GERD, Acid Reflux, and Heartburn -- Medical DUI Defenses

California DUI breath testing contains an inherent margin of error. This can be especially true in people suffering from gastroesophageal reflux disease (GERD), acid reflux, or heartburn.

These medical conditions occur when stomach acid flows back into the esophagus -- the muscular “food pipe” that connects the stomach with the throat.1 This “backwash” is known as “reflux.” During reflux, the contents of the stomach may flow back into the esophagus, as well.

While reflux generally affects the esophagus, it can also carry stomach contents all the way into the mouth. When this happens after you drink alcohol, it creates a serious problem for DUI breath testing machines.

If you are experiencing reflux when you exhale into a DUI breath testing device, regurgitated alcohol from the stomach will mix with alcohol from the lungs.  This will usually lead to a falsely high reading of blood alcohol content (BAC).


To help you understand how reflux can “trick” California DUI breath testing devices, our DUI defense attorneys discuss the following, below:

  1. The science behind DUI breath tests
  2. How reflux can add extra alcohol to a breath sample
  3. How regurgitated alcohol “contaminates” DUI breath testing results

You may also find helpful information in our related articles: California DUI breath testing is subject to a wide variety of errors; Title 17 requirements for collecting, storing, and analyzing California DUI chemical test data; How low-carbohydrate / high-protein diets can "trick" DUI breath testing instruments; "Mouth alcohol" as a DUI defense; "rising blood alcohol" as a DUI defense; and, 20 ways to beat a California DUI.

1.  The science behind DUI breath tests

Most of the alcohol from alcoholic drinks (ethanol) is absorbed in your stomach and small intestine.  From there, it passes directly into your bloodstream.2

A small amount of alcohol, however, is excreted from the bloodstream into the breath.3 DUI breath testing devices measure this alcohol and mathematically convert it into an equivalent amount of blood alcohol.4


However, unlike California DUI blood tests -- which directly measure the amount of alcohol in your blood -- DUI breath tests only approximate BAC.5 Therefore, California DUI breath tests contain an inherent margin of error, even under the best conditions.

2.  How reflux can add extra alcohol to a breath sample

Many people experience acid reflux and heartburn from time to time. When reflux becomes chronic, it is known as gastroesophageal reflux disease (GERD).

Whether chronic or occasional, however, the mechanism of reflux is the same.

In normal digestion, the lower esophageal sphincter (LES) opens to allow food to pass into the stomach.  After eating, the LES closes to prevent stomach contents from flowing back into the esophagus.


If the LES doesn't close all the way… or if it opens too often… stomach acid and contents can flow back up into your esophagus, and even your mouth.6

If this happens… and your stomach contents include alcohol…the regurgitated “mouth alcohol” can falsely inflate the results of a DUI breath test.

3.  How regurgitated alcohol “contaminates” DUI breath testing results

When we exhale, air emerges in the following order:

  1. from the mouth and/or nose, then
  2. from the throat and upper airway, and finally
  3. from the lungs.

DUI breath testing devices are designed to measure the alcohol in “deep lung air” (also called “alveolar” air).  This is the air closest to your blood supply.  It is considered by law enforcement the best for approximating the amount of alcohol in your blood.7

A problem can occur, however, when there is unabsorbed alcohol in the mouth.  This “mouth alcohol” can fool DUI breath machines by combining with the alcohol from deep lung air.8

Prosecutors claim that modern DUI breath testing equipment is sensitive enough to distinguish mouth alcohol from deep lung air.9 However, tests have shown that this simply isn't always so.10

Most mouth alcohol evaporates within 15 minutes. This is why Title 17 of the California Code of Regulations requires that law enforcement continually observe you for 15 minutes before administering a DUI breath test.11

The idea is that by continuously observing you, the test operator can visually ensure that during this time no alcohol is added to your mouth from:

  • ingested sources (such as alcoholic drinks or mouthwashes containing alcohol), or
  • regurgitated sources (such as vomiting or belching).

However, as Victorville, California DUI attorney Michael Scafiddi12 explains:

"Regurgitation caused by GERD, acid reflux, and/or heartburn isn't always apparent to an onlooker.  So even if the officer honestly believes you didn't burp, belch, or regurgitate during the observation period, he or she may simply have been unaware that you did.”


GERD is an under-diagnosed condition.  If left untreated, it can lead to esophageal erosion and even cancer. Your doctor can perform tests to determine if you suffer from GERD.

But even if you don't have GERD, you may still experience periodic reflux and heartburn. A good California DUI defense attorney will conduct a thorough interview to see if reflux might have caused a falsely high BAC reading on your DUI breath test.

If it did, your attorney -- with the help of a DUI expert witness -- will explain the science of DUI testing to the prosecutor… and, if necessary, to the judge and jury.

Hundreds of GERD, acid reflux and heartburn sufferers are wrongly arrested for DUI each year.  If you think you might be one of them, you don't have to suffer alone.

Call us for help…


For more information about California's DUI laws, or to discuss your case confidentially with one of our DUI defense attorneys, please don't hesitate to contact us at Shouse Law Group. Our California criminal law offices are located in and around Los Angeles, Orange County, San Diego, Riverside, San Bernardino, Ventura, San Jose, Oakland, the San Francisco Bay area, and several nearby cities.

Additionally, our Nevada DUI defense attorneys represent clients accused of violating Nevada’s DUI laws. For more information, we invite you to contact our local attorneys at one of our Nevada law offices, located in Reno and Las Vegas.

Legal References

1 See Mayo Clinic, GERD: Definition.

2, How is Alcohol Metabolized?

3 Same.

4 The American Association for Justice, Challenging the DUI Breath Test: Breath Testing Basics and Factors Affecting the Test.

5 Michael P. Hlastala, The alcohol breath test—a review, Journal of Applied Physiology, Vol. 84 no. 401-408, published February 1, 1998.

6 WebMD, What Is Acid Reflux Disease? (“Common symptoms of acid reflux are: Heartburn: a burning pain or discomfort that may move from your stomach to your abdomen or chest, or even up into your throat, and Regurgitation: a sour or bitter-tasting acid backing up into your throat or mouth”).

7 The American Association for Justice, endnote 4.

8 Same.

9 Jeanne Swartz, Breath Testing for Prosecutors: Targeting Hardcore Impaired Drivers, American Prosecutors Research Institute.

10 The American Association for Justice, endnote 4.

11 Title 17 California Code of Regulations, Section 1219.3.

12 Victorville, California DUI attorney Michael Scafiddi is a former DUI enforcement officer who has over 20 years of experience dealing with drunk driving arrests and cases. He defends clients accused of DUI throughout the high desert, including Victorville, Barstow, Baker, Hesperia, Apple Valley and Adelanto.

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