The Special Investigations Unit investigates occurrences across Ontario, encompassing all municipal, regional and provincial police officers. This represents 65 police services and approximately 21,600 officers.

Ontario is unique; it is the only Canadian province and one of the few, but increasing number of jurisdictions anywhere with an independent civilian agency that has full powers and authority both to investigate, and where the evidence warrants, to charge officers with a criminal offence. In the vast majority of investigations, evidence of criminal activity is not found and no charges are laid.

The role of the SIU is not necessarily to lay charges but to investigate and to assure the broader community that the conduct of the police is subject to rigorous independent scrutiny.