Drawing upon data gathered during a three-year ethnographic study of homicide investigation in Britain, this paper explores how detectives, scientists and prosecutors create narratives when building the prosecution case against homicide suspects. Specifically, we unravel how these key prosecution actors use forensic and digital technologies to: (a) build and support the prosecution narrative and (b) test or challenge suspect/defence narratives. As science and technology becomes an ever more embedded part of homicide investigations, we consider whether narratives based on ‘science’ or so-called ‘hard’ data confer legitimacy in ways that other narratives do not. Existing research on criminal justice narratives has tended to explore narratives within the court setting. Our paper will contribute to this research but also consider the largely overlooked pre-trial investigation phase. The paper will also contribute more broadly to the growing body of work within criminology on storytelling and the creation of narrative identity.