Blood feud: Advocacy groups at odds over how to test impaired drivers for marijuana
Edmonton emergency room physician says no one knows the best approach to marijuana-impaired driving
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Two advocacy groups are at odds over whether blood testing should be done on motorists who are impaired by marijuana.
While MADD Canada supports the federal proposal to measure the amount of THC in a driver’s bloodstream, Smart Approaches to Marijuana (SAM) Canada has written to the federal government in opposition to the plan.
“A blood level is absolutely useless,” said Phillip Drum, a pharmacist who works with SAM as well as a U.S. group called Citizens Against Legalizing Marijuana. “It’s not the same molecule as alcohol. It’s residing in the brain, not the bloodstream.”
Drum said the body eliminates 80-90 per cent of marijuana from the bloodstream within an hour when smoked because it is fat-soluble, unlike alcohol.
Impairment doesn’t peak until it starts leaving the blood, so any reading of THC in the blood would be out of line with the driver's actual level of impairment, he argued.
A 2015 U.S. study showed standard roadside field sobriety tests – the same tests used on suspected drunk drivers – conducted by police officers who are trained Drug Recognition Experts are the most reliable way to test for marijuana impairment.
“If the person fails two of the four (tests), with a 96.7 per cent accuracy rate they’re going to be able to determine whether they are under the influence of marijuana,” Drum said.
The next step, he said, would be an oral fluid test to confirm or deny the presence of marijuana or another drug.
MADD Canada CEO Andrew Murie, however, said judges will need more than that to convict impaired drivers.
“If I’m a victim’s family, I would rather appear in front of a judge with evidence that the person who killed my loved one was over a certain level of THC,” Murie said.
“Is it perfect? Absolutely not … But right now, it’s the best we’ve got.”
Murie said courts typically reject evidence from roadside tests because no matter how qualified the officer might be, the result is still viewed as the officer’s opinion.
Blood tests can take hours because they cannot be conducted on site and they require consent, or a warrant if consent is not given.
As a result, in some states like Colorado where the legal limit is 5 ng of THC per millilitre (ml) in the blood, convictions are very low because the marijuana is mostly out of the motorist's bloodstream before the test is conducted.
Canada has set a lower limit, which Murie says is a “very smart” approach.
Under the federal government’s proposed legislation, Bill C-46, having at least 2 ng but less than 5 ng of THC per millilitre (ml) of blood within two hours of driving would be a separate summary conviction criminal offence punishable by fine.
A blood sample could be demanded after a roadside screening and oral fluid test.
Dr. Louis Francescutti, an Edmonton emergency room physician and professor in the University of Alberta’s school of public health, said “both sides are right” and the injury prevention community is still confused on the best way to approach marijuana-impaired driving.
“We know that the risk of injury, including driving injuries, are going to increase as this becomes legalized,” Francescutti said.
“Hopefully we’ve got time for somebody smart to come up with some kind of measure that’s going to be meaningful.”
Canada's Standing Committee on Health closed submissions on Bill C-46 Friday.