Justice William Sullivan has declared a mistrial in the triple murder trial of Lindsay Clancy, a mother accused of strangling her three children to death, after jurors failed to reach a unanimous verdict on whether she was criminally responsible for the killings.

“It is with a heavy heart that we report that we are unable to come to a unanimous decision and will not be able to,” read a note from the jury foreperson on Friday.

The jury was deadlocked 11-1 in favour of acquittal, with one juror refusing to agree to the decision.

Ms Clancy’s lawyer filed an emergency appeal at the Massachusetts Supreme Judicial Court on Friday, seeking an investigation into the juror who held out. However, the motion was denied.

The 12-member jury, comprising nine women and three men, failed to reach a verdict on whether Ms Clancy, 36, was guilty of murdering her three children — Cora, 5, Dawson, 3 and Callan, 8 months.

Ms Clancy, who is now paralysed from the waist down, claimed she heard a man’s voice telling her to kill her children and herself. She admitted to strangling the children on January 24, 2023, while her husband was out running housekeeping errands.

After killing the children, Ms Clancy slit her neck and wrists before jumping from a two-storey building, breaking her spine. She now uses a wheelchair for mobility.

Her lawyer argued that she strangled the children while suffering from postpartum psychosis and should not be held criminally responsible for her actions.

Assistant District Attorney Shanan Buckingham challenged that diagnosis, arguing that Ms Clancy “acted intentionally, rationally and swiftly to accomplish a very specific goal: to kill.”

“This is not a public debate about women’s mental health and how the medical system treats women,” Ms Buckingham told jurors. “This case is about this defendant, Lindsay Clancy.”

Prosecutors argued that Ms Clancy was of sound mind when she committed the killings, saying she deliberately carried them out while her husband was away from home.