Decomposition is the process by which organic material is broken down into simpler forms. It occurs systematically in all biological organisms with the cessation of normal life functions and begins immediately following death.
The extent of decomposition can be used to estimate time since death. There are many factors that affect the decomposition rate, but the progression of decomposition of human body can typically be divided into a number of distinct stages: fresh, bloated, decay, post-decay, and dry/skeletal.
Each stage is also associated with a rough time period during which it is likely to occur, subject to the factors that can alter these time periods.
Let us take a look at all the stages of decomposition.
Stage 1 Fresh (1-2 days)
This stage begins almost instantly from the moment of death. As the heart stops beating, the body’s cells gets deprived of oxygen and pH changes occurs.
The body cells slowly lose their structural integrity and begin to break down, releasing cellular enzymes which break down cells and tissues in a process known as autolysis, decayed by the body’s own enzymes.
No obvious signs of decomposition, however internally bacteria within the gastrointestinal tract begin to digest the soft tissues of the organs.
Throughout this stage certain early post-mortem indicators may begin to occur, such as livor mortis (pooling of blood in the body), rigor mortis (stiffening of muscles) and algor mortis (body temperature reduction).
Let us now take a look at these very important changes.
Algor mortis is translated from Latin as “cold death”.
The core body temperature of a living human being is approximately 37 degrees, though as would be expected, after death the body will gradually lose heat until body temperature comes in sync with the environmental temperature .
Although the rate at which body temperature is lost is dependent on a lot of factors including the clothing worn by the victim, the environment, how the body has been left (uncovered, buried, etc), and the victim’s body weight etc.
Algor mortis is applicable largely up to 24 h after death.
The first published measurements of the intervals of temperature after death were done by Dr John Davy in 1839.
It is also referred to as hypostasis or lividity, this typically occurs relatively soon after death around 30 minutes to 4 hours after death, and is most pronounced approximately 12 hours after death.
It is the pooling of the blood in the body due to gravity and the lack of blood circulation as a result of the cessation of cardiac activity (Knight, 2002).
These factors cause the blood to pool in the lowest points of the body, giving the skin a purplish-red discoloration.
There are two recognized stages of livor mortis, which are a function of whether the blood has begun to coagulate.
Prior to blood coagulation, livor is “unfixed”; if the body is moved, the blood will repool in whichever part of the body is closest to the ground in the new position.
Livor becomes “fixed” when the blood coagulates, preventing the blood from re-pooling if the body is moved into another position.
In addition to the pooling of blood, small vessels breakdown throughout the body producing what is called petechial hemorrhages or Tardieu Spots.
Blanching occurs when you press your finger on your skin and you see a white spot for a few seconds. The lightening of the skin comes from the pressure of your finger pushing the blood away from that area for a few seconds.
Perhaps one of the more well-known post-mortem processes, rigor mortis refers to the stiffening of body muscles due to certain chemical changes.
Muscles require a molecule called adenosine triphosphate (ATP) in order to release from a contracted state (Knight, 2002); after death, the body’s ATP reserves are quickly exhausted and muscles remain contracted until the muscle fibers themselves start to decompose.
Rigor mortis is seen first in the small muscles of the face and jaw. It generally begins several hours after death, peaks around 12 hours after death, and then subsides over the next day or so with decomposition of the muscles.
The timing of rigor mortis is dependent on environmental conditions such as temperature, as well as the physical activity of the decedent around the time of death.
Nysten first demonstrated Rigor mortis.
Stage 2 Bloated (2-6 days)
This stage of decomposition includes the first visible signs of decay, namely the inflation of the abdomen due to a build-up of various gases produced by bacteria inside the body.
Bloating is particularly visible around the tongue and eyes as the build-up of gases cause them to protrude. The skin may exhibit a certain colour change, taking on a marbled appearance due to the transformation of haemoglobin in the blood into other pigments.
At this point a pungent odour of putrefaction may be noticeable.(cadaverine and putrescine gas)
Stage 3 Decay (5-11 days)
The previously inflated carcass now deflates and internal gases are released. As the tissues break down the corpse will appear wet and strong odours are very noticeable.
Various compounds contribute to the potent odour of a decomposing body, including cadaverine, putrescine, skatole, indole, and a variety of sulphur-containing compounds.
These putrid gases and compounds will attract a range of insects. Fluids begin to drain from the corpse via orifices, particularly the nose and mouth.
The internal organs typically decompose in a particular order, starting with the intestines and ending with the prostate or uterus.
Stage 4 Post-Decay (10-24 days)
By the time this stage is reached, decomposition slows, as most of the flesh has been stripped from the skeleton, though some may remain in denser areas such as the abdomen.
The previously strong odours of decay begin to subside, though a cheese-like smell may persist caused by butyric acid. If the body has decayed on soil, the area around the cadaver may also show signs of plant death.
Stage 5 Dry Stage (24+ days)
The final stage of decomposition results in the remains consisting primarily of bones, some dried skin and cartilage. There is typically no odour of decay at this point
Factors Affecting Decomposition
- Body- The first factor is related to body itself; its body size or mass. Large bodies take longer to decompose than small bodies.
The second important consideration related to body is whether or not the body is intact.
If there are wounds on the body, there are more openings for organisms ranging from bacteria
to insects to carnivores to attack, accelerating decomposition.
The third consideration is the clothing. A nude body lying on the ground will decompose faster than a clothed body. Heavy clothing will slow decomposition more than light clothing.
Wrapping a body in plastic or some other similar material will decelerate the process.
- Environment – Weather, climate, humidity, all have affects on the decomposition rate. For example; Cold weather slows the rate; hot weather accelerates it, On the other hand Frozen bodies do not decompose. Direct sunlight and High humidity also accelerates decomposition.
- Soil- A buried body will decompose slowly than one found on the surface, yet acidic soil and high soil moisture content can accelerate decomposition of buried bodies.
- Flora and Fauna- Plants also can accelerate deterioration of the body. Scavengers tend to devour a corpse in a characteristic sequence beginning with the torso and viscera. They may
drag parts of the body to secluded areas for feeding; dis-articulating the body.
- Insects – Nothing affects the rate of body decomposition more than insects.
Insect activity varies area to area and season to season.
Artifactual preservation refers to the preservation of a body or tissues by natural processes, chemical substances, or by the destruction of bacteria which may significantly alter normal decomposition processes. The above factors promote Artifactual preservation of dead bodies.