[T]here is no such thing as absolute and untrammelled “discretion”, that is that action can be taken on any ground or for any reason that can be suggested to the mind of the administrator; no legislative Act can, without express language, be taken to contemplate an unlimited arbitrary power exercisable for any purpose, however capricious or irrelevant, regardless of the nature or purpose of the statute.

We should never lose sight of the fact that even a person accused of the most heinous crimes, and no matter the likelihood that he or she actually committed those crimes, is entitled to the full protection of the Charter [or Constitution]. Short-cutting or short-circuiting those rights affects not only the accused, but also the entire reputation of the criminal justice system. It must be emphasized that the goals of preserving the integrity of the criminal justice system as well as promoting the decency of investigatory techniques are of fundamental importance in applying [the Constitution].

The Crown has a legal duty to disclose all relevant information to the defence. The fruits of the investigation which are in its possession are not the property of the Crown for use in securing a conviction but the property of the public to be used to ensure that justice is done. … [I]nformation should not be withheld if there is a reasonable possibility that this will impair the right of the accused to make full answer and defence. … In contrast, the defence has no obligation to assist the prosecution and is entitled to assume a purely adversarial role toward the prosecution. The absence of a duty to disclose can, therefore, be justified as being consistent with this role.