"Mouth Alcohol" as a Nevada DUI Defense
A Las Vegas Drunk Driving Lawyer Explains the Law

young woman in blue shirt with one hand on stomach and the other over mouth

How “Mouth Alcohol” Can Lead to False Results on a Nevada DUI Breath Test

Nevada DUI breath tests rely on samples of “deep lung” air for accuracy.

But deep lung air passes through the throat and mouth when we blow into a breath testing device. If there is alcohol in the mouth for any reason, then even if little or none is present in the bloodstream, it can lead to a falsely high blood alcohol concentration (BAC) reading on a Nevada DUI breath test.

What causes mouth alcohol?

Mouth alcohol can come from many different sources besides alcoholic beverages. Some of these include (but are not limited to):

  • Medical conditions such as gastroesophageal reflux disease (GERD), acid reflux, heartburn, hiatal hernia or auto-brewery syndrome;
  • Vomiting or burping;
  • Medicines containing alcohol (for example, Nyquil);
  • Mouthwashes or breath sprays containing alcohol;
  • Chewing tobacco; and
  • Dental work (such as dentures) that traps food and liquid in the mouth.

Any of these sources – as well as recently consumed alcohol that has not yet entered your bloodstream – can mean that the alcohol in your mouth is not representative of the amount of alcohol that is actually in your blood.

This in turns means that you could be arrested for DUI – even if you didn't have a drink or you weren't drunk.

To better explain how mouth alcohol can cause elevated DUI breath test results, our Las Vegas and Reno, Nevada DUI defense lawyers discuss the following, below:

Intoxilyzer 8000 DUI breath testing device
The Intoxilyzer 8000 -- Nevada's evidentiary DUI breath testing device

1. Nevada DUI breath testing equipment

Nevada currently uses the Intoxilyzer 8000 for post-arrest evidentiary DUI breath tests. The Intoxilyzer 8000 uses infrared spectroscopy to analyze the amount of alcohol in a person's breath. It then mathematically converts this amount to a roughly equivalent BAC.

Normally, the higher your BAC the more alcohol that is present in your blood. Under Nevada DUI law, an adult is legally considered too drunk to drive if a reliable DUI breath test or DUI blood test shows a BAC of .08% or higher.

But if you have residual "mouth alcohol," your Nevada DUI breath test may  not be reliable.

2. How do Nevada DUI breath tests work?

Initially, when we consume alcohol, it is metabolized by the liver and excreted in the urine (and to a less extent, in our breath).

But the liver can only metabolize so much alcohol at one time. Whatever it can't metabolize remains in the blood until the liver catches up.[1] As our blood circulates, it carries this excess alcohol to our brain and other organs.[2]

Our smallest blood vessels are the capillaries, which are no more than 1/1000 of a millimeter thick. Some of these capillaries pass right under our lungs. Because they are so thin, gases are able to pass between them and the lungs.

When we breathe in, oxygen passes from our lungs to the capillaries. But the process works in reverse as well. Wastes – such as carbon dioxide and excess alcohol – pass from the capillaries into our lungs. When we exhale, these wastes exit our bodies.

The highest concentration of alcohol in the breath is in the alveoli. The alveoli are balloon-like sacs deep inside the lung which inflate when we inhale and deflate when we exhale. Because the alveoli sit right above the capillaries, “deep lung” air is the most representative of the amount of alcohol actually in your bloodstream. This is why you are asked to blow hard when you take a Nevada DUI breath test.

drawing of gas exhange between capillaries and lungs
Ethyl alcohol (ETOH) passing from the bloodstream to the lungs

3. How mouth alcohol can “contaminate” a Nevada DUI breath test

When we put anything with alcohol in our mouth, some of the alcohol is absorbed into the mucosal linings of the mouth. This “mouth alcohol” dissipates fairly quickly. This is why Nevada law requires a law enforcement officer to observe you for 15 minutes before beginning an evidentiary breath test. It is to make sure nothing with alcohol enters or exits your mouth.

If the officer does not properly observe the 15-minute period, your Nevada DUI breath test could produce an artificially inflated BAC. Potential sources of mouth alcohol include not just alcoholic drinks, but chewing tobacco and mouthwashes and cold medicines that contain alcohol.

Even consuming “one for the road” can lead to a falsely high BAC reading. It usually takes at least 30 minutes for consumed alcohol to fully enter your bloodstream. If you consumed an alcoholic drink right before you were pulled over, you might not actually have been drunk when you drove.

This leads to the Nevada DUI defense of “rising blood alcohol.” An experienced DUI lawyer and expert witness can often “back out” your DUI timeline to prove that your BAC was still “on the rise” when you were pulled over and, hence, that you were not drunk when you drove.

But there is also another source of potential mouth alcohol: your stomach contents. If there is alcohol in your stomach and your stomach contents enter your mouth, they might taint your breath sample.

Vomiting, partial regurgitation and burping are obvious ways that alcohol can move from your stomach to your mouth.

But certain medical conditions such as GERD or heartburn -- in which the lower esophageal sphincter (LES) does not close all the way -- can allow stomach contents to flow back into your mouth. There is also a rare condition known as “auto-brewery syndrome” or “gut fermentation syndrome” in which the body self-produces alcohol.

To read more about Nevada DUI and conditions affecting the LES, please see our article: How GERD and Heartburn Can “Trick” a Nevada DUI Breath Test.

To learn about auto-brewery syndrome, please see our article on Auto-Brewery Syndrome and Nevada DUI.

Charged with DUI in Las Vegas or Reno? Call us for help…

male receptionist wearing headset

If you were arrested for DUI in Nevada and think mouth alcohol or a medical condition may be to blame, we invite you to contact us for a free consultation.

Our caring Reno and Las Vegas, Nevada DUI attorneys understand the science behind Nevada DUI breath tests. We know that a high BAC on a Nevada DUI breath test doesn't necessarily mean you were drunk.

Call us at at 702-DEFENSE (702-333-3673) or fill out the form on this page to schedule your free consultation. We'll look at the facts of your case and help you figure out the best defense to your Nevada DUI charges.

If you were arrested in California, you may wish to see our article: Mouth Alcohol as a California DUI Defense.

Legal references:

  1. Alcohol Metabolism, National Institute on Alcohol Abuse and Alcoholism No. 35; PH 371 January 1997.
  2. How is Alcohol Metabolized? From MedicineNet.com.

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