In this article an empirically grounded study of the police practices used when conducting cold case reviews of unsolved homicides is used to illuminate the key features of what is termed ‘retroactive social control’. It is suggested that this mode of social control, that works by placing past events under new descriptions, is an increasingly important feature of how social control is being imagined and delivered, and is predicated upon the capacity to de-stabilize and re-write previous official definitions of a situation. Retroactive social control it is posited encompasses two inter-twined dimensions: the social control of collective memory, in terms of what is remembered and how; and social control through memory, wherein the shaping of the past influences the enactment of control in the present. The focus upon police cold case reviews suggests how forensic evidence and new investigative technologies have played an important role in shaping the development of these innovative aspects of contemporary policing. As such, the empirical focus illuminates a broader trend relating to how developments in science and technology are affording new possibilities in the ways that social control is conceptualized and conducted.