EDMONTON - A trial begins today for an Alberta man charged with the murder of two seniors who disappeared nearly six years ago.

Lyle and Marie McCann, both in their late 70s, were last seen fuelling up their motorhome in their Edmonton-area hometown of St. Albert as they headed out for a holiday in July 2010.

Mounties believe the seniors were murdered along the way, although their bodies have never been found.

Travis Vader, a long-time suspect in the case, has pleaded not guilty to first-degree murder.

The charges were initially stayed against him but reactivated in late 2014.

Bret McCann says he plans to attend the trial each day and hopes to finally find out what happened to his parents.

"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 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."

On July 5, 2010, two days after his parents 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.

Vader, now 44, was arrested on a long list of outstanding warrants on unrelated charges. RCMP quickly named him a person of interest and later a suspect, but he wasn't charged until 2012.

Days before Vader's trial was to begin in 2014, the Crown announced that it had discovered Mounties failed to disclose all evidence to lawyers. It said it wasn't ready to proceed with a fair trial 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. A judge ruled the RCMP made serious mistakes and the delay was troubling, but denied the application.

Beresh said Vader is looking forward to establishing his innocence.

Follow the live coverage from CTV’s Janet Dirks in court below.

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