In 2014, an Oregon state trooper stopped John Hedgpeth for riding a motorcycle without a helmet. Following the stop, the Coos County man was taken into custody for suspicion of driving under the influence of intoxicants. One hour and 45 minutes later, Hedgpeth submitted to a test that indicated a blood alcohol level of 0.09 percent. Oregon’s automatic-intoxication threshold is 0.08 percent.

Slam dunk, right? Not quite.

Hedgpeth was convicted of DUII, but last week the Oregon Court of Appeals reversed the lower court’s ruling. Most of the justices, but not all, agreed with Hedgpeth’s legal team that “it is speculative to find that his BAC was above the legal limit at the time he was driving” almost two hours earlier. The opinion, not surprisingly, received more attention than most of the appeals court’s work.

Fortunately, the decision’s consequences are sure to be fairly limited. The court has not handed a get-out-of-jail-free card to everyone whose blood alcohol is tested long after they’re pulled over. Thorough police work and diligent prosecution will normally fill in the gaps that plagued Hedgpeth’s case. Still, a trip to the state Supreme Court would clarify what the dissenting judges call “the ‘sometimes faint’ line” upon which they and their colleagues disagree.

The problem with Hedgpeth’s prosecution, the court decided, was one of “minimal evidence.” The only proof of intoxication offered was the blood alcohol test, which demonstrated only that his level exceeded the legal limit nearly two hours after he was stopped. It’s generally accepted that blood alcohol levels decline with time, which might suggest that Hedgpeth was even more heavily intoxicated when he was stopped. On the other hand, suppose he’d guzzled a couple of drinks shortly before he climbed on his bike, and suppose that much of that alcohol hadn’t reached his blood by the time he was stopped. This may be unlikely, but it’s certainly possible.

For this reason, explains Deschutes County District Attorney John Hummel, prosecutors almost always offer additional evidence of impairment at the time of a stop. This could include a police officer’s observations of a suspect’s behavior, a roadside sobriety test and so on. Even when such observational tests are not feasible — when a suspected drunken driver has crashed and is unconscious, for instance — prosecutors usually provide testimony from experts who are able to tie alcohol levels, determined by a blood test, back to the time at which the suspect was driving.

For whatever reason, prosecutors in Hedgpeth’s case relied solely upon a delayed blood alcohol test. And to rely upon this evidence alone as justification for conviction, the appeals court wrote, is to engage in mere “speculation.”

The two dissenting judges disagreed, arguing that the lower court found itself on the correct side of the sometimes faint line between “permissible inferences and impermissible speculation.” The “rising-BAC explanation,” the dissenters argued, is just one reasonable inference, which, “under our standard of review … alone cannot be the basis for the conclusion that the evidence is insufficient in this case.”

In other words, explains Hummel partly in jest, “the dissent was like, ‘Oh, come on. Give me a break.’” The driver could have been over or under 0.08 percent at the time he was stopped, he explained, but the dissenting judges would prefer to let judges and juries make the DUII call.

The court’s ruling is, above all, an argument for thorough policing and prosecution. Prosecutors shouldn’t waltz into court with nothing but a blood alcohol test and expect good results. Presumably, though, there will continue to be a small percentage of cases in which a test, and nothing else, is offered as evidence for reasons that cannot be attributed to bad policing and prosecution. Even a small percentage could be significant given the destruction caused by impaired drivers. Oregon saw more than 1,200 deaths in DUII-related crashes between 2003 and 2012, according to the Centers for Disease Control and Prevention. So why not ask the state’s highest court to draw clearly the faint line upon which the appeals court is divided?

The state Department of Justice, says spokeswoman Kristina Edmunson, is still reviewing the decision and deciding what to do.