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Are roadside breath tests a reliable source of evidence?

On Behalf of | Jul 16, 2019 | DUI Charges, Firm News

If you have ever been pulled over on suspicion of drinking and driving in California, you may have been asked to submit to a roadside breath test. These machines are designed to measure your blood alcohol content level without having to take a blood sample. Law enforcement officers in California and across the country use breath test devices to determine whether a driver is intoxicated, without having to take them into the station for a blood test. Yet, these breath test devices may not always yield accurate results and in some cases, these erroneous readings could lead to the wrongful arrest of an innocent person. 

When using a breath test device, you must exhale a breath sample into the mouthpiece. It then measures the amount of ethanol alcohol found in your breath and converts that over to a BAC level. According to research conducted by the State University of New York at Potsdam, there are several factors that can alter these readings, however, and cause inflated results. Some of these factors include the following:

  • Smoke, dirt, car exhaust fumes and pollution in the air

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

  • Electrical interference from police radios and cell phones

  • hematocrit levels in the blood or recent physical activity

Another factor that influences the reading is whether the officer administering the test is doing it correctly. The machine must be calibrated property for the temperature and relative humidity of the environment it is being used in. The only sure-fire way to get a reliable and accurate BAC level reading is through an actual blood test. 

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