Expert Witness Testifying About ‘Mortal Sin’ Leads to Call for Mistrial
Massachusetts law bars the use of a witness's religious beliefs from being used to attack or support their credibility, but that did not stop forensic psychologist Dr. Kirk Heilbrun, a prosecution rebuttal witness, from trying in the Lindsay Clancy trial.
Lindsay Clancy, 36, is on trial in Plymouth Superior Court on three counts of first-degree murder in the January 2023 strangulation deaths of her three young children. Prosecutors argue the killings were carefully planned, while Clancy's defense contends she was suffering from postpartum psychosis at the time and lacked criminal responsibility.
Dr. Heilbrun testified about conversations he had with Clancy regarding the killings, recounting that Clancy had told him she said "go to God, baby" as she strangled each child — an account that echoed earlier testimony from another expert, Dr. Avram Mack. According to Heilbrun, Clancy believed that by killing the children and then herself, the four of them would be reunited in heaven.
Heilbrun then brought up Clancy's Catholic upbringing and recalled asking her, "Isn't suicide a mortal sin?" Defense attorney Kevin Reddington immediately objected and subsequently moved for a mistrial, accusing prosecutors of "deliberate misconduct" for allegedly "injecting Catholic faith" into the proceedings through their questioning of Heilbrun. Prosecutor Jennifer Sprague pushed back, arguing that Heilbrun raised the religious issue on his own, not in response to a leading question.
This was actually the second time the phrase "mortal sin" surfaced during the trial. The previous week, prosecutor Shanan Buckingham asked Clancy's former mother-in-law, Susan Clancy, about her involvement in the Catholic Church, then asked whether she was "aware that murder is considered a mortal sin." Judge William F. Sullivan immediately called a sidebar after that exchange and instructed jurors to disregard the testimony, citing Massachusetts law that bars evidence of a witness's religious beliefs from being used to attack or support credibility.
Following Heilbrun's comment, Judge Sullivan again intervened. He ultimately denied the defense's motion for a mistrial but issued a pointed warning to prosecutors, ordering them not to let Heilbrun discuss Clancy's faith or Catholic teachings further. Addressing the jury directly, Sullivan called the testimony about Clancy's religious upbringing "absolutely inappropriate," stating it was "to be stricken" and "not to be considered," and adding that Heilbrun's "understanding of Catholic teachings is irrelevant [and] immaterial." Several jurors reportedly nodded as he spoke. Sullivan then dismissed the jury for the day.
The case is to continue with one more expert witness left to testify, probably without bringing up "mortal sin.