Decomposition in simple terms is defined as the breakdown of complex organic matter into simpler inorganic matter. The decomposition of the human body is called putrefaction, which is a process where complex organic body tissue breaks down into simpler inorganic compounds or elements due to the action of saprophytic microorganisms or autolysis.

Putrefaction is the last stage in the dissolution of the body and usually follows the disappearance of rigor mortis. During the hot season, it may commence before the rigor mortis has completely disappeared from the lower extremities. After death, the body’s protective functions are absent and its defense barrier is lost.

Mechanism of Decomposition

Decomposition can occur in the cells which are dead while the other cells are still alive. It follows the arrest of a biochemical process that develops, maintains, and preserves the integrity of cellular elements.

During decomposition, the tissue components leak and break up releasing hydrolytic enzymes. The complex organic body tissues are broken down into simpler compounds. The bacteria and other microorganisms thrive on the unprotected organic components of the body.

Thus, two parallel processes of decomposition can be identified- autolysis and bacterial action.

  • Autolysis– The self-dissolution of body tissues by the enzymes released from disintegrating cells. After death, the tissue cells release the autolytic enzymes that soften and liquefy the body tissues. Autolysis is generally initiated 3-4 hours after death and continues for 2-3 days.
  • Bacterial Action– There are a number of saprophytic microorganisms that cannot invade the body during life, but after death, these organisms invade the body and initiate the digestion of fats, carbohydrates, and proteins. The bacterias release their enzymes like lecithinase which hydrolyses the lecithin present in all cell membranes. The bacteria responsible for the hydrolyses include- Streptococci, Staphylococcus, Clostridium welchii, Escherichia coli, and Bacillus proteus. In living beings, these bacteria are present in the intestines, but due to the active defense mechanism of human immunity, they are unable to cause any harm. However, when a person is dead, the defense mechanism becomes inactive and these bacteria can easily kill the cells. They enter the bloodstream from the intestines and initiate the hydrolysis of the cells.

A third kind of post-mortem destruction can be identified in some bodies that are not disposed of such post-mortem destruction is brought out due to the attack of various types of animals such as insects, rodents, canines, foxes, jackals, vultures, fish, etc.

Decomposition Changes in Body

As mentioned earlier decomposition is a conversion process, there are a lot of visible changes that occur in a dead body. Followed by the autolysis and bacterial action, there is a sequence of changes that takes place in the corpse. These changes are:

External Changes in Body

  • Discoloration: Greenish discoloration in the lower abdominal quadrants. The first external sign of decomposition is usually a greenish discoloration over the right iliac fossa over the region of the caecum which lies superficially and the contents of the bowel are more fluid and full of bacteria. Welchii are most abundant in the ileocaecal zone of the intestinal tract. The discoloration occurs from green to black due to the formation of sulphmethaemoglobin (formed due to bacterial action) in the blood vessels that diffuse to surrounding tissues. The discoloration can be observed after 12-24 hours of death. After 24 hours the discoloration is seen in a mosaic pattern, especially at the sites where the veins converge.
  • Distension: Various gases produced during decomposition penetrate into the skin, soft tissue, and organs which manifests as crepitus and distension. The gases like hydrogen sulphide, ammonia, phosphorated hydrogen, and methane are developed below the skin, hollow viscera, etc., which produces the offensive foul smell of decomposition. As time runs the volume of the gases increases causing a pressure effect in the dead body. The pressure effects lead to the processes like bloating of features (the whole body swells up, with bulging of eyes, tongue, genitals, etc.), shifting of postmortem lividity (Due to decomposition the blood clots liquify, which shifts the lividity in any direction).
  • Degradation: Decomposition causes a loss of anatomic integrity of skin and other tissues such as localized peeling of skin (‘skin slippage’), loosening of skin of hands (degloving) and feet (‘destocking’), and loosening of hair and nails. 
  • Postmortem Purge: As the tissues inside the body are liquified, the bloodstained decomposition fluid will drain out through the mouth, nose, and all other natural orifices.
  • Dissolution: Progressive decomposition leads to liquefaction and disappearance of tissues and organs and eventual skeletonization.

Internal Changes in Body

  • The internal organs decompose at different rates and times depending on their cellular composition, structure, vascularity, and accessibility to air and bacteria.
  • The liver becomes softened and flabby due to the evolution of putrefying gases in it, where it is in contact with the transverse colon. It appears spongy and shows a honey-combed structure.
  • Due to the pressure of gases, the diaphragm is moved upwards which leads to the emptying of the heart.
  • The brain shows soft cysts which may mimic encephalomalacia with Swiss cheese patterns of their cavities that can be easily detected.

Marbling of Skin

  • The blood vessels provide an important route through which the bacteria can spread with ease throughout the body. 
  • Their passage is marked by the decomposition of hemoglobin to sulphmethemoglobin in the blood vessels which causes greenish or reddish-brown staining of the inner walls of the superficial vessels.
  • This is seen as linear branching patterns which give a ‘marbled’ (‘road map’) appearance to the skin.
  • Areas where visible: It appears first in the shoulder, roots of the limbs, thighs, sides of the abdomen, chest, and neck. 
  • Onset: In summers, ‘marbling’ is seen in 36-48 hrs after death.

Postmortem luminescence is usually due to contamination by bacteria, like Photobacterium fischeri, the light comes from them and not from putrefying material.

Luminescent fungi, Armillaria mellea, are other sources of light.

Skeletonization of the body: Skeletonization of the dead body takes varying times depending on several factors. In buried dead bodies, total skeletonization may take one year. 

Appearance of Insects on Dead Body

In the study of decomposition changes, along with forensic pathology, another important field is concerned with the estimation of postmortem interval, which is called forensic entomology.

Forensic entomology studies the decomposed body with the help of insects. When a dead body starts putrefying, the flies like blowflies are attracted to the corpse and they lay eggs within 18-36 hours at the injured side or the natural orifices.

The eggs hatch after 24 hours and are converted to larvae or maggots. The maggots crawl to the soft tissue for nourishment, where they reside for 4-5 days and develop into pupae. Then in another 4-5 days, the pupae are converted into adult flies. This life cycle of insects is an important indicator of the postmortem interval.

The presence of maggots can also reveal the presence of drugs in the dead corpse.

Factors Affecting Decomposition

  • Moisture: the moisture accelerates the process of putrefaction as it is an important element required for the process of autolysis. The organ having maximum moisture will putrefy rapidly.
  • Air: Air also facilitates putrefaction.
  • Temperature: High temperature promotes decomposition while low temperature retards the decomposition process.
  • Age and Health Condition of The Body: The body of an adult putrifies rapidly as compared to children and infants. The body of an obese person putrefies rapidly due to the presence of plenty of fat and moisture as compared to the skinny one.


Decomposition is the last stage of postmortem changes and a sure sign of death. The different stages of decomposition are an important indicator of postmortem interval.

Therefore, forensic pathologists can easily estimate the time of death but due to changes in the external features of the deceased body it is difficult to exactly distinguish the injuries. However, a lot of information can be revealed by decomposition of dead body.

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Frequently Asked Questions

1. What Are The Stages of Body Decomposition?

The 5 stages of decomposition of a body are: Autolysis, Puterfaction, Advanced Decay and Skeletonisation.

2. Why Do Bodies Decompose Slowly in Water?

Water generally keeps the body at a low temperature primarily due to anaerobic environment and cooler temperatures. The low temperature inside water delays the bacterial growth which also leads to slow decomposition process.

3. Can a Body Decompose Withour Oxygen?

Yes, a body can decompose without oxygen too. Some of the micro-organisms respire anaerobically and hence they can eat the body and resume the process of decomposition, however the process will be slower than usual.


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