# Can You Be Convicted of Drug DUI in Arizona Just for Having Marijuana in Your System? What State v. Chacon Teaches Us
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**Meta Title:** Arizona Drug DUI & Marijuana Metabolites: State v. Chacon Explained | Gordon Thompson, DUI Attorney
**Meta Description:** An Arizona appeals court upheld a drug-DUI conviction based on trace THC, but rejected the metabolite-only theory. Phoenix DUI attorney Gordon Thompson breaks down what State v. Chacon means for your case.
**URL Slug:** /blog/arizona-drug-dui-thc-metabolite-chacon/
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## Quick Answer
In *State v. Chacon*, the Arizona Court of Appeals upheld a driver’s aggravated drug-DUI conviction — but not for the reason the state’s charging paperwork suggested. The court ruled that a **non-impairing marijuana byproduct alone (Carboxy-THC) cannot support a conviction** under Arizona’s “any drug or metabolite” DUI statute, A.R.S. § 28-1381(A)(3), following the Arizona Supreme Court’s decision in *State ex rel. Montgomery v. Harris*. However, the same court affirmed the conviction anyway because the driver’s blood also contained a trace, unreported amount of **actual THC** — and Arizona law criminalizes driving with *any* amount of an impairing drug in your body, regardless of quantity. If you’re facing a marijuana- or drug-related DUI charge in Arizona, the specific substance found in your blood test — not just the fact that “something” showed up — can decide the outcome of your case.
**Case:** *State v. Chacon*, No. 2 CA-CR 2014-0150 (Ariz. Ct. App. Div. Two, May 28, 2015)
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## The Facts: A Traffic Stop That Turned Into a Drug-DUI Case
A Pima County sheriff’s deputy saw Juan Chacon driving erratically at night — drifting toward the curb with a taillight out. Once stopped, the deputy noticed damage to the car, smelled alcohol, and watched Chacon struggle to get out of the vehicle and sway on his feet. Chacon had no license or ID, and refused field sobriety tests.
A search turned up a marijuana grinder in his pocket. A warrant-authorized blood draw later came back with three findings from the state crime lab:
– **Carboxy-THC** — a marijuana breakdown product that does *not* cause impairment
– **THC** — the actual psychoactive compound in marijuana, at 1.52 nanograms (below the lab’s normal reporting cutoff)
– **Benzoylecgonine (BE)** — a cocaine metabolite that also does not cause impairment
Chacon was indicted for aggravated DUI based on drugs in his system while his license was suspended — but the grand jury only heard testimony about the Carboxy-THC. The THC and BE results surfaced later, closer to trial.
## The Legal Issue: What Counts as a “Drug or Metabolite” Under A.R.S. § 28-1381(A)(3)?
Arizona’s (A)(3) DUI statute makes it illegal to drive with “any drug defined in § 13-3401 **or its metabolite**” in your body — no minimum amount, no impairment required, at least on its face. For years, this “zero tolerance” language meant prosecutors could charge people even when the only thing found was a metabolite that could linger in blood for weeks after someone last used marijuana.
That changed with the Arizona Supreme Court’s 2014 decision in *Harris*, which held that the “metabolite” language only reaches metabolites **capable of causing impairment**. A driver can’t be convicted just because a harmless leftover chemical from past marijuana use — like Carboxy-THC — shows up in a blood test.
*Chacon* asked the follow-up question *Harris* didn’t directly answer: what happens when the blood test also shows actual THC, just in a trace amount below the lab’s normal reporting threshold?
## How the Court Reasoned It Through
### Non-impairing metabolites can’t carry a conviction
The court agreed with Chacon on this point without much difficulty. Because the state’s own expert testified that neither Carboxy-THC nor BE (the cocaine metabolite) can cause impairment, the (A)(3) charge could not rest on those results alone — that’s exactly what *Harris* forbids.
### But trace THC is a different story
Here’s where the case turns. The court held that *Harris* actually cuts the other way when it comes to the drug itself, as opposed to a non-impairing metabolite. *Harris* recognized THC as the primary impairing substance in marijuana, and made clear that a driver violates (A)(3) “if they are discovered with any amount of THC or an impairing metabolite in their body” — regardless of whether they were actually impaired at the time, and regardless of quantity.
The crime lab’s criminalist testified that even a trace amount of THC “in and of itself, can be impairing on the human body.” Combined with the officers’ observations of poor driving, slurred speech, and the odor of intoxicants, the court found that was enough evidence to support the conviction — even though the amount was below the lab’s routine reporting cutoff.
### The state didn’t need a new indictment to use the THC and BE evidence
Chacon also argued his due process rights were violated because the grand jury only heard about Carboxy-THC, not the THC and BE results introduced at trial. The court disagreed, explaining that an indictment doesn’t have to spell out every piece of evidence or legal theory — only give the defendant enough notice to prepare a defense. Because Chacon’s lawyer learned about the THC and BE evidence nine days before trial and didn’t request a continuance or object on notice grounds at the time, the court found no due process violation.
### No Daubert hearing required for below-cutoff drug results
Chacon separately argued he was entitled to a *Daubert* hearing — a proceeding used to test whether scientific evidence is reliable enough to go to a jury — before the state could use the below-cutoff THC and BE numbers. The court rejected this too, distinguishing between challenges to a lab’s *methodology* (a true Daubert issue) and challenges to how much *weight* a jury should give test results near the edge of a lab’s reporting threshold (a jury question, not a gatekeeping question). Because Chacon’s real complaint was about the reliability of a low number, not the science behind the testing method, no hearing was required.
*Note: This is a memorandum decision, meaning it isn’t binding precedent in future Arizona cases. But it applies the Arizona Supreme Court’s binding rule from Harris to a common real-world fact pattern — drivers who test positive for both a spent marijuana byproduct and a small amount of the active drug — which makes the court’s reasoning useful for understanding how these cases actually get argued and decided in Arizona courtrooms.*
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## Does Arizona Require Proof of Actual Impairment for a Drug DUI?
No — not under A.R.S. § 28-1381(A)(3). This provision is a “zero tolerance” statute: if an impairing drug or its impairing metabolite is in your body while driving, you can be convicted regardless of whether you were actually impaired at that moment, and regardless of the amount found. This is different from Arizona’s standard alcohol DUI or “impaired to the slightest degree” theories, which do require some evidence of impairment. It’s also different from a charge based solely on a non-impairing byproduct like Carboxy-THC, which *Harris* and *Chacon* both say cannot support a conviction on its own.
## Can a Trace Amount of THC Below the Lab’s Reporting Cutoff Still Be Used Against You?
Yes, according to *Chacon*. Crime labs use “reporting cutoffs” for quality-control reasons — to make sure numbers reported across different instruments and technicians are reliable — not because amounts below that line are legally meaningless. If a criminalist testifies that even a below-cutoff amount is capable of causing impairment, that testimony can go to a jury, and the jury decides how much weight to give it.
## What’s the Difference Between a Metabolite and the Drug Itself in an Arizona DUI Case?
– **The drug itself** (e.g., THC, active cocaine) is generally treated as capable of causing impairment, and its mere presence — in any amount — can support an (A)(3) conviction.
– **A metabolite** is a breakdown product created after the body processes a drug. Some metabolites (like Carboxy-THC) no longer have any impairing effect and can linger in blood or urine long after use. Under *Harris*, non-impairing metabolites cannot, by themselves, support an (A)(3) conviction.
This distinction is exactly why the specific lab report in a drug-DUI case matters — not just whether “something” tested positive.
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## What This Means for You
If you’ve been charged with a drug-related DUI in Arizona — including an aggravated (felony) charge under § 28-1381(A)(3) — the lab report is where your defense starts, not where it ends. A few practical takeaways from *Chacon*:
– **A positive drug test is not automatically a guilty verdict.** What matters is *which* substance was found — a non-impairing metabolite alone should not support a conviction.
– **”Below the cutoff” doesn’t mean “off the table.”** Prosecutors can still use trace amounts if their expert is willing to testify those amounts can cause impairment — which means cross-examining that expert effectively is critical.
– **Late-disclosed evidence still needs to be challenged the right way, at the right time.** Chacon’s lawyer raised these issues, but the appellate court found the objections came too late or on the wrong legal theory. Timing and framing matter in drug-DUI defense.
– **Aggravated DUI charges carry mandatory prison exposure.** Because Chacon’s license was suspended at the time, this was charged as a felony under A.R.S. § 28-1383, not a misdemeanor. Understanding [DUI penalties in Arizona](https://www.gordonthompsonattorney.net/dui-penalties/) — including how aggravated charges differ from standard misdemeanor DUI — is a critical first step.
There is no one-size-fits-all outcome here. Every drug-DUI case depends on the specific lab report, the specific substance identified, and how the state intends to prove impairment (or argue it doesn’t have to). If you’re facing a drug or marijuana DUI charge anywhere in Arizona, it’s worth having someone who has actually litigated these metabolite and Daubert issues look at your test results before you decide how to proceed. Our [DUI defense strategies](https://www.gordonthompsonattorney.net/dui-defense/) page and [guide to Arizona misdemeanor DUIs](https://www.gordonthompsonattorney.net/guide-to-arizona-misdemeanors-duis/) go into more detail on how these cases are typically built and challenged, and our [case results](https://www.gordonthompsonattorney.net/dui-case-studies/) page shows examples of how these issues have played out for past clients.
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## Frequently Asked Questions
**Can I be convicted of DUI in Arizona just for having marijuana metabolites in my blood?**
Not if the only substance found is a non-impairing metabolite like Carboxy-THC. The Arizona Supreme Court held in *Harris* that the DUI statute’s “metabolite” language only covers metabolites capable of causing impairment. However, if actual THC (not just its non-impairing byproduct) is also found — even in a small amount — that can still support a conviction.
**Does the amount of THC in my blood matter for an Arizona drug DUI charge?**
Under A.R.S. § 28-1381(A)(3), no specific quantity is required by the statute itself. Arizona courts have treated the presence of any amount of an impairing drug as sufficient, provided the state’s expert can testify that the amount found is capable of causing impairment.
**Can prosecutors use drug test results that weren’t presented to the grand jury?**
Sometimes. An indictment generally doesn’t need to specify every theory or every piece of evidence the state plans to use — it needs to give you fair notice of the charge so you can defend against it. If new evidence surfaces before trial, the key legal questions become whether you got adequate notice and a fair opportunity to respond, not whether the grand jury heard every detail.
**What is a Daubert hearing, and can I get one to challenge my DUI blood test?**
A Daubert hearing lets a judge screen expert scientific testimony for reliability before it reaches a jury. Courts are not required to hold one in every case, and they typically deny requests that go to the *weight* of test results (like a number below a lab’s reporting cutoff) rather than to a real flaw in the *testing methodology* itself.
**What’s the difference between misdemeanor DUI and aggravated (felony) DUI in Arizona?**
Aggravated DUI applies when certain factors are present — such as driving on a suspended, revoked, or restricted license, having a minor under 15 in the vehicle, or a prior felony DUI. It’s charged as a felony under A.R.S. § 28-1383 and carries mandatory prison time, unlike standard misdemeanor DUI. See our [DUI penalties overview](https://www.gordonthompsonattorney.net/dui-penalties/) for a full breakdown.
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## Talk to an Arizona DUI Attorney About Your Drug Test Results
Drug-DUI cases built on lab reports and metabolite testimony are technical, and small distinctions — like the one between Carboxy-THC and THC — can be the difference between a dismissed charge and a felony conviction. Gordon Thompson has been defending DUI and criminal cases in Arizona since 1982, with more than 6,000 clients and 47 years of courtroom experience across Maricopa County, Pinal County, and Northern Arizona courts.
**Call or text (602) 467-3680 for a free consultation**, or [contact Gordon Thompson online](https://www.gordonthompsonattorney.net/contact-me/) to have your case — and your lab results — reviewed before your next court date.
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*This article discusses a memorandum decision of the Arizona Court of Appeals, which does not create binding legal precedent under Ariz. R. Sup. Ct. 111(c)(1). It is provided for general informational purposes only and does not constitute legal advice or create an attorney-client relationship. Every DUI case depends on its own facts and evidence. For advice about your specific situation, contact Gordon Thompson directly.*