Here’s the situation: An officer pulls over a driver. They are suspicious that the driver is impaired and they have a DUI on their hands. Specifically, a marijuana DUI.

But proving this is not as simple as breath test, or asking if their names are Cheech, Chong, or Lebowski. Washington state has a 5 nanogram limit, which is determined through a blood test. It’s similar to blowing a .08 on a breath test for alcohol.

Dale Willits.

“We mostly interviewed law enforcement officers, but we also interviewed prosecutors throughout the state,” said Washington State University Professor Dale Willits. “Some of them, not all of them, but some of them express dismay at the nanogram limit, because now they will go to trial and juries will expect to see this 5 nanogram blood test. But blood tests aren’t ordered for each DUI stop.”

Not only that, there is a time limit to the test. If a driver refuses to take one, then the cops have to wait for a judge to issue a warrant, and then there’s the trip to the hospital for the blood draw. It all takes time, during which the level of marijuana in the driver’s blood can go down. And who knows if it was high enough for a conviction earlier?

This is why there is a looming snafu with Washington’s DUI laws when it comes to marijuana. Willits uncovered the issue during a study for WSU, which largely looked at crime rates under legal marijuana.

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