A Quebec woman who was in jail awaiting trial for killing her three children has starved herself to death with legal assistance from right-to-die advocates.

Sonia Blanchette, who was accused of drowning her three children in 2012, died Thursday night in the palliative care ward of Montreal's Sacré-Coeur Hospital, her lawyer Jean-Pierre Ménard confirmed. She was under sedation to ease her considerable suffering in her final days, he said.

Mr. Ménard, a leading advocate for patients' rights and an architect of Quebec's right-to-die law, said Ms. Blanchette decided to stop eating after a long period of reflection. Since December, the lawyer intervened on Ms. Blanchette's behalf at a Montreal jail and two hospitals to ensure doctors would not treat her against her wishes.

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"Over time she decided life didn't have any more interest to her. She reflected for a long time on her condition, her prospects, and decided to put an end to her days," he said. "Her biggest hope was to rejoin her children."

The legal system that has worked toward proving Ms. Blanchette's sanity and put her on trial may have inadvertently helped allow her to die legally. Last year, a court found Ms. Blanchette was fit to stand trial. Under long-standing Quebec jurisprudence, a person who is considered mentally competent can refuse any kind of medical treatment, even if it leads to death.

"She was judged competent to face a trial, so she was apt to decide on her medical treatment, like any other person in the medical system," Mr. Ménard said in an interview. "Listen, her life wasn't very nice, but she had no pathology or mental illness that would justify treating her against her will."

Mr. Ménard led a team that designed the legal framework for Quebec's doctor-assisted death law. The law passed last summer, however, played no part in Ms. Blanchette's case.

Patrick Désautels, the father of the three victims, said Friday he was relieved there will be no trial for his ex-partner. "It doesn't really bother me that she's dead; I don't really have any pity for her," Mr. Désautels told Radio-Canada. "I would have liked to see her spend more time in jail to think about what she did. But she decided otherwise."

Ms. Blanchette was detained at the Tanguay detention centre in Montreal shortly after her children – Lorélie, 5; Loïc, 4; and Anaïs, 2 – were found dead in a home in Drummondville, Que, on Dec. 2, 2012.

Near the second anniversary of their deaths, Ms. Blanchette decided to stop eating. She was shipped to the Pinel psychiatric hospital for evaluation. That's when Ms. Blanchette called Mr. Ménard.

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The hospital started taking away Ms. Blanchette's privileges and were forcing potassium injections and other treatments on her. They were planning to force her to eat when Mr. Ménard intervened. He presented the hospital with a demand to stop treatment, along with a raft of documentation showing she was competent. He also prepared to take them to court. The hospital's ethics committee decided to respect Ms. Blanchette's wishes, Mr. Ménard said.

Ms. Blanchette was returned to the Tanguay jail where Mr. Ménard intervened again when officials put her on suicide watch with monitoring every 30 minutes and again applied pressure to make her eat. Mr. Ménard said her condition declined rapidly from there.

On Dec. 17, she was moved to the Sacré-Coeur palliative-care ward.