Most people assume breathalyzer results are foolproof scientific evidence. You blow into a machine, it spits out a number, and that number represents your actual blood alcohol content. Case closed, right? Not even close.
Breathalyzers are mechanical devices operated by humans, and both the machines and the people using them make mistakes. Understanding how these devices work—and fail—is crucial for anyone facing OUI charges in Massachusetts.
The Mouth Alcohol Problem
Breathalyzers are designed to measure alcohol in your deep lung air, which correlates with blood alcohol content. But they can’t distinguish between alcohol from your lungs and alcohol in your mouth. This is called “mouth alcohol,” and it causes falsely high readings.
Recent drinks are an obvious source. If you had a beer 10 minutes before the test, alcohol residue in your mouth can trigger an elevated reading that has nothing to do with your actual blood alcohol level. The test should be delayed 15-20 minutes after drinking, but officers don’t always wait.
Other sources include mouthwash, breath spray, medication, and even some medical conditions like acid reflux or GERD. People with these conditions can have stomach alcohol come up into their mouth, contaminating the sample.
The Absorption Phase Factor
Here’s something critical that juries often don’t understand: your blood alcohol content changes over time. When you drink, alcohol enters your stomach, gets absorbed into your bloodstream, and eventually gets eliminated by your liver.
During the absorption phase—which can last 30 to 90 minutes after your last drink—your BAC is rising. You might be pulled over at 9 PM with a .06% BAC, but by the time you take the breath test at 10 PM, it reads .10%. Were you actually impaired while driving? Maybe not. Your BAC was still climbing.
This matters legally because the prosecution must prove you were over .08% while operating the vehicle, not an hour later at the police station. The timeline becomes crucial, and an experienced attorney can challenge whether the breath test accurately reflects your BAC at the time of driving.
Calibration and Maintenance Issues
Breathalyzers require regular calibration and maintenance. If the device hasn’t been properly maintained, its results can’t be trusted. Defense attorneys routinely request maintenance records for the specific device used in their client’s test.
Sometimes these records reveal gaps in calibration, repairs that weren’t properly completed, or evidence that the device was giving inconsistent readings. Any of these issues can be grounds to challenge the breath test results or even have them excluded from evidence entirely.
Software and Technology Errors
Modern breathalyzers are essentially computers, and like any computer, they can malfunction. Software glitches, electrical interference, and environmental factors like temperature can affect readings.
In recent years, several breathalyzer models have faced widespread challenges over software errors. Massachusetts actually threw out thousands of breath test results from 2011-2019 because of problems with how the devices were being calibrated and how results were being certified.
Human Error in Administration
Even a perfectly functioning breathalyzer produces unreliable results if not used correctly. Officers must follow specific protocols: observing the suspect for 15 minutes before testing, ensuring the suspect doesn’t eat, drink, smoke, or vomit during that time, and administering the test according to precise guidelines.
Shortcuts or mistakes in this process contaminate the results. Maybe the officer got distracted and didn’t actually observe for the full 15 minutes. Maybe the suspect burped or vomited during the observation period but it wasn’t noted. These procedural errors create reasonable doubt about the results’ accuracy.
A Number Isn’t a Conviction
The key takeaway is that a breath test result—even one over .08%—isn’t the end of your case. It’s one piece of evidence that must be evaluated for accuracy, reliability, and legal admissibility. Numerous factors can produce false positives, and an experienced OUI defense attorney knows how to identify and challenge these issues.
Contact Milligan & Higgins for a free consultation or second opinion. Please send us an email: Intake@milliganhiggins.com or call 781-878-1231.
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