An odor of marijuana, slowed reaction times, divided attention and muscle tremors are all things law enforcement officers look for when trying to determine if someone is driving under the influence of marijuana.
While local officers are currently not often arresting people for driving under the influence of marijuana, the state as a whole is seeing a rise in the number of drivers getting behind the wheel after smoking and, in response, it’s creating a comprehensive public awareness campaign.
A 2018 survey from the Colorado Department of Transportation found that state troopers arrested 421 people for driving under the influence of marijuana that year, a 25 percent increase in DUI citations from 2017.
However, local numbers are much smaller. Dan Mayer, spokesperson for the Grand County Sheriff’s Department, said he estimates there have only been a handful of arrests for marijuana DUIs in the last year.
The Granby Police Department reports three marijuana DUI arrests in the past 18 months compared to 15 arrests for alcohol DUIs in the past year. The Kremmling and Fraser-Winter Park police departments also report that they rarely make arrests for marijuana DUIs.
“We don’t make a huge amount of arrests just for driving under the influence of marijuana,” said Fraser-Winter Park Chief Glen Trainor. “Polydrug use, so marijuana plus alcohol, is probably more common for us.”
In Kremmling, Chief Jaime Lucas and his officers still mostly see drivers under the influence of alcohol.
In order to determine whether someone is under the influence of marijuana, many officers in the county, including the entirety of the Fraser-Winter Park Police Department, are trained in the Advanced Roadside Impaired Driving Enforcement program.
Sgt. Paul Finley, the county’s drug recognition expert, who is specially trained to detect impairment from a variety of sources, said the process to determine whether a driver is under the influence of marijuana isn’t initially that different from the process for alcohol.
First, officers will pull someone over for a traffic infraction and then look for observational and conversational cues that could mean someone is under the influence. Typically, this is an odor of marijuana, slower reactions or, sometimes, visible paraphernalia, Finley said.
“Also the way they’re acting, obviously the easiest ones are the people who are really high and act like your stereotypical stoners,” Finley said. “Other than that, it’s reaction times when you’re asking them questions or for their driver’s license, registration or insurance, if they mess that stuff up and can’t get you the right stuff.”
Officers can also use the standard roadside field tests to determine sobriety, such as the walk and turn or the one-leg stand. Since the way that marijuana affects drivers is different from alcohol, officers use blood tests and breathalyzers to figure out which substances are involved once an arrest is made.
Only blood tests will show the amount of THC in a person’s system, but they cannot be conducted in the field, so all arrests are made based on the observed impairment. In Colorado, drivers with five nanograms or more of active THC in their blood can be prosecuted for a DUI.
“It’s basically instructions to the jury that at that level you can determine whether they were under the influence or not,” Finley said.
Marijuana can stay in a person’s system for up to 30 days, so Finley explained that officers differentiate past and current use based specifically on the active THC level, which makes it more likely that the use occurred recently, as opposed to THC metabolites that would reflect chronic use.
Complicating things more is the fact that, unlike alcohol, there are no standards for how much marijuana use affects people and how because factors like how much they consumed, the form it was in and whether they are chronic or occasional users leads to varied outcomes.
According to Trainor, more regular users are more likely to believe that their use does not impair them while driving and cautioned against that kind of thinking, since any use can put someone at risk of impaired driving.
Finley recommends anyone using marijuana wait at least a couple of hours before getting behind the wheel.
“THC content really peaks within the first 15 to 20 minutes of use and then it will gradually decrease, but it’s like alcohol, where it depends on the user and how habituated they are to that,” he said.