Forensic entomological decomposition
Forensic entomological decomposition is how insects decompose and what that means for timing and information in criminal investigations.
[2] In entomological studies, five stages of decomposition are commonly described: (1) Fresh, (2) Bloat, (3) Active Decay, (4) Advanced or Post-Decay, and (5) Dry Remains.
[2][7] While the pattern of arthropod colonization follows a reasonably predictable sequence, the limits of each stage of decomposition will not necessarily coincide with a major change in the faunal community.
A decaying carcass provides "a temporarily, rapidly changing resource which supports a large, dynamic arthropod community."
– M. Grassberger and C. Frank The fresh stage of decomposition is generally described as the period between the moment of death and when the first signs of bloat are apparent.
[2][6] There are no outward signs of physical change, though internal bacteria have begun to digest organ tissues.
[2] Depending on the rate of decomposition and the development time of particular blowfly species, eggs may hatch and young larvae begin to feed on tissues and liquids while the carcass is still classified in the fresh stage.
[5] Activity of anaerobic bacteria in the abdomen create gases, which accumulate and results in abdominal bloating.
[5][6] The beginning of active decay stage is marked by the deflation of the carcass as feeding Dipteran larvae pierce the skin and internal gases are released.
[2] Feeding larvae of Calliphoridae flies are the dominant insect group at carcasses during the active decay stage.
[2][5] The dry decay stage is characterized by the movement from previously dominant carrion fauna to new species.
Non-carrion organisms that commonly arrive at remains in dry decay are centipedes, millipedes, isopods, snails and cockroaches.
[5] Understanding how a corpse decomposes and the factors that may alter the rate of decay is extremely important for evidence in death investigations.
Corpses with open wounds, whether pre or post mortem, tend to decompose faster due to easier insect access.
Wraps, garments, and clothing have shown to affect the rate of decomposition because the corpse is covered by some type of barrier.
For instance, if a corpse is wearing a heavy jacket, this can slow down decomposition in that particular area and insects will colonize elsewhere.
Higher temperatures favor the reproduction of bacteria inside high nutrient areas of the liver and other organs.
On occasion, drugs that are present in the body at death can also affect how fast insects break down the corpse.
[14] Other researchers in entomotoxicology are developing techniques to detect and measure drug levels in older fly pupae.
To this date, bromazepam, levomepromazine, malathion, phenobarbital, trazolam, oxazepam, alimemazine, clomipramine, morphine, mercury, and copper have been recovered from maggots.
[2][5] Studies have shown that each stage is characterized by particular insect species, the succession of which depends on chemical and physical properties of remains, rate of decomposition and environmental factors.
