You blew a number. The officer acted like the case was over. It isn’t.
A breath test result feels like scientific proof — a machine spat out a number, and the number is over 0.08. But here’s what Jay Cohen learned earning the ACS-CHAL Forensic Lawyer-Scientist designation: the machine doesn’t measure your blood alcohol at all. It estimates it, from your breath, using assumptions about the “average” human body that may be flat wrong for yours.
How the Machine Guesses
Texas uses the Intoxilyzer 9000. It shines infrared light through your breath sample and infers a blood alcohol level using a fixed conversion ratio applied to everyone — regardless of your body temperature, breathing pattern, lung capacity, or medical conditions. When any of those vary from the machine’s built-in assumptions, the number moves. Usually up.
Ways a Breath Score Goes Wrong
- Mouth alcohol. A burp, reflux (GERD), or even dental work can put raw alcohol in your mouth — and a required 15-minute observation period exists precisely because of it. Officers skip or shortcut it all the time.
- Ketosis. Low-carb dieters and diabetics produce compounds that infrared analysis can misread as ethanol.
- Machine maintenance and calibration. Every Intoxilyzer has maintenance records, error logs, and reference-sample history. We subpoena all of it. A machine with a spotty logbook makes a lousy witness.
- Operator error. The operator needs a current certification and has to run the protocol exactly. “Mostly right” doesn’t cut it when your record is on the line.
- Radio-frequency interference and environmental factors in the testing room.
What We Do With All That
We don’t wave our hands and say “machines make mistakes.” We pull the data — maintenance logs, calibration records, the officer’s certification, the observation-period video — and we build the specific, documented reasons your number can’t be trusted. Then the State has a problem: its whole case was the number.
And remember — the legal question isn’t just the score. It’s whether you were intoxicated while driving. A breath test taken an hour after the stop measures the wrong moment.
Breath Test FAQs
How accurate are breathalyzers, really?
Even under ideal lab conditions, breath testing carries a recognized margin of error — and roadside conditions are never ideal. For a score near the legal limit, that margin alone can be the whole case.
I blew over 0.15. Is it hopeless?
No — higher scores raise the stakes (Class A misdemeanor territory for a first offense) but they don’t make the machine more trustworthy. Some of our best outcomes started with ugly numbers. Prior results do not guarantee a similar outcome.
Can I still fight the license suspension?
Yes — but only for 15 days. See our Houston ALR hearing lawyer page and don’t sit on it.
Put the Machine on Trial
The breath test is the State’s favorite witness — and it can be cross-examined. If your case involves a blood draw instead, see how we challenge DWI blood tests. Call our Houston DWI lawyer team at (713) 664-4000 for a free, confidential consult.
Reviewed by Jay Blass Cohen, founder of Blass Law PLLC — ACS-CHAL Forensic Lawyer-Scientist, certified Drug Recognition Expert, and SFST instructor, serving Houston since 2009. This article is general information, not legal advice for your situation. Prior results do not guarantee a similar outcome.