How The Mouth Alcohol Defense Can Help Win A DUI Case

DUI Defense Guide

In this guide, I am going to explain how alcohol that is trapped in your mouth can provide a falsely high reading on a breathalyzer test.


If you indeed did have mouth alcohol we can use that in our defense.

Let’s get started…..

But first, watch this video to understand which medical conditions can contribute to alcohol being trapped in your mouth.

How Does Alcohol Trapped In Your Mouth Cause A False BAC Reading?

A breathalyzer is designed to capture a deep lung sample of your breath so as to presumably register an accurate reading of your blood alcohol concentration.

However, the breathalyzer will also pick up any residual mouth alcohol. This is alcohol from an alcoholic beverage or from some other source that can remain in your mouth or throat for up to 15 minutes.

What Other Sources Can Cause Mouth Alcohol?

Mouth alcohol can come from numerous sources including:

  • Dentures or dental work1.
  • Gerd
  • Mouthwash or Breath Sprays
  • Chewing tobacco
  • Certain medications

Let’s take a look at these cases individually.

How Do Dentures or Dental Work Mouth Alcohol?

If you have braces or dentures it is very possible that any alcohol you drank becomes trapped in the dental work2.

How Do Mouthwash And Breath Sprays Cause Mouth Alcohol?

Some mouthwashes and breath sprays such as Listerin contain alcohol.

Breath Spray

If you used any in the moments before being tested for your BAC, it can potentially cause a positive or high BAC result even though you drank no alcohol.

Additionally, chewing tobacco sometimes contains raw ethyl alcohol. This is the same type of alcohol found in wine, beer, and hard liquor.

When Can Mouth Alcohol Be Used As A DUI Defense?

The mouth alcohol defense can be a legitimate and effective one under some circumstances. However, it is only used in a DUI trial.

Prosecutors will not typically reduce DUI charges if the only defense presented is mouth alcohol.

So How Can Mouth Alcohol Defense Be Used……

Your defense attorney will need to introduce an expert to testify at trial that the result of the breath test was inaccurate due to mouth alcohol.

Mouth Alcohol Expert Testimony

How Does The Forensic Alcohol Expert Make That Determination?

The following is a non-exhaustive list the alcohol expert will consider:

  • The time of initial contact with police and the breath test.
  • The individual health history of the defendant.
  • Any discrepancy between the readings on the breath test.
  • Maintenance records of the breath testing instruments.

Why Is the Time Between Initial Contact With Police And The Breath Test Important?

If there is an insufficient amount of time between the officers first contact and the breath test, there is a higher liklihood that any mouth alcohol has not beeen given enough time to dissipate.

15 minutes

This has been codified in the California code of regulations under title 17 as the 15 minute observation period.

Failure of the police officer to observe you for 15 minutes increases the likelihood of mouth alcohol3.

How Does Individual Health History Affect Mouth Alcohol?

Acid reflux includes a chronic condition called GERD, or gastroesophageal reflux disease which can cause mouth alcohol.

15 minutes

If there is alcohol in your stomach, then a GERD episode could potentially affect the breath test results and show a false high reading.

What Medication Will A Forensic Alcohol Expert Review?

There are a number of asthma medications that may raise a person’s BAC such as Salmeterol even though that person has not ingested any alcohol4.

These medications contain alcohol that under some circumstances might appear in a breath sample.

Why Does A Discrepancy Between BAC Readings Point To The Possibility Of Mouth Alcohol?

Any large variation of readings points to a likelihood that the sample is not based on deep lung air.

15 minutes
15 minutes

When the sample contains deep lung air you can expect to see consistency in the BAC numbers.

Why Are Maintenance Records Important?

The maintenance and calibration records will show if the machines have been properly maintained to make sure that the BAC tests are accurate.

In Closing….

The mouth alcohol defense may be employed by your attorney at a DUI trial with the help of an expert and may help you win a DUI case.

Next Steps If You Need Help

If you have been arrested and would like to learn more about how attorneys charge.

If you want to understand why its important to have an attorney represent you.

If you would like to discuss a pending case with an attorney contact the Aizman Law Firm at 818-351-9555 for a free confidential consultation.

Get Legal Help

Request A Free Consultation 818-351-9555 


  1. J Forensic Sci. 37(4); 999-1007 August 1992 []
  2. Caldwell and Grant, “A Study of Some Factors Affecting the Accuracy of the Breathalyzer,” 8 J Forensic Sci. 149 (1963 []
  3. California Code of Regulations, Title 17 []
  4. Patrick Harding, Breath Alcohol Specificity Study, Indiana University, 2010 []

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