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Forensic Science: Fundamentals & Investigations, Chapter 11 1
Chapter 11 Death: Meaning, Manner, Mechanism, Cause, and Time By the end of this chapter you will be able to:
o Discuss the definition of death
o Distinguish between four manners of death: natural, accidental, suicidal, and homicidal
o Distinguish between cause, manner, and mechanisms of death
o Explain the development of rigor, algor, and livor mortis following death
All Rights Reserved South-Western / Cengage Learning © 2012, 2009
Forensic Science: Fundamentals & Investigations, Chapter 11 2
Chapter 11 Death: Meaning, Manner, Mechanism, Cause, and Time By the end of this chapter you will be able to:
o Estimate the time of death
o Describe the stages of decomposition of a corpse
o Use evidence on stomach contents to estimate time of death
o Use insect evidence to estimate time of death
o Explain how environmental factors can affect the estimated time of death
Forensic Science: Fundamentals & Investigations, Chapter 11 3
Definition of Death
o Cessation, or end, of life
o Irreversible cessation of blood circulation
o Cessation of all brain activity
o Experts do not agree on a single definition
Forensic Science: Fundamentals & Investigations, Chapter 11 4
Introduction
o Autolysis — cell death
Forensic Science: Fundamentals & Investigations, Chapter 11 5
The Manner of Death
o The manner of death can be
1) Natural, the most common
2) Accidental
3) Suicidal
4) Homicidal
5) Undetermined
o Sometimes the manner of death is difficult to determine
Forensic Science: Fundamentals & Investigations, Chapter 11 6
Cause and Mechanism of Death
o Cause of the death
o
o Mechanism of death
is the reason for the death
is the specific change in the body that brought about the cessation of life
Forensic Science: Fundamentals & Investigations, Chapter 11 7
Time of Death—Livor Mortis
The Leaden-Color of Death
o Lividity—With decomposition, blood seeps down and settles in the lower parts of a body
o Red blood cells turn bluish-purple
Forensic Science: Fundamentals & Investigations, Chapter 11 8
Time of Death—Livor Mortis
Forensic Science: Fundamentals & Investigations, Chapter 11 9
Time of Death—Livor Mortis
o Lividity begins about two hours after death
o Discoloration becomes permanent after eight hours
o Ambient temperature affects the speed of decomposition
o Position can determine the lividity of the body during the first eight hours
Forensic Science: Fundamentals & Investigations, Chapter 11 10
Time of Death—Rigor Mortis
The Rigidity of Death
o Without oxygen in the blood—• Calcium accumulates in the muscles
• Muscles stiffen
o Starts in the head and expands throughout
o After about 15 hours—• Muscle fibers begin to dissolve
• Softening begins
Forensic Science: Fundamentals & Investigations, Chapter 11 11
Time of Death—Rigor Mortis
Forensic Science: Fundamentals & Investigations, Chapter 11 12
Time of Death—Rigor Mortis
Live muscle fibers
slide back and forth
After death, muscle
fibers become locked
in a flexed position
Forensic Science: Fundamentals & Investigations, Chapter 11 13
Time of Death—Rigor Mortis
Observation Approx. Time Scale
The body is at its most rigid state
Just over 2 hours
No visible signs of rigorLess than 2 hours
or more than 48 hours ago
Stiffness generally disappears
After 36 hours
Forensic Science: Fundamentals & Investigations, Chapter 11 14
Time of Death—Rigor Mortis
Factors affecting rigor mortis:
1) Ambient temperature
2) Weight of the body
3) Type of clothing, or lack of it
4) General health of person at time of death
5) Level of physical activity at time of death
6) Sun exposure
Forensic Science: Fundamentals & Investigations, Chapter 11 15
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
o Corpse temperature is measured by a thermometer inserted into the liver
o Time of death is expressed as a range of time
Forensic Science: Fundamentals & Investigations, Chapter 11 16
Time of Death
—Stomach and
Intestinal Contents
Forensic Science: Fundamentals & Investigations, Chapter 11 17
Time of Death—Stomach and Intestinal Contents
State of Contents Timing of Death
Zero to two hours after the last meal
Stomach is empty, but food found in small intestine
Death occurred 12 or more hours after a meal
Undigested food present in the stomach
Death occurred at least four to six
hours after a meal
Small intestine is empty;
waste found in large
intestine
Forensic Science: Fundamentals & Investigations, Chapter 11 18
Time of Death—Stages of Decomposition
Decomposition –
rotting of all tissues
and organs
Forensic Science: Fundamentals & Investigations, Chapter 11 19
Time of Death—Stages of Decomposition
1) Within two days of death:
2) After four days:
3) Within six to ten days:
Forensic Science: Fundamentals & Investigations, Chapter 11 20
Time of Death—Stages of Decomposition
1) Within two days of death:
• cell autolysis begins
• green and purplish staining occurs from blood decomposition
• face becomes discolored
Forensic Science: Fundamentals & Investigations, Chapter 11 21
Time of Death—Stages of Decomposition
2) After four days
• skin blisters
• abdomen swells with CO₂ that is released by bacteria in the intestines
Forensic Science: Fundamentals & Investigations, Chapter 11 22
Time of Death—Stages of Decomposition
3) Within six to ten days
• corpse continues to bloat as bacteria continue to feed on tissues; eventually chest and abdomen will burst
• fluids begin to leak from body openings
• eyeballs and other tissues liquefy
• skin sloughs off
Forensic Science: Fundamentals & Investigations, Chapter 11 23
Time of Death—Insects
o Forensic entomologist
• Collects insect evidence from on, above, and below the body
• Records environmental conditions
o Within minutes of a death, certain insects arrive to lay their eggs on the warm body—blowflies
o As the corpse decomposes, other kinds of insects arrive
Forensic Science: Fundamentals & Investigations, Chapter 11 24
Time of Death—Insects
o The insect life cycle provides scientists with a benchmark to estimate a time of death
o Insect evidence cannot provide an exact time of death—fluctuating environmental conditions
o Insect evidence provides a close estimate
Forensic Science: Fundamentals & Investigations, Chapter 11 25
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
Forensic Science: Fundamentals & Investigations, Chapter 11 26
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.
Forensic Science: Fundamentals & Investigations, Chapter 11 27
Time of Death—Blowfly Life Cycle
Forensic Science: Fundamentals & Investigations, Chapter 11 28
Time of Death—Blowfly Life Cycle
Forensic Science: Fundamentals & Investigations, Chapter 11 29
Time of Death—Blowfly Life Cycle
Forensic Science: Fundamentals & Investigations, Chapter 11 30
Time of Death—Blowfly Life Cycle
Forensic Science: Fundamentals & Investigations, Chapter 11 31
Time of Death—Blowfly Life Cycle
Forensic Science: Fundamentals & Investigations, Chapter 11 32
. . . . . . . . . . . . . . . . . Summary
o Several definitions of death
o A body decomposing through three stages—livor, rigor, and algor mortis—provides an estimated time of death
o Stomach contents and insect evidence also aid in estimating the time of death
o Environmental factors affect the estimated time of death