Are alcohol breath tests accurate?

On Behalf of | Feb 6, 2022 | blog, DUI

Although many drunk driving convictions rely on the results provided, several factors may affect the accuracy of alcohol breath tests. In addition to roadside sobriety tests, law enforcement officers commonly ask motorists suspected of driving under the influence to give breath samples to determine their blood alcohol concentration levels. With few exceptions, people must submit to such tests or face potential legal consequences for their refusals.

Understanding the factors that have the potential to impact breath test readings may help drivers protect themselves, as well as their rights and their futures.

Machine-related factors

According to The New York Times, alcohol breath test devices sometimes yield inaccurate results due to issues with the devices or the software they operate on. Scientific instruments, breath tests need regular, proper calibration. If not set correctly, these devices may give readings up to 40 times higher than the drivers’ actual blood alcohol concentration levels. Programming mistakes in the software of these machines also have the potential to cause inaccurate readings.

Human-related factors

Human-related factors also sometimes affect the accuracy of breath test results. To get a BAC level reading from a portable device, a driver must provide a breath sample. However, some motorists, older women in particular, may struggle to produce enough breath to provide a result. According to, other human-related factors affecting BAC readings include using mouthwash or smoking. Likewise, providing a sample within 15 minutes of consuming alcohol will also sometimes yield false results.

Defending against drunk driving charges involves examining the case from every angle, including questioning the accuracy of breath test results.