Russell Hebets Oct. 17, 2017

I was speaking to a friend from out of state recently when I mentioned a Driving Under the Influence of Marijuana case that I recently handled. His initial response, like so many others, was “but I thought marijuana is legal in Colorado.” For anyone out there thinking the same thing, think of alcohol as a surrogate for marijuana. Alcohol is legal in your state, right? Yet people are still charged with Driving Under the Influence of alcohol all the time. The same is true for marijuana, although the similarities largely stop there. Marijuana is different in terms of reasons for use, quantity required to impair someone, dissipation time, symptoms of impairment, and in so many other ways.

After the legalization of marijuana, Colorado law enforcement has made a push to enforce driving under the influence of marijuana cases. The problem is that they don’t have a framework to determine who is under the influence and who is not. Marijuana is not like alcohol. There is no “per se” limit where everyone agrees that someone is under the influence.

How Do Officers Determine Marijuana Impairment?

State troopers, sheriff deputies, and police officers in Colorado all use Standard Field Sobriety Tests to help them determine if someone is impaired by marijuana. The problem here is that these tests were standardized in the 1970’s to detect alcohol impairment, not marijuana impairment. Marijuana, as we said, is fundamentally different than alcohol. Testing someone for marijuana impairment by using alcohol Standardized Field Sobriety Tests is like trying to figure out if you have breast cancer by having a prostate exam. It isn’t going to work.

Does Marijuana Tolerance Affect Impairment?

Marijuana is widely used as medication in our state. Like with most regularly used prescription medications, patients who use marijuana regularly can develop a tolerance to its impairing effects. Medicinal or other habitual marijuana users have been shown to have significantly higher baseline levels of THC (the active ingredient in marijuana) in their systems than an occasional recreations marijuana user. If you took someone who is a daily medical marijuana user, and had a novice marijuana user off the street smoke the same amount of marijuana as the medical user, the novice would probably be glued to the couch unable to move as the medical user was off to work. Despite this difference in effect, they might have fairly similar blood THC levels. THC levels alone cannot tell you whether someone is impaired or under the influence of marijuana.

Is Any Marijuana Too Much?

Some law enforcement agencies have begun arresting people solely based on an admission that the suspect had smoked sometime that day. Unlike alcohol, marijuana stays in your system for weeks, and even active THC has been shown to stay in your blood for days in habitual users. This is despite the fact that the “high” or impairing qualities of marijuana generally dissipate in 2-3 hours after smoking. The shotgun approach that some law enforcement offices are using is leading to many innocent people being arrested and charged with DUI.

How Should Police Investigate Marijuana Driving Cases?

Because there is uncertainty about how marijuana behaves person to person, we see the police erring on the side of caution and arresting otherwise innocent people because they admitted recent marijuana use. A much better approach would be to invest in training for officers to actually make an intelligent decision about someone’s impairment or lack thereof. In the end, driving under the influence of marijuana is illegal, and some cops just tend to paint everyone with the same broad brush once they catch a whiff of marijuana, whether the unlucky driver is under the influence or not. We are not saying that anyone who uses marijuana is immediately thereafter safe to drive. In fact, it is generally advisable to wait a reasonable period of time before driving when possible, if for no other reason than to avoid law enforcement scrutiny if pulled over. However, not everyone who has recently used marijuana is categorically unsafe to drive a car. Each case must be taken individually, and the police must be able to prove that a person is impaired and unsafe to drive beyond a reasonable doubt.