The Skill To Defend You

Researchers say Breathalyzer has flaws

Anyone who is pulled over on suspicion of DUI or OWI knows the drill. While the officer will often ask a series of questions, it often inevitably ends with the driver taking a Breathalyzer, blood or urine test. The most popular roadside test is the breath test with a Breathalyzer, which has been used as evidence in more than one million DUI convictions in America each year. If the officer suspects that the driver is driving while above the legal blood alcohol concentration limit of .08 percent, they can use implied consent to force driver to take this test and then use it as evidence against the driver.

Unfortunately, there are researchers that believe that the commonly used Alcotest 9510 Breathalyzer manufactured by Draeger had bad source code. This means that machine can give false readings of the tested driver being over the legal limit. The two researchers released preliminary findings, but the manufacturer quickly fought back with a cease and desist order to “protect its source code” and essentially shut down the research project.

New concerns about the device

This is not the first skirmish for the Alcotest 9510 – there have also been strong concerns voiced by others that law enforcement officers improperly calibrating the machine, causing it to give an inaccurate reading. Nonetheless, the new research focuses in on other issues.

  1. Breath temperature: The device does not have an adjustment for breath temperature, which fluctuates through the day and can effect the accuracy of the reading.
  2. Fuel cell: The report points out that any fuel cell degrades over time, so a Breathalyzer used thousands of times is going to become less accurate than one used a few times each month. The code for the Alcotest 9510 was written to compensate for the fuel cell’s decline, but recalibration after the first six months will be erroneous.

New research forthcoming

The case involving the above research has stalled, but according to an article in, a new researcher (a software engineer named Sam Felton) claims that he will continue the work with his own analysis of the Alcotest 9510. No word on his findings at this time. However, this is the latest reminder of the fact that Breathalyzers are not 100 percent accurate.

Those who have gotten a result over the legal limit when they took a Breathalyzer test may want to talk to an attorney who has experience handling DUIs and issues involving inaccurate Breathalyzer findings.