Court Upholds THC DUI Conviction in State v. Martell – Marijuana DUI in Arizona

Case: State v. Martell, No. 1 CA-CR 24-0308 | Arizona Court of Appeals, First Division | Decided October 22, 2025

Why This Case Matters for Arizona Drivers

Arizona has legalized recreational marijuana, but getting behind the wheel while impaired by THC remains a serious criminal offense — and a conviction can follow you for life. A new ruling from the Arizona Court of Appeals, State v. Martell, makes clear how courts are thinking about marijuana DUI cases right now: what evidence the State needs, how blood THC levels are interpreted, and when defense strategies like the Willits instruction succeed — or fail.

If you or someone you know is facing a drug DUI charge in Maricopa County or anywhere else in Arizona, understanding this decision is critical.

What Happened in State v. Martell?

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 The decision is not precedential and may be cited only as authorized by rule.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.

The case began when Allen Josue Martell’s vehicle struck metal cable barriers in the median of a highway. A state trooper who was certified as a Drug Recognition Expert (DRE) arrived at the scene and detected the odor of burnt marijuana from inside the vehicle. Martell told the trooper he had smoked three marijuana blunts the night before.

The trooper conducted a roadside DUI investigation. Martell submitted to four field sobriety tests, all of which indicated impairment. He was arrested. A subsequent blood draw revealed a THC concentration of 9.7 nanograms per milliliter (ng/mL) in his system. A burnt marijuana cigarette was also found in the vehicle’s cup holder.

Martell was charged with two counts of aggravated DUI under A.R.S. §§ 28-1383(A)(1) and (A)(2): one for driving with a suspended license while impaired to the slightest degree, and one for driving within 84 months of a previous DUI conviction. Both are Class 4 felonies.

A Maricopa County jury found Martell guilty on both counts. The court sentenced him to a presumptive 10-year prison term. He appealed on two grounds: (1) that the court wrongly refused to give a Willits instruction, and (2) that the evidence of THC impairment was insufficient to support the verdict. The Court of Appeals rejected both arguments and affirmed the convictions.

The Willits Instruction: A Defense Tool That Requires Specific Facts

One of the most important defense arguments in this case involved the Willits doctrine — a legal tool Arizona defense attorneys use when the government loses or destroys evidence that could have helped the defendant.

Under State v. Willits (1964), when the State fails to preserve material evidence, a judge can instruct the jury to draw an inference unfavorable to the prosecution. It is a powerful remedy — but it requires the defendant to prove two things:

1. The State failed to preserve evidence that was obviously material, reasonably accessible, and potentially exonerating; and
2. That failure caused prejudice to the defendant.

In Martell’s case, the vehicle was impounded after the accident. Martell claimed the car had a mechanical alignment problem that may have contributed to the collision — and therefore the vehicle was exculpatory evidence. When the impound lot eventually disposed of the vehicle (because no one retrieved it), Martell argued the State had failed to preserve it.

The Court of Appeals disagreed. The key fact: there was no hold placed on the vehicle. Because Martell’s fiancée — the vehicle’s owner — could have retrieved it at any time, the evidence was reasonably accessible to the defense. The court relied on State v. Geotis (App. 1996), which established that when a defendant (or someone acting on the defendant’s behalf) has the ability to retrieve evidence from an impounded vehicle, the State cannot be faulted for not preserving it. The Willits instruction was properly denied.

Practical takeaway: If your vehicle is impounded following a DUI arrest in Arizona, act quickly. Your attorney needs to assess whether the vehicle itself has evidentiary value — and if so, take steps to preserve or retrieve it before it is disposed of. Waiting is not an option.

THC and Impairment: What the Court Said About the Science

This is the part of the ruling that will affect the most people facing marijuana DUI charges in Arizona.

Unlike alcohol, Arizona law does not set a per se blood concentration level for THC impairment. You cannot be convicted simply because your blood showed a certain number on a lab report. Under A.R.S. § 28-1381(A)(1), the State must prove the driver was impaired to the slightest degree. That standard is low — but it still requires real, probative evidence.

In Martell’s case, the State presented multiple layers of evidence:

• A certified Drug Recognition Expert who detected the odor of marijuana and observed behavioral indicators of impairment
• Four failed field sobriety tests showing lack of balance, leg tremors, and impaired cognitive function
• A blood THC level of 9.7 ng/mL — within the 5–10 ng/mL range that the State’s forensic toxicologist testified is associated with significant signs of impairment based on scientific literature
• Physical evidence: a burnt marijuana cigarette in the cup holder
• Martell’s own admission that he had smoked three blunts the night before

Both the State’s and the defense’s toxicology experts agreed there is no universal THC impairment threshold the way there is with alcohol’s 0.08 BAC. The defense expert noted that chronic users may carry a THC baseline of 5–10 ng/mL without being acutely impaired. The court acknowledged this complexity — but found that when the totality of the evidence is considered, a reasonable jury could conclude Martell was impaired to the slightest degree.

The court also noted that THC is detectable in blood roughly two to three hours after consumption, and that Martell’s level of 9.7 ng/mL was consistent with recent use — not simply residual levels from days-old consumption.

Practical takeaway: There is no “safe” THC blood level in Arizona. The absence of a per se limit cuts both ways: it means prosecutors must build a case from multiple evidence streams, but it also means that even a moderate THC reading, combined with failed field sobriety tests and an officer’s observations, can sustain a conviction. The defense must challenge each pillar of that evidence individually and collectively.

What This Case Could Means If You’re Facing a THC DUI in Arizona

State v. Martell reinforces several realities about marijuana DUI defense in Arizona that anyone charged with drug DUI needs to understand:

1. Field sobriety tests are used against marijuana suspects — even though they weren’t designed for THC. Martell’s defense correctly argued that standardized field sobriety tests have not been validated for marijuana impairment. The court acknowledged this but allowed the test results as evidence of impairment anyway. Challenging how these tests were administered, and the training and qualifications of the officer who administered them, remains an important defense strategy.

2. Your words can hurt you. Martell told the trooper he smoked three blunts the night before — and that admission was cited repeatedly in the court’s sufficiency analysis. You have the right to remain silent. Use it.

3. Aggravated DUI carries severe penalties. A Class 4 felony aggravated DUI conviction in Arizona carries a presumptive prison sentence of 10 years when prior convictions are in play. There is no probation option. The stakes in any aggravated DUI case — whether it involves alcohol, THC, or prescription drugs — demand experienced legal representation from the moment of arrest.

4. Act on your vehicle and evidence immediately. As Martell learned, the defense cannot wait. Evidence that might support your case — mechanical issues, dashcam footage, physical items inside the vehicle — needs to be identified and secured as early as possible.

5. The Willits instruction is available but requires a factual foundation. If law enforcement fails to preserve evidence that could help your defense and you had no realistic ability to obtain it yourself, a Willits instruction can be a powerful tool. Building that argument requires a careful review of the entire fact pattern and a timely motion.

Charged with a THC or Drug DUI in Arizona? Get Experienced Help Now.

Marijuana DUI cases in Arizona are complex. The science is contested. The legal standards are evolving. And the consequences — especially for an aggravated DUI — can be life-altering. Cases like State v. Martell show exactly how courts evaluate this evidence, which is why having an experienced Arizona DUI defense attorney is not optional.

Gordon Thompson has defended DUI and drug DUI cases in Arizona for 47 years and has handled more than 6,000 clients. His practice is limited exclusively to DUI and criminal defense — he handles nothing else. He appears in courts throughout Maricopa County, Pinal County, and select courts in Northern Arizona.

After a DUI arrest in Arizona, you also have only 30 days to request an MVD hearing or your driver’s license is automatically suspended. That clock starts at arrest — not conviction.

Call or text Gordon Thompson today at (602) 467-3680 for a free phone or video consultation. Flat fee pricing. No hidden costs. Real experience when it matters most.

Disclaimer: This blog post is for informational purposes only and does not constitute legal advice. Reading this post does not create an attorney-client relationship. Case outcomes depend on the specific facts and circumstances of each individual case.

Citation: State v. Martell, No. 1 CA-CR 24-0308, Arizona Court of Appeals, First Division (Oct. 22, 2025).