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Why DUI breath tests aren’t reliable

It’s no secret that law enforcement officers rely heavily on chemical breath tests to reliably determine a driver’s blood alcohol content (BAC) before charging someone with driving under the influence (DUI).

However, false positives and inaccurate readings are probably a lot more common than most people realize. If you’ve been charged with drunk driving after taking a chemical breath test, don’t assume that you’re automatically doomed to the harsh consequences that come with a conviction. Your BAC reading can be challenged.

All kinds of things can affect a breath test’s accuracy

There are a number of reasons that your BAC reading can be wrong. False positives and falsely elevated readings can be caused by things like:

  • Improperly calibrated machines: The roadside devices that officers use take a lot of wear and tear over time. They have to be recalibrated regularly in order to remain accurate, or you get inaccurate readings (and those are seldom in a driver’s favor).
  • Acid reflux: Gastroesophageal reflux disease (GERD) and related disorders cause stomach acid to flow backward into your esophagus – and alcohol, food and stress can all intensify that effect. If you suffer from GERD, the alcohol that backed up into your esophagus could have combined with the alcohol in your lungs to create a falsely elevated reading.
  • Diabetes: Roughly one out of every five people with diabetes doesn’t even know that they have it, and that condition can drastically increase the odds of an elevated BAC reading. Diabetics with poorly controlled blood sugar levels can develop a condition known as ketoacidosis, which causes the body to produce its own acetone, and that’s exactly what chemical breath tests try to read.
  • Medication and mouthwashes: Most commercial mouthwashes contain alcohol as a key ingredient, so just rinsing your mouth before you hit the road can lead to a false positive on a breath test. Cold and flu medications that contain menthol or alcohol as some of their ingredients can do the same.

Seeing those flashing red and blue lights in your rearview mirror is enough to give anybody a start – and your anxiety may be well-founded if you end up charged with drunk driving. However, a charge isn’t the same as a conviction. The prosecutor still has to prove their case – and you have the right to seek legal guidance and present an informed defense.