The double-murder case against Travis Vader is partly based on evidence from a jail-house informant paid by the RCMP, according to new documents filed in an Alberta court.

Vader is accused of killing St. Albert seniors Lyle and Marie McCann, who disappeared in July 2010 while driving to B.C. in their motorhome.

Murder charges against Vader that had been stayed in 2014, were reactivated nine months later. The Crown has one year after charges are stayed to reactivate them.

Lawyers for both sides were in court Tuesday for a hearing that will determine if there has been an abuse of process in the Vader case.

He was originally scheduled to go to trial in April 2014. But according to court documents, the RCMP failed to disclose pertinent evidence to the Crown, including details about the informant.

The disclosure problem was so serious that the Crown felt compelled to stay the first-degree murder charges against Vader.

A few months before the 2014 trial was scheduled to begin, the RCMP sergeant in charge of the investigation told Crown prosecutor Michelle Doyle that key information was missing.

A month before the trial, the RCMP provided the Crown with 5,000 documents related to the case.

Doyle said the sheer volume meant it would "take days and probably weeks" to assess the material.  

Vader's lawyers have argued that prosecutors stayed the charges only to put the trial on hold to buy themselves more time to bolster a weak case.

The abuse of process hearing began in November. Briefs submitted by Vader's lawyers today noted problems with the disclosure process.

Missing from disclosure packages were materials that referred to an "in-custody" informant paid by the RCMP. The informant's name is now protected by a publication ban.

"Further concerns arose for Ms. Doyle when she began to prepare to lead evidence from ... an in-custody police agent," the Crown's brief said.

"She learned from the RCMP that there was a whole package of material about (the informant) that the RCMP had not included in the disclosure package, including statements, interviews, and multiple letters of agreement. In her words: 'This was — this was pretty surprising, to say the least.

"The absent materials included documents reflecting the amount of money that had been paid by the RCMP to (the informant)."

The brief also said an RCMP sergeant "discovered that a collection of investigator's notes had been left sealed within a number of envelopes held in the possession ... of the forensic identification section."

The Crown's brief said no justification was offered for the failure to disclose those notes.

After the notes were found, the RCMP initiated a broad audit of disclosure.

Shortly after the abuse of process hearing began last year, Doyle said under oath she had lost all confidence in the RCMP's ability to turn over all evidence in the double-murder investigation.

The hearing continues Tuesday afternoon. The judge is expected to reserve a decision until later in the month.

Vader, 42, is now scheduled to go to trial in March 2016, unless Alberta Court of Queen's Bench Justice Denny Thomas rules there has been an abuse of process.

Lyle McCann, 78, and his wife Marie, 77, were last seen alive on July 3, 2010. Their Hyundai SUV was discovered 13 days later. Their bodies have never been found.