It is a truism that behaviour does not occur in a vacuum. As the economist Herbert Simon observed, rational behaviour is shaped by a pair of scissors, one blade of which is the characteristics of the actor, the other blade being the characteristics of the environment (Simon, 1990). This is equally true for violent behaviour. The past twenty years have seen growing conﬁ dence – at times misplaced conﬁ dence (Cooke and Michie, 2010; Cooke and Michie, this volume) – in our ability to evaluate risk of future violence. However, the primary focus of these efforts has been the characteristic of the actors, not the characteristics of their setting. The preoccupation with the individual is not surprising given that, for most psychologists, their expertise – and their predilection – is the evaluation of the individual; the individual’s psychopathology, their motives, their personality, their functional deﬁ cits. These features are clearly important, but, as Simon noted, they are only one blade of the scissors that shape behaviour.