Breath Test Results Thrown Out in Massachusetts: What the Hallinan Decision Means for OUI Defendants

Last week, the Massachusetts Supreme Judicial Court issued a major ruling in Commonwealth v. Hallinan, 491 Mass. 730 (2023), reaffirming what defense attorneys have known for years: the state’s breathalyzer program was a mess, and the evidence it produced can’t be trusted. The decision formally excludes breath test results from a critical time period—June 2011 through April 18, 2019—unless the Commonwealth can prove their reliability in each individual case.

As a criminal defense attorney, I’ve seen firsthand how breath test results are often treated as ironclad evidence in OUI prosecutions. The Hallinan decision is a long-overdue recognition that science without transparency isn’t justice—it’s just conviction by shortcut.

What Did the SJC Decide?

The Court upheld a lower court finding that the Office of Alcohol Testing (OAT) failed in its obligations to ensure the scientific integrity of breathalyzer machines. Specifically, OAT withheld evidence, failed to disclose critical information about calibration practices, and essentially misled courts and defense counsel for years. The SJC ruled that breath test results from the Alcotest 9510 device during the affected time period are presumptively inadmissible unless the state can meet a high burden to prove reliability.

Who Is Affected?

If you’re facing an OUI charge based on a breath test between June 2011 and April 18, 2019, your defense just gained significant leverage. Prosecutors may now be forced to drop breathalyzer evidence entirely—or prove in court why your specific test should be admissible.

For people who already pled guilty or were convicted during that period, Hallinan could also open the door to post-conviction relief. If your case depended on a breath test, it’s worth revisiting whether that conviction was built on unreliable evidence.

Why It Matters

Hallinan isn’t just about faulty machines—it’s about accountability. When the government presents scientific evidence in court, it has a duty to ensure that evidence is accurate, fair, and disclosed fully to the defense. The misconduct by the Office of Alcohol Testing violated that duty, and the SJC’s decision reflects the seriousness of that breach.

This case should serve as a warning: justice can’t be automated. Breath tests may seem like simple numbers, but behind those numbers is a system that depends on honesty, oversight, and due process. When that system fails, people’s lives are unfairly upended. I’m glad the SJC stepped in—and I’ll continue fighting to make sure my clients are judged by facts, not faulty machines.