DUIs and The Arizona Medical Marijuana Act

On November 20, 2015, the Supreme Court of Arizona held that, while possessing a valid medical marijuana card did not immunize individuals from prosecution under the state's zero tolerance marijuana DUI law, those legally entitled to engage in the use of marijuana could offer an affirmative defense to criminal DUI charges by showing that the level of cannabis metabolite in their system was not sufficient to cause impairment. Dobson v. McClennen2015 WL 7353847 (2015).

The State passed the Arizona Medical Marijuana Act (AMMA) in 2010, which allows qualifying patients to posses and use marijuana. Under the law, patients are "not subject to arrest, prosecution or penalty in any manner, or denial of any right or privilege" for the use of marijuana consistent with the AMMA. A.R.S. § 36–2801. However, the law also states that it will not immunize individuals from operating a motor vehicle while under the influence of marijuana, but that a person is not under the influence merely because metabolites or components of marijuana at levels insufficient to cause impairment are detectable. A.R.S. § 36-2802. 

The state also has on its books a DUI law that prohibits 1) driving under the influence of any drug if the person is impaired "to the slightest degree" (Impairment Law) (A.R.S. § 28–1381(A)(1)) and 2) driving while any amounts of certain drugs are in a person's system, including marijuana (Zero Tolerance Law) (A.R.S. § 28–1381(A)(3)). Patients that test positive for prescribed drugs are not subject to prosecution under the Zero Tolerance Law. A.R.S. § 28-1381(D).

The defendants Dobson and Anderson possessed medical marijuana cards from Oregon and Arizona, respectively. However, the municipal court would not allow evidence of either card to be introduced and the defendants did not seek to introduce any other evidence. The Court dismissed the charges under the Impairment Law, but the defendants were convicted under the Zero Tolerance Law.

On appeal, the Supreme Court of Arizona held that, although individuals may still be convicted for driving under the influence under the Zero Tolerance Law, the AMMA provides an affirmative defense to those charged if they prove that the amount of marijuana in their system did not actually cause impairment. 

The Court noted that the two DUI laws have different affirmative defenses. For instance, a prescription is not a valid defense to a DUI charge under the Impairment Law, presumably because the law was intended to prohibit impaired driving irrespective of the legality of the substance. On the other hand, a valid prescription would provide an affirmative defense to the Zero Tolerance Law. That section was, however, inapplicable here because under the AMMA marijuana use is authorized by "written certifications," not prescriptions. 

The Court did, however, find that the AMMA offered an affirmative defense to the Zero Tolerance Law. In a prior case, the Court held that the Arizona Legislature intended the Zero Tolerance Law to prohibit driving while metabolites that are capable of causing impairment are present in a defendant's system.  State ex rel. Montgomery v. Harris (Shilgevorkyan), 234 Ariz. 343 (2014). Since the AMMA states that the mere presence of marijuana metabolites does not equate to impairment, the Court held that the mere presence of marijuana metabolites cannot be the sole basis of a conviction under the Zero Tolerance Law. 

As a result, in order to convict an individual for a marijuana DUI in Arizona under the Zero Tolerance Law, first the state must prove that metabolites are present, and then the defendant may offer evidence rebutting the presumption that those metabolites caused impairment. The Court acknowledged that this could cause problems for defendants, as there is no commonly accepted level of metabolite that would cause impairment, but stated that the burden was properly placed on defendants that were familiar with the effects of their medicine given the strong pubic interest in keeping the roads safe. 

Here, since the defendants offered no evidence of their level of impairment, the convictions were affirmed. It should be noted that, had the defendant's been prosecuted under the Impairment Law, the burden of showing that the level of metabolites actually caused impairment would have been on the state. 

This case illustrates the myriad of issues confronting states seeking to implement a legal structure that balances the legal use of cannabis and road safety. Many states have existing DUI laws on the books that are already somewhat convoluted for substances other than alcohol. The addition of medical and recreational marijuana laws further confuses the issue, and indeed may directly conflict with existing laws. Impairment testing for cannabis is far behind the curve relative to the rest of the industry, and even if testing methods were accurate, the level of impairment from a given amount of cannabis is largely subjective. Uniform standards for levels of certain chemicals in the blood may facilitate clarity but could create problems based on a person's tolerance and medical needs. Subjective standards, like the one adopted in Arizona, court could create a copious litigation over what constitutes impairment for any given individual, and, at a more basic level, who should be required to prove impairment or lack thereof - the state, as required under the Impairment Law, or the individual, as required under the Zero Tolerance Law.