What is the test for self-incrimination in common law confessions?

The Charter s. 7 protection against self-incrimination applies where a person’s will is overpowered – where the person is moved by strong external influences to make the statement – where the statement is not the product of the exercise by the person of his operating mind – where the statement is involuntary. The basic principle of the common law confessions rule is given constitutional status in Charter s. 7. (R v. G. (B.) [B.G.] 1999 CanLII 690 (SCC), [1999] 2 S.C.R. 475)

The Charter s. 7 protection of the right to silence arises generally only where a suspect makes a statement to police after he has been detained. At that point the accused and the state are in an adversary relationship but the state has greater power so, in fairness, the suspect requires protection from coercion capable of subverting or overpowering his free will in deciding whether to speak or to maintain silence. (R v. Hebert 1990 CanLII 118 (SCC), [1990] 2 S.C.R. 151)