What is a Marijuana DUI in Arizona?

Learn about Marijuana DUI Arizona

A lot of people in Tempe assume that because marijuana is legal in Arizona, they cannot get a DUI for it. That is not how it works. Marijuana legalization did not change Arizona’s DUI laws. You can still be arrested, charged, and convicted for driving under the influence of marijuana, and the penalties are just as serious as an alcohol DUI.

Here is what a marijuana DUI in Arizona actually means, how these cases are investigated, what you are facing if you are charged, and why they are often harder to fight than people expect.

If you or a loved one is facing marijuana charges in Tempe, don’t go it alone. Contact the Law Offices of T. M. Allen for a free case review. Our Tempe drug charges lawyer, Tyler M. Allen, is here to help. 

The Legal Standard: Impaired to the Slightest Degree

Under A.R.S. §28-1381, it is illegal to drive or be in actual physical control of a vehicle in Arizona while impaired by marijuana to the slightest degree. That is the same standard that applies to alcohol DUIs, and it is a low bar intentionally.

With alcohol, there is a clear legal limit: 0.08% BAC. Marijuana DUIs do not work that way. There is no set THC concentration in your blood that automatically means you are impaired. Instead, prosecutors have to show that the marijuana you consumed actually affected your ability to drive at the time you were behind the wheel.

The Arizona Court of Appeals has confirmed this standard: the mere presence of THC in your bloodstream is not enough to convict you of a marijuana DUI. The state must prove actual impairment. That ruling matters, and it creates real room to defend these cases,  but it does not mean the charge goes away on its own.

The THC Persistence Problem

This is the part that makes marijuana DUI cases uniquely complicated. THC, the compound in marijuana that causes impairment, does not leave your body the same way alcohol does. Alcohol metabolizes at a relatively predictable rate. THC can linger in your blood, urine, and tissue for hours, days, or even weeks after use, long after any impairment has worn off.

That creates a real problem. If a blood test shows THC in your system, it does not necessarily tell anyone whether you were impaired when you were driving. You might have used marijuana two days ago, feel completely fine, and still have detectable THC in your blood. Prosecutors and defense attorneys fight over exactly this question in marijuana DUI cases.

The distinction between active THC (which causes impairment) and THC metabolites (which are just byproducts of past use) is a key part of many defense strategies. Understanding this is one reason why having an experienced defense attorney matters in marijuana DUI cases.

How Police Investigate Marijuana DUIs

When an officer pulls someone over and suspects marijuana impairment, the investigation usually unfolds in a few stages.

Field Sobriety Tests

Officers typically administer standardized field sobriety tests, the same ones used in alcohol DUI stops. These include the horizontal gaze nystagmus test, the walk-and-turn, and the one-leg stand. However, these tests were designed to detect alcohol impairment and are less reliable indicators of marijuana impairment. That makes them a contested piece of evidence.

Drug Recognition Experts (DREs)

In more serious cases or when the officer suspects drug impairment, a Drug Recognition Expert may be called in. DREs go through a 12-step evaluation protocol that includes checking your pulse, eye movement, muscle tone, and other physical signs. Law enforcement relies heavily on DRE testimony in marijuana DUI prosecutions. DRE opinions are not infallible, though, and a skilled defense attorney can challenge both the methodology and the conclusions.

Blood Tests

Unlike alcohol DUIs where breath testing is common, marijuana DUI investigations almost always involve a blood draw. If you are arrested on suspicion of a marijuana DUI in Arizona, you will likely be asked to provide a blood sample under the state’s implied consent law (A.R.S. §28-1321). Refusing a blood test triggers an automatic license suspension and can be used against you in court. The blood sample is then sent to a lab and tested for THC and THC metabolites.

What Are the Penalties?

A marijuana DUI is charged the same way as an alcohol DUI under Arizona law. For a first-time offense, that means a Class 1 misdemeanor with the following mandatory minimums:

• 10 consecutive days in jail (9 days can be suspended if you complete a court-approved drug screening and education program)
• Fines and fees totaling $1,250 or more (not including jail costs, program fees, and other assessments)
• 90-day driver’s license suspension
• Mandatory ignition interlock device for 12 months
• Probation up to 5 years
• Mandatory drug screening, education, and possible treatment

Penalties escalate significantly for a second offense within 84 months, and a third offense within that window becomes an aggravated DUI, a felony with mandatory prison time.

A conviction also stays on your criminal record, shows up on background checks, and counts as a prior DUI if you are ever charged again.

Common Defenses in Marijuana DUI Cases

Because marijuana DUI cases turn on actual impairment rather than a hard number, there is often more room to fight them than people expect. Some of the most common defense angles include:

Challenging the traffic stop

An officer needs reasonable suspicion of a traffic violation or crime to pull you over. If the stop was not legally justified, any evidence collected afterward — including field sobriety test results and the blood draw — may be suppressed.

Challenging the field sobriety tests

Standard field sobriety tests were validated for alcohol impairment, not marijuana impairment. There is legitimate scientific debate about how well these tests detect marijuana intoxication, and that debate can be used to undermine the prosecution’s narrative.

Challenging DRE testimony

Drug Recognition Expert evaluations involve a lot of subjective judgment. If a DRE did not follow the protocol correctly, or if their conclusions are not supported by the physical evidence, those opinions can be attacked at trial.

Challenging the blood test results

Blood draw procedures have to follow strict protocols. The sample has to be collected, stored, transported, and analyzed in specific ways. Errors in any part of that chain can create grounds to challenge the results. There is also the question of whether the THC detected was active at the time of driving or simply a metabolite of past use.

No actual impairment shown

If the driving itself was not erratic, if the officer’s observations of impairment were weak, and if the blood test only shows metabolites, a defense attorney can argue that the prosecution simply cannot prove impairment at the time of driving — which is what the law requires.

Marijuana DUIs and Medical Marijuana Patients

Having a valid Arizona medical marijuana card does not protect you from a marijuana DUI charge. The law applies equally to recreational and medical users. If you are impaired while driving, your card is not a defense.

Medical patients who use marijuana regularly may have higher baseline THC levels in their blood even when they are not impaired. That can complicate blood test results, and it is something a defense attorney can raise when challenging the prosecution’s interpretation of the evidence.

What About “Actual Physical Control”?

Arizona’s DUI law applies not just to actively driving, but to being in “actual physical control” of a vehicle. That means you can be arrested for a marijuana DUI while sitting in a parked car if the circumstances suggest you were or could be in control of the vehicle. Factors like whether the engine was running, which seat you were in, and where the keys were all matter.

Arizona recognizes a “shelter rule” defense for people who pulled over specifically to sleep off impairment and posed no threat to the public, but whether it applies depends heavily on the specific facts. Do not assume being parked makes you safe from a DUI charge.

Marijuana DUI Enforcement in Tempe

Tempe sits next to the ASU campus, has a busy nightlife scene along Mill Avenue, and hosts major events throughout the year. The Tempe Police Department is active with DUI enforcement, including saturation patrols and checkpoints,  especially on weekends and during peak seasons. Officers are trained to look for signs of drug impairment alongside alcohol impairment, and marijuana is commonly involved in DUI arrests in this area.

If you are arrested for a marijuana DUI in Tempe, your case will likely move through Tempe Municipal Court for misdemeanor charges, or Maricopa County Superior Court if the charge is a felony. Local prosecutors handle a high volume of these cases and are experienced with them. That is exactly why having a defense attorney who knows this court and how these cases are handled locally can make a real difference.

Charged With a Marijuana DUI in Tempe? Call Tyler Allen.

Marijuana DUI cases in Tempe, Arizona and the surrounding area are not straightforward. The science is contested, the law is nuanced, and the outcome depends heavily on the specific facts of your stop, your test results, and how the investigation was conducted. These are exactly the kinds of cases where an experienced defense attorney can find the angles that matter.

Tyler Allen at the Law Offices of T. M. Allen defends clients in Tempe and throughout Maricopa County against DUI charges, including marijuana DUIs. He will look closely at every part of your case,  the stop, the field tests, the DRE evaluation, and the blood results, and tell you honestly what your options are.

Do not wait. The sooner you have an attorney involved, the better your position. Reach out to the Law Offices of T. M. Allen today for a free consultation.