A number on a breath test machine can feel like the final word in a driving under the influence case. That reading is still a piece of evidence, though, and evidence is open to question.
Grounds for breath test exclusion
Illinois law requires officers to follow specific steps before giving a breath test during a DUI stop. One of the most important rules involves the 20-minute observation period. During this time, the officer must watch you closely to confirm you do not eat, drink, vomit or place anything in your mouth that could alter the sample.
The officer who administers the breath test must also hold a valid Breath Analysis Operator license. If the state cannot show that the officer held current credentials, the breath test results may be excluded from evidence entirely.
Doubts about device accuracy
Breathalyzer devices need routine calibration and upkeep to produce dependable readings. The Illinois Administrative Code sets schedules and methods for testing these instruments, and agencies must keep detailed maintenance records.
The device itself must also appear on the list of approved instruments kept by the National Highway Traffic Safety Administration. If the device used during your stop had a known history of mechanical problems or software glitches, that record might become part of the defense.
Causes behind a false reading
The following medical conditions and outside variables can push a breathalyzer reading higher than your true blood alcohol concentration (BAC):
- Acid reflux or GERD, which may push stomach contents and mouth alcohol toward the device
- Diabetes or a low-carb diet, which might raise acetone that the machine reads as alcohol
- Mouthwash, breath spray or cold medicine made with alcohol
- Asthma inhalers and some other prescription medications
- Paint, solvent or gasoline fumes in the surrounding air
If any of these factors were present during your breath test, they may support a claim that the recorded BAC did not reflect your level of impairment. Defense attorneys can use medical records and expert testimony to show how these conditions applied in a given case.
Impact on your broader defense
Challenging a breathalyzer result goes beyond the criminal DUI case itself. Under Illinois’ implied consent law, you also face a statutory summary suspension if you fail or refuse a chemical test. You may petition the court to rescind this suspension within 90 days of the notice.
If a court limits or excludes the breathalyzer evidence, the state must rely on other signs of impairment. Without that numerical data, prosecutors often face a much steeper challenge in proving their case beyond a reasonable doubt.