Cannabusters myth #25: Roadside THC screening can assess intoxication

Sep 21 2018, 7:04 pm

Every day, in every way, cannabis legalization in Canada is getting closer. But despite all the hype, noise, and publicity, there seem to be recurring cannabis myths flying around that just won’t quit.

With 25 days until federal legalization, Grow’s daily Cannabusters series tackles common myths by cutting through the stigma and sensationalism to bring you the facts about cannabis.

Myth: Roadside screening can accurately detect cannabis intoxication

Fact: The machines can assess whether an individual has consumed cannabis at some point, but not if they’re intoxicated

Bill C-46 was given Royal Assent this summer and is set to come into power in December.

In August, after a 30-day public comment period, Attorney General Jody Wilson-Raybould approved the Drager DrugTest 5000, currently the only approved oral fluid drug screen for THC in Canada.

“This is another step to ensure we can detect and deter impaired driving to keep Canadian roads safe,” said Wilson-Raybould, noting that “impaired driving is the leading criminal cause of death and injury in Canada.”

The machine will be available to police forces across the country, although it’s up to departments to decide what equipment they prefer to use to assess intoxication.

Before C-46, law enforcement needed reasonable suspicion that the driver was intoxicated in order to perform a breath test. Under the new legislation, reasonable suspicion is not required when testing for alcohol – authorities can screen any driver for intoxication at any time, which some lawyers believe is a violation of the Charter rights prohibiting “unreasonable” searches. Drivers who refuse to take the test could face serious criminal charges.

Civil rights groups have argued that this puts vulnerable populations such as racialized communities in danger of being targeted, and it’s well-documented that these citizens are already overrepresented in the Canadian justice system.

That portion of C-46 was hotly contested. The Senate struck it completely, but Liberals in the House of Commons were adamant and restored it to the bill.

Why the tests don’t really work

“Additional research is necessary to define the pharmacokinetics of cannabinoid markers in a variety of biological matrices,” says a recent paper on cannabinoid markers in biological fluids and tissues, authored by Dr. Marilyn Hustis and Dr. Michael Smith and echoed by other experts.

Cannabis intoxication is nearly impossible to determine based on these tests as the concentration can be affected by so many variables, including the frequency of use, potency of the cannabis consumed, whether other drugs were used, and how the cannabis was ingested.

The tests can detect if a driver has consumed cannabis at some point, but not if a driver is intoxicated – and depending on their level of consumption, THC can stay in a user’s system for days, weeks or even months after use.

“There is no one blood or oral fluid concentration that can differentiate impaired and not impaired,” according to Dr. Huestis.

The machines also reportedly don’t give accurate results in temperatures lower than 4ºC, which is problematic in a country known for its long, cold winters.

Medical users also have concerns that Bill-46 could have a negative impact on their independence and mobility.

See also

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