Once death occurs, human decomposition takes place in stages. The process of tissue breakdown may take from several days to years.

Stages

Fresh

The fresh stage of decomposition occurs during the first few days following death. There are no physical signs of decomposition during this time. However, homeostasis of the body has ceased to function which allows cellular and soft tissue changes to occur because of the process of autolysis, the destruction of cells and organs due to an aseptic chemical process. At this point, the body enters algor mortis, the cooling of the body’s temperature to that of its surroundings. When the body’s cells reach the final stage of autolysis, an anaerobic environment is created. This allows the body’s normal bacteria to breakdown the remaining carbohydrates, proteins, and lipids. The products from the breakdown create acids, gases, and other products which cause volatile organic compounds (VOCs), and putrefactive effects. According to Science Direct, VOCs are produced during the early stage of human decomposition.

Putrefaction

Odor, color changes, and bloating of the body during decomposition are the results of putrefaction. The lower part of the abdomen turns green due to bacteria activity in the cecum. Bacteria break down hemoglobin into sulfohemoglobin which causes the green color change. A formation of gases enters the abdomen which forces liquids and feces out of the body. The gases also enter the neck and face, causing swelling of the mouth, lips, and tongue. Due to this swelling and disconfiguration of the face, identification of the body can be difficult. Bacteria also enter the venous system causing blood to hemolyze. This leads to the formation of red streaks along the veins. This color soon changes to green, through a process known as marbelization. It can be seen on the shoulders, chest and shoulder area, and thighs. The skin can blister and have a serous fluid inside. The skin also becomes fragile, leading to skin slippage, making it difficult to move a body. Body hair comes off easily. The color change of the discoloration from green to brown marks the transition of the early stage of putrefaction to the advanced decompositional stages.

Black putrefaction

After the body goes through the bloating stage it begins the black putrefaction stage. At this point the body cavity ruptures, all of the abdominal gases begin to escape and the body darkens from its greenish color. These activities allow for a greater invasion of scavengers, and insect activity increases greatly. This stage ends as the bones become apparent, which can take anywhere from 10 to 20 days after death depending on region and temperature. This period is also dependent on the degree to which the body is exposed.

Butyric fermentation

After the early putrefaction and black putrefaction phases have taken place, the body begins mummification, in which the body begins to dry out. The human carcass is first mummified, and then goes through adipocere formation. Adipocere (grave wax) formation refers to the loss of body odor and the formation of a cheesy appearance on the cadaver. Mummification is considered a post-active stage because there is less definite distention between changes and they are indicated by reduced skin, cartilage, and bone. Mummification is also indicated when all of the internal organs are lost due to insect activity.

Dry decay

When the last of the soft-tissue has been removed from the body, the final stage of decomposition, skeletonization, occurs. This stage encompasses the deterioration of skeletal remains, and is the longest of the decomposition processes. Skeletonization differs markedly from the previous stages, not only in length, but in the deterioration process itself.

The strength and durability of bone stems from the unique protein-mineral bond present in skeletal formation; consequently, changes to skeletal remains, known as bone diagenesis, occur at a substantially slower rate than stages of soft-tissue breakdown. As the protein-mineral bond weakens after death, however, the organic protein begins to leach away, leaving behind only the mineral composition. Unlike soft-tissue decomposition, which is influenced mainly by temperature and oxygen levels, the process of bone breakdown is more highly dependent on soil type and pH, along with presence of groundwater. However, temperature can be a contributing factor, as higher temperature leads the protein in bones to break down more rapidly. If buried, remains decay faster in acidic-based soils rather than alkaline. Bones left in areas of high moisture content also decay at a faster rate. The water leaches out skeletal minerals, which corrodes the bone, and leads to bone disintegration.

Insect activity

Substances produced during the fresh stage attract a variety of insects. Many of the Diptera insects begin to lay their eggs on the body during this stage, especially the Calliphoridae. There is also considerable insect activity by the insects that live in the soil around the body.

During putrefaction the majority of the insects begins with the Calliphoridae, and include Formicidae, Muscidae, Sphaeroceridae, Silphidae, Lepidoptera, Hymenoptera, Sarcophagidae, Histeridae, Staphylinidae, Phalangida, Piophilidae, Aranae, Sepsidae, and Phoridae. Again, there is also considerable insect activity by the soil-inhabiting arthropods.

There is considerable insect activity during black putrefaction. Some of the insects that can be found living in the body are the Calliphoridae larvae, Staphylinidae, Histeridae, Gamasid mites, Ptomaphila, Trichopterygidae, Piophilid larvae, Parasitic wasps, Staphylinid larvae, Trichopterygid larvae, Histerid larvae, Ptomaphila larvae, Dermestes, Tyroglyphid mites, Tineid larvae, and the Dermestes larvae. Some insects can also be found living in the soil around the body such as Isopoda, Collembola, Dermaptera, Formicidae, Pseudoscorpiones, Araneae, Plectochetos, Acari, Pauropoda, Symphyla, Geophilidae, and Protura. Finding these insects is what was found on a body in Australia. The types of insects will differ based on where the body is, although Diptera larvae can be found feeding on the body in almost all cases.

Insects that can be found on the body during mummification include most of the same insects as in putrefaction stage, but also include Acarina, Nitidulidae, Cleridae, Dermestes caninus, and Trogidae. The main soil-inhabiting arthropods include Dermaptera and Formicidae.

At the dry decay stage commonly found insects include Sphaeroceridae, Acarina, Nitidulidae, Cleridae, Dermestes caninus, Trogidae, Tyroglyphid mites, and the Tineid larvae. The soil-inhabiting arthropods are Collembola, Dermaptera, Heteroptera, Coleoptera and their larvae, parasitic Hymenoptera, Formicidae, Diptera larvae, Psuedoscorpiones, Aranae, Plectochetos, Acari, Pauropoda, Symphyla, Geophilidae, Protura, and Aphididae.

I know I’ve talked about entomology before but I thought I’d tell you a bit more about it.

Forensic entomology is the science and study of insects and other arthropods with law-related applications. It can be divided in three subfields: urban, stored-product and medico-legal/medico-criminal.

Urban forensic entomology typically concerns pest infestations in buildings or gardens that may be the basis of litigation between private parties and service providers such as landlords or exterminators. Such questions may include the appropriateness of certain pesticide treatments. Civil law actions and litigations involving athropods in dwelling or as house and garden pests are included in urban forensic entomology. Sometimes used in stored products cases call in to help determine (chain of custody). Chain of custody is when you go back through all points of possible infestation to determine who is at fault. Stored-product forensic entomology is often used in litigation over infestation or contamination of commercially distributed foods by insect.

Medicolegal forensic entomology includes arthropod involvement in events such as murder, suicide, rape, physical abuse and contraband trafficking. In murder investigations it deals with what insects lay eggs when and where, and in what order they appear in dead bodies. This can be helpful in determining the time or post mortem interval (PMI) and location of the death in question. Since many insects exhibit a degree of endemism (occurring only in certain places), or have a well-defined phenology (active only at a certain season, or time of day), their presence in association with other evidence can demonstrate potential links to times and locations where other events may have occurred (e.g., an Ohio man who claimed to have been in Ohio on the date his wife and children were murdered in California was found to have grasshoppers and other nocturnal insects from the west on his car grille, indicating that the car had been driven at night to the western US, and he was subsequently convicted). Another area of medicolegal forensic entomology is the relatively new study of entomotoxicology. This particular branch involves the utilization of entomological specimens found at a scene in order to test for different drugs that may have possibly played a role in the death of the victim. The study of forensic entomology has not remained an esoteric science reserved only for entomologists and forensic scientists. The general public has become fascinated by this study and its applications since its beginning centuries ago.

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Forensic science (often shortened to forensics) is the application of a broad spectrum of sciences to answer questions of interest to the legal system. This may be in relation to a crime or to a civil action. But besides its relevance to the underlying legal system, more generally forensics encompasses the accepted scholarly or scientific methodology and norms under which the facts regarding an event, or an artifact, or some other physical item (such as a corpse, or cadaver, for example) are ascertained as being the case. In that regard the concept is related to the broader notion of authentication whereby an interest outside of a legal form exists in determining whether an object is in fact what it purports to be, or is alleged as being. The word “forensic” comes from the Latin adjective “forensis” meaning of or before the forum. During the time of the Romans, a criminal charge meant presenting the case before a group of public individuals in the forum. Both the person accused of the crime and the accuser would give speeches based on their side of the story. The individual with the best argument and delivery would determine the outcome of the case. Basically, the person with the sharpest forensic skills would win. This origin is the source of the two modern usages of the word “forensic” - as a form of legal evidence and as a category of public presentation. In modern use, the term “forensics” in place of “forensic science” can be considered incorrect as the term “forensic” is effectively a synonym for “legal” or “related to courts”. However, the term is now so closely associated with the scientific field that many dictionaries include the meaning that equates the word “forensics” with “forensic science”.