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Are breath test device results reliable?

On Behalf of | Mar 17, 2017 | Criminal Defense

When people in Pennsylvania are pulled over on suspicion of drunk driving, they may be asked to submit to a roadside breath test. These small portable machines are designed to determine drivers’ blood alcohol content level. Law enforcement officers use the results to ensure that motorists are not driving at or above the legal limit of 0.08 percent. Although using these devices is a standard procedure for law officers across the United States, research shows that the results of these tests are not always accurate. In fact, one in every four people who take a breath test will have elevated BAC results and may be wrongfully charged of a DUI.

According to research performed at the State University of New York at Potsdam, breath test devices are often unreliable when supplying blood alcohol content results. Rather than measure the amount of alcohol in the blood directly from a blood sample, the device uses an exhaled breath sample to determine the presence of ethanol alcohol. It then converts this amount to a BAC level. Problems lie in the fact that there are many factors that can alter the breath test results.

Not only must the officer using the device ensure that it is properly calibrated, but he or she must use it properly. In addition, the following factors may alter test results:

  •          Electrical interference from cellphones and officers’ radios.
  •          Gasoline, paint and tobacco fumes.
  •          Residual blood, food, drink or vomit in a person’s mouth.
  •          Relative humidity and temperature of the air.

Researchers also show that heavy exercise can alter the results as well.

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