SAINT-JEROME, Que. - A man charged with murdering his two young children sobbed on Monday as lawyers tabled photos of the three of them playing and celebrating birthdays.

Defence lawyer Pierre Poupart told the jurors hearing the trial of Guy Turcotte their considerable task centres on whether the once prominent cardiologist intended to kill them.

"What's really at stake is what did he have in his head? Why?" Poupart said.

"Did Guy Turcotte, a human being, cause the deaths of his kids with the intention of doing so?"

Turcotte has admitted to causing the kids' deaths but has denied intent.

The Quebec cardiologist is charged with two counts of first-degree murder in the 2009 slayings of his children Olivier, 5, and Anne-Sophie, 3.

They were stabbed to death in a rented home in Piedmont, Que., where Turcotte was also discovered after having ingested washer fluid.

The defence's first witness was the same as the Crown's first witness: Turcotte's own mother.

Marguerite Fournier presented the jury with a booklet of photos of Turcotte and his children.

The pictures show Turcotte with his kids in various situations: at play, at Christmas, and on birthdays.

"They were moments where we marked the importance of Guy in the lives of the children," Fournier said.

Each photo brought quiet sobbing from the accused.

Turcotte's brother Gilles -- one of six Turcotte children -- also brought some photos that showed the accused as a doting father who loved being around children.

"A lot of people heard him say that 'Olivier is my best friend'," Gilles Turcotte said.