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Arizona Medical Marijuana Card Affirmative Defense to Drug DUI

Posted on December 7, 2021 in

Defendants were medical marijuana cardholders convicted of drug DUI for operating a motor vehicle while under the influence of marijuana or its metabolite. Were defendants immune from drug DUI prosecution under the Arizona Medical Marijuana Act? Conviction affirmed on appeal.

To learn more, read our discussion about drug DUI in Arizona law and how to prepare your DUI defense strategy.

MJ Cardholder Convicted of Drug DUI

Two individuals who had medical marijuana carts (MJ cards) were arrested, charged, and convicted of an (A)(3) DUI. The Arizona Medical Marijuana Act (AMMA) broadly immunizes patients who are MJ cardholders for their medical marijuana use, as follows:

“A registered qualifying patient … is not subject to arrest, prosecution or penalty in any manner, or denial of any right or privilege, including any civil penalty or disciplinary action by a court or occupational or professional licensing board or bureau: (1) For the registered qualifying patient’s medical use of marijuana pursuant to this chapter, if the registered qualifying patient does not possess more than the allowable amount of marijuana.” A.R.S. § 36-2811(B)(1).

Each defendant was charged with two counts of DUI under (A)(1) and (A)(3), however the State dismissed the (A)(1) charges (“impaired to the slightest decree”). Blood test results showed the presence in the body of marijuana and its impairing metabolites. The defendants were tried and convicted in Mesa municipal court. At trial, the judge denied one defendant’s motion to present her Oregon MJ-card as evidence. The other defendant was also precluded from introducing an Arizona MJ-card as evidence.

Conflict Between Medical Marijuana Act and Arizona DUI Law

On the one hand, the Arizona Medical Marijuana Act (AMMA) allows a patient diagnosed with a debilitating medical condition to obtain an MJ-card identifying that person as allowed to possess and use a limited amount of medical marijuana. AMMA, ARS § 36-2801, et seq.

On the other hand, Arizona DUI law makes it a crime to operate a motor vehicle while under the influence of certain impairing drugs, such as marijuana or impairing marijuana metabolites. Arizona DUI, ARS § 28-1381(A)(3).

The Supreme Court of Arizona held that defendant’s MJ-card issued under the AMMA does not immunize that driver from prosecution for drug DUI. However, the MJ cardholder may raise an affirmative defense to an (A)(3) DUI that the amount of marijuana or marijuana metabolite in the body was not sufficient to impair that driver.

Procedural History of Arizona DUI Defense

After trial in Mesa municipal court, both defendants were convicted of the following (A)(3) DUI charge:

A. It is unlawful for a person to drive or be in actual physical control of a vehicle in this state under any of the following circumstances: … 3. While there is any drug defined in § 13-3401 or its metabolite in the person’s body. ARS § 28-1381(A)(3).

Defendants appealed to the Superior Court in Maricopa County which affirmed the convictions (Honorable Crane McClennan presiding). Defendants then sought special action review in the Arizona Court of Appeals. The appeals court affirmed the convictions, holding that the AMMA does not provide immunity from prosecution for driving with an “impermissible drug or impairing metabolite in their bodies” under current Arizona DUI law.

Arizona Supreme Court Resolves Conflict in Medical Marijuana Drug DUI

Because of statewide importance and need for statutory interpretation, the Arizona Supreme Court granted review to answer the question of whether or not the AMMA immunizes the MJ cardholder from DUI prosecution under ARS § 28-1381(A)(3). The high court affirmed the Maricopa County Superior Court’s decision and vacated the Court of Appeals opinion.

The Arizona Supreme Court held that:

“Rather than shielding registered qualifying patients from any prosecution under A.R.S. § 28-1381(A)(3), the AMMA affords an affirmative defense for those patients who can show, by a preponderance of the evidence, that the concentration of marijuana or its impairing metabolite in their bodies was insufficient to cause impairment.”


Here are some highlights from the opinion:

  • Broad immunity not absolute: AMMA immunity from prosecution is broad, but not absolute. Prosecution for DUI is not entirely prohibited because the driver has an MJ-card.
  • Affirmative defense for (A)(3) DUI: The affirmative defense afforded by ARS § 28-1381(D) applies to MJ cardholders. That is, a driver cannot be convicted of an (A)(3) DUI “based merely on the presence of a non-impairing metabolite that may reflect the prior usage of marijuana.” But defendant must show the concentration of marijuana or marijuana metabolite was insufficient to be impairing.
  • Rebuttable presumption: Possession of an MJ-card “creates a presumption that a qualifying patient is engaged in the use of marijuana pursuant to the AMMA, so long as the patient does not possess more than the permitted quantity of marijuana.” The presumption is rebuttable.
  • MJ cardholder’s affirmative defense to (A)(3) DUI charge: An MJ cardholder may be convicted of an (A)(3) DUI if the State proves beyond a reasonable doubt that the driver was operating or in control of the vehicle while marijuana or its impairing metabolite was in the body. First, to establish an affirmative defense to the (A)(3) DUI charge, defendant must show he or she is an AMMA-authorized medical marijuana user (a valid MJ registry card suffices). Second, defendant carries the burden of proving by a preponderance of the evidence that, while driving, marijuana or its metabolite was in the body in a concentration insufficient to cause impairment.

Lastly, the trial court’s exclusion of defendants’ MJ cards was harmless error given defendants failed to offer any evidence that concentrations of the prescribed drug or drug metabolites were insufficient to cause impairment.

Dobson v. Hon. Crane McClennen, 238 Ariz. 389, 361 P3d 374 (Ariz. 2015)

Read more about the case here: Dobson v. Hon. Crane McClennen

For precise language, read the court’s original opinion. Legal citations omitted.