The behavioural and cognitive difficulties of some adults with autism spectrum disorder (ASD) may increase their risk of contact with the criminal justice system (CJS) as a potential suspect. There has been limited investigation of ASD and offending and available evidence is mixed. A retrospective review was completed of medical records of 1570 adults (17-75 years old) who were referred for an ASD assessment over a 17-year period (April 2003 to February 2020). Of the adults diagnosed with ASD, 23% had previous contact with the CJS. Being male or diagnosed with co-occurring attention-deficit hyperactivity disorder (ADHD) and/or psychotic disorder were risk factors for CJS contact. However, the rates of contact with the CJS or for specific offences in the ASD group were never higher than adults referred to our service but not diagnosed with ASD. We did not include a general population comparison group, therefore cannot say how rates of CJS contact in ASD compare with the general population. Further health services research for adults with ASD is warranted, as modifying the treatable risk factors (i.e. ADHD) could reduce contact with the CJS. In addition, joint working between CJS and mental health services could reduce the risk of adults with ASD having CJS contact.