Nail-Biting and the “Baker” Rule: A New Utah Case That Could Get a DUI Breath Test Thrown Out

Utah Court of Appeals • American Fork City v. Barbour, 2026 UT App 107 (decided July 16, 2026)

In a decision handed down this summer, the Utah Court of Appeals reversed a DUI conviction because the driver had been biting his fingernails during the fifteen minutes right before his breath test — and his lawyer never challenged the result. The court ordered a brand-new trial. It is the first Utah case to squarely hold that chewing your fingernails is “something,” not “nothing,” that a person puts in their mouth — which means the officer was required to restart the observation clock before testing.

If you are facing a Utah DUI that hinges on a breath test, this ruling matters. Here is what happened and why.

The fifteen-minute observation period, explained

Before the State can use an Intoxilyzer breath result against you in court, it has to lay a proper foundation. Under long-standing Utah law — State v. Vialpando, 2004 UT App 95 — the government must show three things: (1) a trained technician confirmed the machine was working correctly, (2) a qualified operator ran the test correctly, and (3) an officer watched the person for the full fifteen minutes immediately before the test to make sure nothing went into their mouth.

That third requirement is often called the Baker period, after an old case Utah adopted the rule from. The reason behind it is simple: alcohol lingering in the mouth — or anything burped, regurgitated, or introduced during those fifteen minutes — can throw off a breath reading and make it look higher than a person’s actual blood alcohol level. If something goes into the mouth during that window, the officer is supposed to start the fifteen-minute clock over.

What happened in Barbour

The driver was pulled over in American Fork and eventually taken to a second police station for a breath test after the first machine wasn’t working. The result came back at a .11. He was convicted of DUI at trial.

But the officer’s own body-camera footage told a different story. It showed the driver biting his nails more or less continuously for over two minutes during the observation period, stopping less than a minute before the test. The officer never restarted the clock. On cross-examination, he admitted he could “not recall” whether the driver had even put his hands to his mouth. And the officer never actually testified that he had complied with the observation rule at all.

Despite all of this, the driver’s trial attorney said he planned to file a motion to suppress the breath test — and then never filed it.

Why the conviction was reversed

The appeal was framed as an ineffective-assistance-of-counsel claim — the argument that the trial lawyer failed the client. The court agreed on both parts of that test:

• The lawyer performed deficiently. Suppressing the breath test was the driver’s only realistic path to acquittal, and there was no downside to trying — the worst-case result of a failed motion was a conviction, which is exactly what happened anyway. The court called it “a battle that competent counsel would have fought.”
• The failure was prejudicial. Without the breath test, the State would have had to prove the driver was actually impaired — not just that he had been drinking. Here, the driving was a single brief drift across the median, there was no odor of alcohol at the initial stop, no slurred speech, no stumbling, and the officer never even explained what “clues” he saw on the field sobriety tests. The court found a reasonable probability the jury would have acquitted had the breath test been excluded.

The court also rejected the City’s claim that the rule only covers obvious things like burping or dentures and doesn’t reach “every little brush of the face.” Under Utah law, if a testable substance goes into the mouth, the clock restarts — full stop.

What this means if you’re charged with a Utah DUI

A breath-test number looks authoritative, but it stands on a foundation that can crack. Anything that goes into the mouth during those critical fifteen minutes — nail-biting, burping, chewing gum or tobacco, dentures, acid reflux, regurgitation — can require the officer to start over. When that doesn’t happen, the result may be legally inadmissible.

And when a breath test is suppressed, the whole case can change. The State can no longer rely on a per-se alcohol number and instead has to prove actual impairment beyond a reasonable doubt — a much harder task, as Barbour shows. That is exactly why a careful, experienced review of the observation period, the machine records, and the body-camera footage is so important in every breath-test DUI.

This post discusses a recent appellate decision for general educational purposes and is not legal advice. Every case is different. American Fork City v. Barbour, 2026 UT App 107, is a non-final slip opinion subject to revision before official publication.