Arizona Marijuana DUI Conviction Upheld: What State v. McKinley Means for You

Arizona has legalized recreational marijuana — but that does not mean driving after using it is safe or legal. A May 2024 decision from the Arizona Court of Appeals, State v. McKinley, makes this point with sobering clarity: you can be convicted of DUI for marijuana use even when there is no established blood-level threshold proving impairment, and even if you personally believed you were fine to drive.

If you use marijuana in Arizona — medically or recreationally — and you ever get behind the wheel, this case directly affects you. This article breaks down what happened, what the court decided, and what it means for Arizona drivers.

What Happened: The Facts of the Case

NOTICE: This case is a memorandum decision which means it is not for official publication under Arizona Supreme Court Rule111(c). The decision is not precedential and may be cited only as authorized by rule. Although not official precedent it does give an indication of what the court of appeals thinks about these issues.

On April 18, 2021, Melissa McKinley drove her Ford Taurus into a line of cars stopped at a red light in Bullhead City, Arizona. She was traveling at 40 to 50 miles per hour. There was no sign she braked or tried to avoid the collision.

The impact was severe. The first car she struck — a Dodge Challenger — was pushed 100 to 125 feet into oncoming traffic. The driver broke both heels and suffered permanent facial scarring. A passenger cracked two vertebrae and suffered a head contusion. McKinley’s car then struck two additional vehicles.

An off-duty California Highway Patrol officer who witnessed the crash approached McKinley as she got out of her car. When he asked what happened, she raised her hands and said, “Woo, Jesus took the wheel.” He believed she was under the influence of something based on the crash itself and how she was acting. When she began walking away from the scene, he told her to stay — but she left on foot anyway.

A responding officer caught up with McKinley approximately 200 yards from the crash, walking briskly along the shoulder. She refused to comply with instructions and had to be taken to the ground and handcuffed. At the scene, the officer could smell marijuana from the back seat of his patrol car where she sat. After being read her Miranda rights, McKinley admitted she had smoked marijuana earlier that day and consented to a blood draw. When asked if she’d had anything to drink, she replied, “Nothing but the holy spirit.”

Her blood test showed 13 nanograms of THC per milliliter (plus or minus three nanograms), along with carboxy-THC, a byproduct of marijuana metabolism.

At trial, McKinley testified she had been distracted by memories of a former apartment while driving, and that she did not feel impaired by marijuana on the day of the accident. A jury acquitted her of resisting arrest but convicted her on all remaining charges. She was sentenced to 15 years in prison for the assault convictions.

What the Court Decided — and Why It Matters

1. The DUI Conviction Was Supported by the Evidence

McKinley challenged her DUI conviction by arguing there was not enough evidence to prove she was impaired. The Court of Appeals disagreed.

Arizona’s DUI law requires only that a driver be “impaired to the slightest degree” by any drug:

Both the prosecution’s and defense’s forensic experts agreed: there is no established THC blood level that is presumptively impairing. The defense expert even testified that a regular marijuana user might have 13 ng/mL in their blood days after last using, without being impaired.

But the court ruled that jurors were entitled to consider the totality of the evidence — the nature of the crash, McKinley’s statements, her behavior after the accident, and the known effects of THC (which include euphoria, inattention, impaired thought processing, and slowed reaction times) — and infer that she was driving while impaired.

2. A Car Is a Deadly Weapon — Aggravated Assault Stands

McKinley was convicted of aggravated assault for injuring the driver and passenger of the Dodge Challenger with her car. She argued there was insufficient evidence she acted with the required mental state — “recklessly.”

The court disagreed. Under Arizona law, a person acts recklessly when they are aware of and consciously disregard a substantial and unjustifiable risk that constitutes a gross deviation from how a reasonable person would act. Critically, the statute adds:

This means that even if marijuana made McKinley unaware of the danger she was creating, that unawareness itself constitutes recklessness under Arizona law. Additionally, the court found that driving 40–50 mph into a line of stopped cars at a major intersection in the middle of the day was reckless regardless of marijuana use — the sheer level of inattention was enough.

3. No Need for a Separate “Dangerous Offense” Jury Finding

The court also upheld the enhanced 15-year sentence, ruling that because the jury found McKinley guilty of aggravated assault using a deadly weapon or dangerous instrument, a “dangerous offense” finding was already implicit in the verdict. No separate jury finding was required to impose the enhanced sentence under A.R.S. § 13-704.

Possible Defense Strategies in Marijuana DUI Cases

Just because Arizona’s marijuana DUI law is broadly written does not mean every case is unwinnable. An experienced defense attorney will examine every aspect of the prosecution’s evidence, including:

• Blood draw timing and chain of custody. Arizona courts have recognized that when a blood draw was taken — and how it was handled — can be a game-changer in DUI cases. THC levels drop quickly after use, but interpretation depends heavily on when the sample was taken.
• Challenging the impairment inference. The absence of a legal THC limit cuts both ways. A skilled defense expert can argue that the detected level is consistent with residual, non-impairing THC — especially for regular users.
• Alternative explanations for driving behavior. As McKinley’s own testimony suggested, inattention without impairment can look similar. Distinguishing negligence from recklessness is a legitimate defense strategy.
• Field sobriety test validity. Standardized field sobriety tests were designed for alcohol impairment, not marijuana. Their reliability for THC impairment is scientifically contested.
• Miranda and constitutional issues. Statements made without proper Miranda warnings, or blood draws obtained without valid consent or a warrant, may be suppressible.

Understanding Arizona’s Marijuana DUI Law

Arizona has two separate marijuana DUI provisions:

• A.R.S. § 28-1381(A)(1) — Driving while impaired to the slightest degree by any drug, including marijuana. This is the charge in McKinley, and it requires proof of actual impairment.
• A.R.S. § 28-1381(A)(3) — Driving with any marijuana metabolite in your body. This provision was used to prosecute people for days-old marijuana use — until the Arizona Supreme Court struck down its application to non-impairing metabolites (carboxy-THC) in Dobson v. McClennen (2015).

The McKinley case involved the first provision — actual impairment — not the metabolite provision. This is the more nuanced, evidence-intensive charge, and it is the one Arizona prosecutors now rely on in marijuana DUI cases.

Frequently Asked Questions About Marijuana DUI in Arizona

This FAQ is optimized to answer the questions Arizona drivers are actually asking about marijuana DUI law.