Although the problem of people with disabilities as victims of crime has been well recognized, the known characteristics of people with intellectual disabilities (ID) also make them vulnerable to becoming perpetrators of crimes. Most such crimes are minor, but the 2002 "Atkins v. Virginia" decision called national attention to people with ID and people with dual diagnoses who commit capital crimes. This article reviews the data on offenders with intellectual and dual disabilities and the challenges related to their diagnoses and their roles in the criminal justice system. Offenders with ID are overwhelmingly individuals with mild intellectual disability, and their characteristics largely resemble those of offenders who do not have an ID diagnosis. They do not engage predominantly in any one form of criminal behavior, and their readily identifiable characteristics do not set them apart from offenders without a disability. However, their intellectual limitations make it more difficult for them to understand their Miranda rights; to work effectively with their attorneys; or for those found incompetent to stand trial, to profit from formal programs to restore them to competency. Assessment methods, particularly assessment of malingering of ID, have many limitations when applied in the criminal justice setting.