Mouth Alcohol as a California DUI Defense


"Mouth alcohol" is residual alcohol that lingers in the mouth and leads to a falsely high result on a DUI breath test. This occurs because mouth alcohol masks the deep lung air that breath testing instruments are supposed to measure.1

Every day in California, innocent people are falsely charged with driving with a BAC of 0.08 or above under California Vehicle Code 23153(b) VC because of mouth alcohol. In these cases, mouth alcohol can play a significant role in a DUI defense strategy.

Below, our California DUI defense attorneys answer some frequently asked questions about mouth alcohol and California DUIs:

What causes mouth alcohol?

Mouth alcohol can be caused by any of the following:

  • Medical conditions like gastroesophageal reflux disease (GERD), acid reflux and heartburn,2
  • Medicines containing alcohol (such as Nyquil),
  • Chewing tobacco,
  • Mouthwashes or breath sprays containing alcohol, and
  • Dental work (like dentures) that traps food and liquid in the mouth. 
Chewing tobacco can produce mouth alcohol that, in turn, leads to a falsely high BAC measure.

The presence of any of these factors could mean that alcohol found in the mouth is not representative of the amount of alcohol that is actually in your blood. This in turns means that you can challenge the inaccurate results of your breath test and use the "mouth alcohol" defense to fight your California DUI charges.

Can I have "mouth alcohol" even if I didn't have anything to drink?

Absolutely. Because of mouth alcohol, it is possible to register a BAC over the legal limit--particularly if you are a commercial driver or a minor--even if you haven't had much or anything to drink.

As we discuss above, mouth alcohol can be caused by numerous things other than drinking alcoholic beverages. It can be caused by using mouthwash or alcohol-containing medicine, by chewing tobacco, by medical conditions such as acid reflux, and by dentures--among other things.

The prosecution claims that mouth alcohol quickly dissipates and so is not a valid legal defense. Is this true?

Mouth alcohol can dissipate fairly quickly--but this is most often the case in one of the following two scenarios:

  1. A DUI suspect drinks alcohol right before a breath test, or
  2. A DUI suspect who has been drinking "burps" up a small amount of mouth alcohol.

 In either of these scenarios, mouth alcohol is limited and absorbs quickly into the membranes.

Some forms of mouth alcohol dissipate quickly--but not all do.

But this "excuse" does not diminish the value of mouth alcohol as a California DUI defense in any of the other circumstances we discuss above, such as mouth alcohol from GERD, acid reflux, medicines, mouthwash, etc.

And even in one of those two scenarios where mouth alcohol is likely to quickly dissipate, there is still a chance that mouth alcohol led to you being unfairly charged with DUI--particularly if the police officer did not conduct a proper "15 minute observation period."

What is the connection between mouth alcohol and the "15 minute observation period" in California DUI law?

Under Title 17 of the California Code of Regulations, an officer who arrests you for DUI is required to observe you for fifteen (15) continuous minutes before administering a DUI breath test.3

This is so s/he can be sure that you did not drink alcohol, use mouthwash, burp, regurgitate or do anything else that might cause mouth alcohol to taint your BAC breath test results.

According to Pasadena DUI defense attorney John Murray4,

"California officers frequently fail to honor the 15-minute observation requirement. Many of them don't quite understand what it is for and may wait 15 minutes before a DUI test--but not actually observe the suspect during that time. Instead, they use the time to complete paperwork. And even when an officer does observe you for 15 minutes, s/he might miss a burp or regurgitation that could lead to mouth alcohol."

Call us for help . . . 


If you or a loved one is charged with California DUI and you would like to know more about mouth alcohol, we invite you to contact us at Shouse Law Group. We can provide a free consultation in office or by phone.

We have local offices in Los Angeles, the San Fernando Valley, Pasadena, Long Beach, Orange County, Ventura, San Bernardino, Rancho Cucamonga, Riverside, San Diego, Sacramento, Oakland, San Francisco, San Jose and throughout California.

Legal References:

  1. People v. McNeal (2009), 46 Cal.4th 1183, 1191. ("When a subject blows into a breath-testing machine, the device measures the amount of alcohol vapor expelled into alveolar spaces deep in the lungs [in theory, that is--in practice mouth alcohol can prevent this from happening].")
  2. American Medical Association's Committee on Medical Problems -- Manual for Chemical Tests for Intoxication (1959). ("True reactions with alcohol in expired breath from sources other than the alveolar air (eructation, regurgitation, vomiting) [i.e., mouth alcohol] will, of course, vitiate the breath alcohol results...")
  3. Title 17 of the California Code of Regulations, section 1219.3 -- Breath Collection [15-minute observation period to avoid false BAC results from mouth alcohol]. ("A breath sample shall be expired breath which is essentially alveolar in composition. The quantity of the [California DUI] breath sample shall be established by direct volumetric measurement. The breath sample shall be collected only after the subject has been under continuous observation for at least fifteen minutes prior to collection of the breath sample, during which time the subject must not have ingested alcoholic beverages or other fluids, regurgitated, vomited, eaten, or smoked.")
  4. Pasadena DUI defense attorney John Murray is a leading expert in California DUI defense, including the use of mouth alcohol as a defense against DUI charges. He has extensive experience both in the court systems of Los Angeles County and Ventura County and in California DMV hearings.




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