An RCMP undercover operation against Travis Vader involved an in-custody police agent, court documents reveal.

New documents filed before the court say RCMP did not disclose the information to the Crown Prosecutor, which included statements, letters, and documents showing how much the informant was paid.

In addition, certain recordings from an undercover operation with Vader’s sister, Bobbi-Jo Vader, were also left out of the disclosure package.

Vader’s abuse of process hearing began in Edmonton in December.

Charged with the first-degree murders of Lyle and Marie McCann, Vader’s lawyer says his client has been labelled "public enemy number one," and the case against him should be thrown out.

TIMELINE: Disappearance of Lyle and Marie McCann

The McCanns were last seen in July 2010 while on their way to British Columbia. Their burned out motor home was discovered but their bodies have never been found.

Vader was first charged in connection to their disappearance and death on April 18, 2012. His trial date was set for April 2014. The Crown testified its case was circumstantial, but said it had forensic evidence linking Vader to the McCann’s SUV – inside the vehicle investigators found Marie’s blood and Lyle’s hat with a bullet hole. The Crown was confident he would be convicted.

READ MORE: Forensic evidence ties Travis Vader to St. Albert couple’s SUV: Crown summary 

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According to the crown’s summary of facts, forensic evidence ties Travis Vader, the lone suspect in the couple’s murder, to the couple’s SUV.

Courtesy, Crown Summary of Facts

However, in the months before the trial, the Crown discovered missing disclosure documents from the RCMP.

Lead Crown Prosecutor on the file, Michelle Doyle, said she was "floored" and made it clear to investigators the disclosure fiasco must be fixed.

On March 19, just weeks before the trial date, the Crown stayed the charges. Doyle stated she was concerned that a conviction might not be a fair or just conviction as there might be evidence that might assist Vader.

The stay was lifted nine months later, and the first-degree murder charges were re-applied on Dec. 19, 2014.

Vader’s Defence team says the actions by the Crown led to a nearly two-year delay for his trial. It believes the Crown stayed the charges to buy more time to investigate and build its case against Vader.

The new trial is scheduled for March 7, 2016. Once complete, nearly four years will have passed since Vader was charged.

None of these statements have been proven in court. They are part of the abuse of process hearing.