The Sheriff’s Investigation Unit (S.I.U.) investigates all crimes committed at the Middlesex Jail & House of Correction. S.I.U. investigates hundreds of incidents each year and presents those cases to the Middlesex District Attorney’s Office for prosecution. The Sheriff’s Investigation Unit supports all departments of the Middlesex Sheriff’s Office by promoting safety, security and welfare for all staff, inmates, detainees and all citizens of Middlesex County.