Plymouth, Massachusetts - A judge denied a mistrial motion in Lindsay Clancy’s murder trial on Monday after a prosecution witness brought up Catholicism and "mortal sin," choosing instead to reprimand the state's legal team and keep the high-profile murder case moving toward closing arguments.

Clancy is on trial for murder in the 2023 strangulation deaths of her three young children that she had with ex-husband Patrick Clancy. While she does not deny taking their lives, her defense argues she was in the grips of postpartum psychosis and not criminally responsible.

The courtroom drama erupted Monday after Clancy's lead defense attorney, Kevin Reddington, brought testimony of the prosecution's rebuttal expert witness, Dr. Kirk Heilbrun, to a screeching halt with a strong mid-sentence objection; the judge cleared the jury from the courtroom on Monday to have a rather serious discussion with the defense and prosecution that ended in the latter's favor.

Reddington on Monday afternoon had asked for the judge to declare a mistrial, which was denied, after the forensic psychologist spoke on "mortal sin" in his answer to a question by the prosecution about conversations he had with Clancy after the deaths of her children.

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“One of the things that she said about what happened is that in the course of strangling each child, she said, ‘Go to God, baby. Go to God,'" Heilbrun said during his testimony. "And that was part of her expectation, that she and the children would be together in Heaven with God. She was raised as a Catholic. ... But when I asked her about that, when I said, ‘Isn’t suicide a mortal sin...'”

It was then that Reddington cut him off, and Judge William Sullivan dismissed the jury from the room. Out of the jury's presence, Reddington asked Sullivan to declare a mistrial, pointing to Heilbrun’s mention of "mortal sin" while describing post-crime interviews with Clancy.

While the jury was out of the courtroom, Reddington accused the prosecution of "intentional misconduct," noting this was the second time religious doctrine had been dragged into court. Just last week, prosecutors asked Clancy's mother-in-law whether she was aware that "murder is considered a mortal sin."

While Reddington previously accepted a jury instruction after the first incident, he argued Monday that the pattern crossed the line: "It’s the same thing again: talking about religion, talking about Heaven, talking about killing people and the impact of the effect that it would have on Lindsay as well as her children," Reddington told the judge. "The fact that this is not the first time that it occurred during the trial. ... I believe it was intentional misconduct, and I feel that the court should grant a motion for a mistrial".

Assistant State Attorney Jennifer Sprague argued that Heilbrun was "explaining his reasoning" and shared she didn't think "he was intentionally trying to inflame the jury or cause an issue in this case."

Sullivan then said he would not declare a mistrial, and instead told the witness any talk of religion is inadmissible and issued strong instructions to the jury: "The religion that the defendant was raised with is absolutely an inappropriate area of testimony. It is to be stricken. It is not to be considered. Secondly, the witness’s understanding of Catholic teachings and considerations is immaterial; it’s irrelevant; it is to be disregarded based on that testimony."

Prosecutors are expected to wrap up their rebuttal case on Tuesday before both sides present closing arguments, with jury deliberations starting as early as Wednesday.