• 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…
their whereabouts at that time, and also eliminates those suspects who can.
There are various techniques that can determine time of death, including algor mortis, rigor mortis and the use of insects.
Insects can help determine PMI as they are predictable creatures. By observing and analysing the insect activity on and around the body, time of death can be estimated. This area of science is known as forensic entomology and this is the area discussed below.
What is Forensic Entomology?
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…
2008a)
History of Forensic Entomology
Forensic entomology has been used for a long time in solving crime. The earliest recorded case of insects being used was in the thirteenth century in China. A crime had been committed, a villager was found dead with slashes on his body. After having no luck in questioning suspects, the investigator gathered the villagers together requesting that they each brought their sickles. The sickles were placed on the ground and he noticed that one sickle was attracting a larger number of flies than the others. The flies were drawn to the tiny particles of blood on the blade. The sickles owner confessed to the murder. (Hamilton, 2008b).
Forensic entomology didn’t develop in the west until the 1800’s. A baby’s body was found behind a fireplace in France. Through the use of the insects it was estimated the baby had been dead for 2 years, exonerating the current occupants who had only been living there for a short time. This was a significant case which established forensic entomology as a tool for investigating crime scenes (Hall, 2001a).
Throughout the 19th and 20th centuries studies continued into the connection between corpses and insects. It is this knowledge that forensic entomologists use today in investigating crimes.
Flies and Beetles
In terms of forensic entomology there are two main orders of insects that are important, the Diptera (flies) and the Coleoptera (beetles). (Fig.1, Fig. 2) Figure 1: a Dipteran fly Figure 2: a Coleopteran beetle
The accurate identification of insects ensures that the correct information is used in investigations. The table below shows the main groups of insects of forensic importance.
Table.1, The main taxonomic groups of insects of forensic importance. (Langford et al, 2005b).
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.
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 feed and grow to approximately 10mm in length.
During the third instar stage (4-5 days) the maggots grow to approximately 17mm in length, then enter the prepupa stage between 8 and 12 days after hatching. The maggots stop feeding and leave the corpse, shrinking slightly in length. They leave in search of a safe and dry place to finish their transformation into an adult. This can be up to 6m away.
Between 18 and 24 days the maggots are in the pupa stage. This is where the outside shells harden turning to a yellowish colour and later a red/brown colour.
At the end of this stage the maggots emerge as flies from their casings. 5-18 days after emerging the female will start to lay eggs and the cycle will start again. (Figure 3 shows the life cycle of a blowfly)
(Hamilton, 2008) Figure 3. Life cycle of a blowfly.
Determining PMI
To determine PMI samples are collected from the body and surrounding area (Figure 4). Samples should include any eggs, larva, pupa, and flies both alive and dead.
Figure 4. Sampling at a crime scene.
Samples need to be identified. Sometimes difficult so some specimens are allowed to grow to adults to determine this. Once species has been determined the air and soil temperatures at the time of death and subsequent days before and after need to be clarified. Insects are cold blooded and use the heat from the environment as a source of energy to grow; PMI is based on the speed of insect growth, making the air and soil temperatures vital to an accurate estimation.
If third instar stage maggots are found on the body and we know that it takes approximately 3-4 days to reach this stage we can estimate that time of death was 3-4 days ago. A more accurate way would be to collect some larva and rear them in a lab under environmental conditions equal to the site where they were found. Once they have reached the end of the cycle and become adults you can accurately determine PMI.
Conclusion
The entomological approach to determining PMI is extremely useful though it can not always fully estimate it. There are many environmental factors that affect the events that occur when a person dies. Temperature and humidity can affect life cycles and succession patterns, and new foreign species are a factor that needs to be considered. Also the site where a body is found influences how PMI is determined, for instance a sealed room, burial underground or submersion in water will not provide the same results as a body found in open ground.
“Forensic entomology is still not a near-perfect science but its contributions to the resolution of many civil and criminal cases are appreciated. We can only hope that further improvements in methods and techniques involved in data and sample collection and analysis will create a more reliable and accurate science.”(Forensic Comparison Microscopes, 2007)
References
Books
Hall, R.D., (2001) Introduction: Perceptions and status of Forensic Entomology. In Forensic Entomology: the utility of arthropods in legal investigations. Edited by Byrd, J.H., Castner, J.L., CRC, Florida. pp 8a, 10b.
Hamilton, S. (2008) Forensic Entomology: Bugs and Bodies, ABDO Publishing Company, Minnesota, USA, pp 4a, 8b, 22c.
Langford, A., Dean, J., Reed, R., Holmes, D., Weyers, J., Jones, A. (2005) Practical Skills in Forensic Science. Pearson Education Limited, Harlow, England, pp 456a, 458b.
Material available on the World Wide Web:
Australian Government, Department of Education, Science and Training (undated) Forensic Investigations. Forensic Entomology: Use of insects to help solve crime. [WWW document] http://www.clt.uwa.edu.au/__data/page/112507/fse07_forensic_entomology.pdf. [Date accessed 08/01/10] pp 3.
Forensic Comparison Microscopes, (2007). Forensic Entomology : History, Benefits and Limitations. [WWW Document] http://forensiccomparisonmicroscopes.com/forensic-entomology-history-benefits-and-limitations.html. [Date Accessed 16/01/10].
Images
Figure 1: a Dipteran fly, [WWW image], http://australianmuseum.net.au/Uploads/Images/8802/Fly_big.jpg. [Date accessed 07/01/10].
Figure 2: a Coleopteran beetle. [WWW image], http://australianmuseum.net.au/Uploads/Images/8842/Beetle.jpg. [Date accessed 07/01/10].
Figure 3: Life cycle of a blow fly. [WWW image], http://www.deathonline.net/decomposition/images/lifecycle.jpg. [Date accessed 10/01/10].
Figure 4: Sampling at a crime scene. [WWW image], http://paibiopai.files.wordpress.com/2009/10/picture1.jpg. [Date accessed 16/01/10].
TurnitinUK Originality Report
Death and Decay 1 – How can insects be used to establish Post Mortem Interval (PMI) by LISA POTTER
From Click on 'View\Complete ' to start using TurnitinUK: (Academic Skills)
Processed on 30-01-10 1:17 PM GMT
ID: 5494408
Word Count: 1480 Similarity Index
11%
Similarity by Source
Internet Sources:
7%
Publications:
3%
Student Papers:
9%
sources:
1
4% match (Internet from 26/11/08)
(11-26-08) http://www.clt.uwa.edu.au/__data/page/112507/fse07_forensic_entomology.pdf
2
3% match (student papers from 01/08/08)
Submitted to Cranfield University on 2008-08-01
3
1% match (student papers from 29/01/08)
Submitted to University of Teesside on 2008-01-29
4
1% match (student papers from 22/10/09)
Submitted to College of Technology London on 2009-10-22
5
1% match (student papers from 14/05/09)
Submitted to Coventry University on 2009-05-14
6
1% match (publications)
Merck. "Time of Death", Veterinary Forensics, 06/06/2007
7
< 1% match (student papers from 22/04/09)
Submitted to Glasgow Caledonian University on 2009-04-22
paper text:
3Death and Decay 1 – How can insects be used to establish Post Mortem Interval (PMI)
Introduction
1Post mortem interval (PMI) is the amount of time that has passed since a person died.
7Establishing the time of death is
important, especially if it is suspected that the victim has been murdered. Having a time of death helps investigators centre their investigation on suspects who cannot confirm their whereabouts at that time, and also eliminates those suspects who can. There are various techniques that can determine
6time of death, including algor mortis, rigor mortis and the use of
insects. Insects can help determine PMI as they are predictable creatures. By observing and analysing the insect activity on and around the body, time of death can be estimated. This area of science is known as forensic entomology and this is the area discussed below. What is Forensic Entomology?
5Forensic 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, 2008a) History of Forensic Entomology Forensic entomology has been used for a long time in solving crime. The earliest recorded case of insects being used was in the thirteenth century in China. A crime had been committed, a villager was found dead with slashes on his body. After having no luck in questioning suspects, the investigator gathered the villagers together requesting that they each brought their sickles. The sickles were placed on the ground and he noticed that one sickle was attracting a larger number of flies than the others. The flies were drawn to the tiny particles of blood on the blade. The sickles owner confessed to the murder. (Hamilton, 2008b). Forensic entomology didn’t develop in the west until the 1800’s. A baby’s body was found behind a fireplace in France. Through the use of the insects it was estimated the baby had been dead for 2 years, exonerating the current occupants who had only been living there for a short time. This was a significant case which established forensic entomology as a tool for investigating crime scenes (Hall, 2001a). Throughout the 19th and 20th centuries studies continued into the connection between corpses and insects. It is this knowledge that forensic entomologists use today in investigating crimes. Flies and Beetles In terms of forensic entomology there are two main orders of insects that are important, the Diptera (flies) and the Coleoptera (beetles). (Fig.1, Fig. 2) [pic] [pic] Figure 1: a Dipteran fly Figure 2: a Coleopteran beetle The accurate identification of insects ensures that the correct information is used in investigations. The table below shows the main
2groups of insects of forensic importance.
2Table.1, The main taxonomic groups of insects of forensic importance.
(Langford et al, 2005b).
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
feed and grow to approximately 10mm in length. During the third instar stage (4-5 days) the maggots grow to approximately 17mm in length, then enter the prepupa stage between 8 and 12 days after hatching. The maggots stop feeding and leave the corpse, shrinking slightly in length. They leave in search of a safe and dry place to finish their transformation into an adult. This can be up to 6m away. Between 18 and 24 days the maggots are in the pupa stage. This is where the outside shells harden turning to a yellowish colour and later a red/brown colour. At the end of this stage the maggots emerge as flies from their casings. 5- 18 days after emerging the female will start to lay eggs and the cycle will start again.
4(Figure 3 shows the life cycle of
a blowfly) (Hamilton, 2008)
4[pic] Figure 3. Life cycle of
a blowfly. Determining PMI To determine PMI samples are collected from the body and surrounding area (Figure 4). Samples should include any eggs, larva, pupa, and flies both alive and dead. [pic] Figure 4. Sampling at a crime scene. Samples need to be identified. Sometimes difficult so some specimens are allowed to grow to adults to determine this. Once species has been determined the air and soil temperatures at the time of death and subsequent days before and after need to be clarified. Insects are cold blooded and use the heat from the environment as a source of energy to grow; PMI is based on the speed of insect growth, making the air and soil temperatures vital to an accurate estimation. If third instar stage maggots are found on the body and we know that it takes approximately 3-4 days to reach this stage we can estimate that time of death was 3-4 days ago. A more accurate way would be to collect some larva and rear them in a lab under environmental conditions equal to the site where they were found. Once they have reached the end of the cycle and become adults you can accurately determine PMI. Conclusion The entomological approach to determining PMI is extremely useful though it can not always fully estimate it. There are many factors that affect the events that occur when a person dies, including environmental factors. Temperature and humidity can affect life cycles and succession patterns, and new foreign species are a factor that needs to be considered. Also the site where a body is found influences how PMI is determined, for instance a sealed room, burial underground or submersion in water will not provide the same results as a body found in open ground. “Forensic entomology is still not a near-perfect science but its contributions to the resolution of many civil and criminal cases are appreciated. We can only hope that further improvements in methods and techniques involved in data and sample collection and analysis will create a more reliable and accurate science.”(Forensic Comparison Microscopes, 2007) ----------------------- Order Diptera
1Family Calliphoridae (blow flies) Family Sarcophagidae (flesh flies) Family Muscidae (muscid flies) Family Piophilidae (skipper flies) Family Scathophagidae (dung flies) Family Sepsidae (black scavenger flies) Family Sphaeroceridae (small dung flies, minute scavenger flies) Family Stratiomyidae (soldier flies) Family Phoridae (humpbacked flies or scuttle flies) Family Psychodidae (moth flies, sand flies, and owl
2midge Order Coleoptera Family Silphidae (carrion beetles) Family Dermestidae (skin beetles, leather beetles, hide beetles, carpet beetles and larder beetles) Family Saphylinidae (rove beetles) Family Histeridae (clown beetles) Family Cleridae (checkered beetles) Family Trogidae (hide beetles) Family Scarabaeidae (scarab beetles) Family Nitidulidae (sap beetles) Table 2: Succession of insects on human bodies adapted from Rodriguez & Bass (1983), (Hall, 2001b).
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…
their whereabouts at that time, and also eliminates those suspects who can.
There are various techniques that can determine time of death, including algor mortis, rigor mortis and the use of insects.
Insects can help determine PMI as they are predictable creatures. By observing and analysing the insect activity on and around the body, time of death can be estimated. This area of science is known as forensic entomology and this is the area discussed below.
What is Forensic Entomology?
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…
2008a)
History of Forensic Entomology
Forensic entomology has been used for a long time in solving crime. The earliest recorded case of insects being used was in the thirteenth century in China. A crime had been committed, a villager was found dead with slashes on his body. After having no luck in questioning suspects, the investigator gathered the villagers together requesting that they each brought their sickles. The sickles were placed on the ground and he noticed that one sickle was attracting a larger number of flies than the others. The flies were drawn to the tiny particles of blood on the blade. The sickles owner confessed to the murder. (Hamilton, 2008b).
Forensic entomology didn’t develop in the west until the 1800’s. A baby’s body was found behind a fireplace in France. Through the use of the insects it was estimated the baby had been dead for 2 years, exonerating the current occupants who had only been living there for a short time. This was a significant case which established forensic entomology as a tool for investigating crime scenes (Hall, 2001a).
Throughout the 19th and 20th centuries studies continued into the connection between corpses and insects. It is this knowledge that forensic entomologists use today in investigating crimes.
Flies and Beetles
In terms of forensic entomology there are two main orders of insects that are important, the Diptera (flies) and the Coleoptera (beetles). (Fig.1, Fig. 2) Figure 1: a Dipteran fly Figure 2: a Coleopteran beetle
The accurate identification of insects ensures that the correct information is used in investigations. The table below shows the main groups of insects of forensic importance.
Table.1, The main taxonomic groups of insects of forensic importance. (Langford et al, 2005b).
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.
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 feed and grow to approximately 10mm in length.
During the third instar stage (4-5 days) the maggots grow to approximately 17mm in length, then enter the prepupa stage between 8 and 12 days after hatching. The maggots stop feeding and leave the corpse, shrinking slightly in length. They leave in search of a safe and dry place to finish their transformation into an adult. This can be up to 6m away.
Between 18 and 24 days the maggots are in the pupa stage. This is where the outside shells harden turning to a yellowish colour and later a red/brown colour.
At the end of this stage the maggots emerge as flies from their casings. 5-18 days after emerging the female will start to lay eggs and the cycle will start again. (Figure 3 shows the life cycle of a blowfly)
(Hamilton, 2008) Figure 3. Life cycle of a blowfly.
Determining PMI
To determine PMI samples are collected from the body and surrounding area (Figure 4). Samples should include any eggs, larva, pupa, and flies both alive and dead.
Figure 4. Sampling at a crime scene.
Samples need to be identified. Sometimes difficult so some specimens are allowed to grow to adults to determine this. Once species has been determined the air and soil temperatures at the time of death and subsequent days before and after need to be clarified. Insects are cold blooded and use the heat from the environment as a source of energy to grow; PMI is based on the speed of insect growth, making the air and soil temperatures vital to an accurate estimation.
If third instar stage maggots are found on the body and we know that it takes approximately 3-4 days to reach this stage we can estimate that time of death was 3-4 days ago. A more accurate way would be to collect some larva and rear them in a lab under environmental conditions equal to the site where they were found. Once they have reached the end of the cycle and become adults you can accurately determine PMI.
Conclusion
The entomological approach to determining PMI is extremely useful though it can not always fully estimate it. There are many environmental factors that affect the events that occur when a person dies. Temperature and humidity can affect life cycles and succession patterns, and new foreign species are a factor that needs to be considered. Also the site where a body is found influences how PMI is determined, for instance a sealed room, burial underground or submersion in water will not provide the same results as a body found in open ground.
“Forensic entomology is still not a near-perfect science but its contributions to the resolution of many civil and criminal cases are appreciated. We can only hope that further improvements in methods and techniques involved in data and sample collection and analysis will create a more reliable and accurate science.”(Forensic Comparison Microscopes, 2007)
References
Books
Hall, R.D., (2001) Introduction: Perceptions and status of Forensic Entomology. In Forensic Entomology: the utility of arthropods in legal investigations. Edited by Byrd, J.H., Castner, J.L., CRC, Florida. pp 8a, 10b.
Hamilton, S. (2008) Forensic Entomology: Bugs and Bodies, ABDO Publishing Company, Minnesota, USA, pp 4a, 8b, 22c.
Langford, A., Dean, J., Reed, R., Holmes, D., Weyers, J., Jones, A. (2005) Practical Skills in Forensic Science. Pearson Education Limited, Harlow, England, pp 456a, 458b.
Material available on the World Wide Web:
Australian Government, Department of Education, Science and Training (undated) Forensic Investigations. Forensic Entomology: Use of insects to help solve crime. [WWW document] http://www.clt.uwa.edu.au/__data/page/112507/fse07_forensic_entomology.pdf. [Date accessed 08/01/10] pp 3.
Forensic Comparison Microscopes, (2007). Forensic Entomology : History, Benefits and Limitations. [WWW Document] http://forensiccomparisonmicroscopes.com/forensic-entomology-history-benefits-and-limitations.html. [Date Accessed 16/01/10].
Images
Figure 1: a Dipteran fly, [WWW image], http://australianmuseum.net.au/Uploads/Images/8802/Fly_big.jpg. [Date accessed 07/01/10].
Figure 2: a Coleopteran beetle. [WWW image], http://australianmuseum.net.au/Uploads/Images/8842/Beetle.jpg. [Date accessed 07/01/10].
Figure 3: Life cycle of a blow fly. [WWW image], http://www.deathonline.net/decomposition/images/lifecycle.jpg. [Date accessed 10/01/10].
Figure 4: Sampling at a crime scene. [WWW image], http://paibiopai.files.wordpress.com/2009/10/picture1.jpg. [Date accessed 16/01/10].
TurnitinUK Originality Report
Death and Decay 1 – How can insects be used to establish Post Mortem Interval (PMI) by LISA POTTER
From Click on 'View\Complete ' to start using TurnitinUK: (Academic Skills)
Processed on 30-01-10 1:17 PM GMT
ID: 5494408
Word Count: 1480 Similarity Index
11%
Similarity by Source
Internet Sources:
7%
Publications:
3%
Student Papers:
9%
sources:
1
4% match (Internet from 26/11/08)
(11-26-08) http://www.clt.uwa.edu.au/__data/page/112507/fse07_forensic_entomology.pdf
2
3% match (student papers from 01/08/08)
Submitted to Cranfield University on 2008-08-01
3
1% match (student papers from 29/01/08)
Submitted to University of Teesside on 2008-01-29
4
1% match (student papers from 22/10/09)
Submitted to College of Technology London on 2009-10-22
5
1% match (student papers from 14/05/09)
Submitted to Coventry University on 2009-05-14
6
1% match (publications)
Merck. "Time of Death", Veterinary Forensics, 06/06/2007
7
< 1% match (student papers from 22/04/09)
Submitted to Glasgow Caledonian University on 2009-04-22
paper text:
3Death and Decay 1 – How can insects be used to establish Post Mortem Interval (PMI)
Introduction
1Post mortem interval (PMI) is the amount of time that has passed since a person died.
7Establishing the time of death is
important, especially if it is suspected that the victim has been murdered. Having a time of death helps investigators centre their investigation on suspects who cannot confirm their whereabouts at that time, and also eliminates those suspects who can. There are various techniques that can determine
6time of death, including algor mortis, rigor mortis and the use of
insects. Insects can help determine PMI as they are predictable creatures. By observing and analysing the insect activity on and around the body, time of death can be estimated. This area of science is known as forensic entomology and this is the area discussed below. What is Forensic Entomology?
5Forensic 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, 2008a) History of Forensic Entomology Forensic entomology has been used for a long time in solving crime. The earliest recorded case of insects being used was in the thirteenth century in China. A crime had been committed, a villager was found dead with slashes on his body. After having no luck in questioning suspects, the investigator gathered the villagers together requesting that they each brought their sickles. The sickles were placed on the ground and he noticed that one sickle was attracting a larger number of flies than the others. The flies were drawn to the tiny particles of blood on the blade. The sickles owner confessed to the murder. (Hamilton, 2008b). Forensic entomology didn’t develop in the west until the 1800’s. A baby’s body was found behind a fireplace in France. Through the use of the insects it was estimated the baby had been dead for 2 years, exonerating the current occupants who had only been living there for a short time. This was a significant case which established forensic entomology as a tool for investigating crime scenes (Hall, 2001a). Throughout the 19th and 20th centuries studies continued into the connection between corpses and insects. It is this knowledge that forensic entomologists use today in investigating crimes. Flies and Beetles In terms of forensic entomology there are two main orders of insects that are important, the Diptera (flies) and the Coleoptera (beetles). (Fig.1, Fig. 2) [pic] [pic] Figure 1: a Dipteran fly Figure 2: a Coleopteran beetle The accurate identification of insects ensures that the correct information is used in investigations. The table below shows the main
2groups of insects of forensic importance.
2Table.1, The main taxonomic groups of insects of forensic importance.
(Langford et al, 2005b).
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
feed and grow to approximately 10mm in length. During the third instar stage (4-5 days) the maggots grow to approximately 17mm in length, then enter the prepupa stage between 8 and 12 days after hatching. The maggots stop feeding and leave the corpse, shrinking slightly in length. They leave in search of a safe and dry place to finish their transformation into an adult. This can be up to 6m away. Between 18 and 24 days the maggots are in the pupa stage. This is where the outside shells harden turning to a yellowish colour and later a red/brown colour. At the end of this stage the maggots emerge as flies from their casings. 5- 18 days after emerging the female will start to lay eggs and the cycle will start again.
4(Figure 3 shows the life cycle of
a blowfly) (Hamilton, 2008)
4[pic] Figure 3. Life cycle of
a blowfly. Determining PMI To determine PMI samples are collected from the body and surrounding area (Figure 4). Samples should include any eggs, larva, pupa, and flies both alive and dead. [pic] Figure 4. Sampling at a crime scene. Samples need to be identified. Sometimes difficult so some specimens are allowed to grow to adults to determine this. Once species has been determined the air and soil temperatures at the time of death and subsequent days before and after need to be clarified. Insects are cold blooded and use the heat from the environment as a source of energy to grow; PMI is based on the speed of insect growth, making the air and soil temperatures vital to an accurate estimation. If third instar stage maggots are found on the body and we know that it takes approximately 3-4 days to reach this stage we can estimate that time of death was 3-4 days ago. A more accurate way would be to collect some larva and rear them in a lab under environmental conditions equal to the site where they were found. Once they have reached the end of the cycle and become adults you can accurately determine PMI. Conclusion The entomological approach to determining PMI is extremely useful though it can not always fully estimate it. There are many factors that affect the events that occur when a person dies, including environmental factors. Temperature and humidity can affect life cycles and succession patterns, and new foreign species are a factor that needs to be considered. Also the site where a body is found influences how PMI is determined, for instance a sealed room, burial underground or submersion in water will not provide the same results as a body found in open ground. “Forensic entomology is still not a near-perfect science but its contributions to the resolution of many civil and criminal cases are appreciated. We can only hope that further improvements in methods and techniques involved in data and sample collection and analysis will create a more reliable and accurate science.”(Forensic Comparison Microscopes, 2007) ----------------------- Order Diptera
1Family Calliphoridae (blow flies) Family Sarcophagidae (flesh flies) Family Muscidae (muscid flies) Family Piophilidae (skipper flies) Family Scathophagidae (dung flies) Family Sepsidae (black scavenger flies) Family Sphaeroceridae (small dung flies, minute scavenger flies) Family Stratiomyidae (soldier flies) Family Phoridae (humpbacked flies or scuttle flies) Family Psychodidae (moth flies, sand flies, and owl
2midge Order Coleoptera Family Silphidae (carrion beetles) Family Dermestidae (skin beetles, leather beetles, hide beetles, carpet beetles and larder beetles) Family Saphylinidae (rove beetles) Family Histeridae (clown beetles) Family Cleridae (checkered beetles) Family Trogidae (hide beetles) Family Scarabaeidae (scarab beetles) Family Nitidulidae (sap beetles) Table 2: Succession of insects on human bodies adapted from Rodriguez & Bass (1983), (Hall, 2001b).