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Medical Marijuana and DUIs

Even though both recreational and medical marijuana are legal in Colorado, state law is very clear that driving while high is illegal. Having a medical marijuana card is not a defense to driving under the influence (DUI). On the other hand, the DUI statute CRS 42-4-1301 provides that having a medical marijuana card is not probable cause that a person is driving under the influence, and that the fact of having a medical marijuana card is not admissible evidence in the prosecution of a DUI.

The Colorado DUI law says that marijuana intoxication is inferred where there is “five nanograms or more of delta 9-tetrahydrocannabinol [or THC, the narcotic chemical in marijuana] per millimeter in whole blood.” In July 2015, a woman was acquitted of driving while high on marijuana with 19 nanograms of THC in her system. Her defense attorney successfully argued that 5 nanograms is too low for a habitual user of medical marijuana to be considered intoxicated, and anyway she was pulled over for expired tags, not unsafe driving. This is not an incredible conclusion of such a case; many habitual users, including medical marijuana patients, will have high levels of THC in their blood even if they have not recently used marijuana. This is because the nature of the chemical is that it stays in the body long after ingested.  This point was proven by a Denver writer, William Breathes, in an informal experiment. Breathes, a habitual user of marijuana, had his blood tested after abstaining from smoking for a day and having a doctor determine that he was not impaired at the time of the blood draw. The results were that even though Breathes was sober, his blood contained 13.5 nanograms of THC, well above the legal limit.  Breathes’ findings support an affirmative defense for individuals charged with DUI for having high levels of THC in their blood. Particularly for medical marijuana patients, who might ingest marijuana as much as several times per day, the presence of even high levels of THC in the blood will not be indicative of intoxication at the time of driving.

The Supreme Court of Arizona, where medical marijuana is legal, took up the issue of DUIs and weed in late 2015. The court expanded on their 2014 ruling that the mere presence of THC does not necessarily mean that a person is impaired. In their most recent decision, the Court ruled that having a medical marijuana card could be used in an affirmative defense that the defendant’s use of marijuana was permitted by law and that the level of THC present is insufficient to cause impairment. The Arizona ruling is significant for other states because is adds to the authority that a medical marijuana license is a legitimate part of a DUI defense, and that impairment should not be tied to a standardized THC level.

The issue of DUIs and marijuana has been discussed since medical marijuana was legalized in Colorado, and especially since recreational marijuana became law in 2014. Colorado State Patrol began collecting data on marijuana-specific impairment citations in 2014.  In 2015, the number of total DUI citations decreased and so did the number of marijuana-only citations. It is hard to draw convincing conclusions based on only two years of data, and it is clear that law enforcement is still very much unprepared to competently and efficiently address marijuana use and driving.

For now, a defendant in Colorado at least has the affirmative defense of habitual use of marijuana for medicinal purposes to fight a DUI charge based on high levels of THC in the blood.


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