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Breath test devices can give inaccurate readings

On Behalf of | Sep 13, 2021 | DUI |

When officers in Washington pull motorists over on suspicion of drunk driving, they often use roadside breath test devices. These machines help determine a driver’s blood alcohol content level and whether they are driving while over the legal limit of 0.08.

The issue lies in the fact that handheld breath test devices do not always yield accurate results. Depending on the manufacturer and model of the breath test device used, the results may be inflated, which could lead to an erroneous drunk driving arrest and charge.

Breath tests vs. blood tests

The most accurate way to measure a BAC level is to measure the amount of alcohol that is present in a blood sample. Since it is difficult to take a blood sample on the side of the road, however, officers use breath test devices, which determine the amount of ethanol alcohol is in a breath sample. It then converts the number into a blood alcohol content level.

According to the State University of New York at Potsdam, researchers compared breath test readings to blood test results and found a variance of more than 15%. That means one in four people tested using a breath test device will have inflated results.

Factors that influence results

Researchers also found a number of environmental and physical factors that can influence breath test results, including the following:

  • Relative humidity and temperature of the air
  • Pollution in the air
  • Electrical interference from cellphones and officer radios
  • Residual food, drink, vomit or blood in the mouth
  • Fumes from cleaners, paint, paint thinner or gasoline

It is critical that machines are calibrated properly and the officer knows how to use the device or it can give false readings as well.

When a breath test device says that a driver has a BAC level that is over the legal limit, it does not always mean that the motorist is intoxicated.