1. Chapter 12 Forensic Entomology
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2. Introduction—Objectives
Define forensic entomology.
Describe the anatomy of an arthropod.
Discuss the life cycle of insects.
Estimate time of death using insect evidence.
Examine the effects of insects on human remains.
Forensic Science II: Forensic Entomology, Chapter 12
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3. Introduction—Objectives
Evaluate the use of entomological evidence to solve crimes.
Describe the impact of weather on metamorphosis.
Demonstrate proper procedures for collection and preservation of entomological evidence.
Forensic Science II: Forensic Entomology, Chapter 12
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4. Introduction—Vocabulary
Arthropod—a phylum of animals with jointed appendages and an exoskeleton (from the Greek arthros–jointed; podes–feet)
chitin—a tough polysaccharide; the major component of an arthropod’s exoskeleton
exoskeleton—a rigid external structure made of chitin and protein (protects, provides a point of attachment for muscles; prevents water loss)
forensic entomology—the study of insects in legal situations
Forensic Science II: Forensic Entomology, Chapter 12
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5. Introduction—Vocabulary
invertebrate - organism lacking a backbone
larva (larvae, pl) - immature, feeding stage of insects that undergo complete metamorphosis; the stage between the egg and pupa
maggot - legless larva
metamorphosis - the changes an organism undergoes as it develops into an adult
pupa (pupae, pl) - nonfeeding and relatively inactive developmental stage of some insects
Forensic Science II: Forensic Entomology, Chapter 12
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6. Bugs Don’t Lie July 9, 1997 Champaign County, Ohio
Stepfather, Kevin Neal, claims stepchildren are missing from their back yard
Bodies discovered on September 6th were in the late stages of decomposition
Autopsies revealed
Maggot infestation
Absence of blowflies and screwworms
Presence of cheese skipper fly in its 3rd instar stage
How were these insects evaluated?
Forensic Science II: Forensic Entomology, Chapter 12
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7. Introduction (Obj 12.1, 12.2) Arthropod—an invertebrate
Forensic Science II: Forensic Entomology, Chapter 12
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8. History Forensic Science II: Forensic Entomology, Chapter 12
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9. Insects & Forensics (Obj 12.2)
Forensic Science II: Forensic Entomology, Chapter 12
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10. Insects 29 orders, or related groups, of insects
2 orders are important to forensics
Flies (Diptera)
Beetles (Coleoptera)
Forensic Science II: Forensic Entomology, Chapter 12
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11. Insects at Work (Obj 12.3, 12.5)
Metamorphosis—the maturation process for insects)
Eggs
Larvae
Pupa
Adult
Forensic Science II: Forensic Entomology, Chapter 12
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12. Postmortem Interval (Obj 12.4, 12.6)
Postmortem Interval—the time elapsed since a person died
When longer than 72 hours after death, entomology becomes important
Within 48 hours the female blowfly lays eggs in moist areas of the body
Forensic Science II: Forensic Entomology, Chapter 12
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13. Collecting & Preserving Evidence (Obj 12.6, 12.7, 12.8)
Observe and record all pertinent factors
Weather patterns (rainfall, wind, humidity, temperature, and exposure to light) during the PMI
Avoid disturbing insects within several feet of the body
Measure distance from body to insects
Collect samples of all insect stages on, near, and under the body
Forensic Science II: Forensic Entomology, Chapter 12
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14. Collecting & Preserving Evidence (Obj 12.6, 12.7, 12.8)
1. Estimates on the types and number of insects
2. Key insect colonizations on and near the body
3. Exact positioning of the body using fixed points, if possible: placement of the arms and legs, the position of the head, and parts of the body in the shade and in the sunlight
4. Locations of eggs, larvae, and pupae on the body
Forensic Science II: Forensic Entomology, Chapter 12
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15. Collecting & Preserving Evidence (Obj 12.6, 12.7, 12.8)
5. List of opportunistic feeders and other insects (such rove beetles, ants, wasps, and insect parasites)
6. Insect movements (within 20 feet of the body)
7. Natural and artificial influences that might affect the speed of decomposition, such as burning, covering, or burying the body
Forensic Science II: Forensic Entomology, Chapter 12
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16. Collecting & Preserving Evidence
Forensic Science II: Forensic Entomology, Chapter 12
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17. Factors Affecting Insect Activity
Natural environment and natural light
Natural environment and artificial light
Artificial environment and natural light
Artificial environment and artificial light
Forensic Science II: Forensic Entomology, Chapter 12
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18. Temperature Readings Ambient air Ground Soil
1 foot above the body
4 feet above the body
Ground Soil
Surface
10 centimeters below
20 centimeters below
Center of a large infestation (if present)
Forensic Science II: Forensic Entomology, Chapter 12
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19. More on Collecting and Preserving
Capturing live flies with nets
Pin flies to a board, or
Preserve with 80% alcohol and 20% water
Adult flies
Eggs
Largest larvae
Forensic Science II: Forensic Entomology, Chapter 12
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20. More on Collecting and Preserving
Label vials with
case number
collection time
date
geographic location
the location of the insects on the victim
the initials of the investigator
Forensic Science II: Forensic Entomology, Chapter 12
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21. Chapter Summary
Forensic entomology is the analysis of insect evidence in legal cases.
Insects belong to the phylum Arthropoda, a group of organisms with jointed appendages, segmented bodies, and an exoskeleton.
The first documented use of insects to solve a homicide case was in China in AD 1235
Since, scientists have added to the knowledge of insect behavior and life cycle.
Forensic Science II: Forensic Entomology, Chapter 12
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22. Chapter Summary
Insect evidence is valuable in estimating the postmortem interval.
There are more than 700,000 known species of insects, but only a few have forensic value.
Female blowflies are usually the first insects to colonize a dead body.
The extent of decomposition—especially if it is unevenly distributed on the body—provides information for estimating the time (and perhaps manner) of death.
Forensic Science II: Forensic Entomology, Chapter 12
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23. Chapter Summary
Entomologists record and analyze climate and weather information related to the insect samples.
Temperature, humidity, and other weather and climate elements affect the insects that colonize remains as well as the progression of the insect life cycle.
Processing and preserving insect evidence requires special care, techniques, and materials.
Forensic Science II: Forensic Entomology, Chapter 12
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