Transcript Chapter 11 - Glenelg High School

Chapter 11 Death: Manner,
Mechanism, Cause, and Time
By the end of this chapter you will be able to:
 explain the development of livor, rigor, and algor
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mortis following death
use evidence of these to estimate time of death
use evidence on stomach contents to estimate
time of death
use insect evidence to estimate time of death
explain how environmental factors can affect the
estimated time of death
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Forensic Science: Fundamentals & Investigations, Chapter 11
Death
The Manner of Death
 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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Forensic Science: Fundamentals & Investigations, Chapter 11
Death
Cause and Mechanism of Death
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The reason for the death is the cause of
the death.
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The specific change in the body that
brought about the cessation of life is the
mechanism of death.
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Livor Mortis
The Leaden-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 8 hours.
 Warmth accelerates the process.
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Rigor Mortis
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 15 hours, the muscle fibers begin to
dissolve, and softening begins.
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Rigor Mortis
 At 12 hours after death, the body is at its most rigid
state.
 If a body has no visible signs of rigor, it probably has
been dead less than 2 hours or more than 48.
 If the body exhibits rigor only in the head and neck,
the time of death is just over 2 hours.
 This stiffness will have disappeared for the most part
after 36 hours.
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Rigor Mortis
Many factors affect when rigor mortis sets in and
how long it lasts:
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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
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Algor Mortis
The Chill of Death
 In death a body no longer generates warmth and
begins to cool down.
 To find the standard temperature of a corpse, a
thermometer is inserted into the liver.
 Body heat is lost at about 1 to 1.5 degrees an
hour.
 Time of death determined by temperature
calculations is expressed as a range of time.
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Stomach and Intestinal
Contents
Based on these specifics, give an estimate for
each of these on how much time has passed
since the meal was eaten:
1. Food is still present in the stomach.
2. The stomach is empty but food is found in
the small intestine.
3. The small intestine is empty but waste is
present in the large intestine.
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Stages of
Decomposition
Choose: A. Within 2 days. B. After 4 days. C. Within 6-10 days.
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2.
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8.
9.
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Fluids begin to leak from body openings as cell membranes
rupture.
Discoloration of the face.
The skin sloughs off.
The skin blisters.
Green and purplish staining from blood decomposition.
The corpse bloats.
Eyeballs and other tissues liquefy.
The abdomen swells.
Marbling appearance on the skin.
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Insects
 Besides recording data about the environment
at a crime scene, a forensic entomologist
collects insect evidence.
 Within minutes of a death, certain insects arrive
to lay their eggs on the warm body. Blowflies
are a common example.
 As a corpse progresses through the stages of
decomposition, other kinds of insects arrive.
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Insects
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 (illustration of one shown above)
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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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Insects
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 (illustration of one
shown above) will emerge.
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Insects
 Because scientists know how long it takes for the
various stages of development at given
temperatures, forensics entomologists can
determine when the insects arrived.
 Because life cycles are affected by fluctuations in
the daily environmental conditions, insect evidence
cannot provide an exact time of death.
 Insect evidence, nonetheless, can yield a close
estimate.
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Forensic Science: Fundamentals & Investigations, Chapter 11
. . . . . . . . . . . . . . . . . Summary
 A body decomposes through the 3 changes of
livor, rigor, and algor mortis.
 Forensic scientists use evidence from these to
estimate the time of death.
 They also use stomach contents and insect
evidence to estimate the time of death.
 It is also important to remember how
environmental factors can affect the estimated
time of death.
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Forensic Science: Fundamentals & Investigations, Chapter 11