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Toronto police officers hold a R.I.D.E. spot check in Toronto on Nov. 30, 2016.Christopher Katsarov/The Globe and Mail

From the archives: This article was originally published January 23, 2018

Part of cannabis laws and regulations

I've read that there will be new drugged-driving rules for when pot is legalized this year. But I don't really understand them. So do we have rules now or is it legal to be driving after consuming marijuana? – Katie, Calgary

The proposed rules will make it easier for police to weed out drivers who've been toking.

But until they pass, if police believe you're impaired by any drug, you could still face criminal charges.

"So, right now, police can have you take the standard field sobriety test and if you fail they can demand a drug recognition evaluation," said Andrew Murie, chief executive of Mothers Against Drunk Driving (MADD) Canada. "If you fail that, they charge you with impaired driving and they make a sample demand. It's not tested for level, but cannabis must be in that urine sample for the charge to go forward."

To test you in the first place, police have to suspect that you're impaired – say, because you're driving erratically or they pull you over and smell marijuana. "It's a very low threshold," Murie said.

But right now, there's no set limit on the amount of cannabis that you can have in your blood, the same way there currently is for alcohol.

And that's part of the reason why there are still relatively few drugged-driving charges, even though drugs now show up more often than alcohol in blood tests of drivers killed in crashes. In 2014, just 2.6 per cent of all impaired-driving charges (1,355 out of 51,637) were for drugs.

"Courts don't like these tests because there's not a level of measurement," Murie said.

"And most police forces don't have people trained to do these tests. So there are very few charges and even fewer convictions."


Bill C-46, the proposed changes to impaired-driving laws, sets out specific limits for the amount of THC, the main psychoactive ingredient in cannabis, that you can legally have in your blood while driving.

What you'll be charged with depends on how many nanograms of THC you have per millilitre of blood within two hours of driving.

"They're saying, 'You shouldn't be driving with any cannabis in your body, but there's a difference between low and high levels – so we won't treat low levels in a criminal fashion but there will still be punishment,'" Murie said.

The bill, which is set to be debated when the Senate resumes this month ("The Conservative senators are playing politics with it," Murie said), sets out three offences:

Two nanograms

If you have two nanograms, but less than five, you would face a summary conviction and up to a $1,000 fine.

"With two nanograms, it's not a criminal offence, its a summary offence," Murie said. "You're not fingerprinted, so it would not show up on CPIC [Canadian Police Information Centre], it wouldn't show up on an employment check or a passport application."

In an analysis statement with the draft legislation, Ottawa said that this low offence is "is not directly linked to impairment, but is, rather, based on a precautionary or a crime prevention approach."

Five or more nanograms

If you have five nanograms or more, it gets more serious, just like if you're caught with a blood alcohol concentration (BAC) over .08. It's a hybrid offence and, depending on the seriousness, you could face a fine and jail time. The maximum penalty for a criminal offence would be 10 years. This level of THC is "expected to cause some driving impairment," the statement said.

Combined THC and alcohol

Alcohol and marijuana are a dangerous mix for driving – worse than either alone at the same levels, Murie said. That's why it's also a hybrid offence to have a BAC of .05 combined with a THC level over 2.5 nanograms.

There's debate whether all drivers, especially regular users, will actually be impaired at these levels. And drivers who are heavy users may always be above those levels.

But Murie thinks the law – which sets clear legal per se levels that mean you're legally intoxicated at those levels – is fair.

"I think it's the right legislation," he said. "They'll eventually add per se levels for other drugs as they go along."

The provinces still have to pass their own rules for driving while high. Quebec has proposed a zero-tolerance policy where any driver with a trace of cannabis could be suspended for 90 days. Other provinces, including Ontario and Alberta, have proposed zero-tolerance for new drivers only.

Roadside saliva tests

So how will this actually work on the road?

First, like now, police would still have to reasonably suspect that you're impaired. Then, they could either ask you to take an oral fluid test – where they take a scrape of saliva off your tongue and put it into a machine – or the standard field sobriety test.

"Police will have both options," Murie said. "It's totally up to police. So certain officers will be trained in the standard field sobriety test and they might feel comfortable with that – and others will use the oral fluid test."

The oral fluid test doesn't show a level – it's just a pass or a fail. But the test only reads fail if you are above 5 nanograms – the criminal level, Murie said.

If you failed either test, then police could demand a blood test, which would show your actual blood concentration of THC. That's the test that determines the final charges.

The blood test has to be taken within two hours after you're first pulled over. And how quickly you take the test within that two-hour window is important because the longer you wait, the lower your THC will be.

"You're over the criminal level of 5 with the roadside oral fluid test," Murie said. "But when the actual blood test comes back, it would probably be significantly lower – unlike alcohol, the dissipation rate for cannabis is rapid, so within two hours, 90 per cent has left the body."

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