• How Can Insects Be Used To Establish Post Mortem Interval (PMI)
Teesside University
Applied Science
ICA 2
Lisa Potter
G7149216
Contents
Introduction 3
What is Forensic Entomology? 3
History of Forensic Entomology 4
Flies and Beetles 5
Life Cycle 6
Determining PMI 7
Conclusion 9
References 10
Turnitin Report 11
Death and Decay 1 – How can insects be used to establish Post Mortem Interval (PMI)
Introduction
Post mortem interval (PMI) is the amount of time that has elapsed since a person died.
Establishing the time of death is important, especially if it is suspected that the victim may have been murdered. Having a time of death helps investigators centre their investigation on suspects who cannot confirm …show more content…
Forensic entomology is the study of insects to draw conclusions in legal investigations and present those conclusions in courts of law.
There are three branches of forensic entomology:
Urban investigations – legal investigations involving insect problems in buildings.
Stored product investigations – inspection of stored food for insects.
Medico legal investigation – study of the “necrophagous (carrion-feeding) insects that infest human remains”
(Langford et al, 2005a).
It is the third branch of forensic entomology that is concerned with determining PMI. Once a person has died a predictable series of events will occur. It can take only 10 minutes for the first flies to arrive and start feeding on the body. These flies will then lay eggs, which in turn will hatch and also start feeding on the body. Once they become adults the process will start again. This is their life cycle. It is the forensic entomologist’s job to study the life cycles of insects, providing them with the knowledge to apply this information to the insects they discover on a body.
“Insects are so predictable and reliable that forensic entomology has become a major part of crime scene investigation” (Hamilton, …show more content…
After death insects arrive in a predictable order known as the faunal succession (Australian Government: Department of Education, Science and Training, undated). It is the flies (order Diptera) that seek out the body first, particularly the blowflies (Calliphoridae), which can pick up the scent of a corpse from a distance of 1.6km away (Hamilton, 2008c). Blowflies are followed by the flesh flies (Sarcophagidae). Both these flies are attracted by the odour of fresh corpses and are the most useful in determining PMI. Beetles generally follow the flies, with the carrion beetles (Silphidae) and clown beetles (Histeridae) arriving first. The table below shows the general succession of insects on a corpse. [pic] Life Cycle To determine PMI you must understand the life cycles of the insects concerned. As it is generally the flies that arrive first we will look at the life cycle of a blowfly (although all flies are similar). In the first 60 minutes flies will discover the body and feed on the proteins. They then lay their eggs in natural openings or wounds in the body as this provides moisture, food and protection. Blowflies will lay between 150 – 200 eggs in small mounds, each no longer than 2mm in length. There are three stages of development (instars) once the eggs hatch. During the first instar stage the eggs hatch out into maggots (larva) and start feeding on the corpse and are 5mm long. During the second instar stage, (2-3 days) the maggots continue to
Applied Science
ICA 2
Lisa Potter
G7149216
Contents
Introduction 3
What is Forensic Entomology? 3
History of Forensic Entomology 4
Flies and Beetles 5
Life Cycle 6
Determining PMI 7
Conclusion 9
References 10
Turnitin Report 11
Death and Decay 1 – How can insects be used to establish Post Mortem Interval (PMI)
Introduction
Post mortem interval (PMI) is the amount of time that has elapsed since a person died.
Establishing the time of death is important, especially if it is suspected that the victim may have been murdered. Having a time of death helps investigators centre their investigation on suspects who cannot confirm …show more content…
Forensic entomology is the study of insects to draw conclusions in legal investigations and present those conclusions in courts of law.
There are three branches of forensic entomology:
Urban investigations – legal investigations involving insect problems in buildings.
Stored product investigations – inspection of stored food for insects.
Medico legal investigation – study of the “necrophagous (carrion-feeding) insects that infest human remains”
(Langford et al, 2005a).
It is the third branch of forensic entomology that is concerned with determining PMI. Once a person has died a predictable series of events will occur. It can take only 10 minutes for the first flies to arrive and start feeding on the body. These flies will then lay eggs, which in turn will hatch and also start feeding on the body. Once they become adults the process will start again. This is their life cycle. It is the forensic entomologist’s job to study the life cycles of insects, providing them with the knowledge to apply this information to the insects they discover on a body.
“Insects are so predictable and reliable that forensic entomology has become a major part of crime scene investigation” (Hamilton, …show more content…
After death insects arrive in a predictable order known as the faunal succession (Australian Government: Department of Education, Science and Training, undated). It is the flies (order Diptera) that seek out the body first, particularly the blowflies (Calliphoridae), which can pick up the scent of a corpse from a distance of 1.6km away (Hamilton, 2008c). Blowflies are followed by the flesh flies (Sarcophagidae). Both these flies are attracted by the odour of fresh corpses and are the most useful in determining PMI. Beetles generally follow the flies, with the carrion beetles (Silphidae) and clown beetles (Histeridae) arriving first. The table below shows the general succession of insects on a corpse. [pic] Life Cycle To determine PMI you must understand the life cycles of the insects concerned. As it is generally the flies that arrive first we will look at the life cycle of a blowfly (although all flies are similar). In the first 60 minutes flies will discover the body and feed on the proteins. They then lay their eggs in natural openings or wounds in the body as this provides moisture, food and protection. Blowflies will lay between 150 – 200 eggs in small mounds, each no longer than 2mm in length. There are three stages of development (instars) once the eggs hatch. During the first instar stage the eggs hatch out into maggots (larva) and start feeding on the corpse and are 5mm long. During the second instar stage, (2-3 days) the maggots continue to