Transcript Death: Meaning, Manner, Mechanism, Cause, and Time PowerPoint

Chapter 11 Death: Meaning, Manner,
Mechanism, Cause, and Time
By the end of this chapter you will be able to:
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Discuss the definition of death
Distinguish between four manners of death:
natural, accidental, suicidal, and homicidal
Distinguish between cause, manner, and
mechanisms of death
Explain the development of rigor, algor, and
livor mortis following death
All Rights Reserved South-Western / Cengage Learning © 2012, 2009
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Forensic Science: Fundamentals & Investigations, Chapter 11
Chapter 11 Death: Meaning, Manner,
Mechanism, Cause, and Time
By the end of this chapter you will be able to:
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Estimate the time of death
Describe the stages of decomposition of a
corpse
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
Forensic Science: Fundamentals & Investigations, Chapter 11
Definition of Death
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Cessation, or end, of life
Irreversible cessation of blood circulation
Cessation of all brain activity
Experts do not agree on a single definition
Forensic Science: Fundamentals & Investigations, Chapter 11
Introduction
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Autolysis — cell death
Forensic Science: Fundamentals & Investigations, Chapter 11
The Manner of Death
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The manner of death can be
1) Natural, the most common
2) Accidental
3) Suicidal
4) Homicidal
5) Undetermined
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Sometimes the manner of death is difficult to
determine
Forensic Science: Fundamentals & Investigations, Chapter 11
Cause and
Mechanism of Death
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Cause of the death
is the reason for the death
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Mechanism of death is the specific change in the
body that brought about the
cessation of life
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Livor Mortis
The Leaden-Color of Death
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Lividity—With decomposition, blood seeps down
and settles in the lower parts of a body
Red blood cells turn bluish-purple
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Livor Mortis
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Livor Mortis
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Lividity begins about two hours after death
Discoloration becomes permanent after eight
hours
Ambient temperature affects the speed of
decomposition
Position can determine the lividity of the
body during the first eight hours
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Rigor Mortis
The Rigidity of Death
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Without oxygen in the blood—
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Starts in the head and expands throughout
After about 15 hours—
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Calcium accumulates in the muscles
Muscles stiffen
Muscle fibers begin to dissolve
Softening begins
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Rigor Mortis
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Rigor Mortis
Live muscle fibers
slide back and forth
After death, muscle
fibers become locked
in a flexed position
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Rigor Mortis
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Observation
Approx. Time Scale
The body is at its most rigid
state
Just over 2 hours
No visible signs of rigor
Less than 2 hours
or more than 48 hours ago
Stiffness generally
disappears
After 36 hours
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Rigor Mortis
Factors affecting rigor mortis:
1)
Ambient temperature
2)
Weight of the body
Type of clothing, or lack of it
General health of person at time of death
Level of physical activity at time of death
Sun exposure
3)
4)
5)
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Algor Mortis
The Chill of Death
o Body heat falls after death
• About 1.5 degrees per hour immediately after death
• Slowing to less than 1.0 degree per hour after about 12 hours
• Heat loss is affected by the ambient temperature
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Corpse temperature is measured by a
thermometer inserted into the liver
Time of death is expressed as a range of time
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death
—Stomach and
Intestinal
Contents
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death
—Stomach and Intestinal Contents
State of Contents
Timing of Death
Undigested food present
in the stomach
Zero to two hours after the
last meal
Stomach is empty, but food
found in small intestine
Small intestine is empty;
waste found in large
intestine
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Forensic Science: Fundamentals & Investigations, Chapter 11
Death occurred at
least four to six
hours after a meal
Death occurred 12 or more
hours after a meal
Time of Death
—Stages of Decomposition
Decomposition –
rotting of all tissues
and organs
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death
—Stages of Decomposition
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1)
Within two days of death:
2)
After four days:
3)
Within six to ten days:
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death
—Stages of Decomposition
1) Within two days of death:
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cell autolysis begins
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green and purplish staining occurs from blood
decomposition
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face becomes discolored
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death
—Stages of Decomposition
2) After four days
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skin blisters
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abdomen swells with CO₂ that is released by
bacteria in the intestines
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death
—Stages of Decomposition
3) Within six to ten days
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corpse continues to bloat as bacteria continue to
feed on tissues; eventually chest and abdomen
will burst
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fluids begin to leak from body openings
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eyeballs and other tissues liquefy
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skin sloughs off
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Insects
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Forensic entomologist
• Collects insect evidence from on, above, and below
the body
• Records environmental conditions
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Within minutes of a death, certain insects arrive
to lay their eggs on the warm body—blowflies
As the corpse decomposes, other kinds of
insects arrive
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Insects
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The insect life cycle provides scientists with a
benchmark to estimate a time of death
Insect evidence cannot provide an exact time of
death—fluctuating environmental conditions
Insect evidence provides a close estimate
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death
—Blowfly Life Cycle
1. <8 hours after death—blowfly eggs can be
found in the moist, warm areas of a corpse
2. Within 20 hours —1st of their 3 larva stages
3. Within 2.5 days —2nd of their 3 larva stages
4. 4th or 5th day—3rd of their 3 larva stages
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death
—Blowfly Life Cycle
5. 8 to 12 days—larvae migrates to a dry place
6. 18 to 24 days— Early pupa; immobile;
changes from light brown to dark brown
7. By the 21st-24th day the pupa cases will split
open and adult blowflies will emerge.
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death
—Blowfly Life Cycle
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death
—Blowfly Life Cycle
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death
—Blowfly Life Cycle
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death
—Blowfly Life Cycle
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death
—Blowfly Life Cycle
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Forensic Science: Fundamentals & Investigations, Chapter 11
. . . . . . . . . . . . . . . . . Summary
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Several definitions of death
A body decomposing through three stages—
livor, rigor, and algor mortis—provides an
estimated time of death
Stomach contents and insect evidence also aid
in estimating the time of death
Environmental factors affect the estimated time
of death
Forensic Science: Fundamentals & Investigations, Chapter 11