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Chapter 12 Forensic Entomology © 2012 Cengage Learning. All Rights Reserved.

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Presentation on theme: "Chapter 12 Forensic Entomology © 2012 Cengage Learning. All Rights Reserved."— Presentation transcript:

1 Chapter 12 Forensic Entomology © 2012 Cengage Learning. All Rights Reserved

2 2 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Introduction—Objectives 1. Define forensic entomology. 2. Describe the anatomy of an arthropod. 3. Discuss the life cycle of insects. 4. Estimate time of death using insect evidence. 5. Examine the effects of insects on human remains.

3 3 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Introduction—Objectives 6. Evaluate the use of entomological evidence to solve crimes. 7. Describe the impact of weather on metamorphosis. 8. Demonstrate proper procedures for collection and preservation of entomological evidence.

4 4 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Introduction—Vocabulary o Arthropod—a phylum of animals with jointed appendages and an exoskeleton (from the Greek arthros–jointed; podes–feet) o chitin—a tough polysaccharide; the major component of an arthropod’s exoskeleton o exoskeleton—a rigid external structure made of chitin and protein (protects, provides a point of attachment for muscles; prevents water loss) o forensic entomology—the study of insects in legal situations

5 5 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Introduction—Vocabulary o invertebrate - organism lacking a backbone o larva (larvae, pl) - immature, feeding stage of insects that undergo complete metamorphosis; the stage between the egg and pupa o maggot - legless larva o metamorphosis - the changes an organism undergoes as it develops into an adult o pupa (pupae, pl) - nonfeeding and relatively inactive developmental stage of some insects

6 6 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Bugs Don’t Lie o July 9, 1997 Champaign County, Ohio o Stepfather, Kevin Neal, claims stepchildren are missing from their back yard o Bodies discovered on September 6th were in the late stages of decomposition o Autopsies revealed Maggot infestation Absence of blowflies and screwworms Presence of cheese skipper fly in its 3rd instar stage o How were these insects evaluated?

7 7 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Introduction (Obj 12.1, 12.2) o Arthropod—an invertebrate

8 8 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved History

9 9 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Insects & Forensics (Obj 12.2)

10 10 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Insects o 29 orders, or related groups, of insects o 2 orders are important to forensics Flies (Diptera) Beetles (Coleoptera)

11 11 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Insects at Work (Obj 12.3, 12.5) o Metamorphosis—the maturation process for insects) Eggs Larvae Pupa Adult

12 12 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Postmortem Interval (Obj 12.4, 12.6) o Postmortem Interval—the time elapsed since a person died o When longer than 72 hours after death, entomology becomes important o Within 48 hours the female blowfly lays eggs in moist areas of the body

13 13 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Collecting & Preserving Evidence (Obj 12.6, 12.7, 12.8) o Observe and record all pertinent factors Weather patterns (rainfall, wind, humidity, temperature, and exposure to light) during the PMI o Avoid disturbing insects within several feet of the body o Measure distance from body to insects o Collect samples of all insect stages on, near, and under the body

14 14 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved 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

15 15 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved 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

16 16 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Collecting & Preserving Evidence

17 17 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Factors Affecting Insect Activity o Natural environment and natural light o Natural environment and artificial light o Artificial environment and natural light o Artificial environment and artificial light

18 18 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Temperature Readings o Ambient air 1 foot above the body 4 feet above the body o Ground Soil Surface 10 centimeters below 20 centimeters below o Center of a large infestation (if present)

19 19 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved More on Collecting and Preserving o Capturing live flies with nets o Pin flies to a board, or o Preserve with 80% alcohol and 20% water Adult flies Eggs Largest larvae

20 20 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved More on Collecting and Preserving o Label vials with case number collection time date geographic location the location of the insects on the victim the initials of the investigator

21 21 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Chapter Summary o Forensic entomology is the analysis of insect evidence in legal cases. o Insects belong to the phylum Arthropoda, a group of organisms with jointed appendages, segmented bodies, and an exoskeleton. o The first documented use of insects to solve a homicide case was in China in AD 1235 o Since, scientists have added to the knowledge of insect behavior and life cycle.

22 22 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Chapter Summary o Insect evidence is valuable in estimating the postmortem interval. o There are more than 700,000 known species of insects, but only a few have forensic value. o Female blowflies are usually the first insects to colonize a dead body. o The extent of decomposition—especially if it is unevenly distributed on the body—provides information for estimating the time (and perhaps manner) of death.

23 23 Forensic Science II: Forensic Entomology, Chapter 12 © 2012 Cengage Learning. All Rights Reserved Chapter Summary o Entomologists record and analyze climate and weather information related to the insect samples. o Temperature, humidity, and other weather and climate elements affect the insects that colonize remains as well as the progression of the insect life cycle. o Processing and preserving insect evidence requires special care, techniques, and materials.


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