More than 20,000 DWI Cases Invalidated After Court Finds Alcotest Results Unreliable

In a unanimous decision issued on Tuesday, the New Jersey Supreme Court ruled that 20,667 DWI cases must be either retried (in the case of convictions) or abandoned (if the cases are still pending) due to a finding that the Alcotest machines were improperly calibrated by a New Jersey State Police technician and the results, therefore, unreliable.  To read the full opinion (State v. Eileen Cassidy), click here.


In 2000, New Jersey began using the Alcotest, a product of Draeger Safety Diagnostics Inc. (Draeger), to conduct breath tests. The Alcotest machine analyzes breath samples and produces blood alcohol concentration readings that are then used to determine whether a person’s blood alcohol content is above the legal limit.

In 2004, the current calibration protocol was developed by a director with New Jersey’s Office of Forensic Sciences (OFS). In 2008, the Court found that results from Alcotest machines calibrated pursuant to that protocol were sufficiently reliable to be admissible in drunk-driving cases. State v. Chun, 194 N.J. 54, 65 (2008). The Court also required that the devices be recalibrated semi-annually to help ensure accurate measurements. Id. at 153.

During the calibration process, simulator solutions are heated to 34 degrees Celsius, the generally accepted temperature for human breath. It is essential that the temperature of the solution be accurate in order for the Alcotest’s blood alcohol content readings to be correct. The Alcotest’s calibration procedure requires the test coordinator to insert a thermometer that produces a National Institute of Standards and Technology (NIST)-traceable temperature measurements into the simulator solution used to calibrate the Alcotest and confirm that the calibration unit heated the solution to a temperature within 0.2 degrees of 34 degrees Celsius. When a thermometer’s temperature measurements are “traceable” to the standard measurements of the NIST, those measurements are generally accepted as accurate by the scientific community. There are two other temperature probes used during the calibration procedure. Unlike the NIST-traceable thermometer, they are manufactured and calibrated by Draeger.

Marc W. Dennis, a coordinator in the New Jersey State Police’s Alcohol Drug Testing Unit, was tasked with performing the semi-annual calibrations on Alcotest instruments used in Middlesex, Monmouth, Ocean, Somerset, and Union Counties. He is charged with neglecting to take required measurements and having falsely certified that he followed the calibration procedures. Dennis was indicted in 2016 for failing to use a NIST-traceable thermometer to measure the temperature of simulator solutions used to calibrate 2 Alcotest devices. When Dennis was criminally charged, the Attorney General’s Office notified the Administrative Office of the Courts that evidential breath samples from 20,667 people were procured using Alcotest machines calibrated by Dennis.

Defendant Eileen Cassidy, now deceased, pleaded guilty in municipal court to driving under the influence based solely on Alcotest results showing her blood alcohol level had exceeded the legal limit. Upon learning that the results of her test were among those called into question by Dennis’s alleged falsifications, she moved to withdraw her guilty plea. The Attorney General moved for direct certification. The Court granted the motion and remanded the case to retired Appellate Division Presiding Judge Joseph F. Lisa as Special Master to determine whether “the failure to test the simulator solutions with the NIST-traceable digital thermometer before calibrating an Alcotest machine [would] undermine or call into question the scientific reliability of breath tests subsequently performed on the Alcotest machine.” 230 N.J. 232, 232-33 (2017).

After an extensive evidentiary hearing, in May of this year, the Special Master issued a 198-page report in which he concluded that failure to use a thermometer that produces NIST-traceable temperature readings in the calibration process undermines the reliability of the Alcotest and that the State failed to carry its burden of proving by clear and convincing evidence that the Alcotest was scientifically reliable without a NIST-traceable temperature check.


In the long-awaited opinion, Justice Walter Timpone (writing for the Court), set forth, “We see no reason to question the special master’s determination.”