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Breath Test Defense: Title 17 and Beyond
Breath test results are not infallible. California Code of Regulations Title 17 imposes strict requirements on breath testing — and any violation can suppress the result.
How a breathalyzer works
Breathalyzers measure ethanol in your breath and convert it to an estimated blood alcohol concentration (BAC) using a 2,100:1 ratio. This conversion is an approximation that varies between individuals and conditions.
Title 17 — the rulebook
California Code of Regulations Title 17 governs all chemical testing in DUI cases. Key requirements:
- 15-minute observation period: Continuous observation before the test
- Two breath samples within 0.02%: If samples differ by more than 0.02%, results are unreliable
- Calibration: Every 10 days or 150 tests
- Operator certification: Must be current
- Instrument maintenance: Records must be retained and producible
Common breath test defenses
- Burping or belching during observation
- GERD / acid reflux causing mouth alcohol
- Dental appliances trapping alcohol
- Recent use of mouthwash, breath spray, cough syrup
- Diabetes (acetone in breath)
- Low-carb diet (ketones in breath)
- Faulty calibration records
- Uncertified operator
Subpoena the records
An effective DUI defense requires subpoenaing all maintenance and calibration records for the specific instrument used. Often, the records reveal gaps or violations that justify excluding the test.
If breath test results are central to your case, contact our office for a free consultation.
Frequently Asked Questions
How accurate are DUI breathalyzer tests in California?
Breathalyzers have a ±0.02% margin of error and produce false positives from mouth alcohol, GERD, dental work, or recent drinking. Title 17 of the California Code of Regulations imposes strict procedural requirements; violations can suppress the result entirely.
What is the 15-minute observation period?
Title 17 requires the officer continuously observe the suspect for 15 minutes before the breath test to ensure no burping, vomiting, or anything in the mouth that could distort the reading. If observation is interrupted or shortened, the test result may be excluded.
Can mouth alcohol cause a false high breath test?
Yes. Alcohol from belching, regurgitation, dental appliances, or breath spray can produce readings 20–50% higher than actual blood alcohol. This is why the observation period exists.
How often must California breathalyzers be calibrated?
Title 17 requires calibration accuracy checks every 10 days or 150 tests, whichever comes first. Maintenance records must be available — and missing or late records can be grounds to exclude the test.
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