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Chemical breath tests fail more often than people realize

On Behalf of | Nov 10, 2023 | DUI/OUI |

There are various types of evidence that the state gathers to prove that someone has violated the law. When the allegations are that someone drank an unsafe amount of alcohol before driving, a chemical test result is one of the most authoritative types of evidence available. In some scenarios, such as when a crash occurs and someone goes to the hospital, the state can obtain blood tests to validate allegations of chemical impairment. However, a large percentage of Massachusetts operating under the influence (OUI) charges rely on chemical breath tests.

People often assume that anyone who fails a breath test will surely end up convicted of their pending OUI charge. What many people fail to understand is that a chemical breath test can very easily return false positive results. What makes breath testing so unreliable?

There are many ways to trigger a false positive

Breath tests analyze the chemical composition of exhaled gas to look for certain types of molecules. Unfortunately, there are a variety of compounds that could trigger a false positive result. People who haven’t had anything to drink can still fail a breath test. Someone with acetone on their breath due to weight loss or uncontrolled diabetes would fail a breath test. The same might be true of someone who just used a breath spray or mouthwash moments before a traffic stop. There are even some prescription medications, including asthma inhalers, that can lead to a breath test giving false positive results.

The police department may make maintenance mistakes

To obtain accurate results when performing a complex chemical test, it is necessary to keep the testing device in optimal condition. Police departments need to engage in regular maintenance of their devices. They need to recalibrate them frequently to ensure the accuracy of results. They may also need to update the software occasionally and properly train all officers in their use. Any mistakes in the maintenance of the breath test device used during a traffic stop might lead to unreliable or outright inaccurate results.

When someone fails a chemical breath test but does not understand why, they may need to look more closely at the science around breath testing. Fighting an OUI charge sometimes requires raising questions about the results of the chemical breath test.

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