Marijuana DUI in Phoenix: How Arizona Law Works Under Prop 207

If you've been arrested for a marijuana DUI in Phoenix, you may be confused. Marijuana is legal for adults in Arizona, so how can using it lead to a criminal charge? The short answer: Proposition 207 made it legal to possess and use marijuana, but it did not make it legal to drive while impaired by it. Arizona's DUI law still applies to cannabis the same way it applies to alcohol and other drugs.

The good news is that a marijuana DUI can be harder for the state to prove than an alcohol DUI. Arizona has no legal "THC limit" like the 0.08 limit for alcohol. A positive blood test alone does not automatically prove you were impaired, and the way officers decide someone is "high" involves judgment calls that can be questioned.

This article explains how Arizona law treats marijuana and driving today, how police build these cases, what a blood test can and can't show, and what medical card holders should know. It's general information, not legal advice. Every case turns on its own facts, so talk with a lawyer about yours.

What Arizona Law Says About Marijuana DUI

Arizona's main DUI statute is A.R.S. § 28-1381. Two parts of it matter most for marijuana cases.

The "impaired to the slightest degree" standard

Under A.R.S. § 28-1381(A)(1), it is illegal to drive or be in actual physical control of a vehicle while under the influence of any drug, alcohol, or combination, if you are impaired to the slightest degree. This is the standard most marijuana DUI cases in Phoenix are charged under after Prop 207.

"Slightest degree" sounds like a very low bar, and it is. But the prosecution still has to prove actual impairment beyond a reasonable doubt. That means evidence that marijuana affected your ability to drive safely, not just that you had used it at some point.

The drug and metabolite provision

A separate part of the statute, A.R.S. § 28-1381(A)(3), makes it illegal to drive with certain drugs or their metabolites in your body. This is often called the "metabolite rule." A metabolite is a substance your body produces as it breaks down a drug.

For marijuana, this rule has a complicated history, which we cover next.

The Metabolite Rule: How Marijuana DUI Law Has Changed

Marijuana leaves traces in your body long after any effects wear off. Some of those traces can show up in blood or urine for days or even weeks for regular users.

For years, that created a serious problem. People were charged with DUI based on inactive marijuana byproducts, even when there was no evidence they were impaired while driving.

Here is how the law has developed, in general terms:

1. 2014 Arizona Supreme Court ruling. The court held that the inactive marijuana metabolite commonly called carboxy-THC, which doesn't cause impairment, could not by itself support a DUI charge under the metabolite provision.
2. Medical marijuana protections. Arizona courts have also recognized that registered medical marijuana patients have a defense against a metabolite-based charge if they can show the marijuana in their system was not at a level that could cause impairment.
3. Prop 207 (2020). The Smart and Safe Arizona Act legalized adult recreational use. It made clear that it does not allow anyone to drive while impaired to even the slightest degree by marijuana. In practice, prosecutors in marijuana cases now generally focus on actual impairment under (A)(1).

Because this area of law has shifted over time and can keep changing, it's important to have a lawyer review exactly which section you were charged under and how current law applies to your situation.

How Phoenix Police Investigate a Marijuana DUI

Most marijuana DUI cases start the same way as any other DUI: a traffic stop for speeding, weaving, a broken taillight, or a checkpoint. From there, officers look for signs of marijuana use.

Common observations officers report

• The smell of burnt or fresh marijuana
• Red or watery eyes
• Eyelid tremors or a dry mouth
• Slow speech or delayed responses
• Admissions such as "I smoked earlier today"
• Marijuana or paraphernalia in the vehicle

Many of these signs have innocent explanations. Red eyes can come from allergies, Phoenix dust, fatigue, or long hours at work. The smell of marijuana may come from a passenger or clothing, and on its own it doesn't show when, or whether, the driver used.

Field sobriety tests

Officers may ask you to do standardized field sobriety tests, like the walk-and-turn and one-leg stand. These tests were mainly designed and studied for alcohol impairment. How well they detect marijuana impairment is a fair question to raise in a defense. These roadside tests are generally voluntary, though officers don't always say so.

Drug Recognition Expert (DRE) evaluations

In many drug DUI cases, a specially trained officer called a Drug Recognition Expert, or DRE, does a multi-step evaluation. It usually includes checking pulse, blood pressure, pupil size, muscle tone, and performance on divided-attention tasks. The DRE then gives an opinion on what kind of drug, if any, is causing impairment.

A DRE opinion can sound scientific, but it is still one officer's judgment. A defense lawyer can look at whether each step was done correctly, whether the findings actually point to marijuana, and whether other explanations fit just as well.

THC Blood Tests: What They Show and What They Don't

Under Arizona's implied consent law, A.R.S. § 28-1321, drivers are considered to have agreed to chemical testing when arrested for DUI. Refusing a test usually leads to an administrative license suspension, often 12 months for a first refusal, and police can seek a warrant to draw blood anyway. Refusal can also be used as evidence against you in some situations.

In marijuana cases, the test is almost always a blood draw. The lab may report:

• Active THC (delta-9-THC): the compound that causes the "high"
• Hydroxy-THC: an active metabolite
• Carboxy-THC: an inactive metabolite that can linger long after the effects fade

Here's the key point: there is no accepted THC blood level that proves impairment for everyone. THC levels rise and fall quickly after use, and they don't track impairment the way alcohol levels do. A frequent medical user might show measurable active THC with no impairment, while an occasional user might be affected at a lower level.

Blood test evidence can also be challenged on other grounds:

• How long after driving the blood was drawn
• Whether the draw was done by a qualified person following proper procedures
• Chain of custody: who handled the sample and how it was stored
• Lab methods, calibration, and analyst qualifications
• Whether the blood was obtained legally, with valid consent or a valid warrant

Medical Marijuana Card Holders and DUI

A medical marijuana card does not give you permission to drive impaired. If the state can prove you were impaired to the slightest degree, you can be convicted under (A)(1) like anyone else.

But a card can still matter. As noted above, Arizona law gives registered patients certain protections when the only evidence is the presence of marijuana or its metabolites at levels that wouldn't cause impairment. Card holders also tend to have predictable usage patterns that may help explain blood results.

If you hold a medical card, tell your lawyer right away and keep proof that your registration was valid on the date of the arrest.

Penalties for a Marijuana DUI in Arizona

A first-time marijuana DUI is usually charged as a Class 1 misdemeanor, the same as a first alcohol DUI. Possible consequences can include:

• Jail time (Arizona has mandatory minimums for DUI, though some of it may be suspended)
• Fines, fees, and assessments
• License suspension
• Alcohol/drug screening, education, or treatment
• Probation
• Possible ignition interlock requirements, depending on the circumstances

Penalties increase for repeat offenses. Some situations can make a DUI a felony "aggravated DUI" under A.R.S. § 28-1383, such as driving on a suspended license, having a child under 15 in the car, or a third DUI within a set time period. Exact penalties depend on your history and the facts, and they can change, so get advice about your own case. For more detail, see Understanding Arizona's DUI Penalties and First Offense DUI Arizona: What Happens After Arrest.

A DUI conviction may also affect employment, professional licenses, and commercial driving privileges. Note that a marijuana DUI is a separate issue from old marijuana possession records. Prop 207 marijuana expungement generally applies to certain possession offenses, not DUI convictions.

Common Defenses in a Marijuana DUI Case

Every case is different, and no defense guarantees a particular result. Defenses that may come up in Phoenix marijuana DUI cases include:

• Unlawful stop: If the officer didn't have a valid legal reason to pull you over, evidence from the stop may be suppressed.
• No real proof of impairment: Proof that you used marijuana at some point is different from proof that you were impaired while driving.
• Problems with the DRE evaluation: Steps skipped, findings that don't match marijuana, or other medical explanations.
• Blood test issues: Timing, handling, lab procedures, or how the blood was obtained.
• Video evidence: Body camera and dash camera footage may show driving and behavior that look normal and don't match the police report.
• Medical card protections: Where they apply to the charge filed.

What to Do Next After a Marijuana DUI Arrest in Phoenix

Act quickly. In Arizona, you usually have only 15 days from service of the notice to request a hearing to challenge an administrative license suspension. Missing that deadline can mean losing your license automatically.

Some practical steps:

1. Don't discuss the case with anyone except your lawyer, and don't post about it online.
2. Write down everything you remember: when you last used marijuana, what you ate, what the officer said, and which tests you took.
3. Keep all paperwork, including your citation and any license suspension notice.
4. Gather proof of a medical marijuana card if you have one.
5. Talk to a defense attorney before your first court date.

Jess A. Lorona has over four decades of criminal defense experience and is a former prosecutor, so he knows how DUI cases are built from both sides. Learn more about attorney Jess A. Lorona or the firm's DUI defense services.

Lorona Mead, PLC offers free consultations and is available 24/7. Call (602) 385-6818 or reach out through our contact page to talk about your case.