What is the test for a voluntary confession under the confessions rule?

In R. v. Hebert (1990), 1990 CanLII 118 (SCC), 77 C.R. (3d) 145 (S.C.C.) McLaughlin J. first analyzed the confessions rule as one of being based upon choice and not simply the choice defined negatively in Ibrahim v. R. She said at page 174-5: “The second approach to choice in the confessions rule is much broader. It starts from the proposition that choice involves not only an act but a mental element. On this view, the act of choosing whether to remain silent or speak to the police necessarily comprehends the mental act of selecting one alternative over another. The absence of violence, threats and promises by the authorities does not necessarily mean that the resulting statement is voluntary, if the necessary mental element of deciding between alternatives is absent. On this view, the fact that the accused may not have realized he had a right to remain silent (e.g., where he has not been given the standard warning) or has been tricked into making the statement is relevant to the question of whether the statement is voluntary.”