Article 14 of the Convention Against Torture says it can't. We've ratified the convention, and there's no exception to the convention.
Once you open the door to the use of torture in the minds of police agents or security intelligence agents.... The case you gave there was one where it was helpful to have found the evidence. One would hope that you could find that evidence in other ways by good investigative techniques. But to open the door to use torture is totally against the convention.
If we don't believe in the convention, let Canada withdraw from it, but not be two-faced about it, saying we support the convention and then trying to find a way around it.