Washington lawmakers are currently trying to answer a tricky question: How high is too high to drive? Among the 15 states that sanction medical-marijuana use, 12 have a zero-tolerance policy for driving under the influence of any illicit drug, including reefer. Colorado is attempting to impose a legal limit of five nanograms of THC (the magical, active ingredient in marijuana) per milliliter of blood. Nevada and Ohio have already set much lower limits—prostitution may be legal in Las Vegas, but driving with anything over two nanograms, the rough equivalent of a contact high, is not. Washington currently operates in a gray area. According to Julie Startup, spokesperson for the Washington State Patrol, if a trooper suspects somebody is driving impaired, they'll request a blood sample for toxicology analysis. But while the presence of THC can be used as evidence, it isn't necessarily a definitive way to prove in court that a person is Driving While High. "It's like any other DUI, regardless of whether it's marijuana or prescription medication," says Startup. "We just look for signs of impairment, and if they're showing that in the trooper's estimation, they'll be placed under arrest." So into this murky legal morass swims Rep. Roger Goodman (D-Kirkland), who earlier this year introduced a bill that would amend Washington's current DUI law to include a legal limit of eight nanograms. Even though it's higher (no pun intended) than Colorado's proposed limit, the Goodman ceiling is sparking debate about whether it's an accurate way to gauge if someone is baked to the point of illegality. Seattle DUI lawyer George Bianchi, the Dean of the National College of DUI Defense Attorneys, points to several toxicology studies that inconclusively determined impairment based on THC blood levels. Bianchi specifically cites a paper by renowned toxicologist Dr. Barry Logan, who concluded 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 10 to 20 nanograms of THC per milliliter. They also determined that 18 to 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's 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 [to] base the case strictly on blood level," says Bianchi. "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 Goodman's 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 the law. "There are just too many things to consider to set a specific number," says Vargas. "Pattern of use, for example—[with] 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." DUI attorney–approved or not, Goodman's law still has a long road ahead. Next stop: the Judiciary Committee, where it awaits a hearing.