The Quebec mother lost her two young children who were stabbed to death by their father, the cardiologist Gaston was married to.
After those 2009 slayings, each gory detail was sifted through in a highly publicized trial that served as gossip fodder in Quebec.
Gaston then watched as her ex-husband was found not criminally responsible of the crime in the summer of 2011. He was eventually deemed fit for release from a mental institution, where he'd been housed following a total of 46 months in custody.
So Gaston says she's treating the Crown's appeal of his verdict, to be heard in Montreal this week, with a heavy dose of trepidation and skepticism.
The Crown's appeal of Guy Turcotte's verdict will begin Monday in Quebec's highest court as the Crown seeks to have the judgment annulled and a new trial ordered. That decision will fall to three appellate court judges.
"It's necessary but it's a big stress,'' Gaston told The Canadian Press in a phone interview. ''We're reliving the events again.
"My family's scars were finally starting to heal and now we're being thrown back into it again."
Turcotte's criminal case — and the jury's verdict — infuriated many Quebecers. The case is among several across Canada to spur new federal legislation aimed at making it harder for those found not criminally responsible to gain their freedom.
During the highly publicized murder trial, Turcotte had admitted to stabbing his young children, three-year-old Anne-Sophie and five-year-old Olivier, 46 times.
He then ingested windshield wiper fluid in a failed attempt to commit suicide that night in February 2009.
Turcotte was charged with first-degree murder.
He admitted to causing the children's deaths, but denied criminal intent. The trial heard from numerous witnesses, including Turcotte himself. He testified he didn't remember committing the act and had been experiencing blackouts the night of the slayings.
Medical experts for the defence testified he was suffering from the mental effects of the breakup of his marriage.
The Crown countered that he'd killed the children in a cold-blooded act of revenge. Gaston had just left him for her personal trainer.
An 11-person jury that heard his case in 2011 found him not criminally responsible — the least punitive of the four possible verdicts offered to them by the Quebec Superior Court justice overseeing the case.
The verdict meant that Turcotte was unable to know, at the time, that he was doing something wrong. Acquittal had not been among the options offered to the jury.
The Crown believes the trial judge should never have offered the not-criminally-responsible option. It also argues that the jury wasn't properly instructed and that the judge did not sufficiently review the evidence with the jury.
Turcotte drank washer fluid later that evening in an attempt to kill himself. Crown prosecutor Michel Pennou argued that a not-criminally-responsible verdict should be reserved for cases of mental illness, not cases like this one where a suicide attempt might have triggered an after-the-fact blackout.
"We submit that the mental disorders of a mixed nature — which take into consideration mental illness and other factors, like intoxication — cannot and should not, in law, be equated to a mental disorder if the intoxication contributes materially to the inability of the accused and can be called voluntary," Pennou writes in the Crown's motion to appeal.
"Thus, the trial judge failed in his duty to review the essential parts of the evidence, and to make the connection between the elements of the evidence relevant to the mental disorder defence and the applicable law in matters of non-criminal responsibility," he added.
"This error is fatal to the verdict."
The defence has dismissed the Crown's arguments.
In its own submission, it argues that the Crown had plenty of time to interject before the jury was sequestered, but never raised any objections. The defence says the court should reject the appeal, but if there is to be a new trial, it should be on the far-reduced charge of manslaughter.
"Assuming that the judge's directives were insufficient as it pertains to the summary of the expert evidence ... there is no reason to conclude that the verdict of the jurors would have been different," the defence says.
For Gaston, justice for her young children remains a personal mission. The verdict appeal is the next step in that long, painful process.
But she's not getting her hopes up, given her experience with the justice system.
"My family and I are a little bit skeptical," said the emergency room physician, who is currently on stress leave. "We know the rules and proceedings are very technical and sometimes we feel like (the legal battle) is only going to sap our energy and give nothing back."
Gaston has turned her attention to other causes — namely the issue of paid experts testifying as defence witnesses.
She says there's a major flaw in the justice system, with no control over expert witnesses and the accuracy of their opinions.
Gaston is calling on Quebec's College of Physicians to introduce new controls and reviews for such experts. She says only medical professionals should review their peers.
"Essentially, right now we can buy everything that influences a judge and a jury," Gaston said. "And from the moment there is an appearance that the justice system is not transparent, it's as bad as not being transparent at all."
Separately, the college has set up a task force with the Quebec bar to look into this exact issue. It wants to update its guide for physicians acting as experts, published seven years ago.
Turcotte's case has already prompted reaction from Ottawa.
In February, the government tabled the Not Criminally Responsible Act. The bill would give the court new powers to create a new high-risk category that would hold mentally ill offenders longer, without a formal review, and make it far more difficult for them to leave psychiatric facilities.
It would also keep victims' families in the loop about the status of such individuals and alert them when they are released.
Turcotte's case was one of a handful of high-profile ones cited by the Harper government as it introduced the changes. Others included that of Allan Schoenborn, a B.C. man who killed his three children, and Vince Li, who beheaded a man on a Greyhound Bus in Manitoba.
The bill, C-54, has passed the House of Commons and is currently before the Senate.
Although he has lost his medical licence, Turcotte is now a free man after spending some time in a mental hospital after the trial.
A panel determined in late 2012 that he was fit to be released under certain conditions. He is expected back before a panel for a review later this year.
Gaston said she expects to be there Monday. She wants to hear what's said.
"I think that one day I'll be more at peace when all this courtroom stuff is done — and if we succeed in this battle over experts that I started," Gaston said.
"Whatever happens, at least I know that I tried. That's the thing that's most important to me."