Foreword: Public health, public policy, politics and policing.

Reducing harm from drug use lies at the intersection of public health, public policy, politics and policing. In an ideal world, evidence of public health gains achievable through new approaches or technologies should inform public policy, should help shape political agendas in support of policy change, which should translate into law and regulations - and then to their application. The goal of this transformative process should be to yield the highest attainable health benefits to vulnerable individuals and communities and to society as a whole.