Can You Get a DUI for THC Metabolites in Arizona? Harris & Chacon Explained

Can You Be Charged With DUI for THC Metabolites in Arizona? The Harris Rule, Explained Through State v. Chacon

In Arizona, you can be convicted of drug DUI for having active THC in your blood in any amount — but not for a marijuana metabolite that can’t actually impair you, like Carboxy-THC. That’s the rule the Arizona Supreme Court set in State ex rel. Montgomery v. Harris, and it’s the rule the Court of Appeals applied in State v. Chacon to uphold a conviction based on trace THC found below the crime lab’s normal reporting cutoff. If you’re facing a drug-DUI charge tied to a blood test, the specific substance the lab found, and whether it can cause impairment, may matter more than the number on the lab report.

Case: State v. Chacon, No. 2 CA-CR 2014-0150 (Ariz. Ct. App. Div. Two, May 28, 2015) — Superior Court No. CR20130963001, Pima County.
Note on precedent: This is an unpublished memorandum decision (“NOT FOR PUBLICATION,” Ariz. R. Sup. Ct. 111(c)(1)). It cannot generally be cited as binding precedent. It’s discussed here because it shows how Arizona courts apply the controlling, published rule from State ex rel. Montgomery v. Harris, 234 Ariz. 343, 322 P.3d 160 (2014).

What Happened in State v. Chacon?

A Pima County sheriff’s deputy stopped Juan Chacon after watching him drive erratically in a car with a damaged front end, a flat tire, and no working taillights. Deputies smelled alcohol, and Chacon had slurred speech, swayed on his feet, and had no driver’s license on him. He refused field sobriety tests and was arrested. A search turned up a marijuana grinder in his pocket, and a warrant-authorized blood draw later tested positive for three things: Carboxy-THC (a marijuana byproduct), active THC at 1.52 nanograms, and a cocaine metabolite — both below the state lab’s normal reporting cutoff.

Chacon was convicted at trial of aggravated drug DUI (because his license was suspended at the time) and drug paraphernalia possession, and sentenced to eight years. He appealed.

What Is the Legal Question in a THC-Metabolite DUI Case?

Arizona’s drug-DUI statute, A.R.S. § 28-1381(A)(3), makes it illegal to drive with “any drug” listed in A.R.S. § 13-3401 — or its metabolite — in your body. Marijuana and cocaine are both on that list. Read literally, that statute could apply to a metabolite that stays in your system for weeks after you’ve stopped using a drug, long after any impairment has worn off.

The Arizona Supreme Court confronted that problem in Harris. The question there: does “metabolite” in the statute mean any trace byproduct, or only a byproduct that can actually impair driving?

How Did the Courts Rule? Impairing vs. Non-Impairing Metabolites

In Harris, the Arizona Supreme Court held that the statute’s reference to a drug’s “metabolite” is limited to metabolites capable of causing impairment. A driver can’t be convicted based merely on a non-impairing metabolite that just shows past marijuana use.

Applying that rule in Chacon, the Court of Appeals agreed that Carboxy-THC and the cocaine metabolite found in Chacon’s blood couldn’t support a conviction on their own, because trial testimony established neither one causes impairment. But the court reached a different conclusion for the active THC in his blood:

Any amount counts. The court held Harris‘s language — that a driver violates (A)(3) if “any amount” of an impairing drug is in their body — was binding “judicial dictum,” not just a passing comment, because the Supreme Court used it deliberately to guide future cases.
Below-cutoff results still count. The state crime lab uses internal cutoffs to standardize reporting across instruments, not to define what’s legally significant. THC at 1.52 nanograms, below that cutoff, was still enough evidence to convict, especially combined with the lab analyst’s testimony that any detectable THC “can be impairing.”
The statute doesn’t require a threshold amount. The court noted § 28-1381(A)(3) says “any drug,” not “a certain quantity” of a drug.

The court also rejected Chacon’s separate arguments that his trial should have been delayed pending the Harris decision, that he was entitled to a Daubert hearing on the below-cutoff results, and that he lacked fair notice because the grand jury only heard about the Carboxy-THC finding. On the notice issue, the court found he’d learned about the THC and cocaine evidence nine days before trial, which was enough advance warning under Arizona law.

Is a Non-Impairing Metabolite Enough for a DUI Conviction in Arizona?

No. Under Harris, a non-impairing metabolite like Carboxy-THC — evidence only of past use, not current impairment — cannot by itself support a conviction under A.R.S. § 28-1381(A)(3). This matters because Carboxy-THC can show up in a blood test for days or weeks after someone last used marijuana.

Does a Low or Below-Cutoff THC Result Protect You From a DUI Charge?

Not on its own, at least according to Chacon. The court found that a state crime lab’s internal reporting cutoff is an administrative consistency measure, not a legal threshold, and that even a trace, below-cutoff THC result can support a conviction if the state’s expert testifies that any detectable amount can cause impairment. This is exactly the kind of technical, testimony-dependent distinction where the specific facts of your blood test and the qualifications of the analyst can make a real difference in how a case gets defended.

What This Means for You

If you’re facing a drug-DUI charge in Arizona tied to a blood test, don’t assume the case is decided by a single line on a lab report. What matters is:

Which substance was found. A non-impairing metabolite alone (like Carboxy-THC) is legally different from active THC or another impairing substance.
Whether the state can prove impairment-capability. This usually comes down to expert testimony, which can be challenged.
Whether you got fair notice. If the state adds a new substance or theory late in the case, that can raise due process and disclosure issues worth challenging.
Whether the underlying charge itself is aggravated. Chacon’s case was a felony because his license was already suspended — a factor that dramatically raises the stakes compared to a standard misdemeanor DUI.

These are fact-specific, evidence-heavy issues. The right defense strategy depends on the actual lab report, the analyst’s testimony, and the timeline of your case, not just the statute’s text.

Frequently Asked Questions

Can I be convicted of DUI in Arizona just for having a marijuana metabolite in my blood?

Not automatically. Under Harris, a metabolite only counts toward an (A)(3) drug-DUI charge if it’s capable of causing impairment. Carboxy-THC, which can linger in the body for weeks, does not cause impairment and can’t support a conviction by itself. Active THC, which can cause impairment, does count, regardless of the amount detected.

Does the amount of THC in my blood matter for an Arizona (A)(3) DUI charge?

Under current Arizona case law, no. Courts have held the statute is violated by “any amount” of an impairing drug or metabolite, not just amounts above a lab’s internal reporting cutoff. In Chacon, a result of just 1.52 nanograms of THC, below the state lab’s usual reporting threshold, was still enough to support a conviction.

Is State v. Chacon a binding precedent in Arizona?

No. It’s an unpublished memorandum decision marked “NOT FOR PUBLICATION,” and under Ariz. R. Sup. Ct. 111(c), it generally cannot be cited as precedent. It’s discussed here because it shows how Arizona courts apply the binding, published rule from State ex rel. Montgomery v. Harris.

What should I do if I’m charged with drug DUI in Arizona based on a blood test?

Talk to an Arizona DUI defense attorney before assuming the test result settles your case. Key questions: which specific substance and metabolite did the lab identify, is that substance capable of causing impairment under the Harris standard, how and when was the blood drawn, and did the state give you fair notice of every substance it’s relying on?

Talk to a Phoenix DUI Attorney About Your Blood Test Results

Gordon Thompson has practiced DUI and criminal defense exclusively in Arizona since 1982 — 47 years and more than 6,000 cases, all handled personally, not passed off to a paralegal or associate. If you’re facing a drug-DUI charge based on a blood test, he can review your lab results, the analyst’s methodology, and the timeline of your case to identify where it can be challenged.

Call or text (602) 467-3680 for a free consultation, or reach out online. All-inclusive flat fee, no hidden costs, no separate trial fee.

Can You Get a DUI for THC Metabolites in Arizona?