Montreal police attend the scene of a triple stabbing, at an east-end Montreal apartment, on Friday, March 17, 2023. THE CANADIAN PRESS/Ryan Remiorz

By The Canadian Press

Judge to rule in January if man accused in triple murder was criminally responsible

Dec 4, 2025 | 9:08 AM

MONTREAL — A man who stabbed his parents and grandmother to death inside their Montreal home in March 2023 should be found not criminally responsible for the crimes, both the prosecution and defence told a courtroom on Thursday.

In a joint submission, the Crown and defence said Arthur Galarneau, 22, was suffering from a mental illness at the time of the triple murder. The evidence presented in court included testimony from a psychiatrist who concluded Galarneau was suffering from schizophrenia and could not be held responsible for his actions.

During a two-day hearing that concluded Thursday, details about what happened on March 17, 2023, were released publicly for the first time. The murders, prosecutor Anne-Andrée Charette told the court earlier this week, “represent the culmination of the progressive deterioration of the accused’s mental state over the years preceding the events.”

On the day of the killings, Galarneau’s mother Mylène Gingras, 53, called 911 around 9 a.m. from an apartment in Montreal’s Rosemont-La-Petite-Patrie borough, according to a summary of the Crown’s evidence. During the call with the dispatcher, there was an apparent struggle inside the apartment, and the mother started to scream. She asked the dispatcher for an ambulance, saying, “my son wants to kill me.” Then the line went dead.

Police traced the call to a duplex on Bélanger Street, an address known to police as the home of someone with a history of mental health issues. Officers arriving at the scene could see movement through the front door glass, including a person being dragged across the floor. Charette said officers saw a lot of blood and realized the accused was stabbing his mother.

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The Crown’s evidence continues to say that an officer kicked in the door causing Galarneau to lose his knife. The accused, covered in blood, said, “it’s good, it’s good, I’m finished.” Officers ordered him to the ground but he didn’t comply. Police then used pepper spray as the accused spit on them and tried to bite them.

“He spoke of the devil, of demons and of Satan,” Charette told the court, adding he repeatedly screamed his mother’s name and said he wanted to die.

The accused was charged with second-degree murder in the stabbing deaths of his mother, his father Richard Galarneau, also 53, and his grandmother Francine Gingras-Boucher, 75. All three victims were stabbed repeatedly and a pathologist noted Galarneau’s mother had been stabbed 137 times, suffering 81 defensive wounds.

Galarneau’s father had been estranged from his mother, but had recently moved back into the duplex to help with his son, whose schizophrenia symptoms had become worrisome. The parents had sought help for their son leading up to the killings.

Following his arrest, Galarneau had to be restrained by several hospital staff to administer a sedative. Blood samples later revealed the presence of THC in his system.

During an interrogation the evening of the killings, he said he was in shock and admitted to have consumed drugs and to have not taken his medication.

Dr. Gilles Chamberland, a psychiatrist who examined Galarneau on behalf of the Crown, concluded that the accused was delusional and had lost all notion of right or wrong at the time of the killings. Galarneau could not be found criminally responsible due to his schizophrenia, the doctor said. A defence expert had come to the same conclusion.

During his testimony, the psychiatrist noted Galarneau consistently refused medication after his arrest, leading to a deterioration of his condition.

After a court order for involuntary treatment, the accused has gained insight into his illness and the effectiveness of medication, Chamberland said.

Chamberland recommended strict detention for Galarneau, given that he still suffers from residual symptoms and requires intensive care.

Quebec Superior Court Justice Annie Émond said she will render a decision on Jan. 22. If she agrees with the joint submission, the Crown has said it would seek to declare Galarneau a high-risk offender, which could impose tighter restrictions on his freedom of movement or prevent him from leaving a psychiatric hospital.

Galarneau’s lawyers have said they would contest a high-risk offender designation.

This report by The Canadian Press was first published Dec. 4, 2025.

Sidhartha Banerjee, The Canadian Press