A legal challenge that could derail scores of drunk driving cases will get underway next week in Concord, where lawyers will argue the breath testing equipment used by police across Massachusetts is unreliable, the MetroWest Daily News reported. Judge Robert A. Brennan on Tuesday is expected to consider a motion filed by lawyers representing hundreds of defendants who seek to have the breath testing evidence in their cases thrown out. Brennan, a Salem District Court judge, was picked in 2015 to preside over the consolidated case, which has stalled numerous OUI prosecutions across the state. More than 2,000 people have either joined the challenge or had their cases stayed while the matter is under review. After more than one year of preparation, Brennan is expected to decide whether to initiate a hearing to evaluate whether evidence produced by the Alcotest 9510 -- the breath testing machine used in Massachusetts -- is scientifically sound. A team of lawyers representing the defendants argue the source code of the machines fails to meet accepted industry standards, potentially skewing the results of blood alcohol tests. The devices also have potential security flaws, the defendants argue, leaving them vulnerable to tampering. Prosecutors have asked Brennan to deny the request for an evidentiary hearing. They contend the Alcotest 9510 is similar to an older model used previously in Massachusetts, and therefore doesn't require additional scrutiny. Like its predecessor, the 9510 device uses two different kinds of sensors -- one that relies on infrared light and another that uses electrochemical cells -- to measure alcohol content. Because of the similarity, prosecutors argue the 9510 doesn't employ a "novel" scientific technique worthy of review. Representatives from Draeger Safety Diagnostics, the German company that manufactures the devices, may be called to testify during next week's proceedings. While other courts have previously evaluated challenges to Draeger's equipment -- including in Massachusetts -- the defendants contend a new hearing is necessary because the specific methods prescribed by the state's Office of Alcohol Testing vary from those in other states. The defendants also argue that previous cases failed to evaluate the real-world performance of the machines, instead looking only at how the computer code is written and ignoring whether the instructions are carried out successfully by the equipment. The defendants last year won a court order granting them access to a pair of the devices to observe how they function. Defense experts were allowed to conduct so-called "dynamic" tests, evaluating whether the hardware performs as intended. Legal challenges against the machines began mounting in 2015 after the state's Executive Office of Public Safety and Security disclosed they were never programmed with the correct calibration settings after the state began rolling them out four years earlier. The agency reviewed an estimated 39,000 tests and found that evidence in fewer than 150 OUI cases was tainted by calibration problems. While the machines were updated with a software patch, Massachusetts District Court Chief Justice Paul C. Dawley encouraged judges to grant requests from defendants to put new OUI cases on hold until a ruling is rendered in Concord. The case has since been combined with a similar challenge in Boston Municipal Court.