In recent years violent knife crime has attracted attention in the UK from government and media. This qualitative article utilises Actor-Network Theory (ANT) to theorise and describe the aetiology of urban knife crime. ANT embraces the potentially causal properties of physical places and culture to explain social phenomena. The article attempts to understand violent crime by applying ANT to empirical data in the form of life stories provided by incarcerated white male teenagers. ANT’s metaphysics elides the modernist split between the human realm and brute nature. This techno-social analysis extends our notion of causality, challenging our understanding of delinquency and legal culpability. By foregrounding embedded human and non-human actor networks the causes of reoffending are illuminated as interlocking.