Decades after Robert Latimer killed his severely disabled daughter in what he maintains was an act of mercy, his Vancouver lawyer has filed an application to have his murder conviction pardoned.

Latimer, a grain farmer from Saskatchewan, ended his 12-year-old daughter's life in October 1993 by placing her inside his pickup truck and running a hose from the exhaust pipe into the cab.

After two trials, the first of which was tainted by jury tampering, Latimer was convicted of second-degree murder and sentenced to a mandatory minimum life sentence with no chance of parole for 10 years.

He said his intention was to free Tracey Latimer from her pain, and 25 years later, with medically assisted death now legal in Canada, his lawyer at Gratl & Company is appealing to Prime Minister Justin Trudeau and Justice Minister Jody Wilson-Raybould to either grant him a new trial or a pardon.

"Throughout the legal proceedings, the courts at every level found that Robert Latimer was motivated solely by love and compassion for his daughter," the convict's lawyer, Jason Gratl, wrote in his pardon application.

Robert and Laura Latimer's daughter suffered oxygen deprivation at birth that left her with cerebral palsy, and the symptoms she experienced during her short and difficult life were severe. She was bedridden, suffered several seizures per day, and "never exceeded the mental level of an infant a few months old," Gratl said.

The family told the court they watched their daughter undergo surgeries that only seemed to compound her pain, and were told to treat her with over-the-counter Tylenol, despite her clear discomfort, which she could only communicate through her cries.

According to Latimer's pardon application, doctors withheld some pain-controlling medication from the family over concerns that the drugs could kill her. Latimer was never even presented with the option, his lawyer said.

Gratl pointed to palliative sedation, the process of administering potentially fatal painkillers in chronic cases, which was "relatively common and unequivocally lawful" long before medically assisted death was legalized.

"An unintended secondary lethal effect is neither a legal barrier to meaningfully managing pain nor is there a restriction on managing pain imposed by medical ethics," he wrote.

"The unlawful insistence of members of the medical profession that Tracey should suffer placed Robert Latimer in a position that led him to break the law … If Tracey had received the medical treatment to which she was lawfully entitled, her father would never have intervened."

Gratl argued there was a misconception at trial that the family was responsible for failing to provide their daughter with stronger pain medication, and that it constitutes a miscarriage of justice that warrants a retrial.

Failing that, the lawyer also argues Latimer is a prime candidate for a pardon. He noted that the Supreme Court of Canada, in its decision to uphold Latimer's murder conviction, pointed to the royal prerogative of mercy that would allow the government, but not the courts, to grant him clemency.

"No other case in Canadian history so clearly exhorts the executive of government to exercise the royal prerogative of mercy to rectify an injustice that the Court felt unable to remedy," Gratl wrote.

"A pardon would offer a glimpse of mercy, compassion and justice that the legal system and the medical system did not afford to the Latimers."

The Latimer trial made headlines across the country and sparked a national debate that divided the public. While many people sympathized with the father, others felt his conviction was entirely justified, including the Council for Canadians with Disabilities.

"CCD strongly believes that arguments advanced on behalf of Mr. Latimer in this case involve a threat to the lives and security of people with disabilities," the organization wrote back in 2000.

The CCD did not respond to a request for comment Thursday, but has argued Tracey Latimer's medical issues should not impact her right to life.

Psychiatrist Dr. Derryck Smith noted that while public attitudes on assisted dying have evolved since 1993, the law as it stands remains limited in scope, and would not cover the Latimers' situation.

Only adults who are mentally competent – meaning they are capable of making decisions for themselves – are currently eligible to access doctor-assisted death in Canada.

"Clearly, (in) the Latimer case, this child would not be competent and certainly would not be covered under the current law," Smith said.

Latimer was granted day parole in 2008, and released on full parole in 2010 with conditions. In 2015, the parole board ruled he could travel outside Canada.

With files from CTV Vancouver’s David Molko