Transcript Ch. 11 Power Point

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
In cases of suspicious death, a forensic pathologist
(MD) conducts an examination on the deceased,
called an autopsy.
The autopsy is conducted to determine the manner,
cause, mechanism, and time of death.
Forensic Science: Fundamentals & Investigations, Chapter 11
Introduction
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Death is a process rather than an instant event.
When the heart stops beating, the cells of the body
begin to die because they no longer receive a fresh
supply of oxygen.
As oxygen levels drop, the basic processes of the
body fail to occur. Nerves, muscles, organs, and the
brain stop working.
When a cell dies, it breaks down. Once enough cells
begin to break down, life cannot be restarted.
Cell breakdown is called autolysis.
Forensic Science: Fundamentals & Investigations, Chapter 11
Introduction
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Autolysis—cell breakdown
Forensic Science: Fundamentals & Investigations, Chapter 11
The Manner of Death
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The manner of death can be:
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Natural, the most common—interruption & failure of body
functions resulting from age or disease
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Accidental—caused by unplanned events (car accident,
falling from a ladder, etc.)
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Suicidal—when a person purposefully kills oneself (hanging,
drug overdose, gunshot, etc.)
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Homicidal –death of one person caused by another person
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Undetermined –stated on death certificate if the official cause
can’t be determined (this leaves room for further
investigation)
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.
Examples: disease, physical injury, stroke, heart attack, etc.
Cases of Death by Homicide: bludgeoning, shooting, burning,
drowning, strangulation, hanging, suffocation, etc.
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Mechanism of death is the specific change in the
body that brought about the cessation of life.
Examples: loss of blood (exsanguination), cessation of brain
function, cessation of heart function (heart failure), cessation of
breathing (respiratory failure), etc.
Forensic Science: Fundamentals & Investigations, Chapter 11
During an autopsy, the forensic examiner wants to determine
when the person died. Why???
Time of Death—Livor Mortis
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The Leaden-Color of Death
Lividity—With decomposition, blood seeps down
and settles in the lower parts of a body
Red blood cells turn bluish-purple; the purplish color
is visible on parts of the skin wherever the blood
pools. The process takes time.
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Livor Mortis (cont)
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Lividity (the pooling of blood in the body) begins about two
hours after death.
Discoloration becomes permanent after eight hours.
If death occurred between 2 and 8 hours, lividity will be
present, but if the skin is pressed, the color will disappear.
After 8 hours, if the skin is pressed, the lividity will remain.
Ambient temperature affects the speed of decomposition and
lividity to set in. If the corpse is left outside on a hot, summer
day, livor mortis takes place at a faster rate. If left in a cool
room, livor mortis is slower.
Because gravity pulls the blood toward the ground, lividity can
also determine the position of the body during the first eight
hours.
Lividity can also reveal if a body has been moved. (p. 213)
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Rigor Mortis
The Rigidity of Death (death stiffness)
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Without oxygen in the blood—
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Calcium accumulates in the muscles (due to lack of oxygen)
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Muscles stiffen
Starts within 2 hours after death.
Starts in the head and gradually works its way down to the legs.
After 12 hours, the body is in its most rigid state.
After about 15 hours—
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Muscle fibers begin to dissolve
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Softening begins
The stiffness gradually disappears after 36 hours.*Depending
on body weight and temperature, rigor may remain for 48 hours.
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 12 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:
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Ambient temperature--the cooler the body, the slower the onset of rigor; the warmer the body,
the onset of rigor is faster
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Weight of the body--A person with less oxygen stored (lower in weight) experiences rigor faster; a
person with more oxygen stored (heavier in weight) experiences rigor slower
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Type of clothing, or lack of it--the presence of clothes accelerates rigor mortis; a naked body
cools faster, which slows down the onset of rigor mortis
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Illness--If a person dies with a fever, the body temp will be higher, and rigor mortis will set in faster
Level of physical activity shortly before death—If a person was exercising or
struggling before death, then rigor will progress faster
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Sun exposure--A body exposed to direct sunlight will be warmer, and rigor mortis would occur faster
Because so many variables can affect how fast rigor mortis progresses, a precise time of
death cannot be determined, it can only be estimated.
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Algor Mortis
The Chill of Death—temp loss in a corpse
o Body heat falls after death
• About 1.4 degrees per hour immediately after death
• Slowing to about .7 degree per hour after about 12 hours until
the body reaches the same temperature as the surroundings
• 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
because it can’t be calculated exactly
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—
Stomach and Intestinal Contents
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In general, it takes 4-6 hours for the stomach
to empty its contents into the small intestine
and another 12 hours for the food to leave
the small intestine.
It takes about 24 hours from when a meal
was eaten until all undigested food is
released from the large intestines.
From this, it can be concluded that:
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 Death occurred at least four
found in small intestine
to six hours after a meal
Small intestine is empty;
waste found in large
intestine
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Forensic Science: Fundamentals & Investigations, Chapter 11
Death occurred 12 or more
hours after a meal
Time of Death
—Stomach and
Intestinal
Contents
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death
--Stages of Decomposition
A corpse decomposes in predictable ways over
time that can help examiners judge when
death occurred:
1. Within 2 days after death:
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Cell autolysis begins following death
Green and purplish staining occurs from blood decomposition
The skin takes on a marbled appearance
The face becomes discolored
2. After 4 days:
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The skin blisters
The abdomen swells with the gas carbon dioxide that is released by
bacteria living in the intentines
Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death
--Stages of Decomposition
3. Within 6-10 days:
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The corpse bloats with carbon dioxide as bacteria continue to feed on
tissues. Eventually, the gas causes the chest and abdominal cavities to
burst and collapse
Fluids begin to leak from the body openings as cell membranes rupture
Eyeballs and other tissues liquefy
The skin sloughs off
4. See Figure 11-11 on page 317—Stages of Decomposition
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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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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
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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—
they are attracted to 2 gases of decomposition
As the corpse progresses through the stages of
decomposition, other kinds of insects arrive
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. 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
4. 8 to 12 days—larvae migrates to a dry place
5. 18 to 24 days— Early pupa; immobile;
changes from light brown to dark brown
6. 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—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 because of fluctuating environmental
conditions
Insect evidence provides a close estimate
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