Bret McCann hopes he’ll finally find out what happened to his parents.

It’s been nearly six years since Lyle and Marie McCann, 78 and 77 respectively, were last seen fuelling up their motorhome in their hometown of St. Albert, a bedroom community north of Edmonton.

They were heading out for a holiday in British Columbia and Mounties believe the seniors were murdered along the way, although their bodies have never been found.

A first-degree murder trial is to begin Tuesday for longtime suspect Travis Vader. He was described as a person of interest soon after the McCanns disappeared and eventually charged. But the charges were stayed before being reactivated in late 2014.

It’s been a "long, interrupted march to the courtroom" for the accused, as a judge in preliminary matters has said, and Vader has filed lawsuits against prosecutors and the RCMP claiming malicious prosecution.

Bret McCann doesn’t want to say much about the man accused of killing his parents.

For him, the trial means that for the first time he’ll get to hear all the evidence and the Crown’s theory as to how and why his parents were killed.

"My life’s certainly been on hold," said the 61-year-old, who recently retired from his job as an engineer, in part, to focus on the trial. He plans to attend each day with other family members.

He knows that in the end, despite the verdict, he may not have an answer to perhaps the biggest mystery in the case: where are the bodies?

"Since Day 1, we’ve been trying to find them," he said. "I just don’t know whether after this trial we’ll know that either."

Lyle McCann, a former long-haul trucker, loaded up his motorhome each year to travel with his wife. They drove to the United States in the winter and explored the Praires in the summer.

Their disappearance gripped Alberta and the rest of Canada for much of the summer of 2010.

On July 5 of that year, two days after they were last seen on surveillance video at a gas station, their burned-out motorhome was found in woods near Edson, west of Edmonton. The SUV they had been towing was also found concealed in another location.

Police spent several days combing the area. A $60,000 reward "to help find our parents" is still advertised on highway billboards, with giant photos of the smiling, spectacled seniors.

A year after they vanished, a judge granted an order declaring the McCanns dead so their family could start processing their wills. A memorial service was held on what would have been their 59th wedding anniversary.

Vader was arrested on a long list of outstanding warrants on unrelated charges, but he wasn’t charged until 2012.

Days before Vader’s trial was to begin in 2014, the Crown announced that it had discovered that Mounties had failed to disclose all evidence to defence lawyers and stayed the charges. They were relaid nine months later.

Vader’s lawyer, Brian Beresh, argued in court in January that the case should be dropped over an alleged abuse of process and a two-year delay getting to trial.

Justice Denny Thomas ruled the RCMP made serious mistakes and the delay was troubling, but denied the application.

During the hearing, a publication ban was lifted on court documents detailing some evidence. The documents, not yet presented or proven in court, show that RCMP found Lyle McCann’s hat with a bullet hole in it, along with his wife’s blood, inside their SUV.

Police also recovered Vader’s fingerprint and DNA on a beer can inside the vehicle, the documents said.

They further revealed that Vader used the couple’s cellphone the day they disappeared.

Beresh said much has yet to be revealed in the "interesting" case.

"Mr. Vader is looking forward to establishing his innocence."