Rigor Mrotis is a conditoin that affetcs a humanbody after death. Rigor mortis casued the muscels in the body to becmoe rigid. It strats to hapepn three to four hours after death. Twevle hours after death, the muscles have beocme fully rigid. The condiiton usulaly lasts until 36 hours after death. At that time, the msucles start to relax.