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Are breath test devices accurate?

If you have ever been pulled over on suspicion of driving under the influence of alcohol, you may have been asked to submit to a roadside breath test. Law enforcement officers often use this method to read your blood alcohol content in order to determine whether you are driving while intoxicated. The problem lies in the fact that handheld breath test devices do not always provide accurate and reliable results. The results obtained from these machines may even lead to a DUI conviction.

Rather than measure how much alcohol is in your blood through a blood test, breath test devices evaluate an exhaled breath sample to get a blood alcohol level reading. Research from the State University of New York at Potsdam shows that the BAC level obtained from a breath test device can vary by as much as 15 percent from the BAC level reading obtained by an actual blood test. Approximately 23 percent of people may show erroneous elevated readings from these devices.

There are several factors that can influence breath test device readings, including the following:

  •          Temperature and relative humidity of the air
  •          Residual blood, vomit and food found in the mouth
  •          Electrical interference from police radios and cellphones
  •          Tobacco smoke and pollution in the air
  •          Gas and cleaning fluid fumes

Results can also be in error when the breath test machine has not been properly calibrated or when the law enforcement officer is not using the device correctly.

This information is intended to educate and should not be taken as legal advice.

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