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Maggot Wash

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Forensically, the focus is usually on the days-years time ... (class) Arachnida (spiders, scorpions) (class) Chilopoda (centipedes) (class) Insecta (insects) ... – PowerPoint PPT presentation

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Title: Maggot Wash


1

Forensic Taphonomy
and
Forensic Entomology
Jason Linville University of Alabama at Birmingham
2
Taphonomy
  • Definition
  • The study of the conditions and processes by
    which organisms become fossilized.
  • Forensically, the focus is usually on the
    days-years time frame rather than processes that
    occur over thousands of years.

3
Taphonomy
  • Reconstruct the circumstances of death

Estimate the time of death
4
Taphonomy
  • Forensic Anthropology

Usually deal with skeletonized (older) bodies.
Approximately 6 months for surface burial.
Can interpret
  • General weathering of the bone
  • Damage by carnivore scavengers
  • Trace elements (vegetation, gunshot residue)

5
Taphonomy
  • Forensic Anthropology

Any time since death estimation is just an
estimation. It can be very difficult when
dealing with skeletonized remains.
6

Forensic Entomology
Jason Linville University of Alabama at Birmingham
7
Todays Seminar
  • Forensic Entomology Background

Estimating the Postmortem Interval (PMI)
DNA Analysis of Maggot Crop Contents
8
Forensic Entomology Background
  • Definition
  • Study of insects and their arthropod counterparts
    that interact with legal matters.

Urban Entomology
Stored Product Entomology
Medicolegal Entomology
9
Forensic Entomology Background
  • Definition
  • Study of insects and their arthropod counterparts
    that interact with legal matters.

Urban Entomology Stored Product
Entomology Medicocriminal Entomology
10
Forensic Entomology Background
  • Definition
  • Study of insects and their arthropod counterparts
    that interact with legal matters.

Urban Entomology Stored Product
Entomology Forensic Medical Entomology
11
Forensic Entomology
  • Insects and other arthropods can be used to
    answer

How or where a death occurred?
When did death occur?
  • Postmortem interval (PMI) Time between death and
    discovery of a corpse

12
Forensic Entomology
  • History
  • China - 13th century - sickle
  • Bergeret - 1859 - dead baby
  • Megnin - 1890 - fathered forensic entomology
  • Hall - 1948 - blowflies
  • Greenberg, Nuortova, Marchenko - 70s, 80s

13
Flies and Beetles
  • Definition
  • Study of insects and their arthropod counterparts
    that interact with legal matters.

What is an arthropod? What is an insect?
14
Flies and Beetles
  • Arthropoda (phylum)

(class) Arachnida (spiders, scorpions) (class)
Chilopoda (centipedes) (class) Insecta (insects)
(order) Hymenoptera (ants, bees, wasps) (order)
Blattaria (cockroaches) (order) Diptera
(flies) (order) Coleoptera (beetles)
15
Flies and Beetles
  • Arthropoda (phylum)

(class) Arachnida (spiders, scorpions) (class)
Chilopoda (centipedes) (class) Insecta (insects)
(order) Hymenoptera (ants, bees, wasps) (order)
Blattaria (cockroaches) (order) Diptera
(flies) (order) Coleoptera (beetles)
16
Flies
Some (not all) flies are attracted to dead bodies.
  • Carrion Flies

Calliphoridae (blow flies) Sarcophagidae (flesh
flies) Muscidae (house flies) Phoridae
17
Flies
  • Phoridae
  • Scuttle flies or coffin flies
  • Take advantage of physical barriers larger flies
    cant get to body

18
Flies
  • Calliphoridae (blow flies)
  • Shiny color (bluebottle, greenbottle)
  • Among the first flies to arrive at a corpse

19
Flies
  • Sarcophagidae (flesh flies)
  • Large, gray flies
  • Also among the first flies to arrive at a corpse

20
Beetles
21
Beetles
  • Coleoptera (beetles)
  • Arrive early or late in decomposition process,
    depending on species

22
Flies and Beetles
  • 1. Eggs

2. Larvae
3. Pupae
4. Adult
23
Estimating the Postmortem Interval
24
Estimating the PMI
  • Collection of Insect Samples
  • At the Crime Scene
  • At Autopsy

25
Maggot Mass
26
Cellar floor in an isolated Italian farm house
27
Estimating the PMI
  • Collect Insect Samples

Kill Stops growth (keep some alive for ID).
Preserve Keeps identifiable features intact
Ethanol or Kahles solution
Collect Climatological Data
Environment affects growth rate.
28
Estimating the PMI
  • Once evidence is received, specimens are
    identified to the level of species.

29
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30
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31
Estimating the PMI
  • Identification of the specimen

Question Why is this important?
Answer Different species grow at different
rates
32
Estimating the PMI
Timeline
Egg
Larvae
Pupa
Adult
Sarcophagid bullata
50 hours
110 hours
Sarcophagid cooleyi
40 hours
90 hours
33
Estimating the PMI
Timeline
Egg
Larvae
Pupa
Adult
Sarcophagid bullata
50 hours
110 hours
Sarcophagid cooleyi
40 hours
90 hours
34
Estimating the PMI
  • Identification of the specimen

Sarcophagid bullata
Sarcophagid cooleyi
35
Estimating the PMI
  • Identification of the specimen
  • Morphological means
  • color, hairs and bristles, wing structure
  • male genitalia
  • DNA identification
  • mitochondrial sequence of COI

36
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37
Estimating the PMI
  • After evidence is identified, there are two
    methods for estimating the PMI
  • Succession of insect fauna
  • Estimating age of immature insects

38
Succession of Insect Fauna
The corpse provides an attractive environment for
insects to feed, mate and deposit eggs.
  • The corpse passes through relatively predictable
    stages of decomposition.
  • Different species of insects will be attracted to
    the corpse at different times.

39
Flies
Flies arrive early in the decomposition process.
  • Calliphoridae
  • (blow flies)

Sarcophagidae (flesh flies)
40
Beetles
  • Coleoptera (beetles)
  • Arrive early or late in decomposition process,
    depending on species

41
Succession Data
42
Succession of Insect Fauna
Conditions affecting succession
  • Temperature (hotter faster)
  • Geographic Region (variable insect fauna)
  • Other factors wrapped, buried, indoors

43
Age of Immature Insects
  • Since eggs are rarely deposited on a corpse
    before death...

The age of immature insect specimens is the
absolute minimum amount of time a person has been
dead.
For example A three-day-old maggot on a corpse
would indicate the body has been dead for at
least three days.
44
Complete Metamorphosis
45
Complete Metamorphosis
  • 1. Eggs
  • 2. Larvae
  • 3 stages (instars)
  • Stop feeding during 3rd instar

3. Pupae
4. Adult
46
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47
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48
Growth Data
49
Larval Growth Data
50
Age of Immature Insects
Conditions affecting growth rate
  • Temperature (hotter faster)
  • Other factors drug use, day length

51
Sample Investigation
52
Sample Investigation
  • Details of the Case
  • Dead body discovered at the crime scene (900am)
  • Maggots are found on the body
  • Some maggots are collected and preserved, some
    are collected alive
  • No irregular circumstances
  • Main suspect claims to have seen the victim alive
    two nights earlier

53
Sample Investigation
16 maggots
Additional maggots for identification
54
Sample Investigation
55
Sample Investigation
56
Sample Investigation
57
Sample Investigation
58
Sample Investigation
Identifying the sample
Sarcophagid bullata
59
Sample Investigation
Measuring the size of maggots
1.4
1.5
1.4
1.8
1.8
1.6
1.6
1.7
1.7
1.7
1.8
1.6
1.8
1.6
1.6
1.5
(cm)
Largest size
1.8 cm
60
Sample Investigation
Length
3rd instar
2nd instar
1st instar
Time
Development Rate for Sarcophagid bullata larvae
at 25 C
61
Sample Investigation
Length
1.8 cm
34 hours
Time
Development Rate for Sarcophagid bullata larvae
at 26.7 C
62
Sample Investigation
  • Climatic Information
  • Day body is discovered - average temperature
    20C
  • 1 day earlier - average temperature 21C
  • 2 days earlier - average temperature 20C
  • No other irregular factors

63
Sample Investigation
Sarcophagid bullata
Largest size
1.8 cm
At 26.7 C it would take 34 hours to reach a size
of 1.8 cm
Accumulated degree hours 26.7 x 34 907.8 ADH
64
Sample Investigation
Accumulated degree hours 26.7 x 34 907.8 ADH
  • Day 1 1200am - 900am
  • 9 hours at 20 C
  • 9h x 20 C 180 ADH
  • Day 2 1200am - 1200am
  • 24 hours at 21 C
  • 24h x 21C 504 ADH
  • Day 3 ?
  • 907.8 - (504 180) 223.8 ADH
  • ? h x 20 C 223.8

65
Sample Investigation
  • Day 3 ?
  • 907.8 - (504 180) 223.8 ADH
  • ? h x 20 C 223.8 ADH

223.8 ADH / 20C 11.2 hours
11.2 hours
9 hours
24 hours
66
Sample Investigation
11.2 hours
9 hours
24 hours
44.2 hours at actual temperatures
34 hours at 26.7 C
Victim murdered before 100pm two days before
discovery
67
Sample Investigation
  • Suspect confesses to crime
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