Forensic Entomology Part I

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Forensic Entomology (Part I)
Jason Linville University of Alabama at
Birmingham jglinvil_at_uab.edu
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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.
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Forensic Taphonomy

• Reconstruct the circumstances of death

• Estimate the time of death

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Forensic Entomology
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Forensic Entomology

• Forensic Entomology Background

• Estimating the Postmortem Interval (PMI)

• DNA Analysis of Maggot Crop Contents

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Forensic Entomology

• Forensic Entomology

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

• Forensic Entomology

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

• Forensic Entomology

Study of insects and their arthropod counterparts
that interact with legal matters.
Urban Entomology
Stored Product Entomology
Forensic Medical Entomology
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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.
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Forensic Entomology

• History

• China 13th century. sickle
• Bergeret 1859. dead baby
• Megnin 1890. fathered forensic entomology
• Hall 1948. blowflies
• Greenberg, Nuortowa, Marchenko 70s, 80s

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Forensic Entomology
Forensic Entomology
Study of insects and their arthropod counterparts
that interact with legal matters.
What is an arthropod?
What is an insect?
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Forensic Entomology
Arthropoda (phylum)
class - Arachnida (spiders, scorpions) class -
Chilopoda (centipedes) class Insecta (insects)
order Hymenoptera (ants, bees, wasps) order
Blattaria (cockroaches) order Diptera
(flies) order Coloeoptera (beetles)
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Forensic Entomology
Arthropoda (phylum)
class - Arachnida (spiders, scorpions) class -
Chilopoda (centipedes) class Insecta (insects)
order Hymenoptera (ants, bees, wasps) order
Blattaria (cockroaches) order Diptera
(flies) order Coloeoptera (beetles)
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Forensic Entomology
Flies
Some flies are attracted to dead bodies.
Carrion Flies

• Calliphoridae (blow flies)
• Sarcophagidae (flesh flies)
• Muscidae (house flies)
• Phoridae

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Forensic Entomology
Flies
Some flies are attracted to dead bodies.
Carrion Flies

• Calliphoridae (blow flies)
• Sarcophagidae (flesh flies)
• Muscidae (house flies)
• Phoridae

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Forensic Entomology
Phoridae

• Scuttle flies or coffin flies

• Take advantage of physical barriers larger flies
  cant get to body

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Forensic Entomology gt Flies
Calliphoridae (blow flies)

• Shiny color (bluebottle, greenbottle)

• Among the first to arrive at a corpse

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Forensic Entomology gt Flies
Sarcophagidae (flesh flies)

• Large, gray flies

• Also among the first flies to arrive

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Forensic Entomology gt Beetles
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Forensic Entomology gt Beetles
Coleoptera (beetles)
Arrive early or late in decomposition process,
depending on species
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Forensic Entomology gt Flies and Beetles
Complete Metamorphosis

• Eggs
• Larvae
• Pupae
• Adult

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Estimating the PMI
Once insects are collected (both adults and
immature), they are used to estimate the
postmortem interval (PMI).
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Estimating the PMI
Collection of Insect Samples

• Can be collected at the crime scene
• Can be collected during autopsy

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Estimating the PMI gt Collection

• For each maggot mass

Kill ½ of the maggots collected

• Stops growth for age estimation
• Preserve in ethonal or Kahles solution
• Preservation prevents bacterial degradation

Collect Climatological Data

• Environment affects growth rate
• Collect temperature, humidity, etc.

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Estimating the PMI gt Collection

• For each maggot mass

Keep ½ of the maggots alive

• The species of maggots can not be identified
  (maggots look the same)
• If maggots are raised to adults, the flies can be
  identified to the species level.

Chrysomya megacephala
?
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Estimating the PMI
Analysis of Insects
Once evidence is received, the first step is to
identify the species of samples.
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Estimating the PMI gt Species Identification

• Identification of Insects

Question
Why is species identification important?
Answer
Different species grow at different rates
7-mm maggot may be anywhere from 3 days old to 10
days old, depending on species
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Estimating the PMI gt Species Identification
Timeline
Egg
Larvae
Pupa
Adult
Sarcophagid bullata
50 hours
110 hours
Sarcophagid cooleyi
40 hours
90 hours
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Estimating the PMI gt Species Identification

• Identification of the specimen

Morphology

• Color, hairs and bristles, wing structure
• Male genitalia

DNA identification

• Mitochondrial sequence of the gene region
  cytochrome oxidase I

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Estimating the PMI gt Species Identification
Online genomic database can be searched.
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Estimating the PMI gt Analysis

• After evidence is collected and identified, there
  are two methods for estimating the PMI

• Succession of insect fauna

• Estimating the age of immature insects

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Estimating the PMI gt Analysis gt Succession

• Facts

• 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.

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Estimating the PMI gt Analysis gt Succession

• Most flies arrive early in the decomposition
  process.

Calliphoridae (blow flies)
Sarcophagidae (flesh flies)
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Estimating the PMI gt Analysis gt Succession

• Beetles can arrive early or late in the
  decomposition process (species dependant).

Coleoptera (beetles)
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Estimating the PMI gt Analysis gt Succession
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Estimating the PMI gt Analysis gt Succession

• Conditions affecting succession

• Temperature (hotter faster)
• Geographic region (variable insect fauna)
• Other factors wrapped body, buried, indoors, etc.

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Estimating the PMI gt Analysis gt 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.
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Estimating the PMI gt Analysis gt Age of Immature
Insects

• Remember, flies and beetles undergo complete
  metamorphosis
• Immature specimens egg, maggot, pupa

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Estimating the PMI gt Analysis gt Age of Immature
Insects

• Eggs
• Larvae
• Pupae
• Adult

The first step in age identification is to
identify what stage the insect is in.
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Estimating the PMI gt Analysis gt Age of Immature
Insects
If the samples are maggots, the molting stage can
be identified.

• Larvae

• Larvae grow in three stages called instars.
• During the 3rd instar, maggots will stop feeding,
  leave corpse, and pupate.

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Estimating the PMI gt Analysis gt Age of Immature
Insects

• Instar can be determined by looking at spiracles.

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Estimating the PMI gt Analysis gt Age of Immature
Insects

• 3 footballs 3rd instar
• 2 footballs 2nd instar
• Glob 1st instar

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Estimating the PMI gt Analysis gt Age of Immature
Insects

• PMI estimation can be made based on the stage of
  the immature specimen.
• Species and temperature must be known.

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Estimating the PMI gt Analysis gt Age of Immature
Insects

• PMI estimation can be made based on maggots size
  or development in pupa.
• Species and temperature must be known.

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Estimating the PMI gt Analysis gt Age of Immature
Insects
Conditions affecting growth rate

• Temperature (hotter faster)
• Other factors drug use, day length

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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 temp recorded
• Main suspect claims to have seen the victim alive
  2 nights earlier.

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Sample Investigation
Evidence

• 16 maggots preserved

Additional maggots kept alive for identification
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Sample Investigation
Identifying the Sample
Cochliomya macellaria
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Sample Investigation
Measuring the maggots

• 14 15 14 14 15 14 15 13 13 15 15 14 15 13
  15 14 (mm)

Largest size 15 mm Average 14.3 mm
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Sample Investigation
Maggot length (mm)
Age of maggot (hours)
Development rate for Cochliomya macellaria at 18,
22, and 26C.
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Sample Investigation
Maggot length (mm)
Age of maggot (hours)
If average temperature was 22C, and we use the
measurement of 15mm, then
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Sample Investigation
Maggot length (mm)
Age of maggot (hours)
Maggots are about 96 hours old.
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Maggot Crop Analysis
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Maggot as a Source of Human DNA
CROP
Mouth
Posterior

• Maggots store food in their crops as they feed.
• During later stages of larval development, the
  contents of the crop is emptied into the gut

For example
In Calliphora vicina at room temperature, the
crop is full after 3 days and is emptied by 7
days (approximate)
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Forensic DNA Analysis (review)
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Forensic DNA Review

• DNA is found in the cells in our body.

Nucleus (Brain of the cell)
Mitochondria (more later)
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Maggot Crop Analysis

• Identification of maggot crop contents would be
  helpful in three situations

• Corpse is removed from suspected crime scene

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Maggot Crop Analysis gt Corpse Removed

• A murder victim remains undiscovered.
• Flies discover the corpse and lay eggs.

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Maggot Crop Analysis gt Corpse Removed

• A murder victim remains undiscovered.
• Flies discover the corpse and lay eggs.

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Maggot Crop Analysis gt Corpse Removed

• Maggots hatch and feed on the corpse.

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Maggot Crop Analysis gt Corpse Removed

• Murder victim is removed from crime scene.
• The maggots remain.

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Maggot Crop Analysis gt Corpse Removed
Crop will contain Human tissue
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Maggot Crop Analysis

• Identification of maggot crop contents would be
  helpful in three situations

• There is a question as to the origin of a maggot
  used in a PMI estimation

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Maggot Crop Analysis gt Maggots from Other Source
A turkey is thrown into a dumpster.
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Maggot Crop Analysis gt Maggots from Other Source
A turkey is thrown into a dumpster.
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Maggot Crop Analysis gt Maggots from Other Source
Three days later, maggots have developed on the
turkey.
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Maggot Crop Analysis gt Maggots from Other Source
Also three days later, a dead body is thrown into
the dumpster.
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Maggot Crop Analysis gt Maggots from Other Source
The maggots migrate from the turkey to the human
body.
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Maggot Crop Analysis gt Maggots from Other Source
The maggots migrate from the turkey to the human
body.
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Maggot Crop Analysis gt Maggots from Other Source
Crop will contain Turkey tissue or a mixture of
Turkey/Human tissue
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Maggot Crop Analysis

• Identification of maggot crop contents would be
  helpful in three situations

• There may be a chain of evidence dispute.

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Maggot Crop Analysis gt Chain of Evidence Dispute
Here you go!
Thank you!
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Maggot Crop Analysis gt Chain of Evidence Dispute
2 days later...
Theyre 5 days old!
These arent the maggots I gave you.
Are too!
Are not!
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Maggot Crop Analysis
Poor quality of samples usually prevents analysis.
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Maggot Crop Analysis
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Maggot Dissection
Maggot before dissection
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Maggot Dissection
Cut off posterior segments
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Maggot Dissection
Ventral incision of the cuticle
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Maggot Dissection
Peel back cuticle to reveal crop
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Maggot Dissection
Remove crop