Decomposition of human body involves two processes : autolysis and putrefaction.
Autolysis is Self-digestion of tissues. Soon after death, cell membranes become permeable and breakdown, with release of cytoplasm containing enzymes. Lysosomes and their digestive enzymes (mainly hydrolases) are released from the cells. The proteolytic, glycolytic and lipolytic action of ferments cause autodigestion and disintegration of organs, which occurs without bacterial influence.
This chemical process is increased by heat and is stopped by freezing or inactivation of enzymes by the heat. The earliest autolytic changes occur in parenchymatous and glandular tissues and in the brain. The lining of intestines, adrenal medulla dn pancreas autolyse within hours of death. Autolytic fermentation results in maceration of the dead fetus in utero, early softening and liquefaction of the brain of the newborn and infants, and softening of the internal organs.
Autodigestion by acid gastric juice is a common finding in the newborn and infants, and is seen as softening and rupture of the stomach and lower esophagus. In adults, such digestion may start before death in cases of intracranial lesions. The earliest external sign is a whitish, cloudy appearance in the cornea.
The terms decomposition of human body and putrefaction are used as synonyms. Putrefaction usually follows the disappearance of rigor mortis.
During hot season, it may commence before rigor Morris has completely disappeared from the lower extremities. It is the final stage following death, in which destruction of the soft tissues of the body is caused mainly by the action of bacterial enzymes, mostly anaerobic organisms derived from the intestines. Other enzymes are derived from fungi, such as Penicillium and Aspergillus and sometimes from insects, which may be mature or in larval stage.
The chief destructive bacterial agent is Cl. welchii, which causes marked haemolysis, liquefaction of postmortem clots and of fresh thrombi and emboli, disintegration of tissue and gas formation in blood vessels and tissue spaces. Bacteria produce a large variety of enzymes and these breakdown the various tissues of the body. Lecithinase produced by CI. welchii is most important. This hydrolysis the lecithin which is present in all cell membranes including blood cells, and is responsible for the post-mortem haemolysis of blood.
The other organisms include Streptococci, Staphylococci, bacteroids, anaerobic lacbobacilli, diphtheroids, B. Proteus, B. Coli., B. aerogenes capsulatus, etc. It begins immediately after death at the cellular level, which is not evident grossly. There is progressive breakdown of soft tissues and the alteration of their proteins, carbohydrates and fats. Organisms enter the tissues shortly after death, mainly from the alimentary canal, and less often through the respiratory tract or through an external skin wound.
The fall in the oxygen concentration in the tissues and rise in hydrogen ion concentration after death favor bacterial growth and spread throughout the body. Because the protective agencies of the body are absent, the bacteria spread through the blood vessels using the proteins and carbohydrates of the blood as culture media. Streptococci and staphylococci multiply 10 to 100 times and even more in blood and tissues of corpses kept at room temperatures. The characteristic features of putrefaction are:
(1) changes in the color of the tissues,
(2) the evolution of gases in the tissues, and
(3) the liquefaction of tissues.
The exact chronological order of the appearance of putrefactive changes is highly variable and depends on a broad variety of individual as well as environmental conditions. The same changes seen on surface of the body occur simultaneously in internal organs.
(1) Color Changes
Bacteria spread directly from the bowel into the tissues of the abdominal wall. At an early stage of putrefaction, hemoglobin diffuses through the vessels and stains the surrounding tissues a red or reddish-brown color. In tissues, various derivatives of hemoglobin are formed including sulfur-containing compounds, and the color of the tissues gradually changes to a greenish-black.
The first external sign of putrefaction in a body lying in air is usually a greenish discoloration of the skin over the region of the cecum, which lies fairly superficially, and where the contents of the bowel are more fluid and full of bacteria. Internally, this is seen on the under surface of the liver, where that organ is in contact with the transverse colon. The color results from the conversion of hemoglobin of blood into sulphmet hemoglobin by the hydrogen sulphide formed in the large intestine and escaping into the surrounding tissues. The colour appears in 12 to 18 hours in summer and in one to two days in winter. Green coloration is more clearly seen on a fair skin than on a dark one.
The green coloration then spreads over the entire abdomen, external genitals and then patches appear successively on the chest, neck, face, arms and legs. The patches become dark-green and later purple and dark-blue. They are at first scattered, but later on join together and the whole skin of the body appears discolored. The putrefactive bacteria spread most easily in fluid and tend to colonize the venous system. Wrinkling of the fingertips occurs early which become leathery, and the nails become prominent.
The superficial veins especially over the roots of the limb, thighs, sides of the abdomen, shoulders, chest and neck are stained greenish-brown or purplish-red depending on the total amount of sulph hemoglobin formation within the affected vessels (linear branching pattern) due to the haemolysis of red cells, which stains the wall of the vessel and infiltrates into the tissue, giving a marbled appearance (red, then greenish pattern in skin resembling the branches of a tree). This starts in 24 hours, but is prominent in 36 to 48 hours. The clotted blood becomes fluid, and as such, the position of the postmortem staining is altered, and the fluid blood collects in the serous cavities.
Putrefactive effusion of foul-smelling bloodstained fluid into the pleural cavities usually starts at about the time when the skin becomes macerated. Such effusions usually do not exceed 60 to 100 ml. unless death resulted from drowning, when several hundred ml. of drowning medium which oozed out through the lungs and visceral pleura, may be present in the thoracic cavities. The reddish-green color of the skin may become dark- green or almost black in 3 to 4 days.
The earliest internal change is a reddish-brown discoloration of the inner surfaces of the vessels, especially of the aorta. Internally, decomposition of human body proceeds more slowly than the surface. The same changes of color are seen in the viscera, but the color varies from dark-red to black, rather than green. With this color change, the viscera become softer and greasy to touch. Finally, they breakdown into a soft disintegrating mass.
(2) Development of Foul-smelling Gases
The chemical processes in this stage are those of reduction, the complicated proteins and carbohydrates being split into simpler compounds of amino acids, ammonia, CO, C02, hydrogen sulphide, phosphorated hydrogen, methane and mercaptans. The gases are non-inflammable in the early stages, but as the decomposition of human body progresses, enough of hydrogen sulphide is formed, which can be ignited to burn with a blue flame.
Gases collect in the intestines in 12 to 18 hours in summer, and 1 to 2 days in winter and the abdomen becomes tense and distended. At about the same time, the eyeballs become soft, the cornea becomes white and flattened or compressed. Later, the eyes collapse. The gas formation in the blood vessels may force bloodstained fluid, air or liquid fat between the epidermis and dermis forming small blisters in 18 to 24 hours. Blisters are formed first on the lower surfaces of trunk and thighs, where tissues contain more fluid due to hypostatic edema.
Gas bubbles accumulate in the tissues, causing crepitant, sponge-like feeling which soon begins to distend the body. From 18 to 36 hours after death, the gases collect in the tissues, cavities and hollow viscera under considerable pressure, and the features become bloated and distorted. On opening the abdomen, the gas escapes with a loud explosive noise.
Discolored natural fluids and liquefied tissues are made frothy by gas. Due to the presence of gas in the abdomen, the diaphragm is forced upwards compressing the lungs and heart, and bloodstained froth exudes from the mouth and nostrils (postmortem purge), which can be mistaken for the bleeding following antemortem injury.
Bloodstained frothy fluid has no particular significance. It can be due to rupture of small pulmonary or pharyngeal vessels. The compression of heart, forces out its contents. Pressure of the gases may force food from the stomach into the faces, and this may fall into the larynx. Swelling due to gases is most marked in the face, genitalia and abdomen.
Sometimes limbs are relatively free of putrefaction when changes are marked in the face and trunk. The early changes of decomposition of human body in the face, especially when the head of the cadaver is dependent may be mistaken for signs of strangulation, especially when there is oozing of fluid from the nose.
In 24 to 48 hours, the subcutaneous tissues become emphysematous, due to which even a thin body appears obese. In males, gas is forced from the peritoneal space down the inguinal canals and up to the scrotum, resulting in massive scrotal swelling. The breasts and penis are greatly distended. The eyes bulge from their sockets, the tongue is forced out between the swollen and discolored lips.
In 2 to 3 days the sphincters relax and urine and faeces may escape. The junction of the epidermis and dermis is weakened by the release of hydrolytic enzymes, which causes the epidermal layer to slip off the dermal layer (skin slippage) producing large, fragile sacs of clear or pink-red serous fluid.
These gradually enlarge, join together and rupture, exposing large areas of slimy, pink dermis. The exposed sub dermal tissue dries with a yellow parchment appearance. The breakdown of vessel walls and cell membranes leads to water logging of the tissues which helps the spread of bacteria.
Putrefactive effusion of bad smelling bloody fluid into the pleural cavities usually begins at the time when the skin becomes maccrated. Maggots are produced in one to 2 days which have proteolytic enzymes and penetrate the skin fairly rapidly. This allows air to enter under the skin and more maggots into the body cavity.
The activities of maggots may raise the temperature to something near or even above that of normal body heat. The anus and uterus may prolapse after two to three days, and postmortem delivery of a fetus may take place. Wounds caused before or after death bleed, due to pressure of the gases within the heart and blood vessels, and whether they are antemortem or postmortem cannot be made out.
Meningeal hemorrhage and haematoma persist well. Owing to the pressure of the gas in the blood vessels, hypostatic stains may be displaced in any direction. After three days, the face is so discolored and bloated that identification becomes very difficult.
Urine and feces may escape due to intra abdominal pressure. Bloodstained fluid (tissue liquefaction stained by haemolysis) may leak from mouth, nostrils, rectum and vagina. In fat people, the fat, especially omental and mesenteric may liquefy into a translucent yellow fluid. The hair becomes loose and is easily pulled out. The nails are also loose.
In 3 to 5 days or more, the sutures of skull especially of children are separated and liquid brain comes out. Teeth (anterior teeth and often premolars) become loose and may fall out. The skin shows ‘slippage, and the skin of the hands and feet may come off in a “glove and stocking” fashion.
In advanced putrefaction, conjunctival petechiae may not be distinguished due to haemolysis, and the conjunctivae have a homogeneous grayish to light-greenish appearance. Postmortem luminescence is usually due to contamination by bacteria, e.g., Photobacterium fischeri, and the light comes from them and not from putrefying material. Luminescent fungi, Armillaria mellea, is another source of light.
When the putrefactive juices have drained away and the soft tissues have shrunk, the speed of decay is appreciably reduced. When the nutrient material is used up, the formation of gas stops, and the swelling gradually subsides. The gas leaves the tissues, usually by escaping as a result of damage to the structures or by drainage through a postmortem wound.
The distribution of the putrefactive changes may be influenced by the position in which the deceased was lying after death, e.g. if a person dies with his head in a dependent position, putrefactive changes will be advanced in the head and neck compared with the remainder of the body.
A person dying upon a warm electric blanket may decompose rapidly, the decomposition of human body will be more advanced in those parts of the body in contact with the heated blanket. If only part of the body is in contact with the blanket, there may be a sharp line of demarcation between the decomposition of human body caused by the blanket and the unheated areas of the body.
Rigidity due to Inflation of the Tissues with Gases: In this condition changes of decomposition are well marked (2 to 3 days), the lower limbs are abducted, flexed and rigid, the arms are abducted and flexed, the hands are open and the fingers are wide apart. The rigidity persists till the escape of gases due to advancing decomposition. This condition is especially seen in bodies recovered from water.
(3) Liquefaction of Tissues
Colliquative putrefaction begins from 5 to 10 days or more after death. The abdomen bursts and the stomach and intestines protrude. In children, thorax also bursts. In obese people, the body fats, especially omental, mesenteric and perirenal may liquefy into a translucent, yellow fluid filling the body cavities between the organs.
The tissues become soft, loose and are converted into a thick, semi-fluid, black mass and are separated from the bones and fall off. The cartilages and ligaments are softened in the final stage. Small foetuses rapidly disappear in putrefied blood in cases of ruptured ectopic pregnancy.
Decomposition may differ from body to body, from environment to environment and from one part of the same body to another. Differential decomposition of human body means a situation where one body shows differential stages of decomposition in different parts of the body. Sometimes, one part of the body may be mummified, while the rest may show liquefying putrefaction.
The time required for skeletonisation varies considerably and mainly depends on the ambient temperature, insect colonization of the body and scavenger activity. In a hot humid environment with heavy insect activity a corpse can be skeletonised within a few days. In the case of an exposed body, flies, maggots, ants, cockroaches, rats, dogs, jackals, vultures, etc., may reduce the body to a skeleton within a few days.
When the body is in the water, it may be attacked by fishes, crabs, etc., which reduce the body to a skeleton in a few days. In an uncoffined body buried in a shallow grave, putrefaction is delayed to a moderate extent. In a deeply buried body, the lower temperature, the exclusion of air, absence of animal life, etc., markedly delay decomposition. The important factors are seasonal, climatic variation, the amount of soil water, the access of air, and the acidity or otherwise of the soil water.
If a number of bodies are buried in a common grave without coffins, the bodies lying in the center of the grave will be better preserved than those at the periphery. In bodies placed in airtight coffins, decay process may not occur for several decades, but in a poor coffin which admits air and water, bodies will decompose quickly. In India, an uncoffined buried body is reduced to a skeleton within about a year.
Dis-articulation often occurs from the head downwards and from central to peripheral. Buried bones may decay at different rates, e.g. neutral soil may not destroy the skeleton at all. Acidic soil may cause decay in about 25 to 100 years. In a hot climate, bones on the ground surface may decay in 5 to 10 years. The protein content of the bones decomposes. As the bones contain largely inorganic material. they will crumble, rather than decompose. Flat bones and the bones of the infants and old, breakdown faster.
As the blood decomposes, its coloring matter transudes into the tissues, which gradually change to greenish-yellow, greenish-blue and greenish black color. The viscera become greasy and softened. The softer the organ. the more blood it contains, and the nearer to the sources of bacteria, the more rapidly it putrefies. The lining of the intestine, adrenal medulla and pancreas autolyse within hours of death.
The capsules of the liver, spleen and kidney resist putrefaction longer than the parenchymatous tissues, which are usually converted into bag-like structures filled with thick, turbid fluid material. The organs composed of muscular tissues and those containing large amount of fibrous tissue resist putrefaction longer than the parenchymatous organs, with the exception of the stomach and intestine, which because of the contents at the time of death, decompose rapidly.
As a general rule, the organs show putrefactive changes in the following order.
(1) Larynx and trachea.
(2) Stomach, intestines and spleen.
(3) Liver, lungs.
(6) Kidneys, bladder.
(7) Prostate, uterus.
(8) Skin, muscle, tendon.
Larynx and Trachea : At first the mucous membrane becomes brownish-red and later greenish, and is softened in 12 to 24 hours in summer and 2 to 3 days in winter.
Stomach and Intestines
They putrefy in 24 to 36 hours in summer, and 3 to 5 days in winter. Dark- red irregular patches involving the whole thickness of the wall are first seen on the posterior wall and then on the anterior wall. Gas blebs are formed in the submucous layer which project as small multilocular cysts of varying size into the lumen.
They become softened, dark-brown and change into dark, soft, pulpy mass. The mucosa appears macerated and can be easily peeled off. The mucosa becomes brown by diffusion of blood into tissues with subsequent alteration of the haemoglobin. Other breakdown products reacting with sulphur may stain the mucosa green or black.
In the intestines, when there is much blood or bile pigment in the lumen, it passes into the wall and stains it. Various breakdown products of protein with sulphur produce green or black mucosa.
Spleen : It becomes soft, pulpy and liquefies in two to three days.
Omentum and Mesentery : They putrefy early if loaded with fat. They become greyish-green and dry in one to three days in summer.
Liver : It becomes softened and flabby in 12 to 24 hours in summer. Multiple blisters appear in 24 to 36 hours. CI. Welchii form characteristic small clumps in a tissue space and produce gas, which soon increase in size. These lesions appear first as small, opaque, yellowish-grey, dendritic figures in the parenchyma. When bubbles develop, the organ has a honeycombed, vesicular or ‘foamy’ appearance.
The greenish discoloration extends to the whole organ, which finally becomes coal-black. In newborn children, the liver putrefies earlier than in adults. So called ‘Putrefaction Crystals”, yellowish particles composed of tyrosine and leucine are formed on the surface of the internal organs, especially on the surface and bottom of the liver and the capsule of the spleen.
The liver becomes deep blue if there is much passive congestion; green if there is oozing of bile from the gall bladder, or blue-black in the subcapsular area if the pigment comes from the adjacent loops of intestine. In case of jaundice, the liver becomes green a few hours after death, if the pigment is oxidised to biliverdin. In the early stage, the discolouration is seen round the branches of the portal vein. In advanced putrefaction, the liver becomes green or black.
GALL BLADDER : The gall bladder resists putrefaction for a long time, but the bile pigments may diffuse early through adjacent tissues.
PANCREAS: It becomes softened and hemorrhagic.
HEART : It becomes soft and flabby and the cavity appears dilated.
LUNGS : Gaseous bullae are formed under the pleura which are small, pale-red and scattered, and later join together. Later the lungs become soft, collapse and are reduced to a small black mass.
KIDNEYS :The renal tissue becomes flabby and the surfaces are dull and appear parboiled. The cortex darkens and later becomes green.
ADRENALS : The cortex softens from within forming a core around the softened medulla. Later, the medulla liquefies and the interior of the gland appears as a narrow slit or as a wide cyst-like cavity.
BLADDER : It resists putrefaction for a long time if it is empty and contracted. Urine may show albumin due to transudation of serum proteins from the blood, within 48 hours after death.
PROSTATE : It resists putrefaction for a very long time.
UTERUS : The virgin uterus is the last organ to putrefy. Gravid uterus or soon after delivery, it rapidly putrefies.
CONDITIONS AFFECTING THE RATE OF PUTREFACTION:
(1) Temperature Putrefaction begins above 10°C and is optimum between 21°C and 38°C. A temperature increase of 10°C usually doubles the rate of most chemical processes and reactions. It is arrested below 0°C. and above 48°C. The rate of decomposition is about twice as rapid in summer as in winter. Advanced putrefaction may be seen within 24 to 36 hours in summer. Differences in temperature can cause varying areas in the same body to show different rates of decomposition. Pillows put over and under the deceased’s head prevent circulation of air and cause much more decomposition in the face than is seen in other parts of the body.
A frozen body will not undergo decomposition until it defrosts. If decomposition has already set in, refrigeration of the body may not stop decomposition completely.
(2) MOISTURE : For putrefaction moisture is necessary, and rapid drying of the body practically inhibits it. If organic substance is dried, putrefaction is arrested. After death from general anasarca, putrefaction is very rapid, and bodies recovered from water, if left in the air decompose rapidly. Organs which contain water decompose more readily than the dry one.
(3) AIR : Free access of air hastens putrefaction, partly because the air conveys organisms to the body. In normal condition, the unbroken skin acts as an impermeable barrier to bacteria. Moist and still air helps putrefaction.
(4) CLOTHING : Initially clothing hastens putrefaction by maintaining body temperature above that at which putrefactive organisms multiply for a longer period. If the clothing is tight as under the belts, suspenders, socks, tight-fitting undergarments, and boots, the putrefaction is slow, for it causes compression of the tissues, which drives out the blood from the part, and prevents the entry of internal organisms. Clothes prevent the access of airborne organisms, flies, insects, etc., which destroy the tissues.
(5) MANNER OF BURIAL: If the body is buried soon after death, putrefaction is less. Putrefaction is delayed if body is buried in dry, sandy soil, or in a grave deeper than two metres, and when the body is covered and placed in a coffin because of exclusion of water, air and action of insects and animals. When a body is buried in lime, decomposition is delayed. Putrefaction is rapid in a body buried in a damp, marshy or shallow grave without clothes or coffin, because the body is exposed to constant changes of temperature. Putrefaction is more rapid in porous sandy soil than in soils with an excess of clay. Putrefaction is more rapid if changes of decomposition are already present at the time of burial. In acid peaty soils even the bones may be destroyed.
(B) INTERNAL : (1) AGE : The bodies of newborn children who have not been fed, decompose very slowly because the bodies are normally sterile. If the child has been fed before death, or if the surface of the body has been injured in any way, decomposition of human body tends to take place with great rapidity. Bodies of children putrefy rapidly and of old people slowly.
(2) SEX : Sex has no effect.
(3) CONDITION OF THE BODY : Fat and Flabby bodies putrefy quickly than lean bodies, due to larger amount of fluid in the tissues and excess fat, and greater retention of heat.
(4) CAUSE OF DEATH : Bodies of persons dying from septicaernia, peritonitis, inflammatory and septic conditions, general anasarca, asphyxia, etc., decompose rapidly. In the case of generalized sepsis, bodies undergo rapid decomposition even if they were immediately refrigerated. Putrefaction develops very rapidly in infection due to CI. Welchii, e.g. acute intestinal obstruction, some cases of abortion and in gas gangrene. Putrefaction is delayed after death due to wasting diseases, anemia, severe hemorrhage, debility, poisoning by carbolic acid, zinc chloride, strychnine and chronic heavy metal poisoning, due to the preservative action of such substances on the tissues or their destructive or inhibitive action on organisms, which influence decomposition of human body.
(5) MUTILATION : Bodies in which there are wounds, or which have suffered from other forms of violence before death, putrefy rapidly owing to the ease with which organisms gain access to the damaged tissues. In case of dismemberment, especially if this has been done while the blood is still fluid, the limbs putrefy slowly, because they are drained of the blood, and intestinal organisms do not gain entry. The trunk putrefies rapidly because of the action of intestinal bacteria, and the access of airborne organisms.
In advanced putrefaction, no opinion can be given as to the cause of death, except in cases of poisoning, fractures, firearm injuries, etc.
Putrefaction in Water
Casper dictum states that a body decomposes in air twice as rapidly as in water, and eight times as rapidly as in earth. The variations are very real, and it is not of much practical value. The rate of putrefaction is slower in water than in air. Putrefaction is more rapid in warm, fresh water than in cold, salt water. It is more rapid in stagnant water than in running water.
Putrefaction is delayed when a body is lying in deep water and is well protected by clothing, while it is rapid in a body lying in water contaminated with sewage. As the submerged cadavers float face down with the head lower than the trunk, gaseous distension and postmortem discoloration are first seen on the face and then spread to the neck, upper extremities, chest, abdomen and the lower extremities in that order. When the body is removed from the water, putrefaction is hastened as the tissues have absorbed much water.
The epidermis of the hands and feet becomes swollen, bleached and wrinkled after immersion, and may be removed as a cast of the extremity, after 2 to 4 days. After several weeks in water, macerated flesh may be stripped off from the body by the action of currents or the contact with the floating objects. Fish, crustacea (crabs, lobsters, shrimps, etc.) and water-rats in a sewer may destroy the body. Molds may be located anywhere on the body, but generally are found only on the exposed surfaces.