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If Washington voters approve a ballot measure this fall legalizing marijuana, it would bring big changes – not just in the justice system, but in our communities.We can expect hundreds of official marijuana stores and fewer drug arrests. What about advertising? Night-life? Driving?KNKX is exploring how legalization might impact daily life – even if you never touch the drug.In our series If it’s legal: Five ways legal pot could affect your life, we consider how things could change for all of us.

Will legal marijuana make our roads more dangerous?

Gabriel Spitzer
Sgt. Robert Thompson of the Puyallup Police Dept. makes a traffic stop, looking for impaired drivers.

If Washington voters approve a ballot measure this fall legalizing marijuana, it would bring big changes – not just in the justice system, but in our communities. In our series “If It’s Legal: Five Ways Legal Pot Could Affect Your Life,” we consider some ways things could change for all of us, even people who never smoke pot. We begin with a basic question: would legal marijuana lead to more danger on the roads?

When I hopped into Sgt. Bob Thompson’s unmarked white cruiser, it took me a minute to realize there was a woman cuffed in the backseat. Thompson, a 25-year veteran of the Puyallup Police Department, had just picked her up on a DUI charge, and was bringing her to the police station for her official breathalyzer test.

“How you doin’, Doreen?” he asks.
“I don’t know,” she grumbles.

Inside, she blows into a tube attached to a machine that looks like a big typewriter. The result comes back at .09, exceeding the legal limit for alcohol in the blood. It’s enough to get her booked that night into Pierce County Jail.

A gray area

If this case had been about marijuana instead of alcohol, this would have been a lot more complicated.

Alcohol has a “per-se” limit, meaning if your blood level is over, you’re basically guilty. There’s no equivalent for pot, so even though alcohol is legal and marijuana isn’t, it can be trickier to bust someone for driving stoned than driving drunk.

Initiative 502 aims to change that by establishing a legal limit for marijuana in the bloodstream. It’s part of an effort to allay fears that legalizing pot would lead to more impaired drivers on the roads. And it would change a process that, right now, relies heavily on the officer’s judgment.

It works like this:

An officer makes a traffic stop for whatever reason – it could be something as little as a driver taking a wide turn or failing to dim her brights. If the officer thinks the driver is impaired, she might be asked to take field sobriety tests such as walking a straight line or standing on one leg. If the driver seems shaky, she might have to blow into a portable breathalyzer test to see if she’s drunk.

“And if they’re impaired by drugs, they take them to the station and call for a drug recognition expert to come and do an eval,” Thompson says.

A Drug Recognition Expert, or DRE, is a police officer specially trained to spot signs of drug intoxication, like quivering eyelids, dilated pupils or a racing pulse. Sgt. Thompson has been a DRE since 1997. If he determines the driver is on drugs, he can request a blood test. But even if the blood shows the driver had used marijuana, without a legal, per se standard, it doesn’t prove the person was impaired.  

“Per ses are always better. ... (But) why don’t we have a per se law for drugs? The problem is that it affects people so differently,” says Thompson.

Tricky convictions

That uncertainty can make it hard for prosecutors to get a conviction. Courtney Popp is with the state Traffic Safety Commission, working on DUI cases.

“Prosecutors across the state have expressed frustration that they’re having difficult time proving cases involving marijuana-impaired drivers. Some [jurors] think it’s OK, that if someone’s driving under marijuana they must not really be impaired,” Popp says.

A per-se limit is supposed to give jurors a concrete standard, but Popp says it wouldn’t be so simple. For one thing, it might make it harder to convict a driver who came in under the limit even if he or she was impaired. And even a test that exceeds the limit – 5 nanograms of marijuana’s active ingredient THC in one milliliter of blood – might not be enough.

“The defense is very vigorous in driving-under-the-influence cases, and although it often feels as a prosecutor that if you have a blood test admitted it should be an easy conviction, it’s not always the case.”

Sketchy science

A defense lawyer might attack the science behind a per se standard for marijuana. Attorney and activist Jeff Steinborn certainly would – he’s pro-legalization, but opposes I-502 in part because of its DUI provisions.

“Virtually every one of the people who writes these studies ends up concluding the science really isn’t ready yet for us to draw a connection between a particular level of THC and impairment,” says Steinborn.

The scientific studies back him up, to a point. Pot is not like booze: There’s no broad agreement that five nanograms is the right number, or that there is a right number.

But large, authoritative studies conclude that marijuana does impair driving, and the higher the dose, the worse the effects. Different studies point to different thresholds as the spot where impairment becomes clear, and while those numbers range widely, many are five nanograms or lower.

Still murky

Crowds of young people mingle in front of the bars on Tacoma’s 6th Avenue, smoking cigarettes and mingling.

“Everybody drinky, drinky,” Thompson muses.

Sergeant Thompson is scanning the roads, looking for DUIs. He's one of about half-a-dozen officers plying this strip from the state’s Target Zero task force. Thompson says the drunk drivers he arrests still outnumber stoned ones, but he believes that could tilt if pot is legalized.

“If it gets legalized I just think you’re going see more people that think it’s OK. And it’s something you can buy at the store. I just think we’re going to see an increase in the number of collisions and the number of arrests for people that are under the influence of marijuana,” he says.

As the night wears on, it seems like Thompson is coming up empty. Then he spots a black Lexus with a headlight out. He stops the car, and minutes later, the driver is on the sidewalk, walking a wobbly straight line. Out comes the breath test, and then the handcuffs.

“What’d I blow?” the man asks as he climbs into the backseat of the police car.
“A .125,” comes the answer.

There is no argument: He’s way over the limit. The guy is drunk.

Backers say the marijuana initiative will bring that same kind of clarity to taking stoned drivers off the road. But, like many things in a world where pot is legal, how it plays out could still be pretty messy.

Gabriel Spitzer is a former KNKX reporter, producer and host who covered science and health and worked on the show Sound Effect.