Transcript 15 Time 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
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 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
Accidental
Suicidal
Homicidal
Undetermined
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 (example: gunshot…. because they were
shot))
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Mechanism of death is the specific change in
the body that brought about the cessation of
life– the biological effects of the cause
(example: exsanguination)
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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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
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
reaching full rigor in 12 hours
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
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 at
all
Less than 2 hours
or more than 48 hours ago
Stiffness generally
disappears
After 36 hours
Forensic Science: Fundamentals & Investigations, Chapter 11
Slows rigor
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Things that slow rigor:
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Things that speed rigor:
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Anything that cools or keeps the body cooler
Obesity- allows for higher oxygen retention (cells live
longer)
Naked
Inactivity/ sleep
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Anything that warms the body
Thinness- oxygen depleted/ not as much in the body
Clothed or covered
High activity– warmer/ decreases oxygen/ more
lactic acid
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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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 (.78o C)
• Slowing to less than 1.0 degree per hour after about 12 hours
(.39o C)
• 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 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
—Stages of Decomposition
Choose: A. Within 2 days. B. After 4 days. C. Within 6-10 days.
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Discoloration of the face
Marbling appearance on the skin
Green and purplish staining from blood decomposition
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The skin blisters
The abdomen swells
1. The corpse bloats
2. Eyeballs and other tissues liquefy
3. Fluids begin to leak from body openings as cell membranes rupture
4. The skin sloughs off
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Forensic Science: Fundamentals & Investigations, Chapter 11
Time of Death—Insects
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Forensic entomologist
• Collects insect evidence from on, above, and below
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the body
• Records environmental conditions
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
Egg Larva (Fly larvae are maggots)  Pupa Adult
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
(INSTARS)
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—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