Don’t be too quick to trust your breathalyzer test results.

You have a couple beers with some colleagues one night after work. On your way home, a police officer pulls you over and conducts a breathalyzer test, which you fail. While you might be shocked that just two beers over the course of an evening was enough to put you over the legal limit, you might not question the results. After all, what’s a judge likely to believe in court: your personal perception of your level of impairment, or quantitative evidence?

When it comes to blood alcohol content, it’s easy to assume that numbers don’t lie. However, it’s worth remembering that breathalyzer equipment was designed by humans and is therefore subject to human error. Recent research indicates that we shouldn’t be too quick to trust these machines.

Police officers in Massachusetts conduct breathalyzer tests using the Draeger Alcotest 9510. Critics of this piece of equipment have pointed to engineering flaws that can inflate its results in favor of the prosecution.

Failing to account for human variability

The temperature of any human’s breath changes throughout the day. Normal human breath temperature is considered to be 34 degrees centigrade. However, if your breath is even one degree warmer than that when you take a breathalyzer test, it could alter your results by up to 6% – which alone could be enough to make you appear over the legal limit.

Equipment degradation

One of the sensors the Alcotest 9510 uses to calculate blood alcohol content is a fuel cell – which detects the electrical current in the breath. However, the accuracy of this reading degrades markedly with repeated use. Therefore, the 200^th person tested on this device will have less accurate breathalyzer results than the first person tested on the same device.

If you’re accused of operating under the influence and you believe the accusation is false, it’s critical to hire an experienced OUI attorney who can effectively inject doubt into the reliability of the prosecution’s breathalyzer evidence in court.