PORTLAND — Traffic stops hold a unique place in Oregon law. They are, technically, a “temporary seizure” that allows police to investigate a violation, identify a driver and issue a citation.

At that point, the stop is over. But what if the driver doesn’t leave?

And what if he can’t?

A decision by the Oregon Court of Appeals last week says the answer is complicated.

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The case in question involves a police officer in Marion County who pulled over a driver he recognized from a couple of previous high-speed chases, one of which ended in a struggle with police.

The officer parked behind the car, a Buick driven by Myles Peterson, and blocked him in. He proceeded to get Peterson’s car registration, cited him for running a red light and told him he could leave.

But the officer was still parked behind the Buick, blocking it in. Then he started to chat with Peterson and realized that the registration Peterson showed him was for an Acura, not a Buick.

The officer started a search and found a Visine bottle filled with heroin. A jury used that evidence to convict Peterson of the drug charge.

The court of appeals found that, from the moment the officer told Peterson he could leave, the search was over. And by blocking him in, he created an “unlawful extension,” Judge Timothy Sercombe wrote in the ruling.

“You told him he was free to go, but he wasn’t actually able to leave at that point, was he?” Peterson’s attorney asked the officer during a hearing that was quoted in the ruling.

“If (Peterson) had asked me to move my patrol car at that point, I would have moved my patrol car and he would have been on his way,” the officer replied.

“But without asking you, he couldn’t have left, isn’t that right?” the attorney said.

Such stops have precedence, and the courts haven’t been kind to law enforcement.

In one case, an Oregon State Police trooper told a group of men they could leave, but leaned on the driver’s side door, asked them if they were transporting contraband and asked to search the car. The court said that’s illegal.

Prosecutors said that Peterson should have just asked the officer to move his car.

“We reject that argument because the obligation to unambiguously end traffic stops does not fall on citizens,” Sercombe ruled, “it falls on law-enforcement officials.”