Are roadside breath test readings accurate?

If you have been pulled over on suspicion of drinking and driving, you may have been asked to take a roadside breath test. Law enforcement officers across the country use these devices to measure drivers’ blood alcohol content level and determine whether they are over the legal drinking limit of 0.08. Despite the widespread use of these devices, studies show that the results may not always be accurate. In fact, some may show inflated results that could end up in a wrongful arrest and possible DUI conviction

Studies were conducted by the State University of New York at Potsdam comparing the BAC results from a breath test device to an actual blood test. Researchers found that approximately 23% of people who are tested will show inflated results. As you exhale into the device, the instrument measures the amount of methyl alcohol in the sample. Yet there are other factors that can affect this amount and the breath test reading as a whole. These factors include the following:

  • Smoke and pollution

  • Relative humidity and temperature of the air

  • Static electrical interference from police radios and cellphones

  • Residual food, drink, vomit and blood in the mouth

Furthermore, substances you have inhaled, such as cleaning fluids, paint fumes and gasoline can also affect your BAC level reading. Other factors involve whether the law enforcement officer is using the device correctly and if the device has been calibrated properly. The most accurate way to get a BAC reading is through a blood test. 

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



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