Driving under the influence of alcohol is a serious crime that affects the lives of millions of Americans. In fact, the National Highway Traffic Safety Administration estimates that 1.5 million people in the United States are arrested for a DUI each year. While field-sobriety tests and police-officer discretion aid in DUI arrests and convictions, the gold standard for determining a motorist’s sobriety is the alcohol breath test – commonly known by the brand name Breathalyzer.

Though courts and law enforcement have placed their trust in the accuracy of Breathalyzers, a November investigation by the New York Times found the machines to be wildly inaccurate. The Times’ investigation, along with a court decision in Massachusetts that threw out the results of 36,000 breath tests, calls into question the value of the tests and if they should be used as evidence in DUI cases. Here are the reasons anyone arrested for drunk driving should be critical of breathalyzers.

Incorrect calibration

Machines that calculate blood alcohol content are sensitive tools that require correct calibration and expertise in their use. Breathalyzers need regular calibration and maintenance to provide accurate results. How often the machines need to be calibrated and serviced vary by jurisdiction, but for a breath test to be admissible, the following guidelines are used by most states:

  • The device must be approved by the state for law-enforcement use
  • The device must be properly maintained and calibrated
  • The person administering the test must be certified, and must administer the test according to his or her training
  • The device must capture two readings within .02 percent of one another

A lack of training and miscalibration can greatly skew the tests. In fact, the New York Times found that devices that had been set up improperly or were miscalibrated showed results up to 40 percent too high.

Software errors

Police stations have more sophisticated breath-testing machines than the portable devices used by law enforcement in the field. In theory, the results produced by these machines are more accurate and almost always admissible in court.

But the problem with these machines is that defendants and their attorneys are not able to examine the machines and identify any flaws that may be present in the devices, especially their software. Though the courts have frequently rebuffed attorneys who have tried to inspect breath testing machines, a New Jersey defense lawyer was allowed to have an expert examine one popular model used by police departments nationwide. The expert identified thousands of errors in the machine’s code and the courts ceded that the machines had “mechanical and technical shortcomings.”

Outside factors

Another reason one should question the results of breathalyzer tests is because outside factors can influence the accuracy of the test. If the person being tested had a drink within 15 minutes before the test was administered, trace amounts of alcohol in the mouth can cause an inaccurate result. Products that contain alcohol like mouthwash, breath fresheners and toothpaste can also skew the results, as can smoking, burping or vomiting. Some people, especially older women and those with lung problems, may not be able to blow hard enough into a breath-testing device to give a sufficient sample.

Get help

If you are arrested for suspicion of driving under the influence, you likely want to mount your defense right away. With so much uncertainty surrounding the traditional ways used to determine intoxication, it may be advisable to speak to a lawyer with experience fighting DUI charges.