ST-JEROME - Guy Turcotte, a Quebec cardiologist charged with killing his two children, wept openly in court on Monday on the first day of his trial.

Turcotte, 38, broke into tears as Crown prosecutor Claudia Carbonneau detailed the deaths of his children: Olivier, five, and Anne-Sophie, three. Police found them in their beds in Turcotte's Piedmont, Que., home on Feb. 21, 2009, suffering from multiple stab wounds.

He has pleaded not guilty to two counts of first-degree murder. However, in a statement of admission filed by the defence, he says he committed an illegal act and caused the children's deaths.

Turcotte was a doctor at the local hospital in St-Jerome at the time, about 60 kilometres northwest of Montreal, and the case is a high-profile one throughout the Laurentians region.

He had recently separated from his wife, who was away on a ski trip when her children were killed.

Carbonneau told the court that the day before the killings, Turcotte spoke to Marguerite Fournier, his mother, about his feelings of anguish following the demise of his marriage. Fournier later called the police to her son's rural home, where they found the deceased children and their father, who had ingested a quantity of windshield washer fluid.

Police arrested him on the spot and he has remained in custody ever since. If convicted, Turcotte faces life in prison with no chance of parole for 25 years.

Appearing without shackles in court on Monday, he stared at the floor while the seven women and five men on the jury were given instructions. They are expected to hear testimony from about 30 witnesses by the end of the trial, including Fournier and the children's mother, Isabelle Gaston.

At her children's funeral in 2009, Gaston -- who is an emergency room doctor -- described Olivier as a little boy who was good to his friends and quick to help others out. She said Anne-Sophie loved to playfully quiz her on her medical knowledge.

She also referred to Turcotte as the "best father in the world," according to the reverend who presided over the service.

With files from The Canadian Press