It has been 2,075 days since Lyle and Marie McCann were last seen alive.

On July 3, 2010, the elderly couple was captured on surveillance video in St. Albert getting gas before they headed out on a planned road trip to B.C.

Finally, after years of stops and starts, the trial is set to begin for the McCanns' accused killer.

Travis Vader is charged with two counts of first-degree murder. Those charges have been hanging over his head for almost four years. The 42-year-old has been in the RCMP's crosshairs for even longer than that.

In a January decision on an abuse of process application made by the defence, Justice Denny Thomas wrote: "Mr. Vader's long and interrupted march to the courtroom is troubling.

Trader Vader's first-degree murder trial is set to begin today in an Edmonton courtroom. (CBC)

"For years the alleged murders have cast a shadow over Mr. Vader's life," Thomas wrote, "but that shadow will only lift if Mr. Vader has the opportunity to answer and respond to the allegations against him at a trial."

Vader's lawyer said his client believes he can get justice, and is eager for the trial to begin.  "The trial's put off, then it's back on, then there's the attempt at the stay," Brian Beresh said. "You can appreciate that that's very trying."

The McCann family has also been waiting for some sense of closure. Bret McCann called it a marathon and said he's glad the finish line may be in sight.

"We are keenly looking forward to finding out what happened to my parents," he told reporters in January.  

The McCanns' bodies have never been found. University of Alberta law professor Steven Penney said that's one of the first challenges the prosecution will face.  

"That is not something that is insurmountable from the prosecution's perspective," he said. "But it does present them with a hurdle. Because they're going to actually have to prove beyond a reasonable doubt that these two individuals are actually dead."

That is far from the only battle the prosecution will face during the six-week trial.

The Crown has characterized it as a circumstantial case and has described the lack of timely disclosure of evidence by the RCMP as a "disaster."  

That disclosure issue may not be completely settled.

On Feb. 24, Beresh filed a notice of motion about outstanding issues. He said many have been resolved.  

The defence demanded criminal record checks on 17 Crown witnesses, because Beresh said many "have had serious criminal histories and/or addictions to drugs." That makes their credibility an issue, he said.  

Beresh said he has yet to be given access to some of the more than 2,000 exhibits collected by the RCMP. Not all of them will be used at trial, but Beresh said he wanted to see all of them before the trial began.  

Vader's trial is scheduled to last six weeks, but the defence thinks it could go even longer than that.  

Defence hints at surprises to come

Beresh said he expects some evidence will surprise the public.  

"We have not heard it all," he said. "I think there may be a fair amount of evidence that is new and will surprise a lot of people."  

Mounties can expect to be grilled by the defence about their investigative tactics.  

In his January decision, Justice Thomas called RCMP conduct in the case "negligent" and "egregious." But he also found it was not purposely malicious.  

At the time, Bret McCann said he still has faith in the RCMP.  

"I think they made mistakes," he said. "I think they owned up to them. And at the end of the day, they did an enormous and effective job."

McCann said he hopes that job was effective enough to answer all the questions his family has lived with for the past 2,075 days.

janice.johnston@cbc.ca

@cbcjanjohnston