Aug 25, 2026

PLYMOUTH, Mass. (Court TV) — One of the prosecution’s expert witnesses conceded under cross-examination that Lindsay Clancy was suffering severe adverse reactions to medications in the months before she killed her children.

Lindsay Clancy sits in court on Aug. 25, 2026. (Greg Derr/ The Patriot Ledger (POOL))

Clancy, 36, is charged with three counts of murder in the deaths of Cora, 5, Dawson, 3, and Callan, 8 months. The defendant has admitted that she strangled her young children to death with exercise bands in the family’s Duxbury home, but has argued that she is not criminally responsible because she was suffering from postpartum psychosis at the time.

Psychologist Kirk Heilbrun returned to the witness stand on Tuesday morning after his testimony ended abruptly on Monday afternoon. Under direct examination, he disagreed with the defense expert who found Clancy was psychotic when she killed her children, finding instead that the defendant suffered from bipolar II, depressive symptoms and peri-traumatic dissociation. “She talked about feeling like it wasn’t her, like she was watching herself, like she was going through what she called ‘no thinking,’ no decision-making, only responding to the voice and taking action,” he said.

Heilbrun said he believed Clancy was suffering from mental illness when she took her children’s lives, but maintained that she was still rational enough to make decisions. “There are many ongoing decisions that have to be made to accomplish a killing like this in 18 to 20 minutes,” Heilbrun testified. “For example, why the basement? Who among the children goes first? What do you say to the kids to keep them from panicking?”

Heilbrun said he ultimately found that Clancy’s actions were a “serious suicide attempt accompanied by killing the children out of love.”

Clancy’s attorney, Kevin Reddington, immediately challenged Heilbrun’s credentials during cross-examination.

Reddington: “Have you ever treated a woman in postpartum psychosis?”

Heilbrun: “When I was a staff psychologist at the forensic service at Florida State Hospital.”

Reddington: “When was that, please?”

Heilbrun: “That was back in 1982.”

Reddington also highlighted that Heilbrun is an independent contractor hired by the Commonwealth through the firm Park Dietz and Associates, as was the prosecution’s first rebuttal expert witness, Dr. Avram Mack. Park Dietz provided key testimony in Andrea Yates’ first criminal trial — testimony later found to be inaccurate — resulting in the overturning of her conviction.

Under cross-examination, Heilbrun conceded that the defendant was a “very good mother,” saying, “I knew she was very good with her kids, paid a lot of attention to them, spent a lot of time with them, and really enjoyed it.”

Reddington asked Heilbrun about the psychotropic medications, which included Seroquel, lorazepam and Zoloft, that multiple prescribers had given Clancy in the months before her children’s deaths. “These medications are available because, for what they’re prescribed for, they help most people. They have to go through clinical trials and all sorts of things, but for a few people there are side effects and what we call adverse reactions, and they don’t help,” Heilbrun said. “In fact, they might make things worse, and it appeared to me from viewing the records for Ms. Clancy that she’s one of the few people where the reactions were very very different, very poor.”

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Clancy detailed the moments of her kids’ deaths in a lawsuit she filed against her medical providers earlier this year. While she was seemingly able to recall the details of what happened that evening, Reddington called her memory into question on Tuesday when he pointed out that the defendant had initially claimed that she used a knife to cut the screen of a window before jumping out of it. Evidence presented earlier at Clancy’s trial showed that the screen had been pushed up, not cut.

Reddington: “Would you agree with me, sir, that if a person has a memory while they’re in a psychosis that it’s very possible that they could be imagining that they did something, but just the facts, objective facts, would show she didn’t?”

Heilbrun: “It’s possible that being in an actively psychotic condition could affect the way information is processed and therefore could affect the accuracy of their memory.”

During redirect, Assistant District Attorney Jennifer Sprague had Heilbrun specify that even someone who is experiencing command hallucinations or psychosis can abide by the law and understand the difference between right and wrong.