You see flashing lights in your rearview mirror, and your stomach drops. You’ve had a few drinks, but you believe you’re within the legal limit to drive. The police think otherwise and place you under arrest for suspicion of drunk driving.

At the station, you agree to submit to a breathalyzer test. The breathalyzer machine returns a blood alcohol concentration (BAC) reading above .08. You might think there’s no question that you’re guilty of drunk driving. However, are breathalyzer tests really that accurate?

Numerous factors can impact a breathalyzer result

A person’s BAC can be influenced by several factors, including:

  • The amount of alcohol consumed
  • Individual metabolism
  • Health-related issues

A breathalyzer test measures the amount of alcohol dissolved in the oxygen of the exhaled breath. It can’t account for individual factors that can skew the results. For example, if a person is suffering from gastric reflux, the reading may be higher than the person’s actual BAC.

Breathalyzer tests perhaps provide more of an estimation of a person’s BAC than an accurate reading, and that’s assuming machines are properly calibrated. An investigation by The New York Times found that improperly calibrated machines resulted in BAC readings that were as much as 40% higher than a person’s actual BAC.

Does this mean breathalyzer tests no longer matter?

Despite increasing evidence that breathalyzer tests are not as accurate as were once thought, the results can still be used to support a drunk driving charge. You should discuss your possible defenses with a skilled legal professional who understands how to challenge drunk driving evidence, including breathalyzer test results.