If you smoke a joint Friday night and drive to work bright-eyed and bushy-tailed Monday morning in Michigan, you can be arrested, charged, and convicted as a drugged driver because inactive chemical traces of THC, or metabolites, remain in your bloodstream. The Michigan Supreme Court ruled Wednesday that motorists can be convicted of Driving Under the Influence of Drugs (DUID) even if they are not under the influence of drugs. According to the Supreme Court opinion in the consolidated cases Derror v. Michigan and Kurts v. Michigan authored by Justice Maura Corrigan, actual innocence of driving while impaired is "irrelevant."

In both cases, authorities charged the defendants under the Michigan DUID law based on the presence of cannabis metabolites, an inert byproduct of the body's breakdown of THC, in their blood. The presence of metabolites does not indicate impairment or being "under the influence"; it only indicates that someone ingested THC at some time in the past, as the state Supreme Court acknowledged in its ruling. Both trial courts held that the metabolite was not "marijuana" and thus a controlled substance under state law, a position upheld on appeal.

[inline:checkpoint.jpg width="200" align="right"]Both a majority on the Supreme Court disagreed. Neither the DUID nor the controlled substances law "requires that a substance have pharmacological properties to constitute a schedule I controlled substance," the majority held. Neither does the DUID law "require that a defendant be impaired while driving. Rather, it punishes for the operation of a motor vehicle with any amount of schedule I controlled substance in the body."

Then, breathtakingly, Justice Corrigan wrote, "It is irrelevant that a person who is no longer 'under the influence' of marijuana could be prosecuted under the statute. If the Legislature had intended to prosecute only people who were under the influence while driving, it could have written the statute accordingly."

Now, any Michigan driver who has smoked marijuana in the last few days or, in the case of heavier smokers, up to three or four weeks, is subject to a DUID arrest based on the presence of inert leftover metabolites that do not actually indicate impairment. In a harsh dissent, Justice Michael Cavanaugh warned the court it would criminalize a huge class of people.

"Today's holding now makes criminals out of numerous Michigan citizens who, before today, were considered law-abiding, productive members of our community," he wrote. "Now, if a person has ever actively or passively ingested marijuana and drives, he is [unknowingly] breaking the law, because if any amount of [cannabis metabolites] can be detected -- no matter when [the marijuana] was previously ingested -- he is committing a crime. The majority's interpretation, which has no rational relationship to the Legislature's genuine concerns about operating a motor vehicle while impaired, violates the United States Constitution and the Michigan Constitution."

The ruling could have an impact beyond Michigan. Twelve other states have enacted laws making it a criminal offense to drive under the influence of drugs. They use standards similar to those upheld this week -- the presence of trace levels of drugs or metabolites -- to assume impairment. Unlike drunk driving laws, which assume a certain blood alcohol level after which one is considered impaired, the DUID laws assume that the presence of any metabolite or trace proves impairment.