After death, the body’s protective functions are absent and its defence barrier is lost. Saprophytic micro-organisms which cannot invade the body during life, physical and chemical agents which are present in the environment, all act on the dead body. Further, some body chemicals and enzymes which are helpful agents during life and take part in different metabolic processes, in the absence of physiological control after death, start acting adversely.
Thus, after death, the dead body is subjected to wear and tear. Upto a certain period, while some changes like rigor mortis, continues in the dead body, its gross structure is maintained. But with further progress of time beyond the phase of rigor mortis the tissue composition and the gross structure of the body, start breaking down, due to the process of wear and tear, due to the above reasons. This is decomposition or putrefaction of dead bodies. This process continues till total destruction of all the body parts takes place.
Definition. Decomposition can be defined as a process by which the complex organic body tissues break down to simpler inorganic compounds or elements due to the action of ferments produced by the saprophytic micro-organisms or due to autolysis. The process leads to discolouration of dead body, evolution of foul smelling gas, swelling of the dead body with gradual and total destruction of the different body parts.
Decomposition is the normal fate of an undisposed dead body. Under certain specific environmental conditions modified decomposition of the dead body occurs, in which cases, instead of early and total destruction of the dead body, the dead body is preserved for a pretty long period. The ordinary decomposition is also termed putrefaction and the two varieties of modified decomposition are known as adepocere change and mummification.
Micro-organisms responsible for decomposition – Cl. Welchii. B.Coli, Staphylococcus, Non-haemolytic streptococcus, diptheroids, and proteus are the important ones.
Status of autolysis — In absence of any microorganism also, there will be decomposition of the dead body, e.g. aseptic autolysis occurring in dead foetus in mother’s womb.
Different gases which are produced during decomposition – As the process of putrefaction progresses, some gases are evolved. These are H2S (Hydrogen sulphide), Phosphoretted hydrogen, CO2, CO and marsh gas.
External signs of decomposition (in summer) The first external sign of decomposition appears over the right iliac fossa of the abdomen. A greenish discolouration appears there. Cl. Welchii are most abundant at the iliocaecal zone of the intestinal tract During life they are not very active and cannot invade through the living tissue. After death, when the tissue barrier is lost, they can invade through the intestinal wall They also reach the blood vessels. They break the tissue structure and produce H2S gas. The gas combines with the haemoglobin of blood and forms sulphmethaemoglobin which discolours the vessels and the surrounding tissue Diffusion of gas and invasion of the nearby tissue by the organism gradually cause spreading of the discolouration over a wider area of the abdomen. In this country, this first change of greenish discolouration occurs externally over the right iliac fossa of the abdomen of the dead body by about 12 hours after death, in summer. Rigor mortis is still present in different parts of the body. In winter, this change appears between 36 to 48 hours after death. The discolouration gradually spreads. First, the discolouration is distributed in patches, which gradually coalesce and becomes continuous. The discolouration first spreads all over the abdomen, then over face, neck and thorax and lastly on limbs.
Invasion of blood vessels by the organisms and production of H2S gas and formation of sulphmethaemoglobin there, causes greenish brown staining of the inner walls of the vessels. This makes .the superficial veins prominent and colourful. This phenomenon in the smaller superficial branches of the vessels and the local tissue gives a marbled appearance of the skin of the area. Marbling of the skin becomes prominent by 36 – 48 hours after death in summer. Further changes occur as follows :
Between 12 – 24 hours — Gas accumulates inside the abdominal cavity. The abdomen is tense. Blood-tinged froth comes out through the nose and mouth.
Between 24 – 48 hours — Gas accumulates in the tissues which appear bloated. Subcutaneous tissue becomes emphysematous. Breasts in females, scrotum and penis in males, are swollen. Tongue is swollen and protruded. On the second day, blisters form due to presence of gas in the vessels. Rupture of blisters occur. Cuticle gets denuded.
Between 48 – 72 hours — There is prolapse of uterus and anus. Postmortem delivery of foetus occurs from the gravid uterus. Both antemortem and postmortem wounds ooze. Postmortem staining gets displaced from the original stained areas. Eye balls protrude. Face is extremely swollen, discoloured and the subject is not identifiable from the face. Hair and nails become loose and may be taken out easily.
Between 3 – 5 days – Abdomen bursts. Swelling of the body passes over due to escape of gas through the damaged body parts. Teeth become loose. Skull sutures separate and decomposed liquified brain substance comes out, specially in infants.
Between 5-10 days – Colliquative change (liquefaction) occurs during this period. Soft firm tissues change to thick semisolid black mass. Lately, same thing occurs to cartilages and ligaments.
Skeletonisation of the body – Skeletonisation of the dead body takes varying time depending on various factors. In buried dead bodies, total skeletonisation may take even 1 year. When disposed off carelessly on land or water, skeletonisation may occur within a few months.
Destruction of bones ordinarily takes several years. In adverse circumstances like, when disposed of in a damp area or when aquatic or terrestrial animals eat up parts of the bones, destruction of the bones may occur quite early. On the other hand, when some bones are preserved suitably, they may remain intact for hundreds of years.
Internal changes due to decomposition (in summer):
Larynx and trachea — Decomposition starts between 12 – 24 hours in summer (2-3 days in winter). Mucous membrane of the larynx and trachea first appears brownish and then greenish and gets softened. The mucous membrane may be denuded.
Stomach and intestine—Decomposition starts between 24-36 hrs in summer (3-5 days in winter). At first there is dark red patches in the posterior wall, which gradually spreads to the anterior wall. Then, there is formation of gas blebs, cysts and then the stomach becomes soft, dark brown and lastly changes to a dark poulticeous mass.
Liver —Decomposition in liver starts between 12 – 24 hours after death in summer. At the beginning, the liver is soft and flabby. Blisters appear on the surface. On the second or third day, accumulation of decomposition gas gives honeycomb appearance of the cut section of the liver. Such a liver is more popularly called a “foamy liver”. The liver gradually reduces in size, darkens in colour and ultimately reduces to a coal-black poulticeous mass.
Gall bladder —Decomposition of gall bladder starts with diffusion of bile to the surrounding tissue including the inferior surface of the liver. This occurs by about 24 hours after death or even earlier. The gall bladder collapses. But total disintegration does not occur very early.
Omentum/mesentery — Decomposition becomes quite obvious between 2-3 days in summer with greyish green appearance. Ultimately the mesentery looks blackish.
Brain — Decomposition of the adult brain starts between 24 – 48 hours after death in summer when it appears soft and pulpy. By the third day the brain appears pasty. Between 3-4 days it liquefies. Decomposition of the infant brain occurs early due to some areas remaining unprotected due to the fontanelles.
Heart — in the 2nd and 3rd day, the heart is soft and brownish. It also reduces in size and weight. Bullae containing decomposition gas appear at the under-surface of the pericardium. The chambers of the heart contain frothy blood.
Lungs — By the 2nd and 3rd day, the lungs show signs of decomposition like, deepening of the colour, partial collapse and appearance of bullae of gas on the surface and is less elastic and less spongy. With the progress of time these changes increase in degree. Ultimately the lungs totally collapse, are very small in size and appear blackish.
Kidneys — By the 2nd and 3rd days, the kidneys are reddish brown in colour, soft in consistency and greasy to touch. Gradually the colour darkens, size reduces, and softness increases.
Diaphragm — Being fibromuscular in morphology, it resists putrefaction for a longer period. It is only after some days that it becomes soft and disintegrates.
Blood vessels — Though decomposition of the blood cells stains the walls of the vessels early and makes them prominent externally, yet the vessels or the vascular walls resist decomposition for a pretty long period.
Urinary bladder — Generally speaking, urinary bladder resists decomposition for a long period. In case of cystitis or infection of the urinary tract (upper), decomposition occurs early. Full bladder decomposes earlier than empty bladder.
Prostate — It is the organ in males which decomposes last. However an enlarged and diseased prostate decomposes comparatively early.
Uterus — In females, this is the organ to decompose last. A gravid uterus of course, decomposes earlier than a non-gravid uterus. A parus non-gravid uterus decomposes later than a gravid uterus and a nulliparous uterus decomposes last.
Prostate and uterus being the last organs to decompose, help to know sex of dead bodies from soft tissue, in very advanced state of decomposition where no other soft tissue is in proper anatomical form to tell about the sex of the persons.
Factors which influence the process of putrefaction :
The factors can be divided into external factors and internal factors.
External factors (not related with the condition of the dead body) —
1. Atmospheric or environmental temperature — High atmospheric or environmental temperature promotes early decomposition. The optimum range of temperature for decomposition is 21 °C – 38°C. Beyond this range decomposition occurs at a low rate, at above 10°C and below 45°C. Decomposition virtually ceases below 0°C and above 48°C. Optimum temperature helps decomposition in two ways, (i) by chemical breakdown of the tissues and (ii) by promoting the growth of the organisms responsible for decomposition.
2. Moisture — Presence of moisture promotes decomposition by promoting the growth of the organisms, in absence of moisture, growth of the organisms will not be rapid. If the body dries up quickly, it will prevent putrefaction and will cause mummification of the body.
3. Air – (a) Stagnant air promotes decomposition (b) Air movement retards the process of decomposition by evaporating the body fluid and cooling the dead body.
4. Clothing — In summer, clothings may slightly reduce the rate of decomposition by preventing invasion of the body by airborne organisms. In winter, if the body is covered with clothings then, that will help the process of decomposition by retaining the body heat for a longer period and helping growth of the organisms and the chemical process of break down of the tissue.
5. Environment — If the body is submerged in water then, generally speaking, the process of decomposition is slow, due to early coolihg of the Body. But the rate of decomposition enhances once the body is taken out of the water, because, then the body is saturated with water and also gets the effect of higher atmospheric temperature. The sum effect of the two is rapid growth of the organisms.
In buried dead bodies, the rate of decomposition varies according to the depth of the grave. In surface burial, the rate of decomposition is more than in deep burial, because of abundance of bacteria in surface soil in comparison to deep soil.
6. Invasion of the body by animals and insects —
(a) In water, fish and other aquatic animals like, crabs, tortoise may injure the dead body helping invasion of the body by bacteria which enhances decomposition.
(b) On land, dogs and jackals may partly destroy the dead body and that causes early decomposition.
(c) Invasion of the dead body by maggots is an important cause of early decomposition and destruction of the dead body. Maggots are larvae of flies. “Forensic entemology” studies the various aspects of invasion of the dead bodies by maggots. Usually three types of flies deposit or lay eggs over the moist areas of the dead body or nearby, e.g., common house fly, green bottle fly and blue bottle fly. They lay eggs near the nasal or mouth openings, near the canthuses of the eves or near the axillary folds. Laying of eggs may be as early as 8 – 9 hours after death.
The common housefly however, does not usually lay eggs directly on the dead body. But the green bottle or blue bottle variety does. The two ratter varieties lay eggs usually before the starting of putrefaction. Hatching from the eggs occur between 10 to 12 hours. The first change in the cuticular layer of these two types of larvae or maggots occur after about 12 hours. A similar second change in the larva occurs after about 2 – 3 days stay in the second stage. In the 3rd stage the larva is larger in size and is voracious eater. In this stage it stays for about 6 days. Then in the dark, it moves away from the body to take shelter under the surface layer of the soil, where it moulds to pupa. It takes about 7-8 days to mould once more to change to adult fly.
In case of common house fly, hatching, of the eggs occur after about 10 – 12 hours of laying. The first change in the larva occurs in a day or two. The second change occurs in a day or two more. The larva or the maggot continues for 2-3 days in this stage. Then it moulds to pupa at some hidden place and takes about a week to change to an adult fly.
Hence to determine time of death from the entemological study, one has to identify the variety of the maggot and in which stage it is present in the body. The larva of blue or green bottle fly are larger (2/3″) than those of the common house fly (not larger than 1/2″). The green and blue bottle flies lay eggs in and around summer season. Each of them can lay about 1-2 thousands of eggs. Common house fly lays only about 100 -150 eggs at a time.
Internal factors (body factors) influencing decomposition—
1. Age — In case of intra-uterine deaths, decomposition is aseptic and is only by way of autolysis. In still born foetuses or infants who have not taken any breath nor were given any food, decomposition occurs from outside, as in them there is no scope of any bacteria being in their lungs and G.I. tract. Hence in these cases the process of decomposition is slow, though fluid content of these bodies is more than the others.
2. Sex — Sex does not have much to influence the process of decomposition, except that, a female body, by virtue of its abundant Subcutaneous fatty tissue, retains body heat for a longer period which may enhance the process of decomposition a little.
3. Condition of the body — A thin emaciated body decomposes late in comparison to a well nourished bulky body due to less fluid content in the former, which does not promote growth of the organisms.
4. Cause of death — When death is due to infection or septicaemia, decomposition is rapid for obvious reason.
5. Surface injury on the body — Dead body having external injuries (either antemortem or post mortem) will decompose earlier because, the injured areas will allow invasion of the body by additional bacteria from outside.
Decomposition in water and floatation of a dead body
Usually the process of decomposition in water is slow due to early cooling of the body. But once the body is removed from the water the process is very rapid, due to the facts that, such a dead body is saturated with water and gets optimum temperature in air for the growth of the micro-organisms. In submerged dead bodies decomposition starts early in head and face because head and face being the heaviest part of the body assumes lowest level in water and amount of blood is therefore maximum there. However, accumulation of gas occurs first in the scrotum, as that part of the body is at the highest level.
Factors which influence decomposition in water —
1. Water temperature.
2. Stagnancy of water – In stagnant water decomposition is rapid than in flowing water, because, in the later case, water constantly washes out the organisms from the surface of the body.
3. Quality of the water — The process of decomposition is slow in fresh water and early in polluted water.
4. Aquatic animals — Aquatic animals including fish may cause postmortem injury or mutilation of the dead body which will favour the process of decomposition by allowing invasion of the body by organisms, through the injuries or the mutilated areas.
Floatation of a dead body on water
In our country, floatation of a dead body on water occurs usually by 24 hours after death in summer. In winter it takes about 2-3 days to float. In cold or temperate countries, time required for floatation is about 2-3 days in summer and 1-2 weeks in winter.
The following factors influence floatation of a dead body on water :
1. Decomposition – Early decomposition causes early floatation of the dead body, because, accumulation of gas in the tissue increases the buoyancy of the body.
2. Salty water – Floatation occurs early due to higher specific gravity of saline water.
3. Stagnant water – Promotes early floatation by way of causing early decomposition.
4. Clothings – Help early floatation because, these are lighter than water due to containing air bubbles in between the spaces of the fabrics.
5. Sex – Female bodies are lighter because of more fat content and so female bodies float early.
6. Season – Summer helps early floatation and winter delays the process. Seasons act indirectly by way of influencing decomposition.
Medicolegal importances of decomposition —
1. Decomposition is the surest sign of death.
2. From the stage of decomposition time passed after death can be assessed.
3. Advanced decomposition obliterates the identity of the deceased.
4. Advanced decomposition also obliterates the cause of death of the deceased.