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How Reliable are Breathalyzers?

The question as to the reliability of breathalyzers has become a topic of great debate. Breathalyzers, or breath analysis, are one of the tools most commonly used by law enforcement to determine if someone is driving while under the influence of alcohol above the legal limit.

Despite the intent, more and more scientists and experts agree that breathalyzers generate inconsistent and inaccurate measurements of a person’s blood alcohol content, better known as BAC. Some courts are even throwing out cases involving breath tests due to these inconsistencies.

Opinions regarding the reasons for  the inconsistencies involving breathalyzers vary. The thermometers in the breathalyzers have been cited for some of these inconsistencies. A woman in Washington took her 2002 case to the Washington Supreme Court citing the unreliable nature of the breathalyzers, specifically the thermometer used in the breath test.

Essentially, the thermometer in a breathalyzers is used to test how accurate the readings on the breath machines are. The thermometer must be calibrated with a mixture of water and alcohol that is kept at 34 degrees centigrade. The thermometer gathers a reading from the mixture. In her case, the woman in Washington was able to prove that the thermometers was not certified as reliable;  the case against her was reversed.

Courts in other states have been following suit, and throwing out or reversing DUI cases involving breathalyzers. Four defendants in New Jersey consolidated appeals against the State of New Jersey citing unreliability of the breath tests in State v. McGinley.

The defendants cited new scientific evidence that showed inconsistencies in the Breathalyzer models 900 and 900A. The Court said such models were “scientifically reliable”, but still took this new evidence into consideration. The evidence showed that a variance in blood-breath ratio could produce errors in reading.

These errors showed high readings in 14% of the population. Importantly, as mentioned above, there may be errors in the temperature of the machine, resulting in skewed test results. The body temperatures of the human beings, which vary from person to person, may also affect the readings of the breathalyzers. Lastly, blood particles called Hematocrit vary between males and females and can affect test results.

Other factors influencing tests results can be calibrating errors, the lack of testing blank specimen, and/or making sure a person is not affected by the environment. Most good defense lawyers know how to properly challenge the reliability and accuracy of breathalyzers. Because state laws do vary, you should contact an attorney in the state where you are charged for proper legal advice concerning the facts of your particular case.



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