Nelson Hart's lawyers say the Crown doesn't have any other evidence after the Supreme Court ruled out the use of Hart's confession of murder obtained under a Mr. Big operation.

Hart was convicted in 2007 of two counts of murder in the drowning deaths of Krista and Karen Hart, his twin three-year-old daughters based largely on his confession to undercover officers posing as members of the mob. The sting is known as a Mr. Big operation.

In 2012, a majority of the Supreme Court of Newfoundland Labrador's Court of Appeal overturned Hart's conviction. It questioned the reliability of his confession to the undercover officers.

The Crown then appealed to the Supreme Court of Canada, which ruled on the case Thursday. 

Nelson Hart's lawyers

Robby Ash (left) and Jamie Merrigan (right) are the lawyers for Nelson Hart.

"We are very pleased with the decision from the court," said Robby Ash, one of Hart's lawyer's with the firm Poole Althouse in Corner Brook.

"It addresses the central concerns of Mr. Big's reliability, in particular the reliability of the evidence that arises from Mr. Big's technique." 

The justices ruled that stings like Mr. Big that convicted Nelson Hart pose major problems — namely that they tend to risk becoming abusive and produce unreliable confessions. 

Mr. Big technique 'fraught with danger'

Ash told CBC News that the Mr. Big technique is "fraught with danger" with the operation designed to target a person's weaknesses after a period of lifestyle surveillance.

The police found out through surveillance of Hart that he was poor, had a Grade 5 education and was socially isolated.

"Really, his only social contact was his wife who before she was his wife was his caregiver," said Ash.

Ash doesn't know how the police will react to the Supreme Court decision.

"I think it will impact the degree to which they exert psychological pressure in the steps they take when carrying out these investigations and these stings," said Ash.

"I can't imagine one being carried out in the manner Mr. Hart's was carried out given the comments of the Supreme Court of Canada.

"Historically when the court has closed an avenue to the police in terms of investigation they develop something else to fill the void and then we have to address that again in the future."

When asked what will happen to Hart now, Jamie Merrigan, another of Hart's lawyers, said the Crown now has to decide whether it's going to proceed with a new trial.

"The Supreme Court has ruled Mr. Big's evidence inadmissible and from our perspective that leaves nothing of the Crown's case," said Merrigan.

"Theoretically the Crown could determine that they wish to proceed. If they don't wish to proceed, if they don't set the matter down for a trial, without the Mr. Big evidence, Mr. Hart is a free man. It's a question of when he'll be released."

Ash and Merrigan said they hoped to speak with Hart Thursday.

With files from Glenn Payette