The Stages of Human Decomposition

1. Pallor Mortis

This initial stage of death translates from Latin as “paleness of death” and manifests itself in the flesh of light-skinned humans. The loss of color in the body is the consequence of a deactivated circulatory system, leaving the blood to settle within the body.

Onset: Pallor Mortis can take effect anytime between 15 to 25 minutes after the moment of death.

Forensic Relevance: This stage happens so swiftly that the best expert can guess is that death occurred within the last half-hour.

2. Algor Mortis

This second stage of death translates from Latin as “coldness of death” and happens as the body’s internal temperature slowly equalizes with the temperature surrounding the body.

Here are just a handful of the variables that can play with the internal temperature of a corpse: The reliability of the ambient temperature. Insulation on the body. The conductivity of the resting place.Drugs or diseases within the deceased’s body.

Onset and Duration: While the body will experience its steepest change in internal temperature within the first hour of death (by 2°C), subsequent changes continue to develop at the steady rate of 1°C/hour until such time that body temperature gains parity with the environment.

  • The reliability of the ambient temperature. A body adjusts more easily to an unchanging temperature than one that fluctuates.
  • Insulation on the body. Just like with living, breathing people, the amount of worn clothing can have a huge effect on how well a corpse retains its heat.
  • The conductivity of the resting place. The thermal conductivity of the material a corpse lays on can play a role in heating or cooling a body that goes beyond the influence of ambient temperature.
  • Drugs or diseases within the deceased’s body. Some diseases and medications can play with the body’s internal temperature.

Forensic Relevance: While experts can analyze the severity of algor mortis by rectal measurement of internal temperature, there are so many factors that can interact with their results that it isn’t really worth trying to discern a time of death.

3. Rigor Mortis

This third stage of death gets its name from the Latin words for “stiffness” and “of death” and is one of the most well-known symptoms of death. The term is derived from the outward results of biochemical fluctuations within the body, resulting in rigidity of all musculature.

In a more analytical sense, cessation of breathing in the body starves the body of oxygen necessary for ATP to move joints. When the corpse’s oxygen reserves deplete, the ATP will resort to burning up glycogen in order to move joints; once oxygen and glycogen have been exhausted, the body formally enters rigor mortis. Furthermore, calcium is released into the cytosol and binds with muscle proteins until the muscles reach a point where they are unable to relax until the body transitions into the decomposition phase.

Onset and Duration: Rigidity of musculature starts somewhere between the second and sixth hours post mortem, starting around the eyelids, neck, and jaw; all parts near the top of the body that may also be relevant to the degree of muscle fibers and glycogen saturation. Once the muscles within the head become stiff, the process continues throughout the rest of the entire body over the following four to six hours. As with most stages of death, these start times can quicken or delay based on the health, sex, maturity, and physicality of the deceased. External factors can also play a role in the progression of rigor mortis; warm areas accelerate the process and cold areas slow the process down. A corpse will eventually regain pliability upon transitioning to the putrefaction stage, covered below.

Forensic Relevance: The position that a body locks into as it enters rigor mortis can greatly assist examiners seeking a time of death. If a body is found in an area that would be inconsistent with its pose, it is a fair assessment that the body was tampered with. In investigations where a person has frozen to death, rigor mortis is usually ignored as evidence.

4. Livor Mortis

This fourth stage of death and decomposition has several synonyms. While the Latin name translates as “bluish color of death,” other names for it include hypostasis and suggillation. At this point in the corpse’s degradation, blood pools into the connective tissues of the body, causing the skin to take on a reddish, bruised coloration. The brilliance of this discolor correlates with the level of hemoglobin within the pooled blood. When the heartbeat expires, blood cells are guided by gravity, rather than the capillary system.

Onset and Duration: While livor mortis can begin as early as the first half-hour of death, the slow nature of this process renders it unnoticeable until two hours have elapsed from the time of death. The patches of discoloration will increase in size within three to six hours, reaching a saturation point somewhere between eight to 12 hours post mortem.

Forensic Relevance: Because livor mortis does not manifest in portions of the body that press against something, such as the ground or under a fallen object, it can help investigators determine the time of death and if a body was moved after death. For example, a prone body whose back is saturated with dead blood is proof that the deceased was not laying down or with their back against a wall at the time of death. While livor mortis is not a precise method of ascertaining a time of death, this state can produce a narrower window.

5. Putrefaction

While this is the fifth stage of death, it is the first of them that eschews Latin terminology. The human body is a complicated, tightly-wound organic machine that has an incredible number of subsystems that keep themselves in check. Putrefaction is the point when the necessary equilibrium of substances and biological systems goes amok. The numerous acidic substances within the body run rampant, breaking things down into liquid through a process known as “autolysis,” effectively “self-digestion.” Putrefaction can be detected when the skin transitions from the dark colors of livor mortis to a sickly greenish, beginning around the large intestine and liver-parts of the body that contain the most caustic substances. The skin of a body that has broken down to this point can be as tender as properly made BBQ, potentially sloughing off of the bones and lingering musculature with little-to-no effort.

Onset and Duration: Putrefaction is no different from any other stage of the death cycle; several factors can influence when it takes place. The age of the body, its composition, open wounds and even the cause of death all play a factor in when the body begins to liquefy. Beyond the normal variety of outside factors that can influence all stages of decomposition, the amount of light that shines over the body and the way in which a body is buried can improve or worsen the turning point.

Forensic Relevance: Several chemicals, such as arsenic and zinc chloride are also notable for their ability to prolong the period of time before putrefaction begins. This fact is also a way of detecting the use of poison as a potential cause of death, especially if the time of death is discovered.


6. Decomposition

Despite the name, this is the penultimate stage of the death cycle. The body has destroyed itself sufficiently enough to attract bacteria, fungi and carrion feeders. Two notable byproducts of this feeding frenzy are the evocatively named “cadaverine” and “putrescine”-these are the substances that produce the stomach-churning stench of organic decay. If the body has not already attracted the interest of insects and other carrion feeders, putrefaction is the point where such creatures will burrow into the body or enter its orifices in search of food and suitable material to leave their eggs. The presence of carrion flies or flesh flies is a clue that something dead is in the vicinity as both of these creatures are especially sensitive to the presence of chemicals generated by a carcass.

The tendency for corpses to bloat up can be attributed to the various gasses that build up within the body as the result of irregular chemical reactions from the bacterial and fungal consumption of the body. The phenomena of corpse-bloating happen once gas reaches the capillary system, allowing it to travel throughout blood vessels and inflate limbs. Between the swelling caused by circulating corpse gases and the feeding habits of carrion feeders, the body loses flesh until the point that the skin ruptures and frees the confined gas. Because decomposition and the ensuing release of gas byproducts cannot be stopped, it is a horrible idea to invest in a sealed casket. In this video by mortician and crematory worker Caitlyn Doughty, Doughty comments that “you really want a decomposing body to have access to some sort of air so that it can then dehydrate;” a sealed casket doubles as a time bomb capable of dislodging the casket’s lid or even some of the masonry that houses it.

Onset and Duration: The point that a body has reached the decomposition stage has some level of overlap with putrefaction, varying only by what takes over eating it up. The latter stages of decomposition can be seen in bodies that only retain skin, bones, and cartilage. One notable, if a heartbreaking, exception to the normal process of decomposition can be seen in the bodies of newborns who have never consumed food; as they have never developed the sort of microbes necessary to break down food, the bodies of such children will become mummified instead of slowly dissolving away.

Forensic Relevance: If a corpse remains over natural soil, the high number of stomach acids released by a ruptured corpse will leave a noticeable imprint on the soil. This imprint will manifest as a localized spike in acidity and above-normal levels of nitrogen. In a study published in the September ’92 issue of the Journal of Forensic Science, researchers indicated that a time of death could be better ascertained by analyzing the biochemistry within the immediate vicinity of a corpse.


7. Skeletonization

This is the final step of decomposition and the point where there is no trace of soft tissue nor cartilage. By this point, the only parts of the corpse that remain will be bones, disconnected from each other due to the lack of any connecting tissue, and inorganic materials that the person may have received after undergoing certain medical procedures in life, such as a hip replacement or cranial plate.

Onset and Duration: It can take anywhere from 21 days to years for a body to decompose this far, depending on factors like location, temperature, water levels and the abundance of insect life within the area. Notably, a corpse left in a tropical region needs only a few weeks to reach this point, yet a corpse left in subzero temperatures may never even reach this stage.

Forensic Relevance: Examining the skeletal structure of a human can yield insights into how a person died; physical trauma can be reflected in abnormalities that could be connected to a cause of death. However, the highly variable amount of time necessary for a human body to be reduced to nothing but bones can limit their relevance to cold cases.

Completing the Nutrient Cycle

Just because a body is reduced to its bones, that does not mean that it stops participating in the cycle of life. If a human’s skeletal remains are unmolested from scavengers, the land itself takes a swing after the carnivores and scavengers.

Onset and Duration: Soil with an acidic pH level can erode the bones of an adult human over a two-decade span, while sandy terrain or soil with a balanced pH level can take significantly longer, sometimes centuries to achieve the same result. Instead of eroding the bones into nothingness, regions that are especially arid or whose soils have a basic pH level will slowly fossilize the bones into minerals.

Forensic Relevance: In instances where the deceased has become fossilized, you might call upon the services of an archeologist or anthropologist instead of a coroner.

In Summary

While a human participates in the life cycle, that human’s body participates in a “death cycle” that begins the moment the human experiences death. Where humans grow in size and musculature as they change from toddler to teenager to adult, corpses loses size and musculature as they change from one death phase to another. Hopefully, you have a better grasp of the stages of decomposition than you did prior to reading this.

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