Street-level Theories of Change: Adapting the Medical Model of Evidence-based Practice for Policing

Evidence-based medicine, with its evidence hierarchies and emphasis on RCTs, meta-analyses and systematic reviews, sets the model for evidence-based policy almost everywhere, policing no exception. But how closely should policing follow this model? We argue that RCTs can tell you little about what you need to know for real-world practice: will this policy work where and when you implement it? Defending that it will do so takes good theory. For RCTs to play a role in theory development, they must be set into a larger body of knowledge, including local knowledge about the sites of implementation. Unfortunately the standard EBM model generally ignores the other kinds of knowledge needed. An alternative model for evidence-based policing, similar to that of the new movement for ‘EBM+’ and immanent in the practice of realist synthesis, focuses on the arguments that proposed policing policies will work where and when they are implemented and looks for the evidence needed to support those arguments.