This chapter establishes the foundation for understanding serious and violent offending through the lens of trauma. Drawing on the author’s extensive practitioner and academic experience, it argues for a departure from a reductionist explanation of serious and violent crime. Instead, the chapter proposes that the clustering of trauma in the justice system is a socially driven phenomenon, rooted in early adversity and the deprivation of safety. It critiques existing criminological and psychological theories for their failure to fully account for the trauma-offending link and highlights the need for an integrated, trauma-informed framework. By introducing the concepts of ‘known knowns’ and ‘unknown unknowns’, the chapter sets the stage for a rethinking of criminal justice responses, and for seeing prevention strategies through a public health lens.