Dirk Padgett Law PLLC
Former Special Assistant U.S. Attorney / Former Military Prosecutor / Former Deputy Commonwealth’s Attorney

What causes an incorrect breathalyzer test?

When someone is pulled over, the officer may suspect that the driver was drinking. In those instances, the officer may request the driver to submit to a sobriety test.

When determining whether a driver is sober, the officer will typically begin with a field sobriety test. The officer may also ask the driver to submit to a breathalyzer test to more precisely measure their BAC.

A breathalyzer can provide the police with a more accurate measure of a driver's sobriety. However, the results of a breathalyzer test aren't infallible. Unlike blood tests which are often pretty accurate, it's not uncommon for a breathalyzer to produce a false positive.

There are a number of reasons why a breathalyzer may produce an inaccurate reading. Some of the most common explanations include:

  • The device wasn't calibrated correctly: Breathalyzers require regular calibration to ensure accurate results. If the test was conducted by an officer that wasn't certified to use a breathalyzer or if there weren't two measurable results within .02 BAC of each other, the machine may not have been calibrated properly. This can cause the results from the test to be inadmissible in court.
  • The device's natural margin of error: As mentioned earlier, breathalyzers are inherently less accurate than blood tests. Because of the machine's natural margin of error, someone may receive a reading indicating that they're intoxicated even if they're under the legal limit. For example, a breathalyzer could have a margin of error of .02. If a driver blows a .09, the machine's margin of error could mistakenly say that the driver was over the .08 legal limit.
  • Outside factors caused an incorrect reading: It's also possible that unrelated factors could fool the breathalyzer into thinking someone is intoxicated. Cases involving drivers who used mouthwash, cold medicine or cough drops have resulted in the drunk driving charge being thrown out in court. Dental work, such as crowns or dentures, can also affect the accuracy of a breathalyzer test.

It's unlawful to refuse to take a breathalyzer test in Virginia. That doesn't mean, however, that those who were pulled over should automatically assume that the results from a breathalyzer test are accurate.

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Throughout Mr. Padgett's career, he has worked on cases covering a wide variety of offenses, from white collar crime and larceny to war crimes and capital murder. In 2009, he served as lead prosecutor in the trial of Ibrahim al Qosi, an al Qaeda member and bodyguard to Osama bin Laden, at Guantanamo Bay Prison.

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