The Supreme Court of Canada has decided not to consider an appeal from the man convicted of killing St. Albert, Alta., seniors Lyle and Marie McCann, whose bodies have never been found after the two vanished on a camping trip in 2010.

The top court on Thursday said it has dismissed Travis Vader's application for an appeal. As usual, when dismissing applications for leave to appeal, the court gave no reasons for its decision.

In January 2017, Vader was sentenced to life in prison for manslaughter. A trial judge determined Vader was a desperate drug addict who came across the McCanns and killed them during a robbery.

Vader's defence lawyers filed a notice of appeal two days after the sentence was handed down, arguing he should have a new trial.

At the time, defence counsel Brian Beresh outlined a dozen grounds for appeal, ranging from the "undue delay perpetrated by the police and the Crown" to the fact a life sentence was "demonstrably unfit" for the crime of manslaughter.

Vader's defence also took issue with the trial judge's original decision.

Vader was originally convicted of two counts of second-degree murder, but shortly after, they were downgraded to manslaughter after it was discovered Court of Queen's Bench Justice Denny Thomas had relied on a section of the Criminal Code that had been ruled unconstitutional more than 25 years ago.

Vader sought a new trial. Lawyers for Vader asked the Alberta Court of Appeal for a new trial or for his manslaughter charges to be stayed because of the judge's mistake.

They also argued the RCMP was negligent in handling disclosure at trial, which added two years of delay. The Crown told court there were exceptional circumstances that justified the time it took to complete the trial.

His application was rejected by the Court of Appeal of Alberta in May 2019.

"Based on the facts as he found them, the trial judge was ultimately correct in convicting the appellant of manslaughter," the Appeal Court said in its judgment.

"We see no prejudice having befallen the appellant as a consequence of the trial judge's analysis, and no benefit in a retrial to test again whether the appellant should have been convicted of manslaughter, in the robbery killings of the McCanns."

Lyle, 78, and Marie, 77, were beginning a road trip to B.C. on July 3, 2010, when they disappeared after stopping at a gas station in St. Albert.

Their burnt-out RV was found two days later at a campsite near Edson.

Vader, then 38, was arrested two weeks later at a home near Niton Junction, on outstanding warrants not tied to the case.

'It will never end'

The couple's son, Bret McCann, said Thursday's court decision came as a relief to the family.

"I was just elated when I woke up and saw the news," McCann said in an interview with CBC News. "Everybody is really happy about this."

McCann said that, following the Appeal Court's dismissal, he was hopeful the bid for an appeal would be rejected by the Supreme Court.

"His application to the Supreme Court was basically the same argument," McCann said. "If Alberta had rejected it unanimously, there was a strong possibility that it was going to be rejected at the Supreme Court level.

"There had been no guarantees of course of which way this would go, but there had been good signs."

McCann said, even with the final appeal dismissed, there is no sense of closure for the family.

Vader's defence lawyers are still appealing the sentence, he said. And with credit for time served before he was convicted, Vader would be eligible to apply for early release in 2021, after serving 4½ years.

McCann dreads the prospect of Vader being released. No killer should be granted parole until he reveals the location of the bodies of his victims, McCann said. He's been lobbying for Canada to adopt a "no body, no parole" law for years.

"He's never revealed where the bodies are and he's never admitted guilt and never expressed remorse," McCann said.

"It will never end."