The moment it is deprived of life, the body begins to decompose.

After death, the body cools and stiffens, then relaxes again around the 36th hour. Then begins the process of decomposition, also called putrefaction. This is initiated after 48 to 72 hours if the remains are left in their natural state and in the open air. It begins later if it has benefited from conservation care or is placed in a cold room. 

If the body is left in the open: two or three years

In the open air and without conservation care, decomposition is rapid. Scavenger flies come to lay on the corpse, so that their larvae can feed on it. These maggots can wipe out all the soft tissue in less than a month. The skeleton, it takes two or three years to become dust.

The decomposition time nevertheless depends on the location of the body, its size and the climate. In an arid environment, putrefaction can be hindered: the body dries up before being completely decomposed, then mummifies. Likewise, in areas of extreme cold, the body can be frozen and its decomposition very slowed down.

It also happens, when a body finds itself trapped in adequate sediment, that its skeleton does not deteriorate. This explains why we are still discovering the bones of our prehistoric ancestors today.

In a coffin: over ten years

Unless the coffin is made of wood and has been buried in the ground, insects cannot enter it. In a concrete vault, the only larvae which develop on the remains are those of the rare flies which may have been in contact with the body before it was put into the coffin. They therefore take longer to make the flesh disappear. The decomposition process continues because it is the result of biochemical reactions and the action of bacteria.

When the body is alive, it is the seat of millions of biochemical reactions (hormonal, metabolic, etc.) But, once the heart has stopped, these are no longer regulated. Above all, the cells are no longer irrigated, oxygenated and nourished. They can no longer function properly: organs fail and tissues degenerate.

First hours: cadaveric rigidity and lividity

The blood, which is no longer pumped, accumulates under the effect of gravity in the lower part of the body (that which rests on the bed or the floor), causing wine-colored spots to appear on the skin. skin under the body. We speak of “cadaveric lividities”.

Without hormonal regulation, calcium is massively released in muscle fibers, causing their involuntary contraction: the body becomes rigid. It will be necessary to wait for the dissipation of calcium out of the cells for the muscles to relax again.

The body becomes dehydrated, which causes the toes and fingers to dry out, the skin to contract, and the eyeballs to sag.

First weeks: from putrefaction to liquefaction

The green spot that appears on the wall of the abdomen 24 to 48 hours after death is the first visible sign of putrefaction. It corresponds to the migration of pigments from feces, which cross the walls and appear on the surface.

All the bacteria naturally present in the body, especially in the intestines, start to proliferate. They attack the digestive system, then all organs, producing gases (nitrogen, carbon dioxide, ammonia, etc.) which will swell the abdomen and release a strong odor. Rotting liquid also escapes through the openings. 

Other biochemical reactions also occur: the necrosis of tissues which, due to lack of oxygenation, turn brown then black, and the liquefaction of fats. The skin eventually oozes red and black fluids. Large bubbles, filled with rotting liquids and liquefied fat, appear on its surface. Anything that has not been eaten by maggots ends up being detached from the body in the form of putrid liquids.

Around the skeleton

At the end of this process, only the bones, cartilage and ligaments remain. These dry up and shrink, pulling on the skeleton, which gradually breaks up before starting its own degradation.

For the past ten years or so, in some countries where space to bury the dead is limited, cemetery managers have realized that bodies no longer decompose. When they open graves at the end of the concession, to make room for new burials, they increasingly find that the tenants of the site are still recognizable, even forty years after their death, when they should be nothing more than dust. They suspect our food, which has become very rich in preservatives, and sometimes excessive use of antibiotics, of hampering the work of bacteria responsible for decomposition.

Embalming is not a must (except in the event of repatriation), but it can be requested by families. This involves preparing the deceased, in particular through conservation care intended to slow down the decomposition of the body during the funeral:

• disinfection of the body;
• replacement of blood with a solution based on formaldehyde (formalin);
• drainage of organic waste and gases present in the body;
• hydration of the skin.

The forensic pathologist autopsies the corpses to find out the causes and circumstances of their death. It can intervene on individuals who have just died, but also on remains exhumed years later. To diagnose the time of the crime, he relies on his knowledge of the body’s decomposition process.