Abstract This study examines the interaction between the victim and offender during intrafamilial homicide. It is hypothesised that in order to understand the fatal consequences of the interaction, a psychological model must take into account both the role of the victim, as either a significant person or non-significant object, and the function of the aggression, as either instrumental or expressive. The combination of these two proposed facets gives rise to four hypothesised styles of intrafamilial homicide. This hypothesis was tested by analysing 191 intrafamilial homicide cases from the Chicago HITS database. Fifty two crime-scene actions were analysed using Smallest Space Analysis which revealed four distinct thematic clusters of variables. These themes corresponded to the hypothesised facets of victim role and function of aggression. Two related to expressive acts, (a) those murders where the offender kills multiple members of his family and subsequently takes his own life, and (b) cases where the vi...