Six Factors that Can Impact DUI Breath Tests

In Florida, police officers routinely use Breathalyzer tests to determine if a motorist has been driving under the influence of alcohol. If the results show a breath alcohol level (BAL) of 0.08 or higher – the level classified as legally intoxicated under Florida DUI laws – the driver may be arrested for DUI.

Law enforcement and the courts continue to rely on Breathalyzer tests in charging and sentencing DUI suspects. Some factors – such as a person’s metabolism or problems with the machine itself– can interfere with the accuracy of such tests.

How Breathalyzer Inaccuracies Impact a DUI Defense Case

Proof of blood alcohol concentration (BAC) is instrumental in building a drunk driving case in Florida. This is why many defense strategies seek to challenge the results of Breathalyzer tests. The courts may be compelled to dismiss a DUI case if the defense can prove that a Breathalyzer test was incorrectly administered or compromised because of other factors.

Ways in Which Breath Tests May Fail 

Breathalyzer tests measure the presence of alcohol in a person’s mouth. These tests measure BAC without actually testing the blood. This data is then used to calculate a blood alcohol level and corresponding intoxication. Discrepancies in the tests can arise because of biological or technical factors.

A few of the reasons a Breathalyzer test may fail to provide accurate results include

  • Problems with the machine – One of the most basic factors in challenging a questionable breath test result is to examine the accuracy of the machine itself.
  • A poorly calibrated machine or one with any sort of defect can produce inaccurate results. A 2010 Washington Post story reports that in a two-year span, “nearly 400 people were convicted of driving while intoxicated in the District…based on inaccurate results from breath test machines.” These individuals were subject to fines and jail time.
  • Mouth temperature – Breathalyzer machines are calibrated to a specific temperature. The final reading may be skewed if the DUI suspect’s body and mouth temperature are higher than this calibrated number.
  • Metabolism – A person’s metabolism impacts the rate at which his or her body absorbs alcohol. This means a Breathalyzer test may indicate a person has more alcohol in the blood stream than is actually present.
  • Breath – Breath patterns can influence a Breathalyzer reading in some cases. Holding one’s breath may actually produce an inflated reading, according to one 1982 study.
  • Digestive concerns – Vomiting prior to a Breathalyzer test can interfere with the accuracy of the test. Likewise, individuals who suffer from acid reflux or gastroesophageal reflux disease may register inaccurately high BAL levels.
  • These medical conditions make it possible for stomach contents – including alcohol that has not yet entered the bloodstream – to rise into the mouth. This so-called “mouth alcohol” interferes with a police officer’s ability to collect an accurate reading.
  • Mouthwash – Mouthwash and breath sprays that have high alcohol content can skew breath test results. This is because the residual alcohol in the rinses/sprays is included in the measure of BAL. Some formulas of antiseptic Listerine, for example, contain as much as 26.9 percent alcohol. A quick swish with this product just prior to a breath test may produce a falsely high test result.

For help challenging inaccurate or misleading Breathalyzer or breath tests, contact a DUI defense attorney. Call (877) 663-5110.