"To me, it seems like we've been able to get that word of mouth out talking about alcohol impairment," Chase said. "That’s been preached for many years. But I think there is a bit of a misconception when it comes to drug impairment."

DRE officers follow a systematic, 12-step protocol using clinical signs to determine whether a driver is impaired, whether the impairment is caused by a medical issue or drugs, and if drug use is suspected, what category or categories of drugs may be the cause of the impairment.

"We can’t go in predisposed that the person is intoxicated,"Chase said. "This person may be having a medical event, so the DRE is also used to identify that, instead of wrongfully arresting someone and bringing them to jail."

It's expensive to become a certified expert, so proficient officers must apply and be selected to undergo three weeks of intensive training. The cost to train one officer to become an expert is about $4,000, according to Sgt. Travis Skarr, former state coordinator of the program.

The first two weeks of training, which take place in Bismarck, are book-heavy but include two "wet labs," where volunteers are dosed with enough alcohol to cause impairment, then brought in along with a sober control group for officers to identify who is impaired by alcohol.