Originally Posted by BustedS13
Stage 1: Initial Conditions
The initial conditions for decomposition are determined by the population of flora and fauna in the intestine of the body prior to death. The intestines contain a wide range of bacteria, protozoans, and nematodes. Once the body ceases to keep these fauna in check by normal operation, they will proliferate.
Stage 2: Initial Decay
Intestinal fauna begins to digest the intestine itself, and soon begin to digest the surrounding internal organs. The body's own digestive enzymes also begin to spread throughout the body, contributing to the breakdown of tissue. When individual cells die, they release enzymes which break down the cell material and connections to other cells, initiating a cascade effect.
Within the first 24 hours, blue-green discoloration of the skin around the abdomen becomes apparent. Green-black discoloration develops in the blood as it reacts with hydrogen sulfide. Within 36-48 hours the body begins to bloat, most markedly in areas with loose skin (scrotum, eyelids, penis, etc.). Within 72 hours, the entire body has begun to decompose.
The eyes are a good indicator of time of death in this initial stage. Jack Kevorkian found in his landmark 1961 Journal of Forensic Science article that "boxcaring" in the vessels can indicate time of death to within a half-hour. Corneal film forms over the eyes within minutes if the body dies with eyes open, or within several hours if death occurs with the eyes closed. Black spots appear in the sclera within the first few hours. Bulging from gas formation and eventual retraction due to decomposition make the eyes less useful as decomposition advances.
Livor mortis occurs as blood settles to parts of the body due to the action of gravity, generally presenting as dark blue or dark purple patches. Lividity becomes visible at one half to four hours, well-developed within 3-4 hours, and acheives maximal coloration at 8-12 hours. Lividity can demonstrate the position of the body at the time of death, and any changes in position following death.
Rigor mortis, i.e., the stiffening of the corpse, begins to develop immediately after death. Muscles continue to metabolize for a short time after somatic death, and glycogen continues to be converted into lactic acid. As the pH of the tissue falls, and in the absence of new ATP generation, the actin of the muscle begins to gel and harden. Rigor is perceptible at 1-6 hours after death, at its maximum at 6-24 hours after death, and begins to disappear as the muscles are broken down by decomposition within 12-36 hours, depending on environmental and other factors.
The cooling of the body, or "algor mortis," proceeds at 1.5 degrees per hour at room temperature. Environmental factors can influence the rate of cooling (i.e., heat, humidity, immersion in water, etc.).
Flies are immediately attracted to the body after death, and lay eggs around the bodily orifices and any available wounds. Blowflies and houseflies are the most common early insect responders.
Stage 3: Putrefaction
Within 4-10 days after death, the body bloats from the build-up of gases. The pressure of the gas inflates the body and forces fluids from cells into the body cavity. Hydrogen sulfide, methane, cadaverine, and putrescine are by-products of the decomposition process. They are pushed throughout the body by the bloating action, and by the movement of the young maggots which are now populating the body. Their strong odor attracts additional insects, such as beetles, mites, and parasitoid wasps that lay eggs within the bodies of the maggots on which they prey.
Stage 4: Black Putrefaction
10-20 days after death, the body begins to collapse. The flattened body which remains has "creamy" flesh under black patches where the body is exposed. There is a very strong smell of decay, and most of the body's fluids have now begun to drain from the body and seep into the surrounding soil. Body temperature now begins to increase as a result of insect activity and heat from the chemical action of the advanced decomposition. The body is very attractive to all kinds of insects at this stage. If the body is protected from insects, adipocere begins to form.
Stage 5: Butyric Fermentation
20-50 days after death, the body has become very flattened and is beginning to dry out. The body exudes a "cheesy" smell caused by the prevalence of butyric acid, and this odor attracts new kinds of insects, particularly cheese fly, beetles, and wasps. The surrounding area develops mold as the body begins to ferment.
Stage 6: Dry Decay
50-365 days after death, the body is dry and decay proceeds at a slower rate. Eventually all hair and skin is consumed by moths, bacteria, and mites, leaving only bones.
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