Title: Forensic Entomology
1Forensic Entomology
2What 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.
3What 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.
4How 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.
5How 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.
6How 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".
7How 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.
8Importance 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.
9Importance 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.
10Blowflies
- 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.
11Blowflies
- 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.
12Blowflies
- 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.
13Blowflies
- 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.
14Blowflies
- 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.
15Blowflies
- 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.
16Blowflies
- 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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18Screw 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.
19Blowflies
201st Instar
212nd Instar
223rd instar
23Age based on Mouth Hooks
1st instar maggot
2nd instar maggot
24Mouth sphericales
25Maggots at Work
Maggots can consume 60 per cent of a corpse in
less than a week.
26Life 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
27Life 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
28Life 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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30Beetles
- 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.
31Beetles
- 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.
32- 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.
33What 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.
34What 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.
35What 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.
36What 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.
37What 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.
38What 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.
39What 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.
40Death 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.
41Scene 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.
42Collection 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.
43Collection 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.
44Collection 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
-
45Collection 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.
46Collection 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.
47Collection 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.
48Collection 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.
49Collection 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.
50The End!!!