rehabilitation worker
A person who works in rehabilitation, often in a social welfare or correctional context. The term is a compound of 保護 (protection/care) and 委員 (committee member/worker), but it refers to a practitioner rather than a committee member.
He works as a rehabilitation worker at a correctional facility.
保護司 is a volunteer probation officer, while 保護委員 is a more general term for a rehabilitation worker, often in an institutional setting.
更生保護 refers to the system of rehabilitation and aftercare for offenders, whereas 保護委員 is the person who carries out such work.
Compound of 保護 (protection, care) and 委員 (committee member, person in charge). The exact historical derivation is uncertain, but the term is used in modern Japanese to denote a rehabilitation worker.