Throughout the United States, "per se" DUI laws establish a legal presumption that a driver was intoxicated if he or she had a blood alcohol concentration (BAC) above a certain limit -- across the board it's .08 percent. But, how does law enforcement know that a driver is above the legal limit? In order to establish a DUI suspect's BAC, police officers will ask a driver to submit to a test of some kind. While a blood test produces the most exact results, police officers regularly use breath analyzers to estimate a suspect's BAC at the time of driving.

What Is a Breathalyzer?

Commonly known as "Breathalyzers," breath analysis testing devices are a type of instrument which requires the suspect to blow into it. The instrument will register the driver's BAC level. This type of measurement offers strong evidence concerning a suspect's BAC, but they are not infallible. Courts regularly accept Breathalyzer evidence as sufficient proof of a defendant's BAC, but the police department must demonstrate that the testing device in question can produce reliable results. Many DUI defendants have successfully challenged the Breathalyzer evidence brought against them, thus putting a serious dent in the prosecution's case.

Common Challenges to Breathalyzer Results

The most frequent challenges to Breathalyzer evidence concern whether or not a testing device was in proper working order at the time of the test. Breathlyzers require regular calibration and maintenance to ensure that they deliver results with a sufficient level of accuracy. An improperly calibrated or poorly maintained machine will produce unreliable results that cannot form the basis of a presumption of intoxication under per se DUI laws.

How Often Should a Breathalyzer be Calibrated?

It depends. Each state has its own particular laws and standards regarding when and how a Breathalyzer must be calibrated. For the results of a test to be admissible in court, however, most states follow these basic guidelines:

• The breath device must be on a conforming list of acceptable devices.
• The breath device must be properly maintained and checked for accuracy at regular, set intervals.
• The person administering the test must be certified in the use of that particular device.
• The person administering the test must do so in accordance with his training.
• The person administering the test must ensure the test subject does not burp, regurgitate, eat, vomit, or smoke for a period of time immediately prior to the testing sequence.
• The breath test must capture at least two measurable readings that are within .02 of one another.

How Does One Show that a Breathalyzer Wasn't Working Properly in a Case?

If a defendant can show that the police department did not follow proper calibration procedures, or that the device in question consistently provided erroneous readings, then a court will likely declare the results of a Breathalyzer test inadmissible as evidence of the defendant's intoxication.

A skilled defense attorney can subpoena the maintenance and calibration records of the Breathalyzer on which you tested, possibly using them as evidence that the equipment was not properly tuned to deliver entirely reliable test results.

At that point, the burden will shift back to the government to prove the defendant's intoxication through some other type of evidence such as the odor of alcohol on the suspect's breath, red or watery eyes, bad driving, poor performance on roadside field sobriety tests or a car accident.

A DUI Attorney Can Challenge the Breathalyzer Calibration in Your Case and More

Finding a qualified DUI attorney can mean the difference between a conviction and beating your case. An experienced attorney will be able to discuss the validity of your Breathalyzer results, challenge the Breathalyzer calibration, and advise you on a course of action moving forward. A good first step to defending your rights and getting the best possible outcome for your case is to contact a local DUI attorney.