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How Breath Tests May Give Off Inaccurate Results


Courts give breath alcohol tests considerable weight when determining whether a person has driven under the influence of alcohol in a DWI case. However, breath machines are not infallible. Courts and police departments across the country are grappling with the reality that breath machines may produce false positives.

According to the New York Times, problems with breath machines have become so pervasive that judges have been throwing out the results of breath alcohol tests by the thousands. In spite of manufacturers touting the reliability of breath machine readings to the decimal point, these machines nonetheless can generate unreliable results.


Breath machines require proper calibration to yield an accurate result. According to the New York Times piece, some police departments have failed to calibrate their machines, producing readings that are off by as high as 40%.

The causes of the inaccurate readings varied. Some police departments lacked the right standards to maintain the machines. A deficiency in expertise also caused problems with machine calibration. In addition, programming errors in the machine software contributed to the errant readings in some instances.


The New York Times also reported problems with quality control measures inside some breath machines. In the state of Washington, breath machines failed to correct human breath temperatures, which could trigger a high alcohol reading. In Minnesota, technicians shut off a testing function in their breath machines when it became clear the fuel cells that powered the function were not reliable.


These instances show that breath machines can yield inaccurate results that may produce undeserved punishments. Even if technicians or investigators discover problems with these machines after a DWI conviction, it does not guarantee that a wrongly convicted person will see his or her conviction overturned. This makes it crucial to deal with the question of breath test accuracy during the DWI case itself.