The intellectually disabled (ID) offenders are a subgroup of clinically and legally vulnerable clientele of forensic services, who often manifest complicated comorbid psychiatric illnesses, poor adaptive functioning, and high psychosocial risk factors. Although people with ID make up about 3-5% of the overall population, a proportion of forensic mental health service consumers is estimated to be 7-10 %, which means that they are disproportionately represented. The study is an appraisal of the application of a well-organized biopsychosocial assessment model that aims at enhancing risk formulation, treatment planning, and rehabilitation outcomes in a forensic context. The design was a mixed-methods one applied to three secure forensic units (n=120 Offenders with mild to moderate ID; mean age=29.4±7.8 years; 82% male). The biological (psychiatric comorbidity, neurological conditions), psychological (cognitive functioning, impulse control, trauma history), and social (family support, employment history, substance misuse) variables were evaluated with the help of standardized tools. The comparison of pre- and post-implementation was conducted within 12 months. Findings showed that 71 % of respondents had a comorbid psychiatric diagnosis, 57 % had had substantial adverse childhood experiences, and 49 % showed substance misuse records. After the formal biopsychosocial assessment, individual care plans were augmented by 35%, risk management schemes were concurred by 28%, and reported conduct episodes were reduced by 22% (p < 0.05). Multivariate regression analysis has indicated that trauma exposure (β = 0.41) and substance misuse (β = 0.36) have significant predictive value in institutional aggression. The results substantiate the clinical usefulness of a biopsychosocial assessment framework in forensic ID services, demonstrating statistically significant effects on treatment congruence and behavior change. Such a combination of biological, psychological, and social determinants, within the framework of structured risk formulation, provides a superior approach to tailored intervention mechanisms and to safer, evidence-based forensic care pathways.