In a case with implications for drunken driving arrests statewide, a district court judge has generally affirmed the reliability of breath analysis tests, but left an unknown number of older tests open for challenge.

At issue are results from the Draeger Alcotest 9510, a device that police departments across the commonwealth began using in June 2012. In a closely watched ruling, the judge cast doubt on tests from machines calibrated and certified from the time they were introduced until Sept. 14, 2014.

It is not yet clear how many cases would be affected on the Vineyard; the Cape and Islands district attorney’s office said this week information is being gathered about breath test machines used in the district. 

Defense attorneys representing about 600 defendants in a consolidated case sought to exclude the use of all breath test results from the device as evidence, citing concerns about the accuracy of test results, scientific theories behind the testing, and methodology used by the state Office of Alcohol Testing. 

Thousands of drunken driving cases throughout the state had been put on hold pending the outcome, including at least 12 cases on the Vineyard. 

A 10-day hearing took place in Concord district court in late January. Defendants argued about specifics of the Alcotest device, according to court documents, including whether the source code reliably produced accurate results, whether the device relied on flawed scientific theories regarding blood to breath ratio, whether Office of Alcohol Testing methodology produced unreliable results, and whether the source code contained security vulnerabilities. 

The commonwealth refuted these points, arguing that concerns about the device have already been addressed in a previous court case, and concerns should go toward the weight breath test evidence is given in court, not whether the tests are allowed at all in drunken driving cases. 

In a 33-page decision handed down Feb. 16, district court justice Hon. Robert A. Brennan found in favor of the commonwealth on several of the technical arguments, and said devices calibrated or certified after Sept. 14, 2014 produced scientifically reliable results. 

But the judge further found there were questions about results from Alcotest devices calibrated and certified by the Office of Alcohol Testing before Sept. 14, 2014. 

Because there were no written protocols for using the breath test until 2014, “it cannot be assumed that any particular calibrator understood or routinely applied the proper standards in calibrating the device,” Judge Brennan wrote.

The commonwealth can still present witnesses on a case by case basis to demonstrate that blood alcohol test results in particular cases were produced by a properly calibrated instrument, the judge added. 

Cape and Islands assistant district attorney Tara L. Miltimore said her office is assembling annual certification and calibration dates for breath test machines used by the Cape and Islands police departments.

“Once that material is received, we will make a determination on a case-by-case basis whether we can demonstrate the reliability of the Office of Alcohol Testing’s calibration of a particular device,” she said in a statement.

Edgartown defense attorney Robert Moriarty, who is representing six defendants who have had their cases stayed pending the litigation outcome, said one of his cases falls in the time period in question. Pending appeals, he said, the other cases will return to the trial list at Edgartown district court.