Testing a driver for alcohol impairment is relatively easy.
Decades of research show drunken driving equals bad driving. Standardized tests mark various levels of impairment. And because alcohol passes through the system quickly, detecting its presence indicates recent use.
But determining whether someone is too high to drive is a lot more complicated.
Despite marijuana’s growing acceptance nationwide and its legality for recreational use in California, there is no consensus on how THC, its psychoactive ingredient, affects drivers or what levels constitute driving under the influence. That has left lawmakers, police and users grappling with a critical question: If you’re using marijuana, when is it safe to get behind the wheel?
An Oakland company believes it’s solved one piece of that puzzle. By mid-2020, Hound Laboratories plans to begin selling what it says is the world’s first dual alcohol-marijuana breath analyzer, which founder Dr. Mike Lynn says can test whether a user has ingested THC of any kind in the past two to three hours.
“We’re allowed to have this in our bodies,” Lynn said of marijuana, which became legal to use recreationally in California in 2018. “But the tools to differentiate somebody who’s impaired from somebody who’s not don’t exist.”
Law enforcement agencies already are testing the breath analyzers and competing roadside devices like oral swab tests. But experts say there’s a long way to go before any of the emerging technology can or should be used as evidence in a courtroom.
“Use of marijuana is not the same as impairment by marijuana,” said Dale Gieringer, director of California National Organization for the Reform of Marijuana Laws.
Unlike alcohol, marijuana doesn’t affect the body or brain in a uniform way, Gieringer said. Regarding the breath analyzer, Gieringer said he’d want to see research on its sensitivity to medical marijuana users, who take a certain amount every day to function.
“We would like to see better data before these are arbitrarily deployed,” he said.
Research on cannabis-impaired crashes is in its infancy. Because accidents often involve alcohol in addition to marijuana or other substances, it’s difficult to assign blame to just one.
The California Highway Patrol recently started tracking drug categories involved in collisions. In 2018 CHP investigated 537 traffic crashes in which officers suspected cannabis involvement, and 539 in 2019. The figures don’t distinguish between crashes where the suspect was solely using cannabis and the ones that involved cannabis and other substances.
Lynn, an emergency room doctor at Highland Hospital and reserve deputy for the Alameda County Sheriff’s Office, spoke to The Chronicle recently from Hound’s Uptown Oakland office about his 6-year-old company and the role he envisions for it.
Lynn stressed that his mission is one of fairness. He says he has a more equitable approach for both police and employers than to test with blood and urine, where chemical compounds found in cannabis known as cannabinoids are detectable long after a person is high.
“The challenge I knew from a law-enforcement standpoint is that … all that kind of testing that is available is totally unable to differentiate between someone who used five days ago — and is clearly not impaired — versus somebody who used an hour ago,” he said.
Unlike an alcohol Breathalyzer, Hound Lab’s weed technology doesn’t detect impairment levels with a numerical value. It’s a simple yes or no answer for ingestion in a narrow window of time.
Lynn said it’s up to lawmakers to determine the legal limit of impairment. His company, he says, provides the tools and research to allow others to start to determine what that threshold will be.
“We’ll say ‘it’s in your breath (or) it’s not in your breath,’” he said. “And then the expectation is that, whether it’s law enforcement or employers, they will use that objective data and follow it up with other testing.”
Independent researchers with the University of San Francisco have supported the lab’s initial claims.
In a recent study, 20 people were asked to bring in their own marijuana and to smoke the equivalent of one joint. Researchers did baseline and follow-up captures with the breath analyzer and compared the results against those on advanced blood testing equipment.
The study found that the devices were able to detect THC three hours after it was smoked — which the National Highway Traffic Safety Administration says is the window of peak impairment — and that THC in the breath correlated with the blood tests.
“Both of those are suggesting that THC measurements in breath could be used at the roadside,” lead researcher Kara Lynch said. “But more studies need to be done to determine what level of THC in breath would actually correspond to impairment.”
Hound Labs has already been field testing its device on the roads with the Alameda County Sheriff’s Office and a handful of other agencies, and testing on people pulled over on a voluntary basis.
Sgt. Ray Kelly, a spokesman for the department, said it hasn’t been difficult to get people to participate. Kelly said deputies have run the breath analyzers on about 12 participants, both drivers and passengers, and that the test has no bearing on any potential criminal case.
Driving under the influence of any substance is illegal in California and nationwide. While some states have “per se” laws that set a legal limit of THC in the system and prohibit driving above it, California isn’t one of them.
Critics say such laws are unjust, since blood tests can detect THC long after someone’s impaired.
On California roadsides, officers who suspect a driver is high will typically use cognitive tests and check for physical signs of impairment, but results can be subjective.
Kelly said Hound Lab’s breath analyzer, as well as other products emerging on the market, will be one of many tools to test for impairment. The California Highway Patrol will soon begin a pilot project in the Bakersfield area to field test oral fluid screening devices that detect the presence of a number of substances.
“As a result of (marijuana) legalization, a very competitive market has started,” Kelly said. “Basically, the best product that’s developed will likely win.”
Alameda County Public Defender Brendon Woods said the devices would need strong support from the scientific community before they can be introduced in court, and he said he’s concerned about police conducting tests for something that’s not a crime.
“So that’s the big issue,” he said. “Driving right now, having smoked marijuana, is not illegal. Driving impaired is illegal.”
Woods said he was also concerned about how it could be used as a pretext to stop, detain and search African Americans and Hispanics. He added that even alcohol breath analyzers have been found unreliable.
Impairment data would also need to be distilled for the common user before it can become law, said Keith Humphreys, a psychiatry professor and drug policy expert at Stanford University.
“It’s very hard to obey a law that you need a Ph.D. in psychopharmacology to understand,” he said of marijuana impairment. “I think we’re a long way from being able to do anything meaningful in this domain.”