A growing body of research examines the factors that influence the likelihood of solving homicide cases. Much of this research is North American and based mainly on quantitative analysis of police data. It also tends to focus on factors apparently beyond police control, such as victim or incident-related characteristics, encouraging a somewhat deterministic view of investigative outcomes. This paper uses interviews with homicide detectives and observations of investigations in Great Britain and the United States, to explore factors which in the light of experience ‘on the ground’ appear to affect the chances of solving homicides – the focus being particularly on ‘organisational’ factors related to police policy and practice. Although we find some important differences between nations, the weight of qualitative evidence gathered suggests that the likelihood of solving even the most challenging homicide cases in both nations can be influenced by police agency at the individual and strategic level.