Can I Get a DUI for Being Under the Influence of Medical Marijuana?


Public and medical opinions on the legalized use of cannabis have changed dramatically in the last decade. Data from the American Medical Association finds that two-thirds of Americans are in favor of legalizing marijuana for adult use and even greater numbers approve of its medical use. Patients with qualifying medical conditions in Colorado may gain a registry card for access to legal medical marijuana, but does that protect legal users of medical marijuana from facing charges of driving under the influence (DUI) or driving while ability impaired (DWAI)? No. In fact, research shows that cannabis intoxication significantly impairs driving skills as well as other neurobehavioral abilities. Marijuana—even when legally prescribed and used for medicinal purposes—causes impaired executive function which compromises a driver’s reaction times and other abilities. Law enforcement in Colorado takes any DUI seriously, regardless of the substance.

DUI or DWAI for Medical Marijuana Usage

Driving while impaired is illegal in Colorado regardless of whether or not the intoxication derives from a medically prescribed substance such as prescription painkillers or medical marijuana. If a substance impairs a driver’s ability to operate a motor vehicle, a law enforcement officer has the duty to arrest them for DUI or DWAI. Open-container laws apply to medical marijuana as well as alcohol. It’s illegal for drivers or passengers to have open cannabis packaging inside an operating vehicle even if the vehicle isn’t moving. For moving vehicles, the same laws that apply to alcohol intoxication also apply to medical marijuana intoxication. This means officers may pull over a driver for “reasonable suspicion.” Reasonable suspicion may mean any of the following indicators:

  • Weaving
  • Hugging the middle line
  • Excessively slow driving
  • Erratic braking
  • Tailgating
  • Driving after dark without headlights
  • Reckless driving

Once pulled over, an officer can make a DUI arrest on probable cause. For medical marijuana users probable cause could include a marijuana odor, visible cannabis paraphernalia, reddened eyes, slurred speech, confusion, or difficulty performing routine tasks such as locating a license and registration. An officer can then require the suspect to take a blood test since breathalyzers do not register marijuana use. Refusing a blood test results in automatic license suspension and additional penalties and does not protect the suspect from DUI charges.

What is Marijuana “Impairment” Under Colorado Law?

All marijuana contains an intoxicating psychoactive chemical known as Delta 9 THC. This substance takes many hours to metabolize in the human body. A driver found to have 5 nanograms of THC or more per milliliter of blood gives law enforcement a permissible inference that the driver was significantly impaired. Even if the blood test reveals less than 5ng per milliliter of blood the arresting officer may charge the driver with DWAI if they observe a significant level of impaired ability.

Law enforcement officers in Colorado receive training on detecting marijuana impairment. An average of over 60 arrests per day for marijuana-impaired driving occur in Colorado. Fines and penalties for DUI and DWAI are strict in Colorado and the state does not differentiate between alcohol impairment or marijuana impairment during prosecution or sentencing.