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Not to be outdone by legislators in Colorado , Washington state officials are considering setting a legal limit for the amount of THC


D.W.High: Washington Lawmakers Consider Limit on THC Blood Levels

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Not to be outdone by legislators in Colorado, Washington state officials are considering setting a legal limit for the amount of THC (the magical, active ingredient in marijuana) in a driver's blood.

As reported earlier this week by the AP and Toke Signals scribe Steve Elliott, Colorado is attempting to impose a legal limit of five nanograms of THC per milliliter of blood. Anything more than that, and a motorist would be considered too stoned to get behind the wheel.

Among the 15 states that sanction medical marijuana, Nevada and Ohio have two-nanogram limits for THC. Pennsylvania has a five-nanogram "guideline," but not a limit. Twelve states have a zero-tolerance policy for driving under the influence of any illicit drug, including reefer.

As it stands now, Washington is one of the remaining states that operate in a legal gray area when it comes to driving while high. According to Julie Startup, spokeswoman for the Washington State Patrol, if a trooper suspects somebody is driving impaired, they will request a blood sample for toxicology analysis. But while the presence of THC can be used as evidence, it is not necessarily a definitive way to prove in court that a person was too high to drive.

"It's like any other DUI regardless of whether it's marijuana or prescription medication," Startup says. "It's based upon impairment . . . we just look for signs of impairment, and if they're showing that in the trooper's estimation, they'll be placed under arrest."

Rep. Roger Goodman, a Democrat from Kirkland, introduced HB 1648 earlier this year. The bill amends Washington's current DUI law to include a legal limit of eight nanograms of THC per milliliter of blood.

Even though it's higher (no pun intended) than Colorado's proposed limit, the eight-nanogram figure is sparking debate about whether it's an accurate way to gauge whether someone is too high to drive.

Seattle DUI lawyer George Bianchi, the Dean of the National College of DUI Defense Attorneys, points to several toxicology studies that were inconclusive when it came to determining impairment based on THC blood levels. Specifically, he cites a paper by revered toxicologist Dr. Barry Logan which concludes that, although smoking marijuana definitely impairs drivers, "the passage of time between driving or involvement in a crash limits our ability to get an accurate measurement of the THC concentration at the time of driving."

In 2005, a group of 11 international scientists published a comprehensive study on the effects of THC on driving ability. They concluded that drivers do not pose a crash risk until they reach between 10-20 nanograms of THC per milliliter. They also determined that 18-20 nanograms is the equivalent of a blood-alcohol content (BAC) of .08, the current legal limit in most U.S. states.

As it stands now, Bianchi says, it is difficult for prosecutors to prove someone was driving under the influence based on THC blood levels alone. However, police frequently arrest people -- about half of his clients, he says -- on suspicion of toking and driving.

"If a person is falling down and driving all over the road, that's way different than if someone is speeding and they end up drawing their blood and try base the case strictly on blood level," Bianchi says. "You have to look to the facts of the case. But I've seen several cases where [police] smelled marijuana--maybe a person had a toke earlier that night--and the next thing you know they're drawing blood."

Bianchi, however, says he supports the law because eight nanograms is a "reasonable" standard and would prevent prosecutors from introducing levels of carboxy-THC (a metabolite, which does not make a person high) as evidence of DUI. His opinion contrasts with that of Diego Vargas, another local DUI defense attorney, who is firmly against Goodman's proposed law.

"There are just too many things to consider to set a specific number," Vargas says. "Pattern of use, for example, marijuana and THC, like any other drug, people build up a tolerance and not everyone is affected the same way . . . and I'm arguing against my own financial best interest by saying don't change this law. Defense attorneys will be busier than crazy if this gets passed, but I don't support it. It's just wrong."

HB 1648 was introduced on January 28, with the support of 21 co-sponsors. It was sent to to the Judiciary Committee, where it awaits a hearing.

Here's a PDF of the 2005 study THC and driving ability, courtesy of Bianchi. It's worth noting that the scientists concluded that waiting three hours after a "strong social dose" was enough "to reduce a driver's impairment to that comparable to a BAC of less than 0.03%.":

Marijuana DUI Report

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