A state police technician’s errors in calibrating Alcotest drunken-driving testers could call into question the validity of up to 20,000 breath tests performed on defendants, a special master has reported to the New Jersey Supreme Court after a yearlong study.

The failure to use the type of thermometer specified by the Supreme Court in State v. Chun, its landmark 2008 ruling finding the Alcotest 7110 scientifically reliable, “raises substantial doubts about the scientific reliability of breath test results produced by Alcotest devices calibrated without use of a NIST-[National Institute of Science and Technology] traceable thermometer,” former Presiding Appellate Division Judge Joseph Lisa said in a 218-page report issued to the Supreme Court.