security threat group definition
Security Threat Group (STG) Law and Legal Definition. Security Threat Group (STG) is a formal or informal group of prison inmates. They are basically the prison gangs. Law enforcement officials use the term Security Threat Group to refer such gangs in order to take away the recognition that the term âgangâ connotes. STGs pose threat to the safety of prison officials and other inmates. STGs vary in organization and composition.