Breath tests are a staple of the American criminal justice system. Even if you’ve never had the test yourself, most people are familiar with how a breath test works.

When you consume an alcoholic beverage, the substance makes its way from your stomach and small intestines into your blood stream. Your blood then travels throughout your body, eventually getting to your brain and lungs. As a result, you breathe alcohol out when you exhale.

A breath alcohol test measures the amount of alcohol on your breath to then estimate the amount of alcohol in your blood – or your blood alcohol content (BAC). In nearly every state, it is illegal for those over the age of 21 to have a BAC of .08% or higher while driving.

Driving over the legal limit of .08% comes with serious and often life-changing consequences in an effort to keep roads safer. However, in spite of these stakes, breath alcohol tests are surprisingly less accurate than you’d expect them to be – especially when criminal charges are on the line.

Breath tests: not so accurate

According to an investigation by the New York Times, breath test devices in police stations across the country showed skewed results with concerning frequency. In many instances, police departments did not properly maintain or calibrate their devices due to a lack of knowledge or low department standards. An uncalibrated device could yield results that were up to 40% too high.

Additionally, states often picked device models that technical experts didn’t trust due to disabled safeguards that ensure accurate test results. Many device models were also found to have serious errors in their software’s programming that affected accuracy.

What other factors affect breath test accuracy?

Breath alcohol tests may be portable and convenient for law enforcement, but they are also sensitive machines whose results may be inconsistent due to other factors. According to the investigation, a device may yield an inaccurate reading after detecting alcohol on the breath from things like:

  • Toothpaste
  • Mouthwash
  • Breath mints
  • Hand sanitizer
  • Burping

The criminal justice system relies on the accuracy of breath alcohol tests to keep roads safer, but they are less reliable than you’d think. Inaccurate readings can lead to arrests and wrongful convictions that can follow you for a lifetime.