All living organisms including human beings are reduced from complex chemical composition to a simpler form after death. During this process, every living being becomes a part of food chain or undergoes chemical digestion by autolytic enzymes produced by lysosomes present within one’s own cells.
Casper’s dictum states that if all other factors are equal, then, when there is free access of air, a body decompose twice as fast than if immersed in water and eight times faster than if buried in earth. Temperatures are usually lower in water than on land.
Initial phases of this decomposition process is of forensic significance as its can cause artefacts mimicking injuries or pathological lesions/conditions. Due to scavenging by insects, rodents, birds, fishes and predatory animals, various postmortem injuries may be seen in the body, which if not properly differentiated from ante-mortem injuries can mislead the investigation. Similarly, liquefaction, purging and discoloration of skin may be misinterpreted.
First visible sign of decomposition is greenish discoloration seen over right iliac region of anterior abdominal wall. When hemoglobin comes in contact with methane and hydrogen sulphide excreted by gut-bacteria, it gives rise to a complex sulph-meth-hemoglobin, which is responsible for producing the greenish hue. Since, caecum lies closest to the anterior abdominal wall, this greenish hue is seen first over right iliac region.
Gut bacteria then enter the blood stream and spread throughout the body, resulting in development of linear branching patterns of discoloration along the lines of superficial veins called ‘marbling’.
This greenish discoloration over time will get generalized throughout the body. At the same time, blisters containing reddish brown fluids will begin to appear at multiple places.
The entire body will swell as a result of putrefactive gases produced.Eyeballs will start protruding out and rectal or uterine prolapsed, as a result of pressure built inside the body. Postmortem delivery of dead infant is not uncommon following decomposition of dead pregnant woman. Face, abdomen, genitals, breast start bloating. Hair become loose and fall apart. Blood stained frothy fluid will ‘purge’ out from nose and mouth.
With advancement in decomposition, tissue will start to liquefy and fall apart. Last tissue to liquefy would be prostrate and uterus due to presence of fibrous tissue. Finally, skeletonisation occurs in a variable period of time. and no one can actually guess how much time one would take to be completely skeletonized. This is because there are so many environmental and biological factors involved in this process, which do not follow exact time formula of minutes, hours, days and months.