Transcript FORENSIC BIOLOGY

FORENSIC BIOLOGY
Forensic Biology
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Anthropology/osteology
Odontology
Entomology
Botany
FORENSIC
ANTHROPOLOGY
Hic locus est ubi
mortui viveuntes
docent.
This is the place where
the dead teach the
living.
Anthropology
A forensic anthropologist provides basic
identification of skeletonized or badly
decomposed remains.
From a whole bone or part of a bone, the
scientist may be able to determine:
 Age
 Sex
 Race
 Height
Age Determination
Sutures
Three major cranial
sutures appear as
distinct lines in
youth and
gradually close
from the inside
out.
Age Determination
Basilar Suture
Technically known as the
synchondrosis sphenooccipitalis closes in
females as young as
14 and in males as
young as 16. If the
suture is open, the
individual is generally
considered 18 or
younger.
Gender Differences in Bones
The pelvis of the female is wider. Males have a narrow
subpubic angle (A) and a narrow pubic bone body (B).
Male
Female
Sub Pubic Angle
Gender Differences (cont)
The ribcage and shoulders of males are generally
wider and larger than that of females. In addition,
about one person in twenty has an extra rib. This
is more common in males than in females.
Gender Differences (cont)
Although occurring less consistently, with males the
index finger is usually shorter than the third finger.
In females, the first finger is longer than the third
finger.
Is this a male or female hand
according to the above rule?
Human Stature
Height of a person can be calculated by using the
length of certain bones, including the femur, tibia,
humerus, and/or radius. Below are the average
measurements for both male and female. There
are more specific charts if you know the race of
the individual. (All measurements are in centimeters)
Male
Female
femur x 2.23 + 69.08
tibia x 2.39 + 81.68
humerus x 2.97 + 73.57
radius x 3.65 + 80.40
femur x 2.31 +61.41
tibia x 2.53 + 72.57
humerus x 3.14 + 64.97
radius x 3.87 + 76.50
Race
Race is difficult to determine from most
skeletal remains, especially since there are
no pure races. An experienced forensic
anthropologist can generally place skulls
into one of four groups:
Caucasian
 African American
 Asian
 American Indian
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Racial Differences
What differences do you notice between these
three skulls? Could you tell each race?
Odontology
Many times identity of a
skull can be determined by
comparing a person’s
dental records. Unusual
features including the
number and types of teeth
and fillings, the spacing of
the teeth, and/or special
dental work (bridges, false
teeth, root canals) help to
make a positive
identification.
Odontology and
Identification
Teeth are often used for body identification
because:
 Hardest substances in the body
 Unique to the individual
 Usually a good record of our teeth
General Teeth Information
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32 adult, permanent teeth
20 baby or deciduous teeth
Numbered from 1 to 32 starting from the upper
right (1), to upper left, to lower left to lower right
(32)
Each tooth has 5 surfaces which helps to further
individualized teeth
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M
D
O
F
L
=
=
=
=
=
mesial
distal
occlusal
facial
lingual
Burning
When bodies are burned, teeth and bones will
be some of the last remaining body parts.
These will be used for identification.
F
C
Teeth are brittle
400
Teeth disintegrates.
900
200
480
Cremation
1800
980
Dental gold melts
2000
2200
2200
1100
1200
BURNING RESULTS
Porcelain melts
Hot fire!!
1200
Facial Restoration
After determining the sex, age, and race of an
individual, facial features can be built upon a skull
to assist in identification. Erasers are used to
make tissue depths at various points on the skull.
Clay is build up around these markers and facial
features are molded.
Steps in Facial Reconstruction
Obtain a copy of a skull
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Establish age, sex and
race
Plot landmarks for
tissue thickness
Plot origin and
insertion points for
muscles
Plot landmarks for
facial features
Select a dataset and
mount markers for
tissue thickness
Mount the eyes
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Model muscles on
skull
Add fatty tissue around
eyes and lacrimal
glands
Add eyelids
Add the nose
Add the parotid gland
Add the ears
Cover all with layers of
skin
Detail the face
Final Product
John List killed his entire
family and went on the run.
Seventeen years later, Frank
Bender reconstructed what
he believed List would look
like. It was shown on
America’s Most Wanted,
and he was turned in by the
viewers almost
immediatedly. . . looking
very much like the bust.
Anthropologist
at Work
This anthropologist is
hard at work dusting
away material from
these imbedded bones.
Picture taken at
Chicago’s Museum
of Natural History
Animal Facial Restoration
Determining what T Rex looked like using the bone formation.
From this:
To this:
Animal Structure and Function
Beaver jaw with the end
results seen on the log.
Other Bone Identification
Forensic experts may be called upon to
determine the life and death of humans and
animals in unique circumstances, including:
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Mass Murder (Oklahoma bombing, plane crashes,
World Trade)
Earlier man (mummies, Iceman, Lindow man)
Historical Significance (Holocaust, uncertain death of
famous people)
Prehistoric Animals (Dinosaurs)
Sue, the T Rex at the
Museum of Natural History
Chicago
Entomology
Entomology is the study of insects. Insects
arrive at a decomposing body in a particular
order and then complete their life cycle
based on the surrounding temperature. By
collecting and studying the types of insects
found on a body, a forensic entomologist
can predict the time of death.
“When one biological clock stops, others begin.”
--Neal Haskell, reknown forensic entomologist
HISTORICALLY
1235 A.D., a Chinese death investigator named Sung
Tz’u wrote a book entitled The Washing Away of
Wrongs. It contained one of the first accounts of
the use of insects as forensic evidence. A murder,
in which a sickle was used, occurred in a Chinese
village. There were no suspects, so the investigator
had all the men of the village stand in a line with
their sickles on the ground in front of them. Flies
landed on only one sickle--the one, that although
cleaned, still had enough blood to attract the flies.
The owner then confessed.
Decomposition
Stage
Description
Initial Decay
Carcass appears fresh externally but is
decomposing internally
Putrefaction
Carcass swollen by gas produced internally;
odor of decaying flesh
Black Putrefaction
Butyric Fermentation
Dry Decay
Flesh of creamy consistency with exposed
parts black. Body collapses as gases
escape; odor of decay very strong.
Carcass drying out. Some flesh remains;
cheesy odor develops. Ventral surface moldy
from fermentation
Carcass almost dry
Decomposition
One day old dead pig showing signs of
skin changes and bloating.
(Picture taken on June 20th, 2002)
Decomposition
Advanced stages are seen on this one
week old dead pig. As the larva develop
they migrate from the body and develop
into pupa.
Order of Decomposition
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Autolysis--nonbacterial;
release of gases
Putrefication--slippage of
skin, etc.
Necrophagous arthropods
Arrival depends on:
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Season or climate
Situation of the corpse--open
air, buried or in water;
geographic location; cause of
death and degree of mutilation
Changes in skin by decomposition
Four Main Types
of Carrion Species
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Necrophagous--feed directly on the corpse
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Flies (Diptera)
Beetles (Coleoptera)
Predators
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Burying beetles (family Silphidae)
Rove beetles (family Staphylinidae)
Hister beetles (family Histeridae)
and parasites of the Necrophagous species--attract to other
animals already feeding on the body
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Order of Hymenoptera--ants, bees, and wasps
Beetles
Rove Beetle--Staphylinidae
(Lathrobium sp.)
Carrion Beetle--Silphidae
(Nicrophorus sp.)
Four Main Types
of Carrion Species (cont.)
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Species that feed on both the body and other arthropods
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Ants
Wasps
Some beetles
Arthropods that use the corpse as an extension of their
normal habitat
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Hunting spiders
Black
Green
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THE BLOW
FLY
Acts as both necrophages and as a predator.
One of the most common species on dead bodies
Often arrive within 10 minutes
Feed on any blood or fluids and then start laying
eggs in and around the natural body cavities
If the food source is exhausted, they will prey on
other species in the same genus (Chrysomya)
Collection
Collection are done in three ways:
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Aerial
Hand
Live Sampling
Aerial Collection
Use a net and sweep it back and
forth over the decomposing
body. Place them in a large
jar with ethyl acetate. After a
few seconds, use a funnel to
move dead flies into a vial of
75% ethyl alcohol with a label
of the date, time, case #,
location, sample type and
collector. (In this example a pig is
used as it is the closest to human in
decomposition.)
Hand Collection
Collect a variety of maggots
with forceps. Place them in
boiling water to stretch
them out and fix them.
Then place the maggots
into a vial of alcohol with
a label containing the date,
time, case #, location and
collector.
Live Sampling
“Maggot Motels”
Obtain a styrofoam container with a lid (about the size of
Chinese take-out soup). Use sand or vermiculite for the
bottom substrate. Place aluminum foil with beef or pork
liver for food on top of the substrate. Collect 10 to 15 live
maggots of varying sizes and drop them onto the foil. (You
may also harvest and develop eggs in the “motel”.) Close
the foil around them and allow to develop into pupae and
then into adults. THEY MUST BE ADULTS IN ORDER
TO IDENTIFY THE SPECIES.
Metamorphosis
Complete metamorphosis
(holometabolous)
involves development
from egg to larva to pupa
to adult. The pig ear in
the diagram to the right
shows a layer of what
looks like a white crust.
These are the fly eggs.
Larva
Larva hatch from the eggs
and increase in size by
growth steps called instars.
Eventually the larva
migrate from the corpse
and develop into an
inactive pupal stage.
During this time, the adult
insect develops internally.
Two larval instars.
PMI--Postmortem Interval
An estimation of the duration of PMI involves
setting the minimal and maximal time between
death and corpse discovery and is important in
narrowing the field of suspects.
The minimal PMI is determined largely by
estimating the age of developing immature insects
collect at the time the corpse is discovered.
The maximum PMI is determined from the species
of insects that are present and the weather
conditions necessary for the specific activity of
these species.
Body Changes
Due to Decomposition
1. When the heart stops, the
body turns pale and looks
waxy.
2. Blood settles and discolors
into a purplish red. Eyes
flatten and extremities turn
blue.
3. The appearance of burning
shows up on the drying
mucous membranes.
4. The body putrefies, turning a
greenish color. Bacteria
grows and accumulates.
5. Rot spreads and a foul odor
develops. Body bloats due to
bacterial producing gases in
the intestines.
6. Skin blisters from these
gases, detaches from the
muscles and bursts. Top
layers peel off.
7. In some circumstances, a
cheesy substance called
“adipocere” forms as fatty
tissues harden
Left alone in a warm and moist climate, a body can decompose to a skeleton within a
few weeks. In other conditions it can take months or even years.
Temperature
Ambient heat plays a role
during egg and early
larval development but
after that its effect
decreases rapidly.
Maggot masses generate
their own heat.
Taking temperature of the maggot mass
can find it as high as 125 degrees.
Maggot Mass Activity
QuickTime™ and a
decompressor
are needed to see this picture.
Click on the video to
the left to observe
the maggot mass
in a decomposing
pig carcass (real
time).