Download Death - Cobb Learning

SFS2 Students will use various scientific techniques to
analyze physical and trace evidence.
c. Evaluate how post mortem changes are used to
determine probable time of death
SFS5 Students will evaluate the role of Forensics as it
pertains to Medicolegal Death Investigation
a. Identify the various causes of death
b. Analyze evidence that pertains to the manner of death
c. Interpret various modes of death.
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Forensic Science II: Autopsy, Chapter 8
© 2012 Cengage Learning. All Rights Reserved
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In 1998, Rutherford drove his car off the road.
The car caught fire and Rutherford died.
A $7 million life insurance policy would go to his wife,
but only after an investigation.
An autopsy revealed:
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the skull fragments were in an unlikely position
the bones indicated arthritis
the dentures records didn’t match
Rutherford faked his death.
Forensic Science II: Autopsy, Chapter 8
© 2012 Cengage Learning. All Rights Reserved
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Forensic Science II: Forensic Entomology, Chapter 12
© 2012 Cengage Learning. All Rights Reserved
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By law, deaths occurring under these circumstances
must be investigated:
• Violent crime, suicide, or accident
• Within 24 hours of entering a hospital or having
surgery
• A natural death when a doctor is not present or the
patient is not under the care of a medical facility
• Occurs in police custody or in a correctional facility
• Results from a communicable disease that may
pose a threat to public health.
Forensic Science II: Autopsy, Chapter 8
© 2012 Cengage Learning. All Rights Reserved
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Two systems of death investigation exist in the US
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The coroner system dates to 12C England;
sometimes the position:
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The medical examiner system dates back to 1870
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is an elected official
requires a medical doctor
requires a forensic pathologist.
an experienced physician with
advanced training in pathology
Forensic Science II: Autopsy, Chapter 8
© 2012 Cengage Learning. All Rights Reserved
The Manner of Death
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The manner of death can be natural,
accidental, suicidal, homicidal, or
undetermined.
Sometimes it is difficult to determine the
manner of death.
The most common manner of death is
natural.
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Cause of Death
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Mechanism of Death
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Describes events leading to death
Examples: stroke, drowning,
shooting, etc.
Specific change in body that
brought about death
Examples: loss of blood,
pulmonary arrest, etc.
Forensic Science: Fundamentals & Investigations, Chapter 11
Lividity
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The Color of Death
When red blood cells break down, they turn a
bluish-purple.
With decomposition, blood seeps down and
settles in the lower parts of a body.
The discoloration that accompanies this
becomes permanent after about 10 hours.
Warmth accelerates the process.
The Rigidity of Death
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At death, skeletal muscles cannot relax.
Without oxygen, calcium accumulates in these
muscles.
The muscles become stiff.
This starts in the head and works its way down to
the legs.
After about 12 hours, the muscle fibers begin to
slowly dissolve, and softening begins.
Many factors affect when rigor mortis sets in and
how long it lasts:
• Ambient temperature
• The weight of the body
• The body’s clothing or lack of it
• Any illness the person had at the time of death
• The level of physical activity at the time of death
• Sun exposure
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Approximate times for rigor mortis in
temperate regions (just a reference/estimate)
Body temp.
warm
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Body stiffness
not stiff
Time since death
dead not more than 3 hrs
warm
stiff
dead 3 to 8 hours
cold
stiff
dead 8 to 36 hours
cold
not stiff
dead more than 36 hours
o In death, a body no longer generates warmth and
begins to cool down.
o To find the standard temperature of a corpse, a
thermometer is inserted into the liver (sometimes it
will be done rectally).
o Body heat is lost at about 1 to 1.5 °F an hour.
o Time of death determined by temperature
calculations is expressed as a range of time.
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Temperature of the surrounding
environment
Type of clothing on the body
Wetness of the clothing
Air movement
Layers of clothing
Size of the individual
Forensic Science: Fundamentals & Investigations, Chapter 11
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Forensic Science: Fundamentals & Investigations, Chapter 11
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July 9, 1997 Champaign County, Ohio
Stepfather, Kevin Neal, claims stepchildren are
missing from their back yard
Bodies discovered on September 6th were in the late
stages of decomposition
Autopsies revealed
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Maggot infestation
Absence of blowflies and screwworms
Presence of cheese skipper fly in its 3rd instar stage
How were these insects evaluated?
Forensic Science II: Forensic Entomology, Chapter 12
© 2012 Cengage Learning. All Rights Reserved
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As the body decays, odors
attract insects to the dead
body.
The flies are the first to arrive.
Blowflies and flesh flies are
flesh feeders and will be the
first in line.
If no trauma is present on the
body, female blowflies will lay
eggs in exposed body
openings.
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Factors affecting insect development
 Temperature
 Wind
 Time of day
 Season
 Exposure to elements
Estimation of time of death obtained by raising insects
from scene in same conditions at lab.
Process is known as Accumulated Degree Hours
(ADH)
scienceinschool.org
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1. Blowfly eggs can be found in the moist, warm
areas of a corpse within 8 hours after death.
2. They will have progressed to the 1st of their 3
larva stages within 20 hours.
3. By the 4th or 5th day they will have progressed
to the 3rd of their 3 larva stages.
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4. By the 8th or 12th day the larvae will migrate
away from the corpse to a dry place.
5. Becoming pupa and immobile within 18-24
days, they will change from white to dark
brown.
6. By the 21st-24th day the pupa cases will split
open and adult blowflies will emerge.
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Image: http://www.nlm.nih.gov/visibleproofs
Phormia regina
Spiracles are incomplete
Third-instar larvae
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Spiracles are complete
Third-instar larvae
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Postmortem Interval- the time elapsed
since a person died
When longer than 72 hours after death,
entomology becomes important
Within 48 hours the female blowfly lays eggs
in moist areas of the body
Forensic Science II: Forensic Entomology, Chapter 12
© 2012 Cengage Learning. All Rights Reserved
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Forensic Entomology is
used to determine time
since death (the time
between death and
corpse discovery)
This is called
postmortem interval or
PMI.
scienceinschool.org
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Entomological evidence collection
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Identify the species
Document larvae length
Determine the instar
Determine PMI
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documentingreality.com
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Observe and record all pertinent factors
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Weather patterns (rainfall, wind, humidity,
temperature, and exposure to light) during the
PMI
Avoid disturbing insects within several feet of
the body
Measure distance from body to insects
Collect samples of all insect stages on, near,
and under the body
Forensic Science II: Forensic Entomology, Chapter 12
© 2012 Cengage Learning. All Rights Reserved
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Capture live flies with nets
Pin flies to a board, or
Preserve with 80% alcohol
and 20% water
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Adult flies
Eggs
Largest larvae
Forensic Science II: Forensic Entomology, Chapter 12
© 2012 Cengage Learning. All Rights Reserved
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Ambient air
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Ground Soil
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1 foot above the body
4 feet above the body
Surface
10 centimeters below
20 centimeters below
Center of a large infestation (if present)
Forensic Science II: Forensic Entomology, Chapter 12
© 2012 Cengage Learning. All Rights Reserved
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Time of injury vs. death
Estimation of time of death
Whether or not a corpse has been moved
Instances of insects as weapons
Child and elderly abuse and neglect
Single vehicle car accidents
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“Roach Track” Confusion
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Roaches are notorious for confusing blood spatter
analysis
Blood trajectory is often critical to forensic
investigations
Roaches, silverfish and other household insects often
travel through bloodstained areas
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Shipments of illegal drugs often contain
insect infestations, especially cannabis and
heroine (derived from poppy plants.)
Analysis of insect “stowaways” can allow
investigators to track country of origin, and
in many cases the local area of cultivation.
PMI used to detect illegal drugs/poisons in
fly larvae (consumed from corpses)