People who have speech, language and communication needs (SLCN) are disproportionately found to be subject to Criminal Justice proceedings. Effective communication is key to effective engagement, to accessing support and interventions, and to receiving fair and equitable outcomes. Previous research has shown that there is a need for screening and early interventions for young people who come into contact with the police, in order to reduce rates of reoffending. Based upon quantitative analysis of screening data collected by Liaison and Diversion practitioners in a single UK police force area with an operational Speech and Language Therapist embedded, this research conceptualises police custody as a key gateway to the justice system and a crucial turning point for diversionary practice. The research identifies an urgent need for screening and interventions for adults as well as young people, and for people who have no previous SLCN related diagnosis.