Many of the drivers who call me mention, almost in passing, that they have acid reflux or have been diagnosed with GERD. They rarely think it has anything to do with their DUI. It often has everything to do with it. I am Joel Brand, a California DUI defense attorney, and gastroesophageal reflux disease is one of the most overlooked reasons a breath test reads higher than a person's true blood alcohol level.
What GERD actually is
GERD, gastroesophageal reflux disease, is a chronic condition in which the ring of muscle at the top of your stomach does not close the way it should. Stomach contents travel back up the esophagus toward the throat and mouth. Most people know it as heartburn or acid reflux, but the reflux itself is the part that matters in a DUI case. If you have been drinking, the vapor rising out of your stomach carries alcohol with it, and that alcohol ends up in your mouth and upper airway. A hiatal hernia, where part of the stomach pushes up through the diaphragm, makes this worse and is common in people who have reflux.
Why reflux inflates a breath test
An evidentiary breath machine is built on an assumption: that the air you blow into it comes from deep in your lungs and reflects the alcohol circulating in your blood. It multiplies the alcohol it detects by a fixed ratio to estimate your blood alcohol concentration. That math only works if the sample is clean. When reflux pushes concentrated alcohol vapor from your stomach into your mouth, the machine captures that too and folds it into the number. Because the alcohol coming up from your stomach is far more concentrated than the trace amounts in deep lung air, even a small reflux episode can drive the reading well above your real level. This is the same mechanism behind the mouth alcohol defense, and GERD is one of its most common triggers.
Silent reflux is the real problem
People assume reflux means obvious heartburn, a loud burp, or a sour taste. Often it is none of those things. Silent reflux, sometimes called laryngopharyngeal reflux, moves acid and vapor up the throat without any symptom you would notice. You do not feel it. The officer does not see it. The machine has no way to flag it. Everyone in the room treats the number as reliable when a silent reflux event moments before the test may have contaminated the entire sample. That is what makes GERD so dangerous in a breath case: the contamination leaves no visible trace, yet it can be the difference between a passing and a failing result.
The 15-minute observation rule
California's Title 17 regulations require the officer to continuously watch you for about 15 minutes before an evidentiary breath test, to make sure you do not burp, regurgitate, eat, drink, or vomit. The entire point of that window is to let any mouth alcohol clear before the sample is taken. In practice, that observation is often not honored. The officer is filling out forms, walking you between rooms, or simply not watching your mouth. For someone with GERD, a single silent reflux episode during those minutes defeats the whole purpose of the rule, and if the observation was not truly continuous, the result is open to challenge. See my top DUI defenses for how this fits the bigger picture.
When the two samples disagree
Title 17 also requires two separate breath samples that must agree within a narrow tolerance. Reflux often reveals itself right here. The contaminated sample reads high, the cleaner one reads lower, and the gap between them is larger than a properly run test should ever produce. When I pull the breath records and see two numbers that do not match, GERD is one of the first explanations I look at. A meaningful disagreement between the two readings is a signal that something contaminated the sample.
Your medical history is evidence
If you have been diagnosed with GERD, take medication for reflux, or have simply seen a doctor about heartburn, that history can become real evidence in your case. Prescription records for proton pump inhibitors like omeprazole or esomeprazole, H2 blockers like famotidine, a record of over-the-counter antacid use, an endoscopy report, or a note from your doctor can all establish that you had a diagnosed, active condition at the time of your arrest. The better documented your reflux is, the more weight the argument carries. GERD is one of several medical conditions that can affect a DUI case, and it often overlaps with others I see, like the diabetes defense and the way that gastric surgery changes your BAC.
What GERD does not do
I want to be straight with you, because a defense only works when it is honest. GERD does not lower the amount of alcohol actually in your blood, and it does not make you sober if you were genuinely over the limit. What it does is make a breath number unreliable. That is a critical distinction, and it points to the cleaner test: a blood draw measures the alcohol in your blood directly and is not affected by reflux. If you gave a blood sample, or you can still get one, the weakness of the breath number matters even more. Where the facts support it, I push for the blood result or argue that the breath reading is too unreliable to prove the charge.
How this pairs with other defenses
The reflux argument rarely stands alone. It fits naturally with the calibration defense, where I question whether the machine was properly maintained and calibrated, and the rising BAC defense, where the timing of your last drink means your true level behind the wheel was lower than it was back at the station. Layered together, these arguments attack the reliability of the single number the prosecution is counting on.
Why it matters in court and at the DMV
This defense is just as live at the DMV hearing as it is in the criminal case, because the DMV relies on the same breath number to justify suspending your license. It applies directly to a VC 23152(b) charge, where the breath result is the entire case against you. If reflux made that number unreliable, the case built on it is unreliable too.
Think GERD affected your test? Let's find out.
Whether this applies to you depends on your medical records, the breath records, and exactly how your test was administered, which is what I review. Use the free case analysis on this page, or call me directly at (888) 271-6644. I answer my own phone, 24/7.
From the DUI blog: How GERD or Acid Reflux Can Cause a False High BAC Reading in California.