Are breath test devices always accurate?

August 4, 2022
Are breath test devices always accurate?

If you are pulled over by Missouri law enforcement on suspicion of driving under the influence of alcohol, you may be asked to submit to a breath test. Law enforcement officers in the state, and across the country, use breath test devices as a way to determine your blood alcohol level, as it is impossible to take a blood test along the roadside. The problem lies in the fact that breath tests do not always provide accurate and reliable results. Certain factors can inflate BAC level results, which may lead to false DUI charges and a possible wrongful conviction. Research shows one in four people who use breath test devices will have inflated BAC levels when compared to blood test results.

As you exhale a breath sample into the device, the machine detects levels of ethanol alcohol and then converts that into a blood alcohol level. However, when researchers compared the levels taken from breath test devices and an actual blood test, they found a discrepancy of up to 15 percent. Researchers from the State University of New York at Potsdam found that internal and external factors influenced these levels. These factors include the following:

  •          Residual blood, alcohol and food found in a person’s mouth
  •          Gasoline fumes, cigarette smoke and pollution in the air
  •          Electrical interference from cellphones and/or officers’ radios
  •          Relative temperature and humidity of the air

If the breath test device is not calibrated correctly or if the officer does not use the device properly, it can give inaccurate results as well.

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


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