Are breath test readings accurate?

If you have ever been pulled over by Michigan law enforcement on suspicion of drinking and driving, you may have been asked to take a roadside breath test. These devices are used to determine drivers’ blood alcohol content level and whether it is over the legal limit of 0.08 percent. The problem lies in the fact that, when compared to an actual blood test, the blood alcohol results obtained from breath test devices can have significant variances. In fact, the State University of New York at Potsdam reported that BAC level readings from a breath test device can be as much as 15 percent different than those obtained from an actual blood test. As many as 23 percent of people tested could have inflated results. This is enough to wrongfully arrest and convict you of a DUI.

What makes breath test readings so unreliable. Studies show that different factors contribute to the inaccurate readings given by breath test devices. Chemicals from residual food, drinks, blood and vomit in the mouth can alter the results. The following can also influence results:

  •          Pollution, cigarette smoke and dirt in the air
  •          Relative humidity and temperature of the air
  •          Static interference from cellphones and officer radios
  •          Fumes from gasoline and cleaning products

Breath test devices that have not been calibrated properly or officers who do not know how to use them correctly can also change the results. Other physiological differences can also show up in a breath test, such as hematocrit levels and oxygen levels in the blood.

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

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