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What do defense attorneys look for in DUI breath tests?

A standard part of police traffic stops in which drinking and driving is involved is the breath test. Prosecutors like to use the results of the breath test, commonly known as the Breathalyzer, as evidence in a DUI case. It is supposed to be an objective, scientific way to measure how much alcohol was in the defendant’s body while he or she was driving.

Just as with any scientific instrument, a breath test device must be properly maintained and regularly calibrated, or its results could become skewed. A suspect could be wrongfully charged with DUI because the device incorrectly measured his or her blood-alcohol level at or above the legal limit of .08.

To be acceptable evidence in court, the results of a breath test must have come from a device that

  • Is on a conforming list of acceptable devices
  • Was checked regularly for accuracy at set intervals

The officer administering the test must also have followed procedural rules that are designed to prevent errors. For instance, the officer must be certified to use that particular breath test machine. They must follow their training, and insure that vomit, food, smoke, or gas do not contaminate the test.

Of course, the prosecution cannot necessarily be expected to admit that a breath test was not done properly. It may be up to the defense attorney to investigate the traffic stop that led to the arrest and uncover improper or illegal conduct by law enforcement. If things like this occurred, the attorney may be able to convince the judge to throw the breath test out of court.

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