For the purpose of this debate, under the ‘Not Guilty for the Reason of Insanity’ (NGRI) model, a defendant who was found to have severe mental illness or defect at the time of committing a crime is formally acquitted of a crime, and placed to a mental health facility, with their release being dependent on periodic reviews.
Under the ‘Guilty but Mentally Ill’ (GBMI) model, the defendant is found guilty, receives a regular sentence, part of which is mental health treatment. If found to be mentally fit before the end of their sentence, they must still serve the remainder of the sentence in prison.