Measuring the accuracy of breath test devices

Breath test devices that officers use to determine blood alcohol content may yield inaccurate results.

Many people enjoy having a few drinks with dinner or when going out for the evening with friends. Although drinking isn't against the law in Virginia, it is illegal to get behind the wheel of a vehicle while intoxicated. The state has stringent laws against drunk driving, and people who decide to do so may be pulled over and questioned by a law enforcement officer. In some cases, an officer may ask a suspected drunk driver to submit to a roadside breath test. While the readings of these handheld devices are unlikely to be used in court, they can result in an arrest and DUI charge. However, studies show that roadside breath test readings can be inaccurate and may, in some instances, produce invalid and/or misleading results.

How do breath test devices work?

When a person blows into a breath test device, the machine measures how much ethanol alcohol is in his or her breath sample. The device then converts this value into a blood alcohol content level, which can be used to determine whether a person is driving over the legal limit of 0.08 percent.

Studies that compare breath alcohol content readings from breath test devices to actual blood alcohol levels obtained from blood tests show, however, that the results can vary significantly. According to the State University of New York at Potsdam, these results can differ by as much as 15 percent. That means that nearly one in every four people who use a breath test device could have breath test results that are markedly higher than his or her real blood alcohol content level.

What affects breath test readings?

There are a number of environmental, physical and mechanical issues that can alter the results of a breath test device, according to NBC News. For instance, devices that are not calibrated regularly or used properly by an officer can yield inaccurate breath test results. Furthermore, the moisture content, presence of pollution, humidity and relative temperature of the air can influence breath test results. Researchers also report that physiological factors may play a role in invalid readings. Any residual food, blood or vomit in the subject's mouth, as well as whether he or she has been exercising can inflate breath test results.

Protecting your rights

If you have been charged with a DUI in Virginia, you may face serious charges that can have a long-lasting effect on your life. A DUI conviction can make it difficult to find a job, qualify for a loan or retain the ability to drive. You may want a criminal defense attorney to look at the details of your case, and help you explore your possible legal options.