What Drugs Can Cause a DUI Charge in Utah

Utah Code 41-6a-502 does not limit a DUI to alcohol. Any substance that renders a driver incapable of safely operating a vehicle can support a charge, whether it is an illegal drug, a prescription medication, an over-the-counter product, or an inhalant. What most people never hear is that a second statute sits behind that one, and in many drug cases it is the statute that actually decides the outcome.

Those two statutes work differently, and the difference controls what the State has to prove and which defenses are available. The impairment statute at Utah Code 41-6a-502 requires proof that the substance rendered the driver incapable of safely operating a vehicle, with no numeric drug threshold and no equivalent of the .05 alcohol limit. The metabolite statute at Utah Code 41-6a-517 requires no impairment at all: driving a motor vehicle with any measurable controlled substance or its metabolite in the body is a class B misdemeanor on presence alone. Glen Neeley has defended drug-related DUI cases across Utah since 1998, and as a board certified DUI defense specialist and National College for DUI Defense faculty member he applies forensic toxicology training to both the impairment question and the statutory defenses written into Section 517.

Two Utah Statutes Decide a Drug DUI, Not One

Utah Code 41-6a-502 is the impairment statute. To convict under it, the State must prove the substance rendered the driver incapable of safely operating a vehicle. There is no per se drug threshold, no numeric line like the .05 alcohol limit, and presence in the body does not satisfy it on its own. Whether you were driving safely is squarely in play.

Utah Code 41-6a-517 is the metabolite statute, and it is the one most people have never heard of. In a case not amounting to a violation of Section 502, a person may not operate or be in actual physical control of a motor vehicle with any measurable controlled substance or metabolite of a controlled substance in the body. Impairment is not an element. Presence is the offense, and a violation is a class B misdemeanor that still counts as a prior that can enhance a later DUI.

Section 517 is the prosecution's fallback. Where it cannot prove impairment, it can still charge on the toxicology result alone. Anyone who has been told that a positive test is not enough in Utah has been handed a half-truth that can cost them the case. The practical question in every drug DUI is whether the substance detected is a scheduled controlled substance. If it is, Section 517 exposure exists no matter how well you were driving. If it is not, as with most over-the-counter medications, the State is left to prove impairment under Section 502. That structural split is the same reason a drug DUI is built differently from an alcohol DUI.

The Defenses Written Into the Metabolite Statute

Because Section 517 does not require impairment, its defenses look different, and two of them are statutory rather than factual.

The carboxy-THC exclusion

Section 517(2)(b) provides that the offense does not apply to a person who has 11-nor-9-carboxy-tetrahydrocannabinol as the only controlled substance present in the body. That is the inactive marijuana metabolite, and it lingers for weeks after any psychoactive effect has ended. Where only the inactive metabolite is detected, the per se charge does not reach you at all.

The affirmative defenses

Section 517(3) makes it an affirmative defense that the controlled substance was involuntarily ingested, prescribed by a practitioner for the accused, cannabis in a medicinal dosage form used in accordance with Utah's medical cannabis provisions, or otherwise legally ingested. For a patient taking a prescribed medication, that defense is direct and statutory, which is considerably stronger than arguing tolerance and therapeutic levels.

One caution on cannabis. A physician's recommendation is not a prescription. A medical cannabis patient's defense runs through the medicinal-dosage-form provision, not the prescription provision, and it requires that the cannabis was used in accordance with the medical cannabis act, so card status, product form, and compliance all become central. Note also that Section 517 reaches a motor vehicle while Section 502 reaches any vehicle, a distinction that matters for bicycles and e-bikes.

Marijuana and THC

Marijuana is the most commonly detected drug in Utah DUI cases. THC impairs coordination, reaction time, and judgment during acute intoxication, but THC and its metabolites stay detectable long after those effects end, and regular users may test positive weeks after last use.

The critical distinction is between active delta-9 THC and the inactive carboxy-THC metabolite. Active THC concentrations drop quickly and often become undetectable in blood within hours, so a draw taken well after the stop may reflect residual metabolite rather than active intoxication. Utah wrote that distinction into the statute: where carboxy-THC is the only controlled substance present, Section 517(2)(b) excludes the case from the per se offense and leaves the State to prove actual impairment under Section 502.

Where active THC is present, the analysis shifts. Utah has no nanogram threshold for THC, so the impairment question turns on the observed driving, the officer's observations, and the pharmacology. For medical cannabis patients the Section 517(3) defense applies where its requirements are met, but no card protects against an impairment charge if the State can prove incapability of safe operation.

Prescription Opioids and Pain Medications

Hydrocodone, oxycodone, morphine, and fentanyl are scheduled controlled substances. That means a patient taking them exactly as prescribed can face a Section 517 charge on presence alone, and it also means the Section 517(3) prescription defense applies directly.

Under the impairment statute the analysis is different. Utah does not exempt prescription medications, and a valid prescription is not a defense to Section 502 if the medication actually rendered the driver incapable of safe operation. Here the tolerance argument does real work: patients on a stable dose for an extended period often function normally at concentrations that would impair a first-time user, and impairing effects are most pronounced when a medication is started or a dose is increased.

We build these defenses from medical records, pharmacy fill history, dosage instructions, and, where warranted, treating physician or pharmacology expert testimony on expected concentrations at therapeutic doses. That documentation does double duty, establishing the statutory defense under Section 517 and supporting the impairment defense under Section 502. It is the same evidence that anchors prescription medication DUI cases.

Benzodiazepines and Anti-Anxiety Medications

Alprazolam, diazepam, lorazepam, and clonazepam are scheduled controlled substances, so the same two-track analysis applies: Section 517 exposure on presence, with the prescription defense available, alongside the Section 502 impairment question.

These cases turn on timing. Elimination half-lives vary widely, with alprazolam clearing relatively quickly while diazepam has active metabolites detectable for days, so a positive result may reflect a dose taken the previous evening rather than anything relevant to the time of driving. Under Section 502 that is a strong argument. Under Section 517 it is not, which is precisely why the prescription defense matters so much for these clients.

Combining benzodiazepines with alcohol produces synergistic impairment beyond either substance alone, and these cases are prosecuted aggressively. A result of .05 or higher combined with any measurable controlled substance also makes the offense an extreme DUI under Utah Code 41-6a-501(1)(f), which raises the mandatory jail minimum and, since January 1, 2026, carries a mandatory interdicted person designation.

Stimulants: Methamphetamine, Cocaine, and Prescription Amphetamines

Methamphetamine and cocaine are scheduled controlled substances with no lawful prescription for the forms usually encountered, so Section 517 exposure is direct and the statutory defenses generally do not apply. These cases also frequently involve a separate drug possession charge, and Section 517 expressly contemplates conviction and sentencing under both the metabolite statute and the applicable possession offense.

Prescription amphetamines such as Adderall, Vyvanse, and similar ADHD medications are also scheduled, so a patient faces Section 517 exposure but has the prescription defense available under Section 517(3).

On the impairment side, officers read alertness, agitation, rapid speech, dilated pupils, and elevated heart rate as signs of impairment. A patient taking a prescribed stimulant as directed can show exactly those physiological signs, so the defense has to separate therapeutic effect from impairment. Methamphetamine cases often add extended sleep deprivation, which impairs on its own and complicates the causal attribution for both sides.

Over-the-Counter Medications and Legal Substances

This category works differently, and the difference favors the client. Diphenhydramine (Benadryl and many sleep aids), dextromethorphan (cough suppressants), and pseudoephedrine (decongestants) are generally not scheduled controlled substances, so Section 517 does not reach them. The State must proceed under the impairment statute and prove that the substance rendered the driver incapable of safely operating a vehicle.

That is a meaningfully better position. These cases rest heavily on officer observations rather than toxicology, and standard toxicology panels frequently do not test for over-the-counter compounds at all, which can leave the prosecution without objective support for its theory. Inhalants, including compressed air dusters and similar household products, produce rapid but short-lived intoxication and are prosecuted under the impairment statute on the same terms.

The broader point holds: the legal status of a substance does not immunize a driver. But whether the substance is scheduled decides which statute applies, and that decides what the State must prove.

Challenging Drug Recognition Expert Evaluations

When there is no breath number to rely on, drug cases usually bring in a Drug Recognition Expert. The evaluation follows a 12-step protocol in which the officer sorts the suspected substance into one of seven drug categories, such as central nervous system depressants, stimulants, hallucinogens, and narcotic analgesics, based on physiological observations.

The protocol depends on subjective judgment at multiple points, and validation research has documented meaningful error rates in category identification. Medical conditions including diabetes, neurological disorders, head injury, fatigue, and mental health conditions can produce signs that mimic drug impairment.

We challenge these evaluations step by step: whether the protocol was actually followed, whether the conclusions match the objective data collected, whether the blood draw and laboratory testing corroborates the category the officer identified, and whether non-drug explanations account for the observations. Where independent toxicology or pharmacology testimony can establish reasonable doubt, we retain it.

Protecting Your Rights in a Drug DUI Investigation

You have the right to remain silent beyond providing identification. You are not required to tell an officer what you took, when you took it, or whether you have a prescription, and volunteering that information often supplies the very element the State would otherwise struggle to prove.

Utah's implied consent provisions attach consequences to refusal. A first refusal carries an 18-month license revocation, a refusal with a qualifying prior offense within ten years carries 36 months, and for drivers under 21 the revocation runs until age 21 or two years, whichever is longer. Whether or not you consent, the basis for the request, the way it was made, and the collection procedure all present potential defense issues under Utah's implied consent law.

The Driver License Division case runs on its own track, separate from the criminal charge, and the hearing must be requested within 10 calendar days of the arrest. Do not let that 10-day hearing deadline pass while you wait for a court date.

Utah Drug DUI Questions

Talk to Glen Neeley About a Utah Drug DUI Charge

Free confidential consultation, available 24/7, statewide in Utah. Bring the toxicology report and any prescription or medical cannabis records, and you will get a direct read on which statute you actually face and where the State's proof is weak.