Progress Made on Marijuana Intoxication Measurement Tool

Dec 14, 2017

Dr. Michael Milburn's Druid app helps people who have ingested marijuana or alcohol to determine if they're impaired.
Credit Michael Milburn/Druid

The legalization of marijuana in Washington has been terrific for the state’s coffers. According to the Department of Revenue, marijuana retailers totaled $1.2 billion in sales during fiscal year 2017. That’s about $4.8 million a day. The state’s share of that, in taxes, was about $227 million for the fiscal year.

One of the downsides of legal pot is that law enforcement officers are having a hard time proving drivers are impaired by marijuana. They’re don’t have one simple, accurate method for testing people they suspect are high on pot, as they do for drunk drivers.

For several years, Washington State University Professor Emeritus Nick Lovrich has been part of a team trying to develop a tool to measure marijuana intoxication.

He says trained officers are pretty good at detecting drivers who have been drinking or taking different types of drugs. They’re trained to watch a person’s physical cues and sniff for incriminating odors and they have physical tests to administer. But…

“Cannabis is the trickiest of all of them. It has so much individual variance and reaction to cannabis. The amount of cannabis you’ve smoked in the past determines a lot about how it’s affecting you at that time,” Lovrich said. 

Wednesday in Spokane, Lovrich briefed members of the Washington House Public Safety Committee about the progress, or lack of, that’s been made.

His research team tested more than 40 people who volunteered for a marijuana study in Pullman. Almost half categorized themselves as consistent users, a third were occasional users and a quarter didn’t light up at all. They brought their own weed. It was a strain suggested by the study’s coordinators. Before they lit up, researchers tested their breath, swabbed their tongues and cheeks, and collected saliva and blood. A half hour after they smoked, they went through the same protocol, and then again after two hours.

In the middle of all this, the volunteers put on smocks with a faint smell of marijuana and they submitted to field sobriety tests administered by police officers.

“So how good are those tools? They’re not very good,” Lovrich said.

Lovrich says the officers had trouble detecting who was intoxicated and who wasn’t. He says many chronic users had measurable amounts of THC in their blood, but reported not being affected by it. And then there were the occasional or non-users who took two or three puffs and reported feeling sick.

“They were shocked to see, ‘Jesus, we missed that many of these guys?’ Yeah, especially the ones that smoke all the time” Lovrich said.

He says researchers discovered that, of the physical tests, swabbing the tongue is the most accurate method for discovering THC concentration. He says the blood tests were accurate, but during a traffic stop, they’re considered invasive. And the breath test? So-so. He says it would be very expensive to refine that technology for police use.

Enter a new tool, a computer app named Druid.

“Druid is an acronym for driving under the influence of drugs,” said Druid's inventor, University of Massachusetts Boston psychology professor Michael Milburn.

When it became clear that marijuana would soon become legal in his state, he decided to create a simple test that would help users determine for themselves whether they were too buzzed to drive.

“It has four simple tasks, three of which are video game tasks that measure reaction time, hand-eye coordination and then we also include the single-leg stand from the standard field sobriety test. The app then creates a total impairment score that, if a person is impaired, can say, ‘oh, I better wait an hour before I get in the car,'” Milburn said.

The app measures how the test taker performs and saves the information in a data base. Milburn says his tests have proven the app is an accurate way of measuring alcohol and marijuana consumption, though not when a person is under the influence of both.

So, how did Milburn and Lovrich connect? A member of Lovrich’s team heard Milburn interviewed on public radio and decided he was a guy the team needed to talk to. Now they’re looking to add Druid to WSU’s marijuana study. Ultimately, they hope to test and refine Druid so that law enforcement agencies feel confident adding it to their field sobriety protocol.

“The cop has them do it and can watch them and they’re lifting their leg and touching the screen and if it’s a fail, then that’s an a additional tool that law enforcement has in addition to their own observations and judgment and whatever to make a decision of do I bring this person in or not,” Milburn said.

Milburn and Lovrich say their job is now to distribute their work so that others, including policing agencies, can test and evaluate it. They hope that, within a few years, the combination of Druid, tongue swabbing and more training for officers might become part of the accepted protocol for evaluating drivers and others intoxicated by marijuana. Lovrich hopes it might also become a tool for employers to evaluate whether their employees are smoking on the job.