Human Body Decomposition Over Time

¶ … Human Body Decomposition Over Time in Various Settings

Characteristics of Human Body Decomposition Over Time in Various Settings

The branch of science that investigates the decomposition process of the human body is known as Taphonomy, which encompasses the study of phenomena such as biostratinomy, decomposition, diagenesis, and epibiont encrustation. (Decomposition: Wilipedia) A definition of the term 'decomposition' describes the process whereby the body is reduced into simpler forms of matter. The process of decomposition is affected in varying degrees by a number of factors. These include the following aspects in the order of their commonly assumed importance with regard to the rate of the decomposition process.

Temperature

Bacteria

Access by insects

Burial and depth of burial

Access by carnivores or rodents

Humidity or dryness

Body size and weight

Clothing

(ibid)

Brief overview of the process of decomposition is as follows:

The first activity of bodily decomposition is the growth of various bacteria in the body at the time of death. This is due to the fact that the body's natural defense mechanism against the bacteria is no longer functional. The bacteria then begin to dissolve the body from within, which produces gas. Other features at the time of death are tautness of skin and the loss of tone with regard to sphincters. (McLemore, J. 1993)

Other characteristics are paleness of the skin as well as the lips and fingernails as well as flatness of the eyes due to loss of fluid. Another central characteristic is the change in the appearance of the blood. "The blood, which has become dark purple because of the loss of oxygen, sinks due to the force of gravity and settles on the underside of the body about 30 minutes after death." (Health) Various cells in the body die at different rates. For example, brain cells usually die within 4-7 minutes while skin cells are still alive after 24 hours. (ibid) Liver Mortis takes place within a few hours of death. In this process "blood pools at the lowest portion of the anatomy; often referred to as lividity" and is characterized by large dark red splotches on the corpse. The rest of the body appears much paler than normal. (Chemistry)

Rigor Mortis sets in within four hours of death. This is caused by the lack of adenosine triphosphate (ATP), which provides the energy required for muscle contraction and relaxation. ((McLemore, J. 1993) Rigor Mortis is essentially the state that the dead body achieves when the oxygen supply to the muscles ceases. However, the cells within the body continue with anaerobic respiration. The result of this process is the production of lactic acid which causes stiffening of the muscles in Rigor Mortis. After 36 hours, depending on temperature and various other variables and circumstances, rigor mortis ceases. (Decomposition) At this time the cells in the body die and various enzymes are released which precipitate the process of decomposition.

The stiffening process in rigor mortis takes place first in the smaller muscles and then advances to the rest of the body. There are numerous factors here which are forensically important. For example, "the process of rigor mortis can be accelerated if there was violent exertion before death because the supply of ATP has been used up. Rigor mortis can also be delayed in cases of slow death, such as death by carbon monoxide poisoning where there was no struggle." (McLemore, J. 1993)

Another early sign of decomposition and a factor used in forensic investigations is the fact that decomposing bodies start producing ammonia (NH3) in the lungs relatively soon after death. This fact can be measured as Ammonia is lighter than air and because it diffuses rapidly the rate of production of ammonia decreases with time after death. (How fast does a human body begin to decompose?)

Decomposition in fact begins during the process of rigor mortis. While the body are acidic due to the presence of lactic acid during this period, the larvae of insects can "still feed on serum between the muscle fibers and because the larvae excrete ammonia, they eventually neutralize the acid." (Decomposition)

In terms of the overall process, decomposition can be divided into a number of stages and processes. There are various signs that indicate these stages. After three days the gas inside the corpse forms blisters on the skin. The body then becomes swollen with fluids leaking from the orifices. (McLemore, J. 1993) After three weeks of decomposition the "the skin, hair and nails become loose and are easy to remove; the skin begins to split open, exposing muscle and fat. " (ibid)

The continuation of the process is described in rather lurid detail as follows: Internal organs begin to liquefy. Within... weeks from onset of death, there is a bloody purge of putrefying liquid from the mouth, nose, anus, or any other opening. Soon, within weeks, the body bursts open under pressure, spilling its contents. Reeking liquids sink into whatever is under the corpse, be it a casket lining, a bed mattress, a floor, or soil. Vast quantities of insect larvae may pour out of the body if insects have had prior access to it. Scavengers may pick apart the corpse, which tends to fall apart quite easily in this stage. (Chemistry)

Temperature plays an important role in the decomposition process. In warm to moderate climates the body can be reduced to a skeleton within four weeks; while this process can take up to several months in a cool climate. (ibid)

2. Characteristic factors affecting decomposition

Decomposition begins at the moment of death. In the initial stages decomposition is caused firstly by autolysis or the breaking down of tissues by the body's own internal chemicals and enzymes; and secondly by putrefaction or the breakdown of tissues by bacteria. Both these processes are responsible for the emission of gasses. (Decomposition: Free-template)

Historically there are a number of stages of the decomposition process which have been recognized. These include autolysis, bloat or putrefaction; decay through putrefaction and carnivores and dry decomposition or diagenesis. (Vass A.A. 2001) Modern theoretical perceptions of decomposition tend to divide the process into two central areas. "Current thinking is that it should be segregated into pre- and post-skeleton-ization since stages are not always observed and in fact may be totally absent, depending on the taphonomy of the corpse. (ibid) In essence, the entire process of decomposition is summarized as follows:

these processes together (autolysis, putrefaction and diagenesis) eventually result in complex structures composed of proteins, carbohydrates, sugars, collagen and lipids returning to their simplest building blocks - essentially dust to dust. (ibid)

The following table outlines the formal stages of decomposition.

Table1. Stages of Decomposition

Stage

Description

Initial decay

The cadaver appears fresh externally but is decomposing internally due to the activities of bacteria, protozoa, and nematodes present in the body before death.

Putrefaction

The cadaver is swollen by gas produced internally, taken on a greenish color, and accompanied by the odor of decaying flesh. The skin may turn a greenish color or experience subcutaneous marbling (the outlines of the blood vessels under the skin).

Black putrefaction

The flesh is of a creamy consistence with exposed parts black in color. The body collapses as gases escape and the odor of decay is very strong.

Butyric fermentation

The cadaver is drying out. Some of the flesh remains at first and a cheesy odor is present. Ventral surface is moldy from fermentation

Dry decay

The cadaver is almost dry and the rate of decay is slow. (Source: Majeres, J. 2003)

There are numerous factors which affect the rate and degree of decomposition over time. One of these aspects, which has already been alluded to, is temperature. The general effect of temperature as a central factor in the process is described as follows:

Approximately 24 hours after death, the corpse usually cools to the ambient temperature. The skin of the head and neck becomes a greenish-red color, and this discoloration spreads to the chest, thighs and entire body over the next several days. Facial features are no longer recognizable and the body begins to smell like rotting meat. This process is accelerated in warm climates and slowed in cold climates. (McLemore, J. 1993)

The rate of composition is also largely dependent on temperature with faster decomposition taking place at higher temperatures. This is an important aspect for forensic medicine as it can be used as a determinant in ascertaining the time of death.

Determining the rate of decomposition and the time of death is dependent on a wide array of factors. These include temperature as well as numerous other elements and circumstances, such as water and moisture. "Individuals submerged in water have different rates of decomposition. Injuries affect the rate as well since damage to the skin increases blood loss, as well as insect and bacterial action." (Vass A.A. 2001) The actions of carnivores will also have an effect on the rate of decomposition. It is also significant to note that decomposition does not only refer to the deterioration and dissolution of soft tissue only.

A decomposition does not end after the soft tissue has disappeared. The skeleton also has a decompositional rate that is based on the loss of organic (collagen) and inorganic components. Some of the inorganic compounds we use to determine the length of time since death include calcium, potassium and magnesium. (ibid)

In a temperate climate for example, it normally takes ten to twelve years to decompose fully to a skeleton. Therefore, the high number of variables involved making exact calculations based on a few characteristics of decomposition are extremely difficult and very often all the possible decomposition factors have to be taken into account.

The role played by microbes and bacteria is extremely significant in the decomposition process, but difficult to use as a dependable measurement in forensics as there are a vast amount of different types of bacteria associated with the decomposition of the body. These include Staphylococcus, Candida, Malasseria, Bacillus and Streptococcus spp. As well as putrefactive bacteria anaerobes. (ibid)

As an experienced researcher in this area states, "... every micro-organism known is involved in some aspect of the human decomposition cycle from Acetobacter to Zooglea." (ibid) Bacteria can also increase the body temperature after death." In some rare cases, the body temperature has actually increased after death before it cools down. Pathologists accredit this phenomenon partly to bacterial growth that goes unchecked after death." (McLemore, J. 1993)

Both bacteria and insects play an important role in the initial stages of decomposition. A good example of this was the exhumation of a soldier buried during the Civil War in the United States. When the coffin was opened it was found that the corpse was relatively fresh. This was due to the fact that, "at the time prominent solders were buried in solid lead coffins - the lead had 'sterilized' the body by poisoning the microflora and decomposition had not progressed past initial autolysis. (ibid)

Another factor that can radically affect decomposition and decomposition rates of the human body is moisture and water which will usually increase the rate of decomposition by as much as four times that of decomposition of a body on dry ground. "Immerse the body in water and skeletonization occurs approximately four times faster; expose it to air, and it occurs eight times faster." (Decomposition: Wikipedia) central factor is that changes in decomposition are intimately affected by the environment. "At a moderate temperature, a body is expected to start initial decay within a couple of days (5 p2)... while a cooler temperature generally slows down decomposition and a warmer one speeds it up." (Source: Majeres, J. 2003)

After temperature, chemical and bacterial factors of decomposition, insects are the next most important agents in the process. Assuming that the body is accessible to insects, they will increase the rate of decomposition dramatically. The most common inserts involved in the decomposition process include the fleshflies (Sarcophagidae) and blowflies (Calliphoridae). (Decomposition: Wikipedia)

The presence and life cycles of various insects, which is part of the field of forensic entomology, are used in forensic science to determine the time of death. This process is described as follows:

This method is based on the presence of various types of insects in the corpse. It is believed that when death occurs there is a universal death scent that attracts insects to the corpse. The first to arrive, within 10 minutes of death, are common green flies that feed on flesh and lay their eggs in the mouth, nose and ears. Twelve hours later these eggs hatch into maggots that feed on the dead tissues. (McLemore, J. 1993)

This process is known as PMI-postmortem interval where "an entomologist is able to identify the kind of insect and their stage of life to accurately predict how much time has gone by since insect activity began." (ibid)

The first insects that begin the decomposition process are usually the Diptera and "more specifically the Calliphoridae and Sarcophagidae." (ibid) The females of these flies deposits eggs or larvae in and around the natural orifices of the body, such as the eyes, ears, mouth, and nose and the eggs will also be deposited in any open wounds. (ibid) The insects hatch after about twelve hours and the small larvae begin to feed on the body tissues. (ibid)

After the maggots leave, some 24 to 36 hours after death, beetles arrive to eat the drying skin. Approximately 48 hours after death, other insects, such as spiders, mites and millipedes, arrive to feed on the insects on the corpse. Insects are collected from the remains and cultured to determine the species of insect and to assess their lifespans. The cycles of these insects are very precise and the time of death can be estimated with great accuracy. (McLemore, J. 1993)

There are many other ways that insects can help forensic science. They can be of assistance in determining whether the deceased died indoors or outdoors or during the night or day. Insects can also be used in toxilogical tests in order to determine the presence of drugs such as cocaine. (ibid)

Moisture and immersion in water also affects decomposition in radical ways. Many researchers feel that not enough research has been done on this aspect. This is the view of a study by MacDonell N. et al. entitled Aquatic Foresnics. The study states that findings from research conducted in 1983 point to the fact that "... one of the most important factors that will alter the normal course of insect succession in carrion is immersion fresh water. Many homicide victims are disposed of in bodies of water, which makes determining time of death extremely difficult. " (MacDonell. N. et al.)