- Courtesy CDOT
- Roadside tests are crucial for marijuana DUIs.
The science around proving whether someone’s too high to drive could use a breakthrough.
Current Colorado law specifies that anyone who tests with blood levels of THC higher than 5 nanograms per milliliter can be prosecuted for driving under the influence.
The dilemma: Frequent marijuana users can test above that limit — even if they haven’t smoked or ingested cannabis for days. In fact, research proves that THC can show up in the blood of heavy users for up to a month after they’ve stopped. So, much of the responsibility for detecting impairment falls on peace officers.
But because testing for marijuana isn’t as easy as just blowing into a Breathalyzer, it leaves a lot to subjective observation. And some say having officers determine whether someone seems high is too subjective.
“You need to have properly trained and qualified officers doing the evaluation,” notes local defense attorney Tim Bussey. He cautions that officers can make mistakes when they “rely on hunches or guesses” to determine whether a person is too high to drive.
El Paso County Sheriff’s deputies who suspect a driver is drunk or high typically go through a set of “roadside maneuvers” designed to test for impairment, says spokesperson Jackie Kirby.
In the first test, officers check for involuntary jerking of eyes under the influence of alcohol. Next, they conduct the “walk and turn” and “one leg stand” tests — both “divided attention” tests — to assess a person’s ability to follow instructions and level of physical impairment, Kirby says.
Some Colorado law enforcement officers gain additional training through the nine-day Drug Recognition Expert course, run by the Colorado Department of Transportation. There, they learn to detect whether impairment is from alcohol, marijuana or another substance.
The 12-step assessment process taught in the course actually starts with testing for alcohol, says Highway Safety Manager Glenn Davis, “because if somebody’s impaired and the alcohol is low or zero, then that tells you the impairment’s coming from somewhere else.”
Next steps include checking pupil size under three lighting conditions, “because different drugs make the pupils react in different ways,” as well as examining muscle tone, pulse and blood pressure. The officer will also conduct divided attention tests and an interview. “And at the end of that,” Davis says, “the officer, the DRE, will be able with pretty good accuracy to tell you what is causing those manifestations.”
After those roadside exams, if an officer suspects marijuana intoxication, the person in question will be brought in for a blood test, usually at a nearby hospital.
As of April 11, there were 198 officers trained as drug recognition experts in 70 law enforcement agencies across the state, according to Colorado Department of Transportation spokesperson Sam Cole. Seven of those work in the Colorado Springs Police Department, and one works in the El Paso County Sheriff’s office.
Davis says it’s probably not feasible to have every officer complete DRE training. Instead, CDOT tries to provide training for officers who are highly interested in traffic safety, with a focus on rural and underserved areas. When an officer without the training doesn’t know whether drugs are affecting someone’s driving behavior, they can call a DRE in their agency to the scene, he points out.
“I would say if you have a DRE I think you’re going to get a lot more realistic evaluation of what the person’s impairment was,” he says. “And I even think that’s to the benefit of the person arrested, too.”
- Source: Colorado State Patrol
A bipartisan state bill introduced this year would have done away with the 5 nanogram limit altogether, making officers’ assessments alone enough to prosecute someone for a “tandem DUI per se.” As long as the person tested positive for some level of drugs or alcohol — and an officer had evidence to believe they were “substantially incapable of safely operating a vehicle” — they could be convicted of this type of offense under the bill.
While the bill’s sponsors said eliminating the 5 nanogram limit could actually help frequent smokers who weren’t high while driving, opponents said it would give too much power to law enforcement. The unpopular bill died in committee in February.
Researchers have tried to find an easier, more reliable method for testing THC levels at the scene of a crash, but it’s a tricky problem. THC, unlike water-soluble alcohol, is absorbed in fat cells and thus difficult to measure.
“The way [THC is] metabolized, is it leaves the blood and goes into the brain,” says Ashley Brooks-Russell, an assistant professor of community and behavioral health at the University of Colorado at Denver. “So while it is making someone feel high or having impairing effects, the level is actually going down in the blood.” Alcohol is much simpler to measure: “The more in the blood, the more drunk you are.”
Brooks-Russell and her colleagues at the Colorado School of Public Health are conducting a study to test how smoking weed affects the driving skills of frequent and infrequent users. Participants go for a “drive” in the school’s driving simulator, then are asked to smoke for up to 15 minutes. Then, they’ll try driving in the simulator again.
“Our main question is basically one of tolerance, so we’re recruiting people who use daily and people who use weekly,” Brooks-Russell says.
While companies have developed saliva and breath tests for THC, none of the new technologies has yet taken hold across a wide swath of law enforcement agencies in the U.S. In Colorado, implementing one of these tests would require a statute change, Davis says.
But Brooks-Russell thinks that tests to measure pupil size and eyes’ reaction to light, which researchers are also utilizing in the study, could be a better solution for measuring impairment than a biological test.
“I think everyone just wants something really simple and something equivalent to alcohol, where there’s this social acceptance that like, if you blow a .08 that’s it,” she says. Eye tests, however, “could be the future of assessing impairment.”
“So it wouldn’t be the blood level, which is flawed, and it wouldn’t be an officer’s opinion — which, you know, some people might not be comfortable with taking that,” Brooks-Russell adds.
But as long as current DUI law remains in place, you can technically be prosecuted for driving stoned whether or not you think you’re actually high — as long as your THC levels exceed the legal limit, and an assessment by law enforcement determines you’re impaired.
Should that occur, Bussey says, “You need to seek competent counsel. You need to learn as much as you can about the science... It’s going to be a fight. You’re going to have to fight for your constitutional and statutory rights.”