People with intellectual and developmental disabilities (IDD) are overrepresented in the criminal legal system. Further, many people with IDD move between large state-run institutions and the criminal legal system. In 2019, for example, 29% of people moving into large state-run institutions came from jails, prisons, and other correctional facilities. This Policy Research Brief recommends growing the Medicaid HCBS system; stabilizing the direct support workforce; promoting inclusion of people of color with IDD; screening for IDD in jails; and better training in IDD supports for first responders, self-advocates, and lawyers. [Development of this Policy Research Brief was supported by the Administration on Community Living.]