This brief addresses the question of the various ways in which mental health-related issues have become police responsibility. It provides a detailed understanding of the myriad of ways in which police are often called upon to be the primary responder to mental health-related issues, well beyond the standard media images of individuals in extreme crisis. Drawing upon the results of two separate ethnographies of police practices in Canada, this volume examines how public policing has become entangled in cases of persons with mental illness (PMI). It examines two aspects of the police role and mandate that brings police officers into contact with individuals dealing with mental health disorders: public safety, and crime prevention and response. It explores police perceptions towards the roles they play in the lives of PMI, and police demands in these types of calls for service that have transformed aspects of public policing. Appropriate for policing researchers, law enforcement and public policymakers, this book presents the argument that tackling this matter requires knowledge of police involvement in situations with PMI, as well as a set of evidence-based policy options that will not generate additional resource or other strains.