Medical technology could help police detect if drivers are high on marijuana

ATLANTA — Medical technology used to determine cognitive impairment could help law enforcement gauge if a driver is impaired by marijuana.

Legal blood level limits for drivers under the influence of alcohol have been around for decades. That’s not the case when it comes to marijuana.

The same goes for roadside testing. As the use of marijuana becomes more acceptable, the number of Georgians behind the wheel high on THC, the active chemical in marijuana, is growing.

A report from the CDC found that from 2014 to 2018, the number of people who admit to driving while high on marijuana shot up nearly 50%.


Kristin Weber is the director of strategic sales accounts for the medical technology company, Cognivue.

Weber told Channel 2′s Tom Regan the testing needs to be different because THC affects every person in a different way.

“They can say at .08, your ability is impaired for driving. but with THC, it affects people differently whether you are a regular user, a new user, whether you have other drugs involved. It’s all going to affect you differently,” Weber said.

Cognivue is behind a research effort to cognitive screening to help determine if a driver is impaired by marijuana.

Cognivue’s technology is currently used by health care professionals to analyze brain function and detect early signs of cognitive decline and dementia.

Dr. Jason Agran is the chief medical officer for Cognivue. He explained the computer program screens for cognitive impairment.

“If there is a suggestion of cognitive impairment, it could potentially guide therapeutic applications or further testing,” Agran explained. “An MRI tells you about gross brain dysfunction or changes in the volume of structures. This tells you more about the real process going on in cognition.”

The test is self-administered. Patients move a hand wheel on a screen through a series of tasks including matching symbols, patterns, letters and words.

The tasks measure visual acuity, short-term memory and executive functioning. All of these can be diminished in impaired driver, including drivers high on marijuana.


Tom O’Neill, Cognivue’s president and CEO, gave Channel 2 a first-hand look at how the technology works.

“We are taking the expertise we have for Identifying and testing for cognitive impairment, and we are trying to bring that technology to bear to help law enforcement keep roads and highways safe,” O’Neill said.

As planned, a police roadside cognitive test would be taken on a hand-held computer device, like a tablet.

Agran said it would not be the only factor to decide if a driver is impaired.

“As part of the field sobriety examination, this gives another independent and fair data point to our law enforcement colleagues,” Agran said.

This type of cognitive screen has been effective in the medical field for years, but a leading DUI lawyer, William Head, told Channel 2 he doesn’t believe it will be a useful tool for law enforcement.

“I don’t think it will prove impairment at all. I don’t think it can do that,” Head said.

Head told Channel 2 that about 5% of his cases involve THC impairment. He said a roadside computer-based test, aside from being voluntary, would also be impractical.

“How are you going to totally focus on that screen when a tractor-trailer is coming by?” he asked.

He also said this type of testing wouldn’t hold up in court.

“You might be able to show they have some slowing of reaction time, but you can’t quantitate how that is someone who is on marijuana,” he said.

Cognivue tested the screening device on drug-impaired participants last year, and is now working with police and the state legislature in New York to get the program approved.