Rigor mortis is when the muscles and joints in the body stiffen after death. It is caused by chemical changes in the body’s cells due to death. People who die in a warm environment will experience rigor mortis more quickly than in a cold environment. Rigor mortis can be expected to start between 2 to 6 hours from the time of death and it can last for 12 to 48 hours. The smaller muscles (like eyelids, neck and jaw) will be affected first, followed by the larger muscles.
The body usually returns to a softer state around 36 to 40 hours after the time of death.
If the person has died in an unnatural position, you can try gentle but firm massage and movement of the body’s joints to loosen the rigor mortis and change the position of the person’s body although this does not always work.