Reliability of Breath-Test Results in a Drunk-Driving Case

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Reliability of Breath Test Results in a Drunk Driving Case

In every state in the U.S., a driver with a blood alcohol concentration (BAC) of 0.08 or higher is presumed to be legally intoxicated. Each state has also enacted an "implied consent" law. Implied consent laws provide that every licensed driver within the state is considered to have given his or her consent to submit to chemical testing if a law enforcement officer has reasonable suspicion of intoxication. In most states, test refusal results in license suspension or revocation; if a drunk driving charge results in a conviction, the defendant's refusal to submit to testing could mean additional penalties.

While a blood or urine test to check BAC is arguably more reliable, the breath test is more commonly used in the field. There are several reasons for this, namely because the testing equipment is convenient to transport, and the test is easier to administer, can be used by nonmedical personnel, is less physically intrusive to the person taking the test and produces results faster. However, under certain circumstances, breath tests can be less than reliable as an accurate measure of BAC.

If you are facing drunk driving charges, contact Michael A. Ferraro, Esq., P.C. in Cornwall, New York, to speak to an attorney who is thoroughly familiar with possible breath test weaknesses.

History and science of the breath test

The Breathalyzer® machine was invented in 1954 to collect evidence of alcohol intoxication by measuring BAC through breath analysis. Since that time, several manufacturers have entered the marketplace, and the science behind the machines has evolved. The word "breathalyzer" is now widely used to refer to these devices regardless of manufacturer (much like the term "Xerox" has become synonymous with copy machines and "Kleenex" is a blanket term for facial tissue). Other terms used to refer to these devices include "evidential breath tester (EBT)," "breath analyzer," "breath-analysis product," "breath-alcohol analyzer" and "breath testing device" (or machine). In addition to Breathalyzer®, common brands include Intoxilyzer® and Intoximeter®.

In very basic terms, a breath test machine is designed to measure the amount of alcohol in a deep-lung breath sample and to use that amount to determine BAC. The four main scientific methods used in the various machines are chemical analysis, infrared spectrophotometry, gas chromatography and fuel-cell detection.

Breath test vulnerabilities

Someone accused of drunk driving, working in conjunction with a skilled attorney and a scientific expert, may be able to challenge the breath test results in his or her case. Several different factors could affect the reliability of these results. Depending on the law of the state in which the drunk driving charges were filed, evidence of a problem with the test result could either make the BAC reading inadmissible in court or, at the very least, cast serious doubt on whether the reading is reliable.

Possible reasons to doubt a breath test result:

  • A breath test's assumption of a 2100-to-1 blood-to-breath ratio per representative sample may not be scientifically accurate.
  • The test was not administered correctly. For example, the administrator may not have warmed up the machine to its proper operating temperature or ensured an adequately deep-lung breath sample.
  • The test administrator was not properly trained or qualified beforehand.
  • The equipment was not maintained properly, calibrated correctly or cleaned adequately.
  • The result was affected by some characteristic of the driver, such as age; lung function; overall strength and size; a disease or condition such as asthma, diabetes, eardrum rupture, ketosis, emphysema, bronchitis, dental issues, fever or harelip; shock or trauma; certain types of special diets; or hiccuping, burping, vomiting or hyperventilating. Even severe heartburn or acid reflux could have might skew breath test results.
  • The test administrator did not continuously observe the driver for an adequate period before the test to prevent him or her from putting anything into his or her mouth that could affect the result. For example, a product used in the driver's mouth, such as mouthwash or adhesive, chewing gum, breath mints, breath spray or lip ointment could have an impact on the reliability of the testing.
  • Police radio operation generated electromagnetic waves, causing radio frequency interference (RFI) with the testing equipment.
  • The driver was exposed to a gas or vapor before the test that made it unreliable, such as during painting, floor sanding, varnishing or other activity with chemical exposure. Similarly, an outside environmental cause in the surrounding air (even excessive vehicle exhaust) could have caused a high breath test result.

This long list of potential problems with breath test results is, sadly, not even close to demonstrating all the possible issues with them. If a person charged with drunk driving is able to show that something affected the reliability of his or her test results, the state will need to bolster its case with other types of evidence in order to prove intoxication. This may include observations and testimony from the arresting officer, eyewitness accounts, defendant statements given at the scene, and field sobriety test results.

Speak to a drunk driving defense lawyer

If your situation involves a breath test to measure BAC, an experienced attorney from Michael A. Ferraro, Esq., P.C. in Cornwall, New York, who is thoroughly familiar with proper testing procedure and the science behind the test may be able to provide valuable assistance.

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DISCLAIMER: This site and any information contained herein are intended for informational purposes only and should not be construed as legal advice. Seek competent legal counsel for advice on any legal matter.

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