never test below 5 nanograms but show no signs of impairment while driving, while a novice user might be significantly impaired after cannabis and still have a relatively low THC level, Armentano said. Police in Sonoma County echoed his statement.
“We know there’s thousands of people driving who smoke marijuana and can functionally operate a vehicle,” said Santa Rosa Police Sgt. Summer Black. “Our job is to take them off the road when they can’t.”
Numbers for driving under the influence of cannabis in Sonoma County aren’t clear because local law enforcement agencies do not denote DUIs by drug.
Anecdotally, officials with CHP and Petaluma and Santa Rosa police departments said there hasn’t been a noticeable spike in DUIs where cannabis is the only intoxicant. But DUIs where marijuana is used with other drugs and alcohol are common.
To determine cannabis impairment, the same routine is followed as with impairment of any kind, said Officer Robert Sutherland, one of three drug recognition experts at the Petaluma Police Department.
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