Unit 9A - Environmental Forensics:
5 Stages of Decomposition & additional Characteristics of Decomposition:
There are 5 main stages of decomposition, which can be characterised by various physical
signs and symptoms that the body will endure. Further, this can help to link or suggest an
approximate time of death to cases. There are many factors which can speed up or slow
down a stage of decomposition, such as soil condition, temperature, burial site and exposure
to weather elements. Temperature can affect the rate of decomposition, if the temperature is
too hot, moisture isn’t present for the body to decompose, so it becomes mummified or dried
out. Each stage can be enhanced alongside these external factors and a natural process.
Entomology, the study of insects and their relation to humans, environment and living
organisms, can determine the time of death and which stage of decomposition the body has
endured.
Fresh Stage
As soon as death occurs, the body's breakdown begins. When the blood circulation and
respiration stops, the body no longer can intake oxygen or remove waste products. Excess
carbon dioxide causes the body to be acidic, leading to the cell membrane rupturing. The
membranes then release enzymes which eat the cells from the inside out. The body's
temperature begins to decrease, matching its environment, causing the blood in the body to
follow the gravity to the lowest point of the body. This stage will last between 0-12 hours,
post death. At this stage, the body has no visible signs of decomposition, however, internally
bacteria within the gastrointestinal tract begin to digest the organs soft tissues. Chemicals
which are released during cellular death begin the attraction of flies. Insects will be found
within minutes to hours of the person's death. These early appearing flies seek out the prime
environment to deposit their eggs. At this stage they are limited to the body's orifices and
within external injuries. The moisture levels within the orifices are ideal for young maggot
development.
Livor mortis
Livor mortis is the process where the skin appears a discoloured purple or blue colour, due
to the pooling and collection of blood in the body towards a specific point. The blood stops
circulating around the body and falls at the lowest point. This process first appears as dull
red patches on the body, about 20-30 minutes after death. This indicates the heart has
stopped beating, and therefore, the body is confirmed as deceased. Once a few spots have
appeared, they will slowly come together forming larger patches. When the skin is pressed,
a white colour will appear due to the pressure and diversion of blood circulation. This occurs
8-12 hours after death, and is known as banching. Additionally to the pooling of blood, the
body's small vessels will break down, producing petechial haemorrhages. The pooling of
blood is a physical process based on the loss of blood pressure when the heart stops
beating. Therefore, this will occur at the same rate, disregarding the temperature, so livor
mortis is less susceptible to the environment.
, Livor mortis is vital in cases of carbon monoxide poisoning, hypothermia and cyanide
intoxication. The body will appear a cherry red colour rather than the usual purple or blue
discolouration. The specific colouration can be used to suggest time of death. In the early
stages of livor mortis, discolouring of the skin may appear subtle, as the patch has not
darkened. Clothing and or objects can obscure the discolouration of the skin, so it can be
challenging to observe the true position the body was in until the post mortem is carried out.
Liver mortis has been proven less successful if significant trauma or wounding has occurred
on the body. This is the loss of blood within the body, following its trauma. So, determining
time of death within the body is challenging as it will pass through open wounds before
pooling within the body begins.
Rigour mortis
Rigour mortis is the muscles stiffening inside the body after death, this process begins
approximately 2 hours after the death has happened. This process begins in the facial
muscles, extending to the limbs. The process is completed after 6-8 hours after death.
Muscle stiffness occurs due to the body losing its adenosine triphosphate, this chemical is
the relaxing muscle chemical. As the body now cannot intake oxygen, aerobic respiration of
muscles stops entirely. After 15-25 hours after death, the body becomes rigid, stopping the
release of lysosomes within the body. Once the lysosomes stop being released, actin and
myosin begin dissolving the body's stiffness.
Rigour mortis is helpful in determining time of death, based on the extent the muscles have
stiffened. If the body's muscles are completely stiff, it can be approximated that time since
death was 5-12 hours ago. Additionally, it can be crucial in determining cause of death, if the
body has stiffened in a particular position. This could indicate their resting position, for
example, sitting in a chair or laying in bed.
Rigour mortis lasts such a short amount of time after the death happened, so, if the body is
discovered too late, this stage would have been comp;eted. This poses an obstacle, as there
is less evidence to determine the positioning of the body, and time of death based on body
stiffness. Rigour mortis is affected by temperature, warmer temperatures will cause the
chemicals to change within the body happen faster. If the body is exposed to freezing or left
in freezing water, Rigour mortis isn’t experienced, and will only occur when the body has
thawed out. Therefore, this will change the estimation of death, as a body could have passed
away much longer than what stages of decomposition have occurred.
Algor mortis
Algor mortis is the body cooling down after death to its environmental temperature. It occurs
due to “cessation of the thermoregulation” of the body. So, the body no longer regulates
temperature and lacks both cooling and or heating mechanisms, therefore, the body
matches to its environmental temperature. Body temperature is maintained by blood
circulation, so when the heart stops during death, the blood circulation stops and the body
now reaches its ambient temperature. It is an accurate stage to estimate the time since
death.
