Tools for Intellectual Disability in the Criminal Justice System

Individuals with intellectual disabilities experience substantial disadvantages when interacting with the criminal justice system, frequently resulting in unequal treatment and limited effective access to justice. Early identification is essential to enable appropriate procedural adjustments; however, formal diagnostic assessment is not feasible at the initial stages of criminal proceedings. In response, several intellectual disability identification tools (IDITs) have been developed for use in criminal justice settings. This study presents a systematic review conducted in accordance with PRISMA guidelines to map and evaluate the available scientific evidence on IDITs within the criminal justice system. A total of 762 articles were identified, and 16 empirical studies met the inclusion criteria. Nine IDITs were identified across prison, probation, juvenile justice, forensic and police settings. The Hayes Ability Screening Index (HASI) and the Learning Disability Screening Questionnaire (LDSQ) demonstrated the strongest evidence of diagnostic validity, with area under the curve (AUC) values close to 0.90, indicating high discriminative capacity. The Screener for Learning Disabilities and Intelligence (SCIL) showed more moderate accuracy (AUC = 0.78). Across diagnostic studies, instruments generally prioritised sensitivity over specificity, resulting in potential over-identification. By contrast, the remaining tools were assessed through studies examining construct validity, implementation processes, or practical utility within specific criminal justice settings. Implementation and utility findings indicate that barriers are predominantly ecological rather than technical. Although administration time is brief, the overall screening process—including explanation, consent and documentation—can be difficult to integrate into routine practice. Studies report professional resistance when screening is perceived as increasing workload. Limited specialised training, comorbidity with mental health conditions, acute stress and language barriers further undermine consistent application and accuracy. Overall, IDITs constitute feasible and relatively accurate screening mechanisms; however, their effectiveness ultimately depends on organisational commitment, adequate training and structural conditions that support equitable access to justice.