A decision is expected Tuesday in an abuse-of-process application by Travis Vader, who is alleged to have killed St. Albert seniors Lyle and Marie McCann in the summer of 2010.

A successful application could see the prosecution halted in the case, which would mean Vader would not stand trial for the murders of the McCanns. And if the decision is that the trial should go ahead, defence lawyer Brian Beresh has argued certain evidence should be excluded.

During the application, Beresh has argued the prosecution should be halted because of a two-year delay in the case, which occurred when the charges against Vader were stayed in March 2014, just weeks before his trial was due to begin. The murder charges were recommenced late in December 2014. 

Beresh has argued that the stay was used to buy more time to collect evidence against Vader. And, court documents say, "to gain unfair advantages in the conduct of the trial by granting itself two years of additional time for preparation and investigation."

The Crown has blamed delays on an Alberta RCMP "fiasco" that included significant disclosure problems the Crown said jeopardized Vader‘s right to a fair trial. 

University of Alberta law professor Steven Penney said a stay on Tuesday would be the end of the prosecution, subject to an appeal by the Crown. Unlike the earlier stay of the charges against Vader, charges stayed by a judge cannot be recommenced. 

"In this context, a stay that’s issued by a judge is equivalent to an acquittal," Penney said.

"It’s not like a prosecutorial stay that was entered in this case, where you have the right to initiate the proceeding again within one year, which is exactly what they did. This is a very different kind of stay. "

Penney said the finality of the decision makes it difficult to obtain a stay of proceedings for an abuse of process.

"Courts are reluctant to issue a stay because of the obvious social interest of having a trial on the merits, and getting at the truth and ensuring that, if a person really did commit the crime, that the person is accountable," he said.

"So it’s fair to say they are rare. Having said that, it’s by no means unprecedented."

Penney said charges are stayed if a judge finds that a fair trial could not be granted, or if the behaviour of the state has been so outrageous or abusive that it would be an affront to justice to continue with the prosecution.  

"That’s a pretty high threshold to overcome," he said. 

If the judge declines to enter a stay, Vader’s trial is slated to proceed this spring. 

In that event, Beresh would seek a court order prohibiting the use of evidence not disclosed to the defence before the stay in March 2014, including some RCMP interviews with Vader.

Documents released over the past months have showed that forensic evidence tied Vader to the investigation, including Vader’s fingerprint on a beer can in the cupholder of Lyle and Marie McCann’s SUV, and "the blood of Marie McCann and Lyle McCann’s hat with a bullet hole in it." 

Lyle McCann, 78, and his wife Marie McCann, 77, were last seen on the morning of July 3, 2010, buying gas at a Superstore in St. Albert.

Their burning motorhome was found near a campground southeast of Edson two days later, and the Hyundai Tucson SUV they had been towing behind the motorhome was later found. 

— with files from Ryan Cormier