You just got stopped for DUI. The officer asked you to perform some field sobriety tests and take the portable breathalyzer. You agreed. After all, you figured you only had a couple beers, the result would be well below the limit, and you’d be on your way home.

But to your surprise, the breathalyzer came back reading over .08. How could that happen?

First, let us clarify that you should not be stopped for DUI unless you gave the officer probable cause to stop you. Did you run a stop sign or were you weaving? After the officer approaches you, he or she should not ask you to perform field sobriety tests unless the officer has a reasonable belief that you are intoxicated. If you do not perform well, the officer can ask you to take the portable breathalyzer. Bear in mind that you have the right to refuse all tests.

The result from the portable breathalyzer cannot be used as evidence in court, but it can give the officer the probable cause necessary to arrest you and take you to the police station for the official breathalyzer. Again, you have the right to refuse.

But if you take the breathalyzer, can you get an exaggerated reading even though you drank very little? The answer is yes. Since the breathalyzer is measuring molecules of alcohol in your breath, even a little contamination can affect the result.
A variety of factors can cause a falsely high reading.

Did you rinse with alcohol or mouth wash? The alcohol remaining in your mouth can show up on the test. Did you regurgitate? Did you cut your mouth recently or do you suffer from mouth sores? A cut or sore can leak blood into your mouth. Since your stomach’s contents or your blood is denser than your breath, these substances in your mouth can increase the concentration of alcohol in your breath and throw off the reading. Are you diabetic or dieting? The resulting acetone can register falsely as alcohol. Do you work around solvents? Some of these chemicals can work their way into your blood stream and come out in your breath.

If any of the above factors apply, you may be able to challenge your DUI. An experienced DUI attorney can evaluate these and other defenses to your breathalyzer reading.

If you have questions about your DUI or other criminal or traffic matters, please contact Matt Keenan at 847-568-0160 or email

(Besides Skokie, Matt Keenan also serves the communities of Arlington Heights, Chicago, Deerfield, Des Plaines, Evanston, Glenview, Morton Grove, Mount Prospect, Niles, Northbrook, Park Ridge, Rolling Meadows, Wilmette and Winnetka.)

About mdkeenan

A criminal and school law attorney with over 17 years of experience, I have successfully represented clients all over the Chicago area. My practice includes DUI, felony, criminal, misdemeanor, homicide, internet crime, retail theft, traffic offenses, cyberstalking, drug crimes, weapons violations, domestic battery and juvenile crime. I also represent families involving school cases. My clients come from all over the Chicago area including Skokie, Wilmette, Niles, Northbrook, Glenview, Evanston, Winnetka, Highland park, Northfield, Park Ridge, Des Plaines and Mount Prospect. I am a member of the ACLU and the Illinois State Bar Association. I serve as a volunteer for First Defense Legal Aid. Se habla espanol.
This entry was posted in breathalyzer/field sobriety test and tagged , , , . Bookmark the permalink.