This book examines the various systems, processes, and agencies responsible for overseeing police conduct across Canada, the United Kingdom, Australia, New Zealand, and to a lesser extent, the United States, and Republic of Ireland. It argues that while police oversight systems have improved in their capacities to hold police accountable internationally, they continue to be plagued by internal and external issues that inhibit their full potential in serving as high-standard gatekeepers for police conduct. The lack of legislative and investigative powers, independence, and authority contribute to the limited efficacy of police oversight systems and thereby jeopardize the capacity for which the various agencies can deliver, maintain, and uphold accountability of our law enforcement. This book provides an in-depth discussion of the disparate police oversight systems across multiple jurisdictions. Specifically, serious incident response teams—those responsible for investigating critical incidents involving the police and the public—and complaints agencies are examined to illustrate how these oversight systems function and the role they play in holding police accountable. The book carefully details the similarities, differences, issues and challenges, and leading practices between and within jurisdictions to highlight the complex nature of police oversight and the constant pressure to improve and respond to public demands for accountability. This book will therefore be of interest to students and scholars of policing studies, as well as professionals and policymakers engaged with policing.