There are several ways for Texas police officers to gather evidence of an alleged driving while intoxicated (DWI) offense. The cameras in their police cruiser may capture video footage of someone’s poor driving before they initiate a traffic stop. They may also ask the motorists to exit the vehicle and perform field sobriety tests on camera.
Finally, they may ask the driver to perform a chemical breath test. People tend to put a lot of faith in chemical testing. People often assume that DWI defendants are guilty if they failed a breath test. A driver who knows they only had one beer may start questioning their own memories because they fail a breath test.
Media depictions of forensic science intended to dramatize the criminal justice system have contributed to the level of trust people have in chemical testing. Despite what people often believe, breath tests aren’t always as accurate as people assume. In fact, they can easily return false positives or inaccurately high test results under a variety of different circumstances.
Why chemical breath tests fail
A breathalyzer or portable chemical breath test device is a complex piece of machinery. It analyzes exhaled gas to look for alcohol molecules. Small issues can compromise the accuracy of the test results produced.
Sometimes, the issue has to do with how the officer administers the test or how the police department maintains the device. If there hasn’t been a recent calibration of the device, the results might be inaccurate. Gaps in maintenance records or proof of outdated software can raise questions about the accuracy of test results.
Other times, there may be a medical explanation for why a driver failed a breath test. Certain medications can affect breath test accuracy. There are also a variety of different health conditions that can produce false positive results on a breath test. In fact, even specialized diets sometimes affect breath test results.
Drivers who fail a breath test but know that they didn’t have too much to drink can use that knowledge to begin developing a defense strategy. Fighting DWI charges might involve raising questions about the accuracy of a test.