Marijuana and driving impairment: Rep. Claire Levy on setting a standard in Colorado

Over the past year, we've intermittently heard about arrests for allegedly driving under the influence of medical marijuana, with the most sensational being Joshua Wittig's involvement in a crash that took the life of John Paul Hines in October. Against this backdrop, Boulder Representative Claire Levy says she's planning to introduce a bill during the next legislative session to establish a marijuana-impairment standard for drivers in Colorado.

Driving safety has long been an important issue for Levy, who co-sponsored a texting ban that became law in 2009. Her current cause "is related in some ways," she acknowledges. "We need to get rid of whatever extraneous distractions and behaviors make our highways unsafe for other people."

Regarding a need for a marijuana-impairment threshold, she says, "It is theoretically illegal to drive while your ability is impaired with alcohol or drugs of any sort -- but because we don't have a firm standard for determining if you're impaired by marijuana or prescription drugs, I think the attitude of many is, 'It's okay, because there isn't a standard.' But everyone is aware of the .08 blood-alcohol-content standard for alcohol -- and while we may not know what that feels like or how many drinks that is, we know there's a standard."

With marijuana, she adds, "There's a perception among some that if you have a medical marijuana card and it's legal for you to use marijuana, it's legal for you to drive under the influence of marijuana. So the bill will set a firm per se standard based on a blood draw -- and that'll give notice to the community that uses marijuana exactly how much they're allowed to ingest if they're going to get behind a wheel of a car."

Is this a solution in search of a problem? After all, the number of arrests for driving under the influence of marijuana is extraordinarily small compared to those involving alcohol. But Levy believes the issue is real.

"If you ask the state patrol, the sheriff's department and police officers who are pulling people over for erratic driving or accidents, they'll tell you that more and more people are driving while they're high, and that's leading to more accidents," she says.

A number of states already have such standards on the books, and while Levy concedes that she hasn't yet had a chance to research their experiences in detail, she's backing an impairment limit of 5 nanograms of THC per milliliter of blood.

"Some states have a zero-tolerance standard, which I couldn't support," she says. "And originally when proponents of this idea came to me, they were looking at two or three nanograms per milliliter. But the drug advocacy task force batted that around, and the perception among some people was that it was too low a threshold, and it might catch people who had residual THC in their system but whose driving wasn't actually impaired. That's one of the big concerns in the medical-marijuana community and marijuana users in general, because it can stay in your system for a while.

"So we looked for a standard that would support a conclusion you were impaired at that time. A number of toxicologists had input on this, and five is pretty well accepted as a level that you would have a hard time arguing you weren't impaired."

Although Levy admits that some locals may perceive her forthcoming measure as anti-MMJ, she stresses that "I am not hostile to it in any way -- and I actually think it could lead to more support for broader public acceptance of marijuana use. When the general public sees dispensaries on so many street corners and read about the prevalence of medical-marijuana cards, they may think everyone is driving around stoned. And I think a law like this can help with public acceptance of medical marijuana use.

"It's just like bartenders and liquor store owners and users of alcohol who are happy to have an evidence-based threshold for driving under the influence -- because they can talk about the differences between responsible alcohol use and irresponsible alcohol use. And I think that's the same thing that would be considered for marijuana use. I don't think anyone, not even the strongest advocates of legalizing marijuana, would argue that we should allow unlimited smoking while driving."

Since first floating this notion, Levy says she's gotten a mix of support and questions from constituents wondering if marijuana testing would be accurate and scientifically defensible. If the final legislation manages to balance these concerns, she thinks it will attract bipartisan support -- and as evidence, she notes that Representative Mark Waller, a Republican from El Paso County, will likely co-sponsor the bill in the Colorado House.

"He says he views this as a basic public-safety issue," she says. "And so do I."

More from our Marijuana archive: "Medical marijuana fallout: Kids getting addicted to their 'medicine,' psychiatrist says."