The ex-wife of Quebec cardiologist Guy Turcotte shook in disbelief in a Montreal courtroom Tuesday as her ex-husband was found not criminally responsible in the deaths of their children.

Turcotte had admitted to stabbing the two children -- Olivier, 5, and Anne-Sophie, 3 -- in 2009, but denied he had intended to do so. Tuesday's ruling found mental issues caused him to commit the stabbings.

Experts who had testified in his defence during the three-month trial said he suffered a psychotic break upon learning his wife was cheating on him.

Turcotte said he only remembered parts of the evening that he killed his children at a rented home in the Laurentians, a picturesque skiing region north of Montreal.

The verdict came after a sensational trial that riveted much of Quebec. It included about 40 witnesses and saw many graphic details emerge. The jury deliberated for six days before delivering their verdict.

The panel of seven women and four men had been instructed to choose from the following possible verdicts: second-degree murder, manslaughter or not criminally responsible by reason of mental illness. Not guilty was not an option, as Turcotte had admitted to the killings.

Before welcoming the jury back into the courtroom, the judge warned those assembled to leave if they thought they might not be able to restrain themselves when the verdict was announced.

Several jury members could be seen crying, while the children's mother, Isabelle Gaston, was visibly shaking and holding back tears. Turcotte was also in tears as the verdict was read out.

While the defence had experts testify that Turcotte wasn't in control of his actions, the Crown's experts stated otherwise. The prosecution said the killing was motivated by a spited lover who wanted to get back at his wife.

CTV Montreal's Stephane Giroux said that during the trial, court heard that the wife was having an affair with Turcotte's best friend.

On the day of the killings, Turcotte spent time reading passionate emails between his wife and her lover, and he became increasingly upset. Turcotte was so upset and distressed that he drank about five litres of windshield-washer fluid, according to evidence.

But as he began to lose consciousness after consuming the fluid, he thought that he could never leave his children behind. Moments later, he went to the children and stabbed them both dozens of times, court heard.

Following the verdict, prosecutor Claudia Charbonneau could only reflect on the nature of the justice system.

"We never know what the jury talks about, what was important for them, that's our system, our criminal justice system."

Gaston -- Turcotte's ex-wife -- said she was in shock, but praised the work of police and prosecutors -- "even with this verdict."

"Even if it had been first-degree murder I could not have been satisfied because it would not have brought back my children in this life," she told The Canadian Press.

She asked reporters to leave her alone so she could continue to recover from the pain of losing her young children.

"I hope their short path in my life and now a little bit in yours, makes us understand that no adult has the choice of life and death on children."

"Whatever the torments or the paths of life an adult could have, it shouldn't be a reason (for) violence."

When defendants are found not criminally responsible of serious crimes, they are often held in a mental institution until they are deemed no longer a danger to the public.

It is unclear where Turcotte will be housed, but his trial judge and lawyers were expected to come to some decisions about his future on Tuesday.