A forensic unit is usually located in a "state hospital". Depending on the state, it is where patient is sent by the court to "serve their time" for any number of crimes from stealing to murder. The idea is to provide treatment rather than punishment. Unlike a civil commitment, the patient will often not be released once stable. For example, if they have been sentenced to 200 years for murdering several people, stable or not, on the forensic unit they shall sit. Again this varies by state but I hope it answers your question.