In this introductory article we begin by setting out the aims of this special issue, including: why the expertise paradigm may prove fruitful in understanding the proximal processes surrounding cognition, emotion and behavior at the scene of the crime; and to draw together strands of an emerging field at this important time in its development. We then go on to outline what we see as the key components of perceptual and procedural expertise as defined in mainstream cognitive psychology. We then review strands of complementary knowledge from allied fields in cognitive science that have developed in parallel and lend support for core basic elements of expertise. Adopting the notion that expertise is on a continuum and that most individuals will not reach the extreme end of competence, we describe a model of functional expertise which most people could achieve with practice. Finally, we then discuss ‘dysfunctional expertise’ that offenders might display through practice in a particular criminal domain and consider how this might enhance our understanding and prevention of criminal behavior.