Driver impairment assessment unclear for cannabis users

Sep 13, 2018

With the legalization of cannabis only a month away, the federal government is inching towards establishing regulations for cannabis and driving under its influence.

Despite criticisms that its functional temperature range isn’t appropriate for Canadian winters, Canada has officially approved the Draeger DrugTest 5000 as the device that will be used by law enforcement officers in roadside stops when drivers are suspected of operating their vehicles under the influence of intoxicating substances.

Investigation has shown that driving impaired after using cannabis can double the chance of car crashes, and that one in seven licensed Canadian drivers has admitted to driving within two hours of imbibing the drug.

However, activists have voiced concern that civil liberties will be affected by the government’s reliance on inconclusive science to develop its zero tolerance policies, and that sober drivers will be branded as criminals and given records if they have lingering amounts of THC in their systems from prior usage. Rob De Luca, spokesman for the Canadian Civil Liberties Association and director of the CCLA’s public safety program, believes we’re headed down a path of targeting racialized communities as well as medical cannabis users. While he doesn’t deny that drug-impaired driving is dangerous and acknowledges that cognitive and psychomotor performance are affected by marijuana, he worries about the arbitrary criminalisation of certain Canadian populations.

“It’s going to criminalize a host of individuals who are basically going about their day, thinking they’re doing completely legal behaviour, the impact of bringing the full weight of the state and the criminal justice system against someone who may not have been impaired behind the wheel — that’s a remarkable thing.” Rob De Luca, Spokesman for Canadian Civil Liberties Association

Following the introduction of the Draeger device, Canada has also officially set the legal THC concentration limits over which drivers will be considered impaired. Complicating this decision is that fact that while THC is the active component of cannabis, it can remain in the user’s system long after the high has worn off, leaving test results easily contested. Unlike alcohol, which is eliminated from the body at a constant rate, cannabinoids like THC are stored in fat and are released sporadically. Additionally, those who use cannabis regularly—like medical cannabis users—can develop a tolerance to the drug, as well as present THC in their systems for longer periods of time. In one American study, chronic cannabis smokers were shown to have low quantities of THC in their blood up to thirty days after use.

Additionally, unlike alcohol, cannabis affects individuals differently, depending on usage history and even how much fat each individual stores in his or her body. Dayong Lee, toxicology manager with the Houston Forensic Science Center, says that level of personalized reaction to the drug “makes it very complex to evaluate what a blood concentration means in terms of someone’s performance or behaviour.”

Canada has regulated that drivers with more than five nanograms of THC per millilitre of blood will be penalized with compulsory fines of $1,000 as well as jail time after a repeat offense. If the bloodwork comes back with low levels of alcohol and a 2.5 ng/ml of THC, the individual will also face charges. Summary offenses will include any amounts of THC between two and five nanograms of THC in blood, which will carry a maximum fine of $1,000 as well as a criminal record that can be suspended after five years.1

However, since the science that backs such regulations is not sound, many Canadians are protesting the fact that these offenses carry such serious repercussions. According to Vancouver lawyer Kyla Lee, “The government should take every public safety approach that’s appropriate, but they shouldn’t take it when the scientific foundation is not clear…Meanwhile, people (will be) getting criminal records for drugs, which will render them inadmissible to the United States and have all sorts of consequences for employment, families, life insurance, etc..” Additionally, Dayong Lee “can think of less than 10 studies that support the five nanograms being impaired,” and is backed by forensic toxicologist Marilyn Huestis, who, while at the US National Institute on Drug Abuse, did not see a relationship between blood concentration levels of THC and impairment. According to her philosophy for identifying impaired driving, “the first thing is that you show the person is really impaired. Because some people might have five (nanograms) or two (nanograms) and maybe they’re not impaired…Then you do the biological sample to point (out) which drugs are causing the impairment.”