Rigor mortis or postmortem stiffening is the one of the stages of the changes that occurs in the dead body. It initiates after primary flaccidity in which the body relaxes after death and stiffening starts after that. In this all muscles of the body are affected. It starts developing after two to six hours after death. It first begins in the eyelids, then on neck and jaw and finally to upper and lower parts of the body. It develops due to the accumulation of lactic acid in the body. The accomplishment of rigor mortis results in the softening or relaxation of the body which is called as secondary relaxation.
