Jury selection begins Monday in the trial of a Massachusetts mother who strangled her three children while receiving medical treatment for psychiatric problems they developed after giving birth.

Lindsay Clancy has pleaded not guilty to murder charges in the deaths of her children Cora, 5, Dawson, 3, and Callan, who was 8 months old when the siblings were killed on Jan. 24, 2023.

Clancy, now 36, threw herself out of a window after killing the children and was paralyzed in the fall. She is admitted to a state hospital.

The trial is expected to explore the complicated and rare phenomenon of postpartum psychosis, which affects a very small percentage of women who develop delusions and sometimes hallucinations after giving birth. Clancy’s (and her husband’s) lawyers say she was not responsible for her actions.

Prosecutors say the killings were intentional and well-planned, not the work of someone who had lost control.

The day it happened, Clancy, a former labor and delivery nurse at Massachusetts General Hospital, asked her husband, Patrick Clancy, to go out for takeout and pick up something at the pharmacy. He then used exercise bands to strangle his children at the family’s home in Duxbury, about 30 miles (48 kilometers) south of Boston.

Eighteen jurors, including six alternates, are expected to be chosen in several days. The trial is expected to last several weeks.

Clancy’s attorney, Kevin Reddington, does not deny that she killed the children, but plans to present an insanity defense.

“This whole case is an extreme tragedy,” he said.

Clancy and her husband filed lawsuits earlier this year accusing her medical providers of failing to properly diagnose, treat and monitor her for a “serious postpartum psychiatric condition.”

Lindsay Clancy’s lawsuit details how she was depressed, had trouble sleeping and repeatedly heard voices urging her to harm her children and herself. He spent several days in a psychiatric hospital just weeks before the murders.

“Lindsay Clancy did everything a mother in her situation could do. She recognized that something was wrong with her. She sought medical treatment. She went to emergency rooms. She called crisis hotlines. She checked into hospitals. She took the medications she was prescribed. She reported her worsening symptoms to her providers. She told them that the medications were making her worse,” the lawsuit says.

On the day of the murders, Clancy said he heard voices saying, “This is your last chance. Kill the children so you can kill yourself.”

Both sides have Clancy’s husband on their witness list. He has said in interviews that he forgives his wife.

In a GoFundMe post several days after the murders, Patrick Clancy wrote that “the shock and pain is unbearable and unrelenting,” but urged the public to see Lindsay Clancy as they saw her before the murders.

“The real Lindsay loved and cared generously for everyone: me, our children, my family, friends and her patients. The very fibers of her soul are loving. All I wish for her now is that she can somehow find peace,” it said.