R. v. Oickle, 2000 SCC 38 holds a court considering the common law confession rule:
must consider whether the police made any threats or promises. The Supreme Court states that whether there is a quid pro quo for the confession will usually determine whether the statement was voluntary.
must look for oppression. That is, where there is distasteful or inhumane conduct that would amount to an involuntary confession.
must consider whether the suspect has an operating mind. The suspect is sufficiently aware of what he or she is saying and who they are saying it to.
can consider the degree of police trickery. While trickery in general is allowed it cannot go so far as to "shocks the community".