Driving while impaired. Also known as DWI, or (in some states) DUI. It’s against the law, and most folks would tend to agree that that’s a good thing. After all, nobody approves of impaired driving. But when we consider our DWI laws, it’s important that we look at them from a rational point of view. A DWI implies a couple of things. It implies that someone was driving, sure, but it also implies that the someone in question was also impaired. That seems intuitive enough, right?

Well, maybe not for everyone in every case.

Last week, the Arizona Supreme Court struck down the State’s “per se” marijuana law. The ruling arose from the case of an Arizona man named Hrach Shilgevorkyan who was stopped by police for speeding and later admitted to having smoked marijuana the night before. A blood test was performed, and it revealed that he did, in fact, have marijuana in his bloodstream. Specifically, he had an inactive (non-impairing) metabolite of marijuana in his system. Hrach was prosecuted for DWI driving while impaired, despite the fact that he didn’t have any active THC (or metabolite hydroxy THC) in his system. This past Tuesday, Arizona’s High Court said,

“We are not persuaded and reject the State’s argument that [the law] creates a flat ban on the presence of any drug or its metabolite in a person’s body while driving or in actual physical control of a vehicle, even when the only metabolite found is not impairing…”

The Court pointed out that the language of Arizona’s statute doesn’t make a distinction between a metabolite that causes impairment and one that doesn’t. Such a statute makes it difficult to determine whether or not criminal charges are warranted. The State prosecutors argued that the statute’s reference to “its metabolite” (when referring to drug compounds detected in a driver’s system) covered all compounds related to drugs, not just those that actually cause impairment.
The high court panel wrote,

“Most notably, this interpretation would create criminal liability regardless of how long the metabolite remains in the driver’s system or whether it has any impairing effect.”

This interpretation “leads to absurd results.”

The opinion affects not only motorists who use marijuana illegally, but also the estimated 40,000 people who participate in the state’s medical-marijuana program. Of course, it shouldn’t matter if the person is legally allowed to ingest pot to treat ailments like chronic pain or glaucoma; traces of metabolites simply do not prove impairment.

The public can sometimes react with a knee-jerk to laws that are labeled DWI or Driving While Impaired or DUI, but it’s important that we don’t lose track of the common sense meaning of the word impairment.