With marijuana smokers celebrating 420 this weekend, the Washington State Patrol was keeping an extra eye out for impaired drivers.

State troopers arrested 19 people for driving under the influence on Friday night and another 13 on Saturday across King County, Trooper Rick Johnson said.

It’s not clear how many of the drivers were suspected of being stoned on pot — as opposed to alcohol or other types of drugs. The totals are up slightly from the 10 arrests made last year on April 20, the day designated by marijuana users to celebrate the drug.

“We know it’s a celebratory day for the cannabis culture. And yes it is legal here, and we understand that,” Johnson said. But it’s still illegal to drive while high. “The assumption is there’s going to be more people partaking on that day, or the weekend.”

Johnson noted there were no serious injury accidents over the weekend on local freeways.

Another Trooper, Chelsea Hodgson, reported they arrested a driver “who admitted to smoking marijuana an hour before being stopped at 4:20 p.m.” on 420, and that he was on his way to a fast-food restaurant in Port Orchard.


So how do troopers tell when drivers are high? Unlike for drunken drivers, there’s no breath-test that can gauge THC content in someone’s system on the spot.

Johnson said police officers rely on their experience and use a variety of tactics. The first test, before pulling someone over, is to gauge their driving — some people can drive “super fast” or “super slow” while high, he said.

When troopers walk up to a driver’s window, they might smell an odor of marijuana, though that alone is not enough to arrest. They will give field sobriety tests. They could ask for a breathalyzer — and if the person failed the field sobriety test and blows under the legal limit for alcohol, that could be an indication they’re on other drugs, Johnson said.

The WSP also uses drug recognition experts to do extra tests. Lastly, if officers suspect impaired driving, they’ll get a warrant to draw blood, sometimes inside the WSP’s “mobile impaired driving unit,” which was fashioned out of a 36-foot motor home.