What is evidence as evidence is used? A case of dualism?

How 'evidence' is conceptualised, generated and deployed in meso-level policy implementation on the ground is critical to health delivery. Using the case of a large-scale health service reconfiguration in northwest England, this study began as a narrative investigation into how different data types and sources are prioritised as NHS administrative structures change over time. During the research, one unpopular reconfiguration decision, the downgrading of a hospital, was challenged using judicial review. Suddenly, a key decision was being based not upon 'facts and data' type evidence but upon evidence of adherence to administrative procedure. This transferred focus away from the ever-shifting categories and hierarchies of data 'types' towards an emphasis on process. By comparing two deliberative contexts-committee and judicial review-this article proposes that evidence can be understood as simultaneously entity and process. As health service reconfigurations continue in response to austerity, integration agendas, evolving organisational landscapes, and demographic and political change, it is increasingly important to recognise the different meanings and uses of evidence.