With states like Colorado legalizing the sale of marijuana, jurisdictions are scrambling to deal with the consequences. Last month, the Arizona Supreme Court ruled 4 to 1 that draconian laws designed to handle driving under the influence (DUI) of alcohol could not be applied directly to pot because of the way the drug interacts with the bloodstream.
Under DUI laws, a person is automatically guilty of a crime if his blood contains a certain quantity, 0.08 percent, of alcohol in his bloodstream when measured after driving, regardless of whether he was actually impaired behind the wheel. The drunk driving standard creates issues with stoned driving, because there are two distinct byproducts of marijuana use in the bloodstream, known as “metabolites,” but only one of them causes impairment.