As first responders, police officers are routinely called upon to deal with a wide range of crime, public disorder and social problems. The occupational focus on low-level street crime and order maintenance led Robert Reiner to describe policing as a form of ‘moral street-sweeping’. Police interactions with persons with mental illness (PMI) have intensified following de-institutionalisation and community-based care in recent decades. It has reached the point in many jurisdictions that general-duties policing may be viewed as a form of ‘mental health street-sweeping’. Part I of the chapter examines the range of coercive powers available in Australia to police PMI. Moving beyond the ‘law in books’ to evaluate the ‘law in action’, Part II examines how the police interactions with PMI are governed by specialised intervention programmes that embed ‘therapeutic partnerships’ between police, ambulance and mental health services. Part III outlines the deficiencies of policy development which is crisis-driven, in favour of an holistic model based on ‘systems thinking’, an approach where policy lessons drawn from adverse incidents serve restorative rather than retributive ends, and reforms are guided by principle and informed by the best available evidence.