What is the effect of the Police Rule on the role of informers in criminal investigations?

10 The rule is of fundamental importance to the workings of a criminal justice system. As described in Bisaillon v. Keable, 1983 CanLII 26 (SCC), [1983] 2 S.C.R. 60, at p. 105: The rule gives a peace officer the power to promise his informers secrecy expressly or by implication, with a guarantee sanctioned by the law that this promise will be kept even in court, and to receive in exchange for this promise information without which it would be extremely difficult for him to carry out his duties and ensure that the criminal law is obeyed. In R. v. Scott, 1990 CanLII 27 (SCC), [1990] 3 S.C.R. 979, at p. 994, Cory J. stressed the heightened importance of the rule in the context of drug investigations: The value of informers to police investigations has long been recognized. As long as crimes have been committed, certainly as long as they have been prosecuted, informers have played an important role in their investigation. It may well be true that some informers act for compensation or for self-serving purposes. Whatever their motives, the position of informers is always precarious and their role is fraught with danger. The role of informers in drug-related cases is particularly important and dangerous. Informers often provide the only means for the police to gain some knowledge of the workings of drug trafficking operations and networks. . . . The investigation often will be based upon a relationship of trust between the police officer and the informer, something that may take a long time to establish. The safety, indeed the lives, not only of informers but also of the undercover police officers will depend on that relationship of trust.