Forensic Entomology

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Forensic Entomology

• Chapter 9

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What is Forensic Entomology?

• Forensic Entomology is the use of the insects,
  and their arthropod relatives that inhabit
  decomposing remains to aid legal investigations. 
  
• The broad field of forensic entomology is
  commonly broken down into three general areas
  medicolegal, urban, and stored product pests. 
• The medicolegal section focuses on the criminal
  component of the legal system and deals with the
  necrophagous (or carrion) feeding insects that
  typically infest human remains.
• The urban aspect deals with the insects that
  affect man and his immediate environment.

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What is Forensic Entomology?

• This area has both criminal and civil components
  as urban pests may feed on both the living and
  the dead.
• The damage caused by their mandibles (or
  mouthparts) as they feed can produce markings and
  wounds on the skin that may be misinterpreted as
  prior abuse.
• Urban pests are of great economic importance and
  the forensic entomologist may become involved in
  civil proceedings over monetary damages.  
• Stored product insects are commonly found in
  foodstuffs and the forensic entomologist may
  serve as an expert witness during both criminal
  and civil proceedings involving food
  contamination.

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How diverse is forensic entomology?

• The diverse applications of forensic entomology
  include the detection of abuse in children and
  neglect of the elderly. 
• There have been many published cases that detail
  parents intentionally using wasps and bees to
  sting their children as a form of punishment. 
• Entomological evidence has been used to prove
  neglect and lack of proper care for wounds
  existing on the elderly under both private and
  institutional care.

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How diverse is forensic entomology?

• It is theorized that the stings (or mere
  presence) of bees and wasps may be responsible
  for a large number of single occupant car
  accidents that seem to lack a definitive cause.  
  
• Insects have been suspected of causing aircraft
  crashes through the obstruction of essential
  instrumentation, and even implicated in the
  obstruction of fuel lines causing engine
  failure. 
• Forensic entomologists are also requested to
  examine the fragmented remains of insects that
  have impacted and lodged on the front fascia,
  windshield, and radiator of automobiles. 
• Analysis of such remains can yield evidence to
  the probable path of an automobile through
  particular areas when pinpointing the location
  and areas of travel are of unique importance.

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How diverse is forensic entomology?

• Insects can also affect the interpretation of
  blood spatter pattern analysis.
• Roaches simply walking through pooled and
  splattered blood will produce tracking that may
  not be readily recognizable to the untrained
  observer.
• Specks of blood in unique and unusual areas (such
  as on ceilings) may mislead crime scene
  technicians unless they are aware of the
  appearance of blood contaminated roach tracks.
• Similarly, flies and fleas may also track through
  pooled and spattered blood.
• However, flies will also feed on the blood and
  then pass the partially digested blood in its
  feces, which are known as "flyspecks". 

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How diverse is forensic entomology?

• Flies will also regurgitate and possibly drop a
  blood droplet on a remote surface, which may
  serve to confuse bloodstain analysis. 
• Fleas feeding on the living pass a large amount
  of undigested blood (used as the larval food
  source) on many household surfaces. 
• If a crime occurs in a heavily infected
  apartment, fecal drops already present would
  serve to confuse analysts as those droplets would
  test positive for human blood. 
• Therefore it is important to recognize and
  properly document the natural artifacts that may
  occur from the presence, feeding, and defecation
  of roaches, flies, and fleas. 
• Insects that feed on living, decomposing, or
  dried vegetable material are submitted to the
  forensic entomologist in an effort to determine
  the country or point of origin.
• This is particularly important with vegetative
  material such as imported cannabis.

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Importance of Bugs

• Insects have existed on earth for about 250
  million years comparatively humans have existed
  for about 300,000 years. 
• Such an enormous amount of time has allowed
  insects to attain a wide diversity in both form
  and development. 
• There are currently about 700,000 described
  species and it is estimated that there may be
  more than 10 million species of insects yet to be
  described. 
• Some insects have evolved a gradual or
  "paurometabolous" development in which there is
  an egg that hatches into an immature or "nymph",
  which resembles the adult form, but is smaller
  and lacks wings. 

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Importance of Bugs

• Most forensically important insects undergo a
  complete or "holometabolous" development.
• There is an egg stage (except for a few insects
  such as the flesh flies that deposit living
  larvae) which hatches into a larval form and
  undergoes a stepwise or incremental growth. 
• This pattern is caused by the successive molts
  (shedding of the outer skin that has become too
  small) that the larva must undergo before it
  finally enters the inactive pupal stage. 
• The pupa is simply the hardened outer skin of the
  last larval stage and the adult will develop
  inside of this protective skin.

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Blowflies

• Blowflies often are an attractive blue-green,
  metallic color, leading to the common English
  names, blue-bottles and green-bottles - and the
  common Australian name, blue-arsed flies.
• They also come in a non-metallic, brown form, but
  all blowflies are usually relatively large flies.
  
• Blowflies can pick up faint traces of the odor of
  decay and can fly up to 10 miles from their
  birth-place in search of a suitable corpse in
  which to lay their eggs.

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Blowflies

• Female blowflies will often use their tongue-like
  mouthparts to feed on the protein secretions
  oozing from a corpse, prior to laying their eggs
  through their pointy ovipositor.
• Blowfly eggs are 2 mm long and are laid in clumps
  that resemble miniature rice balls.
• A single female can lay nearly 2,000 eggs during
  her life, and 5,645 eggs have been counted from a
  small piece of meat (150 g) after five hours
  exposure.
• The eggs hatch after between 12 hours and 2 days,
  depending on the temperature.

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Blowflies

• Blowfly maggots are of two forms smooth maggots,
  and 'hairy' maggots.
• The smooth maggots belong to pioneer flies that
  are purely corpse feeders.
• 'Hairy' maggots will often feed on corpses, but
  they are also active predators that feed on
  smooth maggots.
• Although they look hairy, the 'hairs' are really
  papillae (protrusions of the body), which deter
  other predators from consuming them. Because they
  are predators, the arrival of the secondary flies
  that produce hairy maggots is normally later that
  of the pioneer maggots.

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Blowflies

• Blowfly larvae feed using their mouth hooks and
  rapidly increase in size.
• They shed their skins (molt) two times during
  their development.
• Each stage of development is called an instar and
  the time it takes to develop between instars is
  fairly constant, although it is dependent upon
  temperature.
• The identification of larvae of a particular
  instar, combined with a knowledge of recent
  weather conditions, allows forensic entomologists
  to determine the time of death in murder
  investigations.

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Blowflies

• When the third-instar larva has finished growing,
  it leaves the corpse and burrows into the ground
  where it develops into a pupa.
• It takes around 14 days for the pupa to
  reorganize itself and emerge as an adult fly, but
  can take much longer in cold weather.

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Blowflies

• The pupae of blow flies are often overlooked, as
  they closely resemble rat droppings or the egg
  case of cockroaches. 
• The pupal stage is an extremely important stage
  to the forensic entomologist and a thorough
  search should be made for the presence of pupae
  at any death scene. 
• If the adult insect has not emerged, the pupa
  will appear featureless and rounded on both ends. 

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Blowflies

• If the adult insect has emerged, one end will
  appear as if it has been cut off, and the hollow
  interior will be revealed.   
• Most adult blow flies appear a metallic green or
  blue and are easily recognizable. 

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Screw Worms

• The adult secondary screwworm, Cochliomyia
  macellaria, emerging from the puparium. 
• This newly emerged adult will attain its typical
  bright green coloration and will be ready for
  flight in a few hours. 
• The empty case that it leaves behind will remain
  in the environment for extended periods of time. 
  
• Therefore, a careful search should always be
  conducted for the presence of the puparium. 
• Its presence is often useful in establishing the
  maximum postmortem interval estimation. 
• Since the puparium is composed of the outer skin
  of the larvae, many identifying characteristics
  are retained and a species identification may be
  obtained even though the adult fly is not
  recovered.   

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Blowflies
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1st Instar
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2nd Instar
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3rd instar
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Age based on Mouth Hooks
1st instar maggot
2nd instar maggot
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Mouth sphericales
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Maggots at Work
Maggots can consume 60 per cent of a corpse in
less than a week.
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Life Cycle

• Eggs
• present in clumps of up to 300
• laying to hatching takes 1 day
• Larva - 1st instar
• initially feeds on fluid exuded from the body
• migrates into body
• hatching to first molt takes 1 day
• Larva - 2nd instar
• moves around in maggot mass
• first molt to second molt takes 1 day

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Life Cycle

• Larva - 3rd instar
• still moves in mass
• greatly increases in size
• second molt to pre-pupa takes 2 days
• Pre-pupa
• migrates away from the corpse seeking a suitable
  pupation site, (usually in soil)
• does not feed
• transforms into pupa
• pre-pupa to pupa takes 4 days

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Life Cycle

• Pupa
• resides within puparium
• undergoes transformation from larval body form
  adult fly
• does not feed
• pupa to emergence takes 10 days
• Adult fly
• mates on emergence from pupa
• feeds on protein from body fluids
• lays eggs on corpse
• emergence to egg laying takes 2 days

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Beetles

• The beetles (order Coleoptera) are one of the
  largest groups of animals and they also undergo
  complete development. 
• Because of their development the larvae appear
  very different from the adult form. 
• Although the larvae or "maggots" of a large
  number of blow fly species may look almost
  identical the larvae of beetles may look very
  different from one species to the next. 
• Beetle larvae recovered from corpses can be
  easily differentiated from maggots as they have 3
  pairs of legs and the maggots found on
  decomposing remains will not have any legs. 

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Beetles

• Once a larva as been identified as that of a
  beetle, further field identification can be
  accomplished because of the wide diversity of
  larval forms. 
• The bodies of beetle larvae may range from almost
  white, robust, and hairless to dark brown,
  slender, and quite hairy. 
• Others may appear almost black and have armored
  plates on their back. 

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• The larvae shown here are from four different
  beetle families, and are representation of the
  body types that can be found in each of the
  respective families. 
• The families are (from left to right)
  Dermestidae, Staphylinidae, Silphidae,
  Scarabaeidae.  Larvae such as these are typically
  found later in the stages of insect succession,
  after the early arriving flies. 
• The Dermestids are commonly called skin beetles
  and their larvae are commonly used in museums to
  clean bones of their associated tissues. 
• Staphylinds (commonly called rove beetles) and
  Silphids (called carrion, sexton, or burying
  beetles) are both predaceous on maggots.  Their
  larvae are commonly found on carcasses in the
  late stages of decay.

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What information can a forensic entomologist
provide at the death scene?

• Forensic entomologists are most commonly called
  upon to determine the postmortem interval or
  "time since death" in homicide investigations. 
• The forensic entomologist can use a number of
  different techniques including species
  succession, larval weight, larval length, and a
  more technical method known as the accumulated
  degree hour technique which can be very precise
  if the necessary data is available. 
• A qualified forensic entomologist can also make
  inferences as to possible postmortem movement of
  a corpse.  Some flies prefer specific habitats
  such as a distinct preference for laying their
  eggs in an outdoor or indoor environment.  

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What information can a forensic entomologist
provide at the death scene?

• Flies can also exhibit preferences for carcasses
  in shade or sunlit conditions of the outdoor
  environment. 
• Therefore, a corpse that is recovered indoors
  with the eggs or larvae of flies that typically
  inhabit sunny outdoor locations would indicate
  that someone returned to the scene of the crime
  to move and attempt to conceal the body.

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What information can a forensic entomologist
provide at the death scene?

• Similarly, freezing or wrapping of the body may
  be indicated by an altered species succession of
  insects on the body. 
• Anything that may have prevented the insects from
  laying eggs in their normal time frame will alter
  both the sequence of species and their typical
  colonization time. 

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What information can a forensic entomologist
provide at the death scene?

• This alteration of the normal insect succession
  and fauna should be noticeable to the forensic
  entomologists if they are familiar with what
  would normally be recovered from a body in a
  particular environmental habitat or geographical
  location. 
• The complete absence of insects would suggest
  clues as to the sequence of postmortem events as
  the body was probably either frozen, sealed in a
  tightly closed container, or buried very deeply.

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What information can a forensic entomologist
provide at the death scene?

• Entomological evidence can also help determine
  the circumstances of abuse and rape.
• Victims that are incapacitated (bound, drugged,
  or otherwise helpless) often have associated
  fecal and urine soaked clothes or bed dressings. 
  
• Such material will attract certain species of
  flies that otherwise would not be recovered. 
• Their presence can yield many clues to both
  antemortem and postmortem circumstances of the
  crime. 

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What information can a forensic entomologist
provide at the death scene?

• Currently, it is now possible to use DNA
  technology not only to help determine insect
  species, but to recover and identify the blood
  meals taken by blood feeding insects. 
• The DNA of human blood can be recovered from the
  digestive tract of an insect that has fed on an
  individual. 
• The presence of their DNA within the insect can
  place suspects at a known location within a
  definable period of time and recovery of the
  victims' blood can also create a link between
  perpetrator and suspect.

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What information can a forensic entomologist
provide at the death scene?

• The insects recovered from decomposing human
  remains can be a valuable tool for toxicological
  analysis. 
• The voracious appetite of the insects on corpses
  can quickly skeletonize the remains. 
• In a short period of time the fluids (blood and
  urine) and soft tissues needed for toxicological
  analysis disappear. 
• However, it is possible to recover the insect
  larvae and run standard toxicological analyses on
  them as you would human tissue. 
• Toxicological analysis can be successful on
  insect larvae because their tissues assimilate
  drugs and toxins that accumulated in human tissue
  prior to death.

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Death Scene Procedures

• It is important to note that the collection of
  insects and other arthropods from a death scene
  may disturb the remains. 
• Therefore, the forensic entomologist (or the
  crime scene personnel charged with making the
  collection) should contact the primary
  investigator and make plans for the collection of
  entomological evidence. 
• Once a course of action as been determined,
  utmost care should be taken during insect
  collection so that the remains are disturbed as
  little as possible. 
• Before collections are made notes should be taken
  as to the general habitat, ambient weather
  conditions, and location of the body.  
• Observations should also be made to describe the
  microhabitat immediately surrounding the body.

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Scene observations and weather data

• Observations of the scene should note the general
  habitat and location of the body in reference to
  vegetation, sun or shade conditions, and its
  proximity to any open doors or windows if
  recovered within a structure. 
• Locations of insect infestations on the body
  should be documented as well as noting what
  stages of insects are observed (such as eggs,
  larvae, pupae, or adults). 
• It is also useful to document evidence of
  scavenging from vertebrate animals and predation
  of eggs and larvae by other insects such as fire
  ants. 

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Collection of climatological data at the scene.

•   Such data should include
• Ambient air temperature at the scene taken
  approximately at chest height with the
  thermometer in the shade.  DO NOT EXPOSE
  THERMOMETER TO DIRECT SUNLIGHT!
• Maggot mass temperature (obtained by placing the
  thermometer directly into the larval mass
  center).
• Ground surface temperature.
• Temperature at the interface of the body and
  ground (simply place the thermometer between the
  two surfaces).
• Temperature of the soil directly under the body
  (taken immediately after body removal).
• Weather data that includes the maximum and
  minimum daily temperature and rainfall for a
  period spanning 1-2 weeks before the victims
  disappearance to 3-5 days after the body was
  discovered.  Such information can be gathered by
  contacting the nearest national weather service
  office, or your state climatologist.

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Collection of insects from the body at the scene

• The first insects that should be collected are
  the adult flies and beetles. 
• These insects are fast moving and can leave the
  crime scene rapidly once disturbed. 
• The adult flies can be trapped with an insect net
  available from most biological supply houses. 
• They are inexpensive and readily obtainable. 
• Once the adult flies have been netted, the closed
  end of the net (with the insects inside) can be
  placed in the mouth of a "killing jar" (which is
  a glass container with cotton balls or plaster
  soaked with ethyl acetate, or common fingernail
  polish remover). 
• The jar is then capped and the insects will be
  immobilized within a few minutes.
• Once they are immobile they can be easily
  transferred to a vial of 75 ethyl alcohol. 
• Beetles can be collected with forceps or gloved
  fingers and placed directly into 75 ethyl
  alcohol.  

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Collection of insects from the body at the scene

• It is extremely important that the collected
  specimens are properly labeled. Labels should be
  made with a dark graphite pencil, NOT IN INK. 
  The label should be placed in the alcohol along
  with the specimens, and alcohol can dissolve the
  ink from the paper!   However, pencil is not
  affected by alcohol and should be used for
  labeling purposes.   The collection label should
  contain the following information
• 1). Geographical Location
• 2). Date and hour of collection
• 3). Case number
• 4). Location on the body where removed
• 5). Name of collector
• A duplicate label should be made and affixed
  to
• the exterior of the vial

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Collection of insects from the body at the scene

• Once the adults have been collected the
  collection of larval specimens from the body can
  begin. 
• First the investigator should search for the
  presence of eggs, which are easily overlooked. 
• After this step, the larvae should be readily
  apparent on the body. Generally speaking, the
  largest larvae should be actively searched for
  and collected.  
• Additionally, a representative sample of 50-60
  larvae should be collected from the maggot mass. 
  
• These insects can be placed directly into a
  killing solution or ethyl alcohol. 
• However, the specimens are better preserved if
  they are placed in boiling water for about 30
  seconds. 
• Obtaining boiling water at a scene is difficult,
  so boiling of the larvae upon returning to the
  proper facility is satisfactory.

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Collection of insects from the body at the scene

• If the larvae are boiled with about 48 hours of
  initial preservation, a good specimen should
  result.  
• It is important to note that some forensic
  entomologists prefer not to have the submitted
  larvae boiled. 
• Therefore, the investigator should discuss
  preservation techniques with their cooperating
  entomologist. 
• In any case the exact preservation techniques
  should be documented and forwarded to the
  forensic entomologist. If the body has more than
  one area of colonization (more than one maggot
  mass) each site should be treated separately.

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Collection of insects from the body at the scene

• Once the preserved collections have been made,
  duplicate samples should be made for live
  shipment. 
• Living specimens can be placed in specimen
  containers or Styrofoam cups with tight fitting
  lids along with some moist paper toweling, or
  most preferably a food substrate such as beef
  liver or pork meat. 
• Tiny air holes should be poked in the lid using
  an ice pick or similar instrument. 
• This cup should be placed into a slightly larger
  container that has about 1/2 inch of soil or
  vermiculite in the bottom to absorb any liquids
  that may accumulate and leak. 
• This entire container should be enclosed in an
  appropriate shipping container and shipped
  overnight to a forensic entomologist.

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Collection of insects from scene after body
removal

• Many of the insects that inhabit a corpse will
  remain on, or buried, in the ground after the
  body has been removed. 
• The steps listed above should be followed when
  collecting insects from the soil (i.e. both a
  preserved and a living sample should be taken). 
• Soil and litter samples should also be taken both
  immediately under where the body was positioned,
  and from the immediate surroundings. 

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Collection of insects from scene after body
removal

• It is not necessary to dig deeply. 
• A good technique is to collect the leaf litter
  and debris down to the exposed upper surface of
  the soil, and then make a separate collection
  from about the first two or three inches of
  topsoil. 
• Each soil collection area should be about 4-6
  inches square, and be taken from underneath the
  head, torso and extremities. 
• All soil samples should be placed in a cardboard
  container for immediate shipment to a forensic
  entomologist. 
• These collections should be labeled and forwarded
  to the forensic entomologist along with the
  insects collected from the body.

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The End!!!