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How do police determine if someone is high while driving?

On behalf of Dolan + Zimmerman LLP April 17, 2019

Picture this: You’re driving home from a friend’s house. You are just blocks away from home when you see the flashing red lights in your rearview. You aren’t speeding. You’ve been using your turn signals. Even your tags are up-to-date. So just what is going on?

The officer claims you swerved. Now he has a flashlight in your face and is starting to ask you questions.

Isn’t marijuana legal in Colorado?

While it is legal for people who are 21 and older to smoke or consume marijuana in Colorado, it is still against the law to drive while under the influence of cannabis. If an officer believes a driver is impaired by or under the influence of any substance – including one that is legal, such as marijuana or alcohol – that officer can still make the decision to go ahead and arrest the driver.

The hypothetical scenario we started this post off with happens all the time in the Boulder area. For many young college students, this is their first run-in with the law and one that can really shake a person to their core.

How can an officer tell if you’re high?

Unlike with alcohol, there is no roadside breath test for you to blow into. Rather, it is solely up to the officer to decide whether or not they believe that you are impaired by or under the influence of marijuana. Some officers have gone through more advanced training to learn how to accurately spot the signs of marijuana impairment, but not all have.

To make the determination, the officer is going to rely on their observations of your actions and what you say. If your driving seemed to the officer to be consisted with impaired or intoxicated driving, if you seem uneasy on your feet, if your reaction times are slow, if your pupils are dilated, if you smell like marijuana, or if you show other indication of impairment or intoxication, the officer may conclude that you have been using marijuana. If you admit to using marijuana, that can also contribute to an officer’s decision to arrest you.

Is there a legal marijuana limit in Colorado?

There is a not a legal limit for driving under the influence of marijuana in Colorado in the same way that there is for driving under the influence of alcohol. Instead, Colorado’s DUI statute states that if a driver’s blood contains five nanograms or more of delta 9-tetrahydrocannabinol per milliliter of whole blood, that gives rise to a permissible inference that the driver was under the influence of one or more drugs.

This quasi-legal limit is controversial, since it is not clear that THC causes impairment or intoxication at the same level in all people regardless of their history and frequency of marijuana use. In any event, when the police are making their initial decision, they do not have access to blood test results, which can take weeks or months to process. The police use their own discretion when deciding to make an arrest.

The scientific and legal complexity of the investigation and prosecution of marijuana related impaired and intoxicated driving charges makes it essential that you avoid making any admissions about your marijuana use, and that you consult with an attorney as soon as you can.

The future of roadside drug testing

The Colorado State Patrol is in the final stages of testing a new oral fluids device. If this device is approved, this will give officers another tool to use in order to decide whether or not it is appropriate to make an arrest.