The Assessment of Risk and Manageability in Intellectually Disabled IndividuaLs who Offend (ARMIDILO) was developed to address the need for assessment tests specifically designed for intellectually disabled (ID) individuals who offend. This is the first study focusing on the application of the ARMIDILO by using comparative current risk assessment tests to evaluate the ARMIDILO as an effective risk assessment tool. In this research 16 ID people who have recorded sexual and or violent behaviour offences were evaluated using the Violent Offender Risk Assessment Scale (VORAS), Static-99 and ARMIDILO risk assessment tests. The ARMIDILO, VORAS and Static-99 assessments were completed using individual history files kept within the Regional Forensic Psychiatric Service. The VORAS and Static-99 were adapted to incorporate reported, but not charged or otherwise litigated offences and convictions. The adapted tests were then compared against the ARMIDILO as a risk assessment tool. Analysis of the ARMIDILO showed strong validity in assessing ID people who offend. The main strength of the ARMIDILO is in identifying the risk needs of the ID person who offends and may be an effective management test when used in assessing individual needs and program implementation. Risk assessment through the ARMIDILO showed similar results to Static-99 but compared only moderately with the VORAS in measuring the risk of re-offending. Future research with a larger population may further validate the reliability of the ARMIDILO as an assessment tool. Adaptation of the current score sheet for use by non-clinical and correctional staff may prove cost effective.