When a police officer thinks your driving is suspicious, they can pull you over to ask questions and screen you for signs of impairment. If your answers or the way that you speak reinforces their suspicion, they may ask you to perform a field sobriety test followed by a chemical breath test.
Even if your nerves or a medical condition affect your performance on the field sobriety test, you probably think the breath test will exonerate you. If you haven’t had anything alcoholic to drink, the test should come back negative.
Unfortunately, the test instead showed that you had alcohol in your system, possibly an amount well over the legal limit. How could that happen if you haven’t been drinking?
Conditions inside your body can affect the chemical test
There are multiple ways that you could potentially fail a breath test because of your health or your diet. For example, if you have the rare condition known as auto-brewery syndrome, you might fail a breath test without having anything to drink.
Even more common conditions, like diabetes, can affect chemical breath testing. In fact, diets like the keto diet could also result in a false positive on a chemical breath test. There are also prescription medications, like asthma inhalers, that can compromise the accuracy of chemical breath testing. Although officers should take those known facts into consideration before arresting someone, they often arrest those even with clear explanations other than alcohol that could explain the test results.
The issue could be with the unit or the way the officer administered the test
If you have ruled out medical conditions, diet and prescription medication as potential causes of an inaccurate test result, it could be the test itself that is the problem.
Perhaps the officer did not properly calibrate the device. Maybe it is overdue for crucial maintenance or a software upgrade. The officer performing the test might even make a mistake during test administration that affects the accuracy of the results.
Understanding how breath tests return false positives can help you decide the best ways to defend yourself against pending driving under the influence (DUI) charges.