Forensic Entomology : Forensic Entomology By Brianna Idelman
Bio 7 Slide 2: What Is Entomolgy ? The word “entomology” is coined from the greek words “entomon” (insect )+ “logia” (study of). The word Entomon is of the word entomos which means “having a notch or cut at the waist”. This refers to segmentation as the common characteristic of arthropods. Forensic Entomology : Forensic Entomology Forensic entomology is a science dedicated the application, analysis, and study of insects and other arthropod biology to criminal matters to establish facts that can be presented in a legal proceeding.
primarily associated with death investigations; however, it may also be used to detect drugs and poisons, determine the location of an incident, and find the presence and time of the infliction of wounds. A Brief History : A Brief History Until recently, insects as a part of crime scenes were regarded as something to be disposed of as soon as possible.
Although insects weren’t considered real evidence until recently, it is not a new idea:
In the 13th century, a “death investigator” named Sung Ts’u wrote the first book about forensic entomolgy, in which he tells of a murder in a chinese village in which the victim was repeatedly slashed with a sickle.
The magistrate ordered all the men in the village to assemble with their sickles, and in the heat, the flies were attracted to one sickle, because of the blood residue and small tissue fragments clinging to it. They determined that he was indeed the murderer.
After confrontation, the owner of the sickle confessed to the crime (1). A Brief History Contd. : A Brief History Contd. Not until 1668 was the link between fly eggs and maggots discovered in the West.
A man named Francisco Redi, made a major discovery when he studied meat exposed to flies and meat protected from flies Until his studies, people didn’t realize that maggots hatched from eggs that flies laid on exposed meat
It was believed that they arose spontaneously from rotting meat. His discovery did not lead immediately to use of entomological evidence in a forensic investigation.
The first record of its use in forensic investigation in the West, dates from 1855, in Paris, France.
Progress was uneven and sporadic until entomological evidence came to full force in a brutal murder case in the 1930’s The Decomposing Body : The Decomposing Body A decomposing body can be compared to a newly emerged volcano.
It is a resource waiting to be colonized by plants and animals
The first plants (primary successors) begin to change the island and make it viable for other other species.
The same can be said for a decomposing body, a theory called succession
The body is not only a food source, it’s an element in insect reproduction
The first insects to appear on a decomposing body, make it more attractive to other insects. This goes on until the body is fully decomposed and only a skeleton is left
Unlike an island though, the body is a temporary microhabitat
It is a rapidly changing, and disappearing food source Decomposing Body : Decomposing Body Carrion Species : Carrion Species A carrion is an animal that feeds on flesh
There are four agreed upon species of carrions
Domain Eukarya, Kingdom Animalia, and Phylum Arthropoda.
Necrophagous species: feed directly on the corpse
Primarily flies (order Diptera) and Beetles (order Coleoptera)
Predators/ parasites of Necrophagous species: not attracted to the dead body, but the other insects feeding on it.
Primarily rove beetles & Hister beetles (family Staphylinidae & Histeridae)
Parasites: Primarily of the order Hymenoptera- ants, bees, and wasps
Parastic on maggots and pupae of flies. Some wasps lay eggs inside maggot or pupa, and when eggs hatch, feed on developing fly.
Necrophages and Predators: feeds on corpse and other insects
The most common ones are of the genus Chrysoma (blow fly)
Not all blow flies, but some like the species Chrysoma rufifacies
arrive within minutes of death & can switch from decomposer to predator
Extensions: use corpse as extension of their normal habitat
Hunting spiders that congregate around corpse to prey on insects
They sometimes use the corpse to anchor webs, as part of habitat. PICTURES : PICTURES What do these insects tell us ? : What do these insects tell us ? Time of Death
The most common use of insects in forensic investigations is to determine time of death based on the Post-mortem interval (PMI)
Post-mortem interval- is the span of time between the discovery of the body and the time of death.
From the presence of insect eggs and insects themselves at various stages of their life cycle ( egg, maggot, pupa, etc.), the forenesic entomologist can determine PMI
Once a species on a corpse has been identified, and the life cycle stage has been identified the Forensic Entomologist (FE) has to consider climatological conditions (temperature and humidty).
Under a given set of climatological conditions, insects mature at a constant rate, making it possible to determine when the body was first infested with the species. Therefore, the PMI can be estimated (2). Developmental Time in Blow Fly Species : Developmental Time in Blow Fly Species Flies (Diptera) are the most common group of insects Forensic Entomologists use in determining PMI (3). http://www.forensicentomologist.org/ >
From the American Board of Forensic Entomology (4). What Else ? : What Else ? While PMI is extremely important, insects can also tell us much more about a forensic case.
The FE can tie a body to a specific geographical area based on the species of insects and eggs found.
This can be especially important and can tell investigators if the body has been moved, or has stayed in the same place since death because some insects are endemic to certain areas.
Not only a corpse has insects, other evidence can be observed by a forensic entomologist as well.
Example: the radiator grill of an automobile collects any insects that hit the car. By looking at the dead insect remains, a FE can reveal any place the car has traveled and this information can then incriminate or free a suspect from further investigation based on alibi. Insect on car radiator grille : Insect on car radiator grille