Rigor mortis usually start to occur around 1 to 2 hours after death, it first starts in the eyelid muscles and gradually it develops in all parts of the body. Usually within about 12 hours after death rigor mortis is well established, then it persists for about another 12 hours and then gradually disappear in the same order it developed within about 12 hours. So, altogether by about 36 hours rigor mortis is not seen in the corpse. This is a rough guideline for how long rigor mortis take to appear and disappear, although the actual timing may change due to various factors.
How Long Does It Take For Rigor Mortis To Start?
Order of development of rigor mortis:
Rigor mortis appear early in small and active muscles which contains small amounts of plasma.
- 2 hours – first to appear in papillary muscles (muscles in the eyes) – this causes postmortem pupillary contractions (semidilatation).
- 2 hours – lower jaw
- 4-6 hours – head, face and neck
- 4-6 hours – trunk
- 6-8 hours – large joints
- 8-10 hours – small joints
- 12 hours – fully established rigor mortis1
Factors Influencing The Onset Of Rigor Mortis
There are many factors that influence the onset and duration of rigor mortis. The above mentioned time values are a rough guideline but the timing can change according to the following factors.
Condition of the body. Rigor mortis occur early in thin, emaciated subjects, whereas rigor mortis occur late in well built, healthier, and muscular subjects.
Age of Deceased. In newborns or neonates rigor mortis occur very rapidly, this duration is even shorter in stillborns. It is said that rigor mortis doesn’t occur in fetus less than 7 months. Rigor mortis also occur early in children and old people.
Cause Of Death. Rigor mortis sets in earlier and disappear quickly in case of death due to tetanus, strychnine poisoning, in death following violent spasms and convulsions such as epilepsy, electrocution, lightening; or death after many hours of violent activity (like soldiers who died in a battlefield) and in fire arm and cut throat injuries.
It also sets in early when death occurs due to tuberculosis, plague, cholera, typhoid, uremia, nephritis and cancer.
Rigor mortis is late in onset when death occurs due to pneumonia, asphyxia, hanging, apoplexy, carbon monoxide or dioxide poisoning, arsenic or mercuric chloride poisoning, and nervous disease causing paralysis of muscles.
Environmental Factors. The occurrence of rigor mortis is very rapid if the corpse is exposed to warm and moist climate. If the corpse is exposed to temperature of 75°C the stiffening becomes more prominent due to coagulation of all muscle proteins in the body. This will be seen as heat stiffening.2, 3
With cold weather the opposite happens. The onset of rigor mortis is delayed if the corpse is exposed to cold climate. Temperature below 5°C completely stop the occurrence of rigor mortis in the body. But, if the temperature is raised afterwards rigor mortis occur in the normal way.
Summary
Rigor mortis usually starts to occur 1-2 hours after death, it first starts in the eyelid muscles and then lower jaw, head, face and neck muscles. In about 4-6 hours it’s present in the trunk, 6-8 hours in the large joints, and in 8-10 hours the smaller joints. Usually within about 12 hours after death rigor mortis is well established, then it persists for about another 12 hours and then gradually disappear in the same order it developed within about 12 hours. This is a rough guideline for how long rigor mortis take to appear and disappear, although the actual timing may change due to various factors such as condition of the body, age of the deceased, cause of death and the environmental factors.
