## Facts

- Kristina R. Dobson and Marvelle D. Anderson were charged in municipal court with two DUI offenses: impairment DUI under A.R.S. § 28-1381(A)(1) and per se drug DUI under A.R.S. § 28-1381(A)(3).
- Blood testing showed marijuana and an impairing marijuana metabolite in each defendant’s body.
- Both defendants were medical-marijuana cardholders (Dobson held an Oregon card; Anderson held an Arizona card under the Arizona Medical Marijuana Act (AMMA)).
- The trial court excluded evidence of Dobson’s card and granted a motion in limine barring evidence of Anderson’s card.
- The prosecution dismissed the impairment DUI counts and proceeded only on the per se marijuana counts under § 28-1381(A)(3).
- On a stipulated record, both defendants were convicted under § 28-1381(A)(3); the superior court affirmed.
- The court of appeals accepted special action jurisdiction but denied relief, concluding the AMMA did not provide immunity from § 28-1381(A)(3).
- The Arizona Supreme Court granted review to determine whether the AMMA either immunizes cardholders from § 28-1381(A)(3) prosecutions or supplies a limited affirmative defense.

## Issues

1. Whether the AMMA immunizes a registered qualifying patient from prosecution under A.R.S. § 28-1381(A)(3) for driving with marijuana or its metabolite in the body.
2. If not, whether the AMMA provides an affirmative defense to an A.R.S. § 28-1381(A)(3) charge when the marijuana or metabolite concentration is insufficient to cause impairment, and who bears the burden of proof.

## Decision

- The court held that the AMMA does not grant blanket immunity from prosecution under A.R.S. § 28-1381(A)(3).
- The court held that the AMMA provides a limited affirmative defense for registered qualifying patients charged under § 28-1381(A)(3) if they prove the marijuana or metabolite was present in a concentration insufficient to cause impairment.
- The defendant bears the burden to prove this affirmative defense by a preponderance of the evidence.
- The court vacated the court of appeals’ opinion but affirmed the defendants’ convictions because they presented no evidence establishing the affirmative defense.

## Legal Principles

- A.R.S. § 28-1381(A)(3) criminalizes driving with any amount of marijuana or its metabolite in the body, without requiring proof of actual impairment.
- The AMMA’s provision that a registered qualifying patient shall not be considered “under the influence” solely because of metabolites or components in an insufficient concentration to cause impairment does not eliminate § 28-1381(A)(3) liability.
- For registered qualifying patients, the AMMA supplies an affirmative defense to a § 28-1381(A)(3) charge when the defendant proves the detected marijuana or metabolite concentration was insufficient to cause impairment.
- The State must prove the statutory elements of § 28-1381(A)(3); the AMMA defense does not alter those elements.
- The defendant must prove the AMMA-based affirmative defense by a preponderance of the evidence.

## Conclusion

Medical-marijuana cardholders in Arizona may be prosecuted for per se marijuana DUI under A.R.S. § 28-1381(A)(3), but they can avoid conviction by proving, by a preponderance of the evidence, that the marijuana or metabolite in their body was present at a concentration insufficient to cause impairment.


Dobson v. McClennen, 238 Ariz. 389 (Ariz. 2015)