Quick answer: Probably not as much as you’ve been told. The “GERD defense” is popular on DUI lawyer websites, but the peer-reviewed research largely does not support it — controlled studies of subjects with severe reflux have generally found breath results tracking blood results closely. I’d rather tell you that than sell you a theory that falls apart under cross-examination. There is a narrow, honest version of the argument, and there are breath-test challenges that work far better. Both are below.
The Theory, and Why It Sounds Convincing
The argument goes like this. A breath machine assumes the air it samples came from deep in your lungs, where it has equilibrated with your blood. If you have gastroesophageal reflux disease, stomach contents can travel back up the esophagus — and if you’ve been drinking, those contents include undigested alcohol. That raw alcohol vapor reaches your mouth and throat, the machine samples it, and the reading reflects what’s in your stomach rather than what’s in your blood.
It’s a tidy story. It’s also the kind of story that gets repeated across hundreds of law firm websites, usually with a dramatic figure attached — that reflux can quadruple a reading, turning a 0.05 into a 0.20. You will find that claim in a lot of places. What you will rarely find attached to it is a citation.
What the Research Actually Found
Researchers have tested this directly, and the results are not what the defense bar tends to advertise.
- Kechagias and colleagues (1999) dosed subjects with severe, documented GERD and took paired blood and breath samples at short intervals over four hours. Their conclusion was blunt: the risk of alcohol erupting from the stomach and falsely raising a breath-alcohol result is highly improbable.
- Booker and Renfroe (2015), in the Journal of Forensic Sciences, ran fifteen subjects — ten of them with GERD — up past 0.150 and sampled blood and breath every twenty minutes for eight hours. They found close agreement between blood and breath values.
There’s also a design reason the effect is hard to produce. Evidential breath instruments are built to catch mouth alcohol — they watch the shape of the breath curve for the characteristic spike-and-drop that contamination produces, and Maryland’s testing protocol includes an observation period before the sample precisely so that mouth alcohol dissipates. The machines are not naive to this problem.
So when a lawyer tells you that acid reflux is going to win your case, be careful. A prosecutor with a competent toxicologist will have these studies in hand, and an argument that collapses on cross does more than fail — it costs you credibility on everything else you’re saying.
The Honest Version of the Argument
That said, the Booker and Renfroe authors did not close the door entirely, and the caveat they raised is the part worth knowing.
They suggested it may be possible for alcohol vapor to pass continuously from the stomach into the esophagus in a way that a machine would not flag as classic mouth alcohol. Where they did see contaminated samples, two things were true: it happened only when there was a high concentration of alcohol still sitting in the stomach, and the contamination was irreproducible in magnitude — the readings didn’t repeat consistently.
That last word is where the real argument lives. Maryland’s protocol takes duplicate breath samples, and they’re expected to agree within a tolerance. If your two samples disagree, that is a fact worth pressing hard — and if you have documented reflux and you were tested shortly after drinking on a full stomach, the disagreement acquires a plausible explanation. That’s a narrow, evidence-based argument. It is not “I have heartburn, therefore the machine is wrong.”
What Actually Beats a Breath Test
In my experience the breath cases that get won are won on procedure and paperwork, not on physiology. The questions worth asking:
- Was the observation period actually observed? The rule requires continuous observation before the sample so that mouth alcohol clears. Officers are busy; they fill out forms, walk away, take a call. If the observation didn’t really happen, the foundation for the result is shaky — and this is the single most productive line of attack.
- Was the instrument properly calibrated and maintained? Calibration and maintenance records are discoverable, and gaps in them are common.
- Was the operator certified and current? Certifications lapse.
- Do the duplicate samples agree? If they don’t, that’s a real problem for the State — and, as above, the place where a reflux argument might legitimately attach.
- Was your BAC still rising? The reading reflects the moment of the test, not the moment you were driving. If you were still absorbing, those are different numbers.
- Was the stop itself lawful? If the stop fails, everything downstream of it goes with it.
More on the machine itself in a word on the Maryland breath test, and on what to do with a bad reading in I failed the breath test — how can a lawyer help?
Related Questions
- A word on the Maryland breath test
- I failed the breath test — how can a lawyer help?
- Can you refuse a breathalyzer in Maryland?
- Standardized field sobriety tests in Maryland
- DUI vs. DWI in Maryland
Frequently Asked Questions
Will my GERD diagnosis get my DUI dismissed?
On its own, no — and any lawyer who promises otherwise is overselling. A documented reflux condition can be one supporting fact in a broader challenge, particularly where your duplicate breath samples disagree or the observation period wasn’t properly kept. It is not a standalone defense, and the published research is not on its side.
What about a big spicy meal right before the test?
Same answer, with the same caveat. Where researchers did see breath samples contaminated by stomach alcohol, it required a high concentration of alcohol still in the stomach — which is a genuinely different situation from ordinary heartburn. If you drank heavily on a full stomach and were tested soon after, the timing is worth examining. But “I’d eaten Thai food” is not a defense.
Doesn’t the machine detect mouth alcohol anyway?
That’s the design intent — instruments watch the breath curve for the signature of contamination, and the pre-test observation period exists to let mouth alcohol clear. This is exactly why the reflux theory underperforms in practice, and it’s also why the observation period is the better target: the safeguard only works if the officer actually followed it.
Why is this defense on so many lawyer websites, then?
Because it’s memorable and it gives an anxious client something to hope for. I’d rather be straight with you. There are real, effective ways to attack a Maryland breath test — the observation period, calibration records, operator certification, sample agreement, the lawfulness of the stop. Those are where cases are actually won, and that’s where I’d spend your money.
A Bad Breath Reading Is Not the End of Your Case
I’ve handled thousands of Maryland traffic and impaired-driving cases, and I’ll tell you honestly which arguments have legs and which ones don’t. A number on a machine is not a conviction — but the way to beat it is by taking apart how that number was produced, not by reaching for a theory the science doesn’t back. Let’s look at what actually happened in your case.
Toll-free: 1-877-566-2408. Hablamos Español. See how I defend Maryland DUI charges, or read the complete Maryland DUI & DWI guide.
Last updated: July 2026.