Transcript The Manner of Death

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
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
Terry Schiavo
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Pig Decomposition
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The Body Farm
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Definition of Death
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17th century, before the stethoscope, anyone
in a coma or a slow heart rate was presumed
dead and was buried
Cessation, or end, of life
1. Irreversible cessation of blood circulation
2. Cessation of all brain activity
3. Experts do not agree on a single definition
Introduction
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Autolysis—cell breakdown
The Manner of Death
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The manner of death can be
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Natural, the most common, caused by interruption
and failure of body functions resulting from age or
disease
Accidental
Suicidal
Homicidal
Undetermined
Sometimes the manner of death is difficult to
determine
The Manner of Death
What is the Manner of Death in these cases?
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A man with a heart condition is attacked and
dies from a heart attack during the assault.
An elderly woman dies after being kept from
receiving proper health care by her son.
Cause and
Mechanism of Death
Cause of the death is the reason for the death
o Proximate cause of death – underlying cause of
death
o Mechanism of death is the specific change in
the body that brought about the cessation of life
**usually only “Cause” and “Mechanism” are listed on the death certificate**
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Forensic Pathology
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Time of Death—Livor Mortis
The 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
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
Lividity can determine the position of the
body during the first eight hours
Dual lividity could occur if the body was kept
in one position two hours after death and
then moved to a second position before the
lividity became permanent.
Time of Death—Rigor Mortis
The Rigidity of Death (Stiffness)
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Without oxygen in the blood—
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Starts in the head and expands throughout
Begins after 2 hours
After about 15 hours—
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Calcium accumulates in the muscles
Muscles stiffen
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Muscle fibers begin to dissolve
Softening begins
Ends after 48 hours
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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Time of Death—Rigor Mortis
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Observation
Approx. Time Scale
The body is at its most rigid
state
12 hours
No visible signs of rigor
Less than 2 hours
or more than 48 hours ago
Stiffness generally
disappears
After 36 hours
Time of Death—Rigor Mortis
Factors affecting rigor mortis:
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Ambient temperature
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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
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Time of Death—Algor Mortis
Death heat (describes temperature loss)
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
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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Death occurred 12 or more
hours after a meal
Time of Death
—Stomach and
Intestinal
Contents
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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 C
Discoloration of the face A
C
The skin sloughs off
The skin blisters
B
Green and purplish staining from blood decomposition A
C
The corpse bloats
Eyeballs and other tissues liquefy C
B
The abdomen swells
Marbling appearance on the skin
A
*The speed of decomposition depends on the person’s:
1) age 2) size of body 3) nature of death 4) health
Decomposition – Dirty Jobs
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Decomposition – Dirty Jobs
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Decomposition – Dirty Jobs
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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
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
*The stages of larva can be determined by the number of spiracle slits
at their posterior end
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*An immature form of an animal that undergoes metamorphosis, for
example a maggot, is a larva.
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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Timeline
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1.8 days
First Stage (instar 1) V-shaped
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2.5 days Second Stage (instar 2) two
spiracles
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4-5 days
spiracles
Third Stage (instar 3) three
Time of Death - Insects
Accumulated Degree Hours (ADH)
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Immediately preserve some insects from the crime
scene.
At the crime lab, raise some of the insects from the
crime scene in the same conditions as those found
at the crime scene.
Record the length of time for development under the
specific conditions found at the crime scene.
Compare the insects raised at the crime lab to those
found at the crime scene.
A “maggot milkshake” is a blended group of maggots that have fed on
tissue and now are used to determine drug usage of the corpse.
Time of Death—Insects
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The insect life cycle provides scientists with a
benchmark to estimate a time of death
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Insect evidence cannot provide:
*exact time of death
*fluctuating environmental conditions
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Insect evidence provides a close estimate and may
provide proof that the corpse has been moved.
. . . . . . . . . . . . . . . . . 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