The New Jersey Supreme Court on Tuesday threw out the results of Draeger Alcotest breathalyzer tests. The devices, in use for nearly two decades, were not properly calibrated, throwing into doubt over 20,667 drunk driving convictions obtained through the use of the Alcotest 7110 device that the court ruled credible a decade ago (view ruling).

The problem with the machines emerged with the 2016 indictment of Sergeant Marc W. Dennis, the state police official in charge of verifying breathalyzer accuracy for Middlesex, Monmouth, Ocean, Somerset, and Union Counties. Sergeant Dennis was caught lying about using proper temperature measurements in calibrating the machines. This was not a minor oversight, as the reliability of the breath test measurement hinges on accurate readings. The calibration test uses four sample solutions that simulate human breath at specific alcohol levels. For an accurate reading, these solutions must be heated to between 92.8 and 93.6 degrees degrees Fahrenheit -- roughly, the temperature of human breath.

A small inaccuracy in these machines can have a big impact. State law makes it a crime to drive with a blood alcohol concentration of 0.08, so having the machine display that number results in a conviction, while a 0.07 blood alcohol reading generally results in a dismissal of charges. Eileen Cassidy used the evidence of the official misconduct to re-open her conviction for driving under the influence (DUI), which was based entirely on the reading of an improperly calibrated machine on September 8, 2016. Although she died from cancer earlier this year, the high court took up her case to set the precedent for how all the other appeals should be handled.

Prosecutors in an attempt to save all the past convictions insisted that it did not matter whether the critical temperature measurements were made with a thermometer certified under the strict National Institute of Standards and Technology (NIST) procedures. The court relied on a special master's report synthesizing the view of scientific experts who concluded that the NIST certification mattered. This thermometer is the only calibration instrument not provided by the manufacturer.

"If you put everything into Draeger's hands as far as certifying the solutions, the instrument, the calibrating unit and everything else, what if -- what if there is a bias or an error in Draeger's laboratory?" forensic chemist Thomas A. Brettell asked during testimony."What impact would that have on the breath test program in New Jersey?"

If the calibration temperature measurement is just one degree low, the breathalyzer would produce readings that are seven percent too high -- the difference between a legal 0.07 blood alcohol reading and a 0.08 reading resulting in a DUI conviction.

"We order the state to notify all affected defendants of our decision that breath test results produced by Alcotest machines not calibrated using a NIST-traceable thermometer are inadmissible, so that they may take appropriate action," Justice Walter F. Timpone wrote in the unanimous court ruling.

The high court waived time limits so that old cases could be reopened. It also canceled Cassidy's conviction.

A copy of the ruling is available in a 3mb PDF file at the source link below.