Guy Turcotte turned himself in to police Wednesday evening after Quebec's Court of Appeal overturned the not criminally responsible verdict for killing his own children in 2009, thereby calling for a new trial.

He is expected to be arraigned on Thursday afternoon in a St. Jerome courtroom.

Turcotte, a former cardiologist who spent 46 months in the Pinel Psychiatric Institute before he was freed and deemed not a danger to anyone else, is set to stand trial again on two accusations of first-degree murder. Turcotte is expected to remain detained at least until his trial.

His ex-wife and the mother of the two slain children has been fighting for a new trial ever since Turcotte was found not criminally responsible.

"I feel like it should be like that and there's only two people that lost their life and for that reason it gives me the energy to say okay I'm going back because yeah - not going in the process, not doing this Court of Appeal, for me it would have been like the machine is bigger than our values," said Isabelle Gaston.

Pleased that Turcotte will once again face the justice system, she says her love for her children gives her strength.

"They are the persons that I always keep in mind. The persons, my love for them is a like a light that brings me to the good direction."

In its ruling, the Court of Appeal overruled the verdict rendered on July 5, 2011, deciding that Judge Marc David had made an error in law when it came to instructing the jury about mental illness.

Turcotte admitted drinking methanol and then killing his children because he did not want them to find his body. The only decision for a jury was to decide whether his state of mind allowed him the capacity to know what was right or wrong.

Appearing before the Court of Appeal earlier this year, the Crown argued that should never have been an issue because Turcotte chose to drink methanol before committing his crime.

The defence argued Turcotte had a mental disorder brought about by the breakup of his marriage, and was suicidal; therefore drinking the poison was part of the mental illness.

In its decision, the Court of Appeal decided the jury was not instructed on an important decision it had to make: "Whether it was the mental disorder or the intoxication with the windshield washer fluid that made Turcotte incapable of rational judgment."

The prosecution also argued that in his directions to the jury, the judge did not make sure that what they called contradictory and convoluted expert testimony was clear to the jury.

"The judge made specifically that mistake, of telling the jury that they could consider a combination of both in deciding whether he was not criminally responsible," explained attorney Jeffrey Boro.

Speaking Wednesday afternoon, Crown spokesperson Jean-Pascal Boucher explained that Crown prosecutor Rene Verret from Quebec City will handle the case.

Turcotte killed Anne-Sophie and Olivier in 2009. When he was freed from the Pinel Institute, psychiatrists said that Turcotte was no longer taking medication, had changed in tone and attitude, and was receiving adequate family support.

Court of Appeal: Guy Turcotte decision