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

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
© 2012 Cengage Learning. All Rights Reserved

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
© 2012 Cengage Learning. All Rights Reserved

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
© 2012 Cengage Learning. All Rights Reserved

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
© 2012 Cengage Learning. All Rights Reserved

6. 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
© 2012 Cengage Learning. All Rights Reserved

7. 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
© 2012 Cengage Learning. All Rights Reserved

8. 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
© 2012 Cengage Learning. All Rights Reserved

9. 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
© 2012 Cengage Learning. All Rights Reserved

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

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

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

13. 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
© 2012 Cengage Learning. All Rights Reserved

14. 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
© 2012 Cengage Learning. All Rights Reserved

15. 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
© 2012 Cengage Learning. All Rights Reserved

16. 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
© 2012 Cengage Learning. All Rights Reserved

17. 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
© 2012 Cengage Learning. All Rights Reserved

18. 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
© 2012 Cengage Learning. All Rights Reserved

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

20. 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
© 2012 Cengage Learning. All Rights Reserved

21. 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
© 2012 Cengage Learning. All Rights Reserved

22. 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
© 2012 Cengage Learning. All Rights Reserved

23. 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
© 2012 Cengage Learning. All Rights Reserved

24. Accuracy
Insects begin colonizing at a dead body immediately after death
Dependent on season and environment
Rate of development of the species can be used to estimate time since death
Can give an estimate up to a year

25. Accuracy
Entomological evidence is the most accurate and frequently the only method available to determine the elapsed time since death
Due to rigor, algor, and livor mortis being useless after 72 hours

26. Accuracy Insects are also used to
Determine whether the body has been moved after death
Determine whether it has been disturbed
Determine the presence or position of wound sites
Determine whether the victim used drugs or was poisoned
Determine the length of time of neglect or abuse in living victims

27. Insect Biology
Insects are the most diverse and abundant forms of life on earth.
There are over a million described species- more than 2/3 of all known organisms
There is more total biomass of insects than of humans.
Insects undergo either incomplete or complete metamorphosis (Egg to larva to pupa to insect)
Larva have a soft tubular body and look like worms. Fly species larvae are “maggots”

28. Image: http://www.nlm.nih.gov/visibleproofs

29. Decomposition Begins at the moment of death, caused by two factors
Autolysis
The breaking down of tissues by the body's own internal chemicals and enzymes
Putrefaction
The breakdown of tissues by bacteria
These processes release gases that are the chief source of the characteristic odor of dead bodies
These gases swell the body

30. Decomposition Scavengers play an important role in decomposition
Insects and other animals are typically the next agent of decomposition, if the body is accessible to them
The most important insects that are typically involved in the process include the fleshflies (Sarcophagidae) and blowflies (Calliphoridae)
The green-bottle fly seen in the summer is a blowfly
Larger scavengers, including coyotes, dogs, wolves, foxes, rats, and mice may eat a body if it is accessible to them
Some of these animals also remove and scatter bones.

31. Factors Involved in Decomposition
In a roughly descending degree of importance, those factors include:
Temperature
The availability of oxygen
Prior embalming
Cause of death
Access by insects
Burial, and depth of burial
Access by scavengers
Trauma, including wounds and crushing blows
Humidity, or dryness
Rainfall
Body size and weight
Clothing
The surface on which the body rests

32. Differentiate between PMI and Time of Death
These may not always equate.
Post mortem interval is restricted to the time that the corpse or body has been exposed to an environment which would allow insect activity to begin.
Closed windows
Body in box or bag
Cold temperatures
Deeper burial

33. Major Groups of Insects Associated with Cadavers
Flies
Blowflies
Flesh Flies
House Flies
Cheese Skippers
Beetles
Carrion Beetles
Dermestids
Scarab Beetles

34. Blow Fly Metamorphosis
Adult
Pupa
Eggs
3rd Instar Larva
1st Instar Larva
2nd Instar Larva
It takes approximately days from egg to adult depending on the temperatures and humidity levels at the location of the body.
Image:
Information: and

37. Succession
Fresh
Bloated 1 2 3
Post-Decay
Dry
Decay 4 5 6

38. Five Stages of Decomposition Fueled by Insect Activity.
A. Fresh Stage
B. Bloated Stage
C. Decay Stage
D. Post-decay Stage
E. Dry Stage

39. Fresh Stage (Days 1-2) Blowflies have detected the cadaver
Eggs are being laid, often around the eye, nostrils, mouth, followed by anus or genital openings
Eggs

40. Stage 1 of Decay

41. Bloated Stage (Day 2-6) Cadaver begins to swell and putrefy
Flesh flies appear
Small maggots are feeding
Putrefaction begins. Gasses produced by anaerobic bacteria inflate the abdomen.
Pig’s eye

44. Stage 2: Bloat Stage

45. Decay Stage (Days 5-11) Adult blowflies no longer attracted.
Large masses of maggots feeding externally and internally
Predators and parasitoids of maggots arrive
Abdominal wall breaks allowing gasses to escape. Carcass deflates.

46. Stage 3: Active Decay

47. Post-Decay Stage (Days 10-25)
Cadaver is drying out. Large maggots are leaving or have left
In dry habitats, remains are skin, cartilage, and bones.
In wet habitats, wet, viscous material in the soil under the remains.

48. Dry Stage Skin and bones
Insects with the ability to digest keratin (clothes moths and dermestid beetles).

49. Stage 4:Dry Decay

50. Stages of Decay Video

51. Decay Rates Are Variable
Studies of decay rates of 150 human corpses at in the Anthropological Facility in Tennessee (The Body Farm)
Most important environment factors in corpse decay:
Temperature
Access by insects
Depth of burial
Other Factors
Chemical-- embalming agent, insecticides, lime, etc.
Animals disrupting the corpse

52. Determining Whether the Body has been Moved
Insects present on the deceased body that are not prevalent to the crime scene can indicate that the victim was murdered elsewhere and was dumped at another location

53. Drugs
Insects that feed on the body of individuals that have been poisoned can be examined to determine what type of drug or toxin the person was poisoned with
It is important to note that specific drugs either speed up or slow down larval development
Can influence entomologist’s final report

54. Challenges to Forensic Entomology
3 challenges exist
Temperature
Temperature of crime scene and the temperature that the insects have been exposed to us unknown
Season
Entomology is valuable only in spring, summer, and fall
Exclusion of insects
Insects are excluded based on condition of body

56. The End

57. Let’s give it a try …
Click the image above or click here to visit the website at