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Evaluating inaccuracies in breath test results

Taking a roadside breath test may be intimidating, especially if you have been pulled over by a law enforcement officer. Officers use breath test devices to measure a driver’s blood alcohol content level and determine if he or she is driving above the legal limit. Yet, inaccuracies in breath test device results may lead to wrongful DUI charges

Hand-held breath test devices work by measuring the amount of ethanol in an exhaled breath sample. When comparing the blood alcohol content results obtained from a breath test device to those obtained from an actual blood test, the results are alarming. The difference can vary by more than 15% in some cases. At least one in every four people who use a breath test device will have inflated results. 

Part of this discrepancy may be due to the fact that some breath test devices measure more than just the amount of ethanol in the breath sample. The devices may also measure methyl groups, which can be found in many other substances. According to research performed by the State University of New York at Potsdam, factors that can alter breath test results include the following:

  • Electrical interference from officer radios and cell phones

  • Dirt, pollution, moisture and tobacco smoke in the air

  • Residual food, blood or vomit in a person’s mouth

  • Misuse of the device by law enforcement officers

If the breath test has not been calibrated properly or not adjusted for the temperature and humidity of the air, it can give false results as well. Law enforcement officers should keep these factors in mind before charging a person with DUI.



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