Judge William Sullivan issued the decision in the high-profile case, potentially clearing the way for Clancy to be retried next year in the deaths of her three young children in 2023. Clancy has never denied killing the children, but her defense has argued she was suffering from postpartum psychosis and could not control her behavior.

Clancy's legal team had asked the court to end the case, arguing that the trial judge should not have declared a mistrial when jurors could not reach a unanimous verdict. They contended that the judge should have removed the single juror who favored conviction and allowed deliberations to continue.

Sullivan rejected that argument, writing that he saw no other option than to declare a mistrial. "Because the court concludes that there was manifest necessity for a mistrial based on the jury's deadlock, a retrial on the murder indictments does not violate Clancy's right not to be placed in double jeopardy," Sullivan wrote.

The defense motion, filed by attorney Martin Weinberg, also argued that the judge should have thoroughly questioned jurors after the foreperson sent two notes saying the one juror who favored conviction was not following the court's instructions on reasonable doubt. Sullivan said such questioning is barred by law.

"Because the secrecy of jury deliberations is a bedrock of our judicial system, any inquiry into the jury's deliberative process would improperly intrude into the jury's function," Sullivan wrote.

The judge also said he did not find the foreperson's claim credible that the holdout juror—identified in court papers by the pseudonym Juror Doe—was refusing to follow the law. "In context, the notes appear to express the foreperson's belief that Juror Doe must be refusing to follow the law because Juror Doe would not agree with the majority's view of the case," Sullivan wrote. "Given that the jury unquestionably had reached an impasse, the Court did not and does not view the foreperson's notes as reliable evidence of Juror Doe's inability or refusal to deliberate or follow the law."

Prosecutors have acknowledged that Clancy had mental health problems but said she acted deliberately and understood her actions were wrong. A spokesperson for Plymouth County District Attorney Timothy Cruz declined to comment on Monday's ruling.

Prosecutors have said they intend to retry Clancy, but they have not settled on whether they will pursue the same charges or opt for a reduced charge that might be more acceptable to a jury.

In a separate ruling Monday, Sullivan denied a prosecution request for a gag order while the case remains pending, which prosecutors had sought to avoid influencing a future jury. Clancy's attorney Kevin Reddington gave interviews during the trial, while prosecutors generally did not speak to reporters. Clancy's lawyers argued that a gag order would amount to an unconstitutional restraint on speech.

Sullivan also denied a defense motion to preserve certain records related to the first trial that potentially could have been used to further investigate the conduct of the juror who wanted to convict Clancy. "In the Court's view, Clancy is not entitled to any of the materials sought in this motion," Sullivan wrote.

The next hearing in the case is scheduled for Nov. 16.