When Breath Tests Lead To False Positives

May 7, 2019 | DUI Defense

On behalf of Kestenbaum Law Group posted in dui defense on Tuesday, May 7, 2019.

Breathalyzer tests are not perfect, and California residents might like to know about situations when a breath test can provide faulty results. In some cases, those on the keto diet may test above the legal limit for alcohol even when within an accepted range. False positives may also happen when one has medical conditions like acid reflux or diabetes.

Acetone is a byproduct of the ketosis process, which involves the liver breaking down fat. Some acetone is found in the breath as isopropyl alcohol due to ketosis. Not all devices may be able to gauge BAC correctly; less expensive breath test products are likely not sophisticated enough to differentiate between isopropyl alcohol and ethanol alcohol. This could lead to an incorrect BAC reading.

Breath testing utilizes semiconductor technology. A metal film measures molecules expelled from a person’s breath by gauging the resistance against the metal film. The amount of molecules expelled when under the influence of alcohol is different than when expelling normal air.

The devices that police officers are equipped with are said to be able to tell the difference between isopropyl and ethanol, but there may not be enough research on this topic to say for sure. Fortunately, a breath test is usually not the only method officers use when attempting to ascertain whether someone is above the legal limit. However, those with ignition interlock devices who receive false positives may run into problems.

There are several areas an attorney might consider when mounting a client’s DUI defense. First, an attorney might question whether an officer had enough probable cause to stop or test a motorist. The validity of any test results may also be scrutinized. Any field sobriety test has the potential for error. For example, people with balance issues may have difficulty walking in a straight line for the walk-and-turn test.