When marijuana becomes legal on Oct. 17, most police forces won’t be changing how they weed out stoned drivers.

“We’re already doing testing for drug-impaired driving at the roadside,” said Sergeant Richard Butler, with the Calgary Police Services drug-recognition unit. “We use the standard field sobriety test and that’s what we will continue to use.”

On August 27, Ottawa approved the Draeger Drug Test 5000, a device that allows officers to test driver’s saliva for THC, the main psychoactive ingredient in cannabis. Right now, it’s the only approved device.

But police in Vancouver, Calgary, Toronto, Montreal and Halifax – along with the provincial force in Quebec – say they haven’t purchased the device. Last week, Vancouver police chief Adam Palmer said in a radio interview that Vancouver wouldn’t be using the Draeger device. Others say they’re waiting for other devices to be approved.

“As further devices are expected to become approved shortly we are waiting to have more information before we choose a course of action,” Halifax police said in an e-mail statement.

BUSINESS AS USUAL

So, most forces will be doing what they’ve been doing. If cops suspect you might be impaired while driving, they can make you do the roadside sobriety test – which can include standing on one leg. Then, they can call a drug-recognition expert for further tests, including a lab test of blood, saliva or urine. In court, officers have to prove that you were impaired.

But Bill C-46, the new impaired-driving law, sets out per se limits – the amount of THC you can legally have in your blood while behind the wheel.

If you’re over these limits – two nanograms of THC per millilitre of blood for a summary conviction (essentially a warning with an up to $1,000 fine) and five nanograms for a criminal conviction – you can be charged.

It’s the same way alcohol has been treated since the .08 blood-alcohol content (BAC) was introduced in 1969.

“The limits take away the argument of whether the person was impaired or not,” said Andy Murie, chief executive of MADD Canada. “If you’re over, it’s an offence.”

The law gives officers the option of demanding a roadside saliva test. In about four minutes, the device will either show positive if you’re over the 25-nanogram limit. It won’t show the actual level of THC – it’s just positive or negative.

“With oral-fluid screening, there are some fundamental problems with it,” said Superintendent Scott Baptist, Toronto Police traffic services district commander and co-chair of the Ontario Association of Chiefs of Police traffic-safety committee. “All it’s going to do is confirm that there’s THC in the saliva, that’s it – it doesn’t give an indication of the level of impairment.”

If you fail the saliva test, then you’ll be required to take a blood test – a urine test won’t be allowed as evidence that you’re over per se limits – to determine your exact THC level and whether you’re above the per se limits.

“Don’t forget, the oral-fluid test is just the screening tool; you get convicted based on the blood test,” Murie said. “If you fail the screening, they got to make a demand for blood and you’ve got the right to talk to legal counsel.”

It could be two or three hours until you get the blood test. After two hours of smoking pot, blood levels of THC decrease by 90 per cent.

So, if those blood tests show that you’re over five nanograms, it’s likely that your levels were higher when cops first pulled you over, Murie said.

POTENTIAL PROBLEMS

Lawyers say there are potential problems with the saliva tests.

“I foresee a lot of ways we could challenge it,” said Sarah Leamon, a Vancouver criminal-defence lawyer. “If it’s held at any more than a 10-degree angle or used below 4 C, it could cause inaccurate results.”

Leamon says the tests could also face multiple challenges under Canada’s Charter of Rights and Freedoms.

“I’m not confident it will generate results that are reliable,” Leamon said. “And they take so long to administer at the roadside, you could be detained for upwards of 20 minutes – the court has said your rights are suspended while an officer is collecting a breath sample for alcohol, I don’t think they’ll be able to say the same thing for the oral fluid test taking so long.”

In an e-mailed statement, Draeger Safety Canada said the device is used in countries with “even colder weather, including Russia and Poland” with no issues.

“The question of impairment is a decision for law enforcement and courts to make,” the company said. “Our technology simply provides police with a highly accurate way to detect the recent use of drugs, at the levels set forth by the government.”

There have been worries that drivers could get busted because they’d smoked weed days ago and could still have cannabinoids in their bodies.

But the tests only detect Delta 9 THC, which is only present in your system for four to six hours after using, Draeger said.

“The test does not detect metabolites, which is the degradation of THC that can stay in a person’s system for days and weeks,” it said. “Therefore, it is impossible for the device to detect past usage.”

The Centre for Addiction and Mental Health (CAMH) is recommending that people wait at least six hours before driving after using pot.

But there are rare cases in which heavy users – people who have been using large amounts daily for years – might test positive for THC in saliva and blood tests.

“In such users, THC metabolites get stored in fatty tissues and are released more slowly over time,” Mark Asbridge, associate professor in Dalhousie University’s department of community health and epidemiology, said in an e-mail. “Whether these people are still impaired, however, has not been examined.”

ARE DRIVERS ACTUALLY IMPAIRED?

MADD’s Murie expects the per se levels to also be challenged in court – the same way the .08 BAC was challenged for years.

“I imagine they’ll go all the way to the Supreme Court for a final verdict,” Murie said. “We’re not kidding ourselves.”

The limits reflect the levels of THC that would cause impairment in an average person, Asbridge said.

“There will be people who are not impaired at five nanograms,” Asbridge said. “There will be others who are impaired at two nanograms or less.”

With five nanograms of THC in their blood, drivers have at least a 35 per cent greater chance of getting in a crash, said Robert Mann, a social and epidemiological research scientist at CAMH.

“People will always argue, as they do for alcohol, that they’re not impaired at the legal limit,” Mann said. “The science is telling us that people are affected at these levels, that driving skills are affected at these levels and that collision risk is elevated at these levels – that’s the bottom line.”


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