A small number of 39,000 breath analysis tests conducted by police on suspected drunk drivers were flawed because of mistakes officers made calibrating the machines and not because the tests themselves were malfunctioning, Public Safety Secretary Daniel Bennett said on Tuesday.
The announcement came after concerns over the accuracy of test results prompted at least eight district attorneys to suspend use of breath tests as evidence. But a state review found fewer than 150 cases in which the machines were improperly calibrated by the user, and no evidence the Draeger 9510 breath test machines were functioning improperly.
“Motor vehicle operators and the law enforcement community must have faith that breath tests are accurate and reliable, and we have taken the steps necessary to make sure that is the case,” Bennett said.
He said he will work with district attorneys to find the 150 people whose prosecutions may have been affected by flawed testing.
The results of the review, however, did not assuage everyone’s fears, and the Massachusetts Bar Association renewed calls for Attorney General Maura Healey to establish an independent investigation into the tests’ reliability.
“We want to make sure that everyone has a fair trial and a trial that’s based on scientifically proven evidence. And in this case, we don’t have that,” said Martin W. Healy, chief legal counsel for the association, who wrote a letter to the attorney general calling for her to appoint an investigator without ties to law enforcement.
Healy expressed concern about how quickly the state investigation was conducted. He said that many attorneys would continue raising questions about the breath tests and that they should not be used as evidence until an independent review is published.
“Any time there is a question about the validity of evidence used in a criminal proceeding, the attorney general is concerned,” said Christopher Loh, the attorney general’s spokesman. “We will review the letter and determine the next best steps to address this issue.”
Bennett said his office is now “working with the appropriate district attorneys to identify each individual whose breath test was affected by operator error, so that we can ensure that the operator errors did not unfairly impact any OUI prosecutions; and so that prosecutions of those suspected of operating under the influence can go forward based on all of the available evidence, including breath tests.”
According to his office, state regulations require that police calibrate the machines to operate in a range between 0.074 and 0.086. That figure is more stringent than the manufacturer routinely sets for machines, the state said.
When law enforcement started using an updated Draeger model in 2011, the state did not ask the company to calibrate the machines to Massachusetts’ unique standards. The company has since agreed to provide a software patch for the machines, Bennett’s office said.
Last week, Suffolk, Worcester, Norfolk, Plymouth, and Northwestern district attorneys announced they were suspending use of breathalyzer results as evidence in pending drunken-driving cases. They joined DAs for Middlesex and Essex counties and the Cape and Islands who had already announced temporary bans on breathalyzer evidence.
Jake Wark, a spokesman for Suffolk District Attorney Daniel F. Conley, said the research by Bennett’s office has confirmed what Conley’s office already concluded. “Our review of past cases involving breathalyzer evidence continues, but we’ve found nothing to suggest that our very small number of affected cases will increase,’’ he said.
For the moment, he said, prosecutors will continue seeking continuances in cases involving breathalyzer evidence, but they expect those cases to begin moving forward “in the near future.”
Cape and Islands District Attorney Michael O’Keefe said he also expects to lift the embargo in the next several days.
Middlesex District Attorney Marian Ryan said her office is “awaiting further information from the Massachusetts Executive Office of Public Safety and Security, and we will continue to review cases as we move forward.”
A spokesman for Worcester County said District Attorney Joseph D. Early Jr. is awaiting more information before making any changes to his office’s temporary ban. A spokeswoman for the Essex County District Attorney said prosecutors were still reviewing the findings.
Philip A. Tracy Jr., a senior partner at DiMento & Sullivan, said doubts about the breathalyzers will linger because of past scandals, including the 2012 discovery that state chemist Annie Dookhan fabricated evidence in thousands of samples she tested.John R. Ellement can be reached at email@example.com.