Aim: Forensic (FS) users with intellectual disabilities (ID) have speech, language and communication needs (SLCN) that are significantly higher than the general population, but often the needs are overlooked or attributed only to the intellectual disability. This paper brings together the latest evidence on the prevalence, detection and impact of undetected SLCN in forensic ID services, and introduces a structured communication screening pathway that is suggested for routine practice. Methodology: The literature review was undertaken using peer-reviewed literatures published in the past 15 years. There were 19 sources that met the inclusion criteria with thematic synthesis used to synthesize them. Results: Communication difficulty rates reported in the sources included ranged from about 20% to 67%, including higher rates for adults with ID in community and secure settings, and for young offenders in secure settings. There are focused screening tools for youth justice and general learning-disability liaison and diversion, but few specific and validated communication screening tools are available for adult forensic ID services. Key barriers to identification were identified as diagnostic overshadowing, gaps in the workforce training and poorly coordinated commissioning. Originality/value: This paper brings together fragmented evidence and suggests a staged screening pathway for forensic ID services that can be adapted and uses it to fill the gap between the extensive youth justice evidence base and the less extensive adult forensic ID literature.