Healthcare inequalities for black and minority ethnic (BME) patients in forensic mental health services in the UK are stark. Despite the level of attention given to this over the last 15 years there has been little progress to address disparities. There is a great deal of confusion over what is understood by culture, and what aspects of culture signal specific needs of BME patients. In addition, we have a lack of empirical research demonstrating what it means for psychiatrists to be culturally competent. These are all important barriers against progress in this area. Using a homicide case study that illustrates the typical issues encountered in practice, we explore how to use a cultural formulation in order to assess the role of culture within a forensic psychiatry setting. Finally, practical advice is offered to assist expert witnesses in preparing court reports that adequately consider the significance of defendants' cultural beliefs and practices.