What is the standard of conduct of a police officer in an assault case?

As stated by McLachlin C.J.C. for the majority in Hill v. Hamilton- Wentworth Regional Police Services Board at paragraph 68: ...At the outset of an investigation, the police may have little more than hearsay, suspicion and a hunch. What is required is that they act as a reasonable investigating officer would in those circumstances. Later, in laying charges, the standard is informed by the legal requirements of reasonable and probable grounds to believe the suspect is guilty; since the law requires such grounds, a police officer acting reasonably in the circumstances would insist on them. The reasonable officer standard entails no conflict between criminal standards (Charron J., at para. 175). Rather, it incorporates them, in the same way it incorporates an appropriate degree of judicial discretion, denies liability for minor errors or mistakes and rejects liability by hindsight. In all these ways, it reflects the realities of police work.[Emphasis added.]