Nelson Hart has always argued that videotapes collected through an RCMP sting should have been barred from his trial. ((CBC) )

Court documents have been filed to launch an appeal for a man who was convicted of murdering his twin daughters in a central Newfoundland lake.

Nelson Hart, 42, who was convicted of two counts of murder in 2007, believes he was the victim of an unlawful sting operation.

A jury found Hart guilty of drowning Krista and Karen, who were three years old, at Gander Lake in 2002.

Hart was convicted on evidence that included covertly recorded videotapes of Hart meeting with an undercover RCMP officer. Hart, who believed the man was a criminal boss, was told he would need to prove his toughness — and reveal what he did to his daughters — in order to advance in the organization.

"When they got out of the car, I took them down the wharf, and to look at the fishes," Hart told an officer at a meeting in a Montreal hotel room in 2005.

"When they looked at the fishes, that's when I struck them and they went over the wharf, and that's how they drown."

A few days later, Hart accompanied an undercover officer to the scene, and showed him how he did it.

Hart has been seeking an appeal since he was convicted, although he has in the past refused to co-operate with the process.

Authorities went too far: claim

Documents filed with the appeals division of Supreme Court of Newfoundland and Labrador argue that authorities went too far with the so-called Mr. Big scenario that was used to secure a confession.

"The actions were designed to circumvent the protections afforded by the Charter," the appeal reads.

The appeal also focuses on Hart's dissatisfaction  with Derek Hogan, the legal aid lawyer who represented Hart at trial. Hart had also asked Justice Wayne Dymond to be allowed to testify in camera — that is, without the public in the court.

Dymond said no to the request.

The appeal argues that Dymond erred when he did not look more closely into Hart's complaints about his lawyer, and that Hart should have been allowed to testify in camera.

Hart's lawyers are asking the appeals court to decide on several possibilities, including acquitting Hart altogether or ordering a new trial.

The appeal is scheduled to be heard in early June.

With files from Glenn Payette