Judge William Sullivan ruled Wednesday that Clancy’s defense cannot use an upcoming hearing to investigate whether the juror misrepresented his past involvement with the criminal justice system on a jury questionnaire. The ruling draws on a decision in the Karen Read case, which held that a mistrial’s necessity must be assessed based on what was known when the judge declared it.

Clancy’s attorney, Kevin Reddington, had sought to preserve juror records and question the juror, who was reported to have been the only juror voting to convict. The defense argued that information about the juror’s history, including a restraining order that was active when he was selected, could bear on whether he should have served. The juror has denied lying on his questionnaire and has not been charged in connection with the case.

Sullivan wrote that evidence emerging after a mistrial about possible grounds to remove a deliberating juror does not establish whether there was a “manifest necessity” for ending the trial. He also cited the Read case’s warning that relying on jurors’ post-trial accounts could create confusion and controversy in cases that ended in deadlock. Sullivan noted there had been no suggestion of a questionnaire lie before he declared the Clancy mistrial.

The ruling does not change a Nov. 2 hearing, when the defense and prosecutors are scheduled to argue Clancy’s motion to dismiss the case. The judge said that hearing will proceed without the proposed new evidence.

Clancy, of Duxbury, faces three first-degree murder charges in the deaths of her three children. At trial, her defense argued she was experiencing postpartum psychosis; the defense did not dispute that she killed the children before attempting suicide. The jury’s deadlock led to a mistrial last month, and the Plymouth County District Attorney’s Office has not announced whether it will seek a retrial.