Guilty but mentally ill (GBMI) refers to a finding that an offender is guilty of the criminal offense with which they are charged but, because of their prevailing mental condition, they are generally sent to psychiatric hospitals for treatment rather than to prison.

Once they have been declared cured or well however, such offenders can be transferred to correctional facilities to serve out their sentences.

Other /More definition:
Guilty but mentally ill (GBMI) refers to a verdict that requires a convicted criminal to serve the full sentence designated for his or her crime, with the expectation that he or she will also receive treatment for mental illness