I am Joel Brand, a California DUI defense attorney, and in this post I want to talk about something that gets overlooked far too often after a DUI arrest: the connection between gastroesophageal reflux disease, commonly called GERD, and an inflated breath test result. If you have acid reflux and you were just arrested for DUI, this information could be important to your defense.
How Breath Testing Is Supposed to Work
A breath testing machine does not measure alcohol in your blood directly. It measures alcohol in the air that comes from your deep lung tissue and then calculates what your blood alcohol concentration, or BAC, must be. That calculation depends on one key assumption: the only alcohol vapor in your breath comes from your lungs. When that assumption breaks down, the number the machine prints out may not match reality. You can read more about the science behind this in the library article on the mouth alcohol defense to a DUI.
What GERD and Acid Reflux Actually Do
When you have GERD, stomach contents, including stomach gases that contain alcohol if you have been drinking, can travel back up your esophagus and into your mouth and throat. This is called regurgitation or reflux. Even a small, silent episode of reflux, one you may not even feel, can deposit alcohol vapor from your stomach directly into your mouth and upper airway right before or during the breath test. The machine cannot distinguish between lung air and stomach air. It captures all of it, adds it together, and reports a single number. That number can be significantly higher than what a blood test would show.
The Science Behind the Inflation
Breath machines use a partition ratio, a fixed mathematical conversion factor, to translate breath alcohol into estimated blood alcohol. That ratio assumes a stable relationship between the two. Stomach alcohol that leaks into the mouth bypasses the lungs entirely and is not subject to that ratio in the way the machine expects. The result is a reading that can overstate your true BAC. This is related to, but distinct from, other instrument accuracy issues you can read about in the article on the bad calibration defense to a DUI.
Why Officers Are Supposed to Watch for This
California's breath testing protocols require the officer to observe you for at least fifteen minutes before the test. The purpose of that observation period is partly to watch for any belching, burping, vomiting, or regurgitation that could contaminate the sample. If the officer missed a reflux episode, did not document it, or did not restart the observation period after one occurred, that is a procedural failure. Officers make procedural mistakes more often than people realize. You can see common examples in the article on common mistakes police make at a DUI stop.
Silent Reflux Is the Hidden Problem
One of the most difficult aspects of this issue is that GERD episodes are often silent. You do not burp loudly or vomit. Stomach acid and vapor simply drift upward without any obvious sign. The officer watching you may see nothing unusual. You may feel nothing unusual. But the contamination still happens. This means neither the officer nor the breath machine has any warning that the sample is compromised. The machine produces a confident-looking number, and everyone moves forward as though that number is reliable.
How a Documented Medical History Can Help
If you have been diagnosed with GERD, take prescription medication for acid reflux, or have visited a doctor about reflux symptoms, that medical history becomes potentially relevant evidence. Prescription records, doctor notes, and pharmacy records can establish that you had a diagnosed condition at the time of the arrest. The stronger and more documented your history, the more weight this argument can carry. This is one of several medical conditions that can affect a DUI case, and the article on that page explains the broader landscape.
This Is Not a Magic Defense, But It Is a Legitimate One
I want to be honest with you. Raising GERD as a factor in your case does not automatically eliminate the breath test result or guarantee any particular outcome. California prosecutors are aware of this defense, and they will argue that the observation period and the machine's design adequately account for it. What this argument does is give your attorney a factual basis to challenge the reliability of the test number, to request a closer look at the machine's calibration logs and maintenance records, and to present expert testimony if the case goes to trial. You can learn more about how trial challenges to breath evidence work in the article on what to expect at your DUI trial.
Blood Testing as a Potential Comparison Point
If a blood sample was also taken in your case, your attorney can sometimes use the blood result to show a meaningful discrepancy compared to the breath result. A breath number that is noticeably higher than the blood draw taken shortly afterward is exactly the kind of gap that raises questions about breath test reliability. If you chose the blood test and are waiting on results, the article on post-arrest chemical test choices has useful background on how that process works.
What the DMV Proceedings Mean for This Issue
Your California DUI arrest triggers two separate proceedings: one in criminal court and one at the DMV. The DMV hearing focuses narrowly on whether you were driving with a BAC at or above 0.08 percent. The reliability of the breath test number is directly relevant to that question. An attorney who handles the DMV hearing can introduce evidence about your GERD and challenge the test result there as well. You can read about the DMV process in the article on understanding the DMV hearing and how to prepare.
Steps to Take Right Now
If you have GERD or acid reflux and were just arrested for DUI in California, here is what I recommend. First, write down everything you remember about the night of the arrest, including whether you felt any reflux symptoms, ate a large meal, or took any reflux medication. Second, gather your medical records and prescription history related to GERD as soon as you can. Third, do not discuss your symptoms or your medical history with anyone other than your attorney. Anything you say to friends, family, or on social media can find its way into the case. Fourth, contact a DUI defense attorney before your first court date. The timeline after a DUI arrest moves quickly, and the first ten days are critical for protecting your rights on both fronts.
Why a Detailed Case Review Matters Here
Every DUI case turns on its own specific facts. The brand and model of the breath machine used, the officer's training records, the length and quality of the observation period, your medical history, and whether a blood test was also administered all matter. A general overview of DUI defenses cannot tell you whether the GERD argument is strong in your particular case. That requires looking at the actual police report, the breath test logs, and the DS-367 form. You can learn more about what information that form contains in the article on DS-367 mistakes that can help your DUI case.
If you were just arrested for DUI in California and you have GERD or acid reflux, I want to look at your case. You can get a free written case analysis right here on this page. Call me directly at (888) 271-6644. I answer my own phone, 24/7. You can also read more from the DUI blog for additional guidance on what happens next.