Breath test readings are not always accurate

On Behalf of | May 10, 2021 | DWI

When law enforcement officers detain motorists on suspicion of drunk driving, they often use breath test devices to determine their blood alcohol content level. If the BAC level reads over the legal limit of 0.08, officers may arrest and charge the driver with a DUI.

Yet, studies show that breath test device readings are not always accurate. There are a number of factors that can alter breath test results, and could possibly lead to a wrongful DUI charge and conviction.

How do breath test devices work?

Once a driver exhales into a breath test device, the device measures the amount of ethanol alcohol in the sample. It then converts this number into a BAC level. However, when researchers compared the breath test readings to the results obtained from a blood test, they discovered a 15% variance, according to the State University of New York at Potsdam. This means that approximately one in four drivers given a breath test would have inflated results.

What are the factors?

Part of this considerable difference is attributed to the many factors that can alter breath test results. Studies show the following contribute to erroneous breath test device readings:

  • Relative humidity and temperature of the air
  • Pollution and smoke in the air
  • Residual blood, vomit, food or drink in the mouth
  • Electrical interference from police radios and cellphones
  • Misuse of breath test device
  • Fumes from gasoline, cigarette smoke and cleaners

Breath test devices that are not calibrated frequently and properly can also give false readings.

While officers are not able to administer blood tests to test BAC levels along the roadside, it is critical to know that the readings obtained from breath test devices are not always accurate and reliable.