SAINT-JEROME - Dr. Guy Turcotte finally has begun to tell his side of the story; it starts with an unhappy childhood, followed by a happy hour where he met the love of his life in a bar.

Speaking slowly but clearly, Turcotte spoke Monday about a childhood where he was the awkward outcast, about his 11-year journey to becoming a cardiologist, and how he came to meet his now-estranged wife.

His demeanor on the stand was more composed than earlier in the day when he sobbed as his lawyers tabled photos of Turcotte playing with his children and celebrating birthdays and holidays.

Turcotte has spent much of the last two weeks sobbing as the Crown presented evidence against him in the first-degree murders of his children Olivier, 5, and Anne-Sophie, 3.

He has admitted to causing the kids' deaths and committing an illegal act, but has denied intent to kill.

The children were stabbed to death in 2009 in a rented home in Piedmont, Que., where Turcotte was also found after having ingested washer fluid.

The jury has heard two weeks' worth of Crown witnesses. The couple's life coach recounted last week that Turcotte had told him the little boy pleaded with him to stop his knife attack.

His estranged wife, Isabelle Gaston, an emergency-room physician, told the jury about a rocky 10-year relationship that ended when she had an affair with her personal trainer.

Turcotte's much-anticipated testimony, which will continue Tuesday, started with a discussion about his childhood.

He was the third of six children, in a suburb south of Montreal, and grew up in a devout Catholic family in an overflowing house where there wasn't much communication.

He was not popular, not very athletic and his early years were tough: he was the target of jeering and always, "the last to be chosen on teams," Turcotte testified.

"I was the little guy everyone laughed at and made fun of. I wore big glasses and I was timid," Turcotte said.

He said he had a number of relationships, but everything changed when he met Isabelle Gaston at happy hour in a Quebec City bar in 1999.

"I was attracted to her right away. We spent the whole night together and I fell in love that day," Turcotte said.

He described Gaston as having lots of charm, smiling, full of energy, intelligent and a leader.

"I found myself lucky to be with this girl," Turcotte said. "I'm surprised she was attracted to a guy like me: I think I'm pretty ordinary and she was just so hot."

The couple split once in 2001 following an argument where punches were thrown by both.

But after a few months, the relationship was rekindled. Not long after, he proposed to her on Mount Washington.

Defence lawyer Pierre Poupart told the jurors on Monday they'll have to determine whether the once-prominent cardiologist intended to kill his children.

"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?"

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, depicting the kids at play, at Christmas, on birthdays, on outings and traveling.

Each photo brought quiet sobbing from the accused.

Turcotte's older brother, Gilles, 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.

Despite describing their relationship as close, Gilles Turcotte said his brother never confided in him regarding his marital difficulties.