Judge William Sullivan has denied a request by Lindsay Clancy's attorney Kevin Reddington to declare a mistrial, citing prosecutors' mention of Clancy's religion during recent testimony.

"I am not going to declare a mistrial at this time," Sullivan said.

Reddington had accused prosecutors of "intentional misconduct" after they asked forensic psychologist Kirk Heilbrun about a conversation he testified he had with Clancy, during which Heilbrun said they discussed her Catholic upbringing and the notion of suicide as a "mortal sin."

The phrase "mortal sin" has come up previously in this trial -- Clancy's former mother-in-law, an active churchgoer, was asked by prosecutors last week if she was "aware that murder is considered a mortal sin" -- with Sullivan instructing jurors at the time "not to consider" it "for any reason or any purpose."

At the time, Reddington did not move for a mistrial, calling it a "tactical decision," but said Monday that the most recent example was too much.

"It's the same thing again: talking about religion, talking about heaven, talking about killing people and the impact or the effect that it would have on Lindsay, as well as her children," he said.

Prosecutors pushed back on Reddington's motion for a mistrial Monday, arguing they did not intentionally invoke Clancy's religion, and that the remarks were relevant to the witness's testimony.

“There was no intentional conduct by the Commonwealth," prosecutor Jennifer Sprague told the judge. "That was not where I intended to go with this questioning, and I don't think that the witness intended to do any harm either, he was just explaining his rationale."

After denying the defense's request for a mistrial, Sullivan again instructed jurors to ignore recent testimony related to Clancy's religion, calling it "an inappropriate area of inquiry" and saying Heilbrun's "understanding of Catholic dogma or Catholic teaching is irrelevant."

Sullivan then sent the jury home for the day.

Testimony will resume with the same witness tomorrow morning at 9 a.m. ET.

For their second rebuttal witness, prosecutors called forensic psychologist Kirk Heilbrun to testify about his evaluation of Lindsay Clancy.

Heilbrun, who told jurors he met with Clancy four times this year and reviewed her medical records and clinicians' notes, testified that Clancy suffered from the side effects of the medications she was prescribed and that her medical providers disagreed on her diagnosis.

Heilbrun also testified that he believed Clancy suffered from bipolar II disorder, but testified that he did not observe manic episodes.

This was one of several competing assessments detailed by prosecutors and defense lawyers, with prosecutors pushing back on the bipolar diagnosis and defense lawyers arguing Clancy suffered from bipolar disorder with postpartum psychosis.

Heilbrun testified that Clancy began taking Zoloft, an antidepressant used to treat major depressive disorder, in October 2022, just a few months before she killed her children, at which point "things started getting very difficult."

Heilbrun told jurors that Clancy's anxiety got measurably worse after taking the medication and she continued to suffer from insomnia.

"Late in November [2022], she was still having a lot of trouble sleeping. She thought that she was close to what she called the end of her rope. She was feeling off and disconnected and sort of like a zombie," he testified.

He testified that Clancy began to suffer "horrible intrusive thoughts" in December 2022 -- the month before the killings -- including thoughts of potentially harming her children.

However, Heilbrun testified that Clancy's intrusive thoughts were not "auditory hallucinations" as alleged by defense lawyers.

Heilbrun also told jurors that Clancy had "a small shred of hope" following a brief inpatient stay in January 2023, but that her conditions eventually worsened.

"Over the course of the time that she was going through these experiences, between mid-October [2022] and late January [2023], she'd had a lot of providers offer a lot of diagnoses, and there were a lot of complicating considerations," he testified.

Lindsay Clancy's defense attorney Kevin Reddington attempted to push back on Monday against a prosecution expert who has testified that, in his opinion, the Massachusetts mother did not appear to be affected by postpartum psychosis when she killed her three children.

Forensic psychiatrist Avram Mack, whom prosecutors first called to the witness stand Friday, has at times refused to answer Reddington's questions during the defense's cross examination, and Judge William Sullivan has intervened multiple times.

"It's your understanding from reviewing her medical records that Lindsay never indicated that she was not participating in reality, that she was in a disassociated state, that she was out of touch with reality -- you're telling this jury you never saw that?" Reddington asked.

"I don't see that as a sign, strictly speaking, of psychosis, Mack said. "It may have been in some cases, but I don't see any signs of psychosis or delusions."

After a heated back-and-forth concerning how postpartum psychosis might manifest in some patients, Mack asked, "Are you referring to postpartum psychosis and illness? Or the findings of psychosis and somebody's postpartum?"

Reddington returned a sharp rebuttal.

"I'm asking you about Lindsay Clancy... the young lady that is sitting right here that you're testifying against in front of this jury that she is responsible for the death of her children,” answered Reddington.

Prosecutors are now re-directing Mack.

Prosecutors in Lindsay Clancy's murder trial are set to call a series of expert witnesses Monday, as they attempt to push back on the defense claim that the Massachusetts mother was in the throes of postpartum psychosis when she killed her three children.

The defense rested its case on Friday after calling 10 witnesses, including members of Clancy's immediate family and a series of medical experts, across one week of testimony.

Prosecutors plan to call a total of three medical experts in these final days of trial--the first of whom was called to the witness stand Friday-- as part of a rebuttal case, before jurors can hear closing arguments, which could begin as early as Tuesday.