Recent legislation awaiting Gov. Jerry Brown’s signature not only seeks to implement a statewide regulatory system on the medical marijuana, but also calls for a study on how law enforcement can better detect stoned drivers.

Nestled within one of the bills — Assembly Bill 266 by Assemblyman Rob Bonta (D-Oakland) — is a sentence that calls for the state to commission the UC San Diego’s Center for Medicinal Cannabis Research to develop a study that identifies how cannabis impacts motor skills. The language was written by Assemblyman Tom Lackey (R-Palmdale), a retired California Highway Patrol sergeant of 28 years who said he was motivated to coauthor the bill to give officers another tool to get impaired drivers off the street and to save lives.

“We’ve done a good job of reducing alcohol DUIs,” he said. “With drug impairment we have a long way to go. I believe this is a pioneering effort to allow that to take place.”

Lackey — who made his first visit to Humboldt County on Tuesday along with two other bill authors to call on Gov. Brown to sign the bills — said that the study could provide data that he hopes will result in an improved field sobriety test specifically for marijuana impairment.

The three-bill package known as the “Medical Marijuana Regulation and Safety Act” is currently sitting on Gov. Brown’s desk. If signed, the bills would create a licensing and regulatory scheme for all aspects of the medical marijuana industry including cultivation, distribution, transport, dispensary sales, laboratory testing, environmental protections and storage.

No established limit

Unlike with alcohol, where a legal blood alcohol concentration has been established, local law enforcement officials say they are currently limited in their methods of detecting drivers under the influence of the marijuana’s main psychoactive component, THC, with no set level of impairment and no easy detection method like a Breathalyzer.

“We do not have a cutoff point where we can say we know they are impaired,” Humboldt County District Attorney Maggie Fleming said. “The proof goes back to whether or not their driving showed they were impaired.”

When prosecuting someone for driving under the influence of marijuana, Fleming said evidence usually includes patrol car dash cam videos, testimony by drug recognition experts and observations by a law enforcement officer.

Even if such a level were established, a local defense attorney and several studies state that THC processing by the human body is more complicated than alcohol and other drugs. A former president of the DUI Lawyers Association and current member of National College of DUI Defense, Eureka-based attorney Manny Daskal said some studies have shown that drivers actually exhibited safer driving habits and kept more room between themselves and other drivers to compensate for their impairment, though other studies refute the findings.

“Right now the research isn’t there for them to accurately predict when impairment occurs or at what level it occurs,” Daskal said.

Regardless of what type of drug a California Highway Patrol officer suspects a driver is impaired by, Humboldt County CHP Public Information Officer Cy May said they will perform the same field sobriety test.

“Usually we’re not sure it’s cannabis,” May said, adding there are certain giveaway signs.

Such signs include marijuana odor emanating from the car or driver, bloodshot or dilated eyes, and a higher pulse rate.

When testing motor skills, May said an officer can employ a nystagmus test in which an officer moves a finger around the driver’s face and asks the driver to follow it with their eyes. When an officer pushes their finger toward the driver’s face, May said a drug impaired driver will often converge or cross their eyes, but then one of their eyes will go back to normal right away.

Another motor skill test employed by the CHP is a Romberg test in which an officer tells the driver to close their eyes for a period and asks the person how much time they think elapsed when the officer tells the driver to open them.

“They all may show us signs and symptoms of impairment, but that may not show direct correlation with marijuana impairment,” he said.

May said two other signs of THC impairment are a green coating on the tongue caused by smoking and an inability to balance, but Daskal said studies have shown that the balance test is the only reliable field sobriety test to detect THC impairment.

Safety studies

Two studies by the National Highway Transportation Safety Administration released in February found that 12.6 percent of surveyed drivers had evidence of marijuana use in their systems — up from 8.6 percent in 2007 — while those driving under the influence of alcohol dropped by one-third in the same time period.

Another study by the administration found that marijuana users were 25 percent more likely to be in a crash than non-marijuana users, but that the increased risk “may be due in part because marijuana users are more likely to be in groups at higher risk of crashes” — such as young men.

“When you take all the confounding factors into account there is not much of an indication that marijuana causes an increase of crashing,” Daskal said.

Speaking at Tuesday’s rally in Eureka, Lackey said a September 2015 report by the Rocky Mountain High Drug Trafficking Area showed a 32 percent increase in marijuana-related traffic deaths in Colorado in 2014 — the same year recreational marijuana use became legal — compared to 2013.

“We will not stand for that in California,” he said to the crowd.

While these studies state the risk of a crash is much higher when THC impairment is factored in, others — like a 2010 study in the The American Journal on Addictions — state some experimental studies have shown it can have the opposite effect.

“Several reviews of driving and simulator studies have concluded that marijuana use by drivers is likely to result in decreased speed and fewer attempts to overtake, as well as increased ‘following distance,’ ” the study states. “The opposite is true of alcohol.”

However, the study does state THC-impaired drivers have a harder time staying in their lane and have a slower reaction time.