Late post-mortem changes
Decomposition is a process originating as result of the breakdown of the body by enzymes. These enzymes can be from the body itself (the process is then called autolysis) or from other organisms, (heterolysis). Generally the process is known as putrefaction.
Although both these processes set in immediately at death, the condition is only visible at a later stage. The environmental temperature plays an important role: in a refrigerator the process will be suppressed, while in a warm environment it will be accelerated. There is therefore a considerable amount of variation.
Autolysis is especially visible in the pancreas (racemose gland) where the enzymes leak out of the cells after death and digest the surrounding tissue. The spleen is often autolytic in cases of sepsis (autolysis means the spontaneous disintegration of tissues of an organ see - above).
The bacteria which play the most important part in putrefaction originate from the alimentary canal. They include oxygen-dependent (aerobic) and non-oxygen-dependent (anaerobic) organisms. The latter group is mostly responsible for the production of gas and the offensive odour of a decomposing body. In persons who die due to septicaemia there already is an abundance of organisms in the body at the time of death, which naturally will accelerate the whole decomposition process.
During putrefaction the whole body discolours to greenish-black, becomes bloated due to gas production, and the skin strips (slips) off (fig 3.9). The blood vessels of the skin often show up prominently due to the broken-down blood (haemolysis) which reacts with the hydrogen sulphide produced by bacteria. This gives the effect of marbling. The process of liquefaction of the soft tissue is often promoted by the activity of maggots.
Mummification occurs in dry climates, where the body literally dries out like biltong. This happens in hot as well as cold, dry climates, for example the Namib desert and also on Mount Everest. It can also occur in cases where the body is lying in an environment with a high acid content. In the case of the Tollund man, who was found in the swamps of Jutland, which have a high acid content, the features were exceptionally well preserved.
In the case of the bodies of newborn babies who are concealed shortly after birth in a cardboard box, drying out also occurs. This is because newborns are microbiologically sterile (they have not yet been colonised by micro-organisms) and putrefaction is very slow.
Maceration refers to autolysis (spontaneous disintegration) in a foetus which dies while inside the mother (intra-uterine death). As the contents of the uterus is sterile, there is no putrefaction. In maceration the skin softens and large fluid-containing blisters appear, and the skin then strips away. At the same time the internal organs soften and the bones gradually loosen from the cartilage and tendon attachments.
In this condition water binds with the body fat and forms a wax-like substance with a rancid odour. Bacterial enzymes contribute to the process. It is also known as saponification or transformation of body fat into soap.
Wax formation usually develops over a period of weeks to months and it suppresses further decomposition of the body. Should the process manifest in the face, it can preserve the features to an extent. It can also preserve wounds and other signs of trauma.
After all soft tissue has been destroyed, whether on account of decomposition or, amongst others, maggot and rodent activity, only the skeleton remains. Cartilage and ligaments can survive for some time. Exposure of the bones to the elements eventually causes bleaching. Finally only porous brittle bone that fragments into minute pieces during handling remains.
The skeleton can be useful for a considerable time for identification of the deceased and determining how long the person has been dead.