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3 factors that affect breath test accuracy

On Behalf of | Oct 25, 2022 | Criminal Defense

Among other evidence-gathering tactics, law enforcement often asks motorists stopped on suspicion of drunk driving to submit to breath testing to determine their blood alcohol concentration levels. Though serving as the key piece of evidence in many DUI cases, these tests sometimes yield inaccurate results. Consequently, people may wrongly face criminal charges.

To help protect their rights, it benefits drivers to understand the factors that may affect the accuracy of alcohol breath tests.


According to the National Library of Medicine, the timing of when law enforcement administers breath tests may impact the precision of device readings. BAC breath tests return the most accurate results if performed within six to 12 hours after someone’s last drink. Therefore, testing outside this window sometimes yields incorrect readings.

Incorrect maintenance of the device

According to, breath test devices also occasionally give inaccurate BAC readings because of issues with their calibration or maintenance. Failing to update the software regularly or correctly tune these devices may cause them to return incorrectly high or low results. Likewise, testing devices with insufficient charge or low battery power may not provide accurate readings.

Interactions from other products

Using certain products before testing can potentially impact the precision of alcohol breath tests. For example, trace amounts of alcohol from mouthwash or breath fresheners may cause false high readings. Likewise, smoking also has the potential to affect the accuracy of breath tests.

A DUI arrest can have serious repercussions on a person’s life, both in the present and into the future. Therefore, an individual facing a drunk driving charge needs to build a solid defense, which may include questioning the accuracy of the breath test results.

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