Drug DUI
You do not need alcohol to get a DUI in Arizona. Under A.R.S. 28-1381, driving while impaired to the slightest degree by any drug—whether it is marijuana, a prescription medication, or an illegal controlled substance—is a criminal offense. Drug DUI cases present unique challenges for both the prosecution and the defense because, unlike alcohol cases, there is no universally accepted threshold for impairment.
Marijuana DUI After Legalization
Recreational marijuana became legal in Arizona in 2020 under Proposition 207. Adults 21 and older can legally possess and consume marijuana in private settings. But Proposition 207 did not change the DUI laws. There is no legal limit for THC while driving.
Prosecutors rely on the “impaired to the slightest degree” standard combined with officer observations, field sobriety test performance, and blood testing. The problem with blood testing for marijuana is that THC metabolites can remain in a person’s blood for days or even weeks after use. The presence of metabolites does not prove impairment at the time of driving.
We had a client last year—a medical cardholder—who was pulled over for a tail light and ended up facing a drug DUI based on THC metabolites alone. No erratic driving, no failed field sobriety tests, nothing except a blood draw that showed old metabolites. We retained a pharmacology expert who testified about the disconnect between metabolite presence and real-time impairment, and the case was dismissed before trial.
This is a significant area of defense opportunity. An experienced DUI defense attorney can challenge the prosecution’s impairment evidence, question the reliability of the drug recognition evaluation, and present expert testimony on the pharmacology of THC.
Prescription Drug DUI
Taking your prescribed medication and then driving to work can, under Arizona law, result in a DUI charge if the medication affects your ability to drive. Medications commonly implicated include benzodiazepines like Xanax and Valium, sleep medications like Ambien and Lunesta, opioid pain medications, certain muscle relaxants, and some antihistamines.
Having a valid prescription is not a legal defense. The prescription authorizes you to possess and consume the medication. It does not authorize you to drive while impaired by it. However, the existence of a prescription is relevant context that a defense attorney can use to frame the case, particularly when the impairment evidence is thin.
Drug Recognition Evaluations
In drug DUI cases, officers sometimes call a Drug Recognition Expert (DRE) to perform a 12-step evaluation protocol designed to identify the category of drug causing impairment. The protocol is standardized by the International Association of Chiefs of Police and involves physical assessments, vital sign checks, and observations.
DRE evaluations are not infallible. The protocol depends heavily on the individual officer’s training, experience, and subjective interpretation. Defense attorneys frequently challenge DRE testimony by highlighting inconsistencies, questioning the officer’s qualifications, and presenting competing expert opinions on reliability.