The former lawyer for Nelson Hart says the Supreme Court's decision to order a new trial for Hart is a practical approach to dealing with the nature of the case.

Earlier this week, Canada's top court upheld the decision for Hart, who confessed to murdering his twin three-year-old daughters to an RCMP officer who played "Mr. Big," a pretend underworld boss.

'To me, the response by Mr. Big is exactly the reason why the Supreme Court of Canada had to come up with an analysis or a functional approach to this kind of evidence' - Rosellen Sullivan, Nelson Hart's former lawyer

Lawyer Rosellen Sullivan said the evidence uncovered during the undercover investigation wasn't a reliable way to approach the case.

"The issues that the Supreme Court addressed are exactly the issues that we had when we were preparing the factum for the appeal, and it's just a really practical approach to how you deal with the reliability of a 'confession' that has no way of testing its reliability."

The court took aim at the Mr. Big scenario in its decision; the technique involved police pretending to be criminals in order to lure suspects into confessing crimes.

"When you have someone who says, 'Oh, I drowned them,' and then his evidence is a re-enactment of how that happened — that adds nothing to the inquiry as to how those girls died — they still drowned. There was nothing that you could test, there was no circumstantial guarantee of trustworthiness," she said.

Mountie's response fuelled by 'malice and anger' 

When the court released its decision, the Mountie who played Mr. Big in the sting said future investigations would be hurt by the ruling, and he felt horrible about the decision.

Sullivan added Mr. Big's response to the Supreme Court's decision showcases how important the ruling is, and why the nature of the case itself needed special focus from the country's top court.

"To me, the response by Mr. Big is exactly the reason why the Supreme Court of Canada had to come up with an analysis or a functional approach to this kind of evidence," said Sullivan.

"Mr. Big's malice and anger about this, and he thinks he's perfectly right, which is exactly why the Supreme Court of Canada has to have rules as to these kinds of cases, because you have a state of Mr. Big's, you have $500,000 behind Mr. Big, who are convinced they have their man. Now, don't forget in this case, without this 'confession,' there's no crime — it's not like we're trying to figure out who shot someone — there's no crime."

Hart will learn next week how Crown prosecutors in Newfoundland and Labrador will respond to the Supreme Court decision.

A hearing has been set for Tuesday in Gander.