Eminem has not been in jail. Maybe you are thinking about his arrest in 2000 when he was arrested for pulling what turned out to be an unloaded gun or when he assaulted a bouncer. He received probation for assault and possession of a concealed weapon.
Marshall Mathers III, also known as Eminem, was arrested in June of 2000 twice. The charges in Warren were for carrying a concealed weapon and for assault. He was also arrested for brandishing a gun in a parking lot disagreement in Royal Oaks.