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 deatho Distinguish between four manners of death:

natural, accidental, suicidal, and homicidalo Distinguish between cause, manner, and

mechanisms of deatho Explain the development of rigor, algor, and

livor mortis following death

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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 corpseo 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 lifeo Irreversible cessation of blood circulationo Cessation of all brain activityo Experts do not agree on a single definition

Forensic Science: Fundamentals & Investigations, Chapter 11 4

Introduction

o Autolysis—cell breakdown

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The Manner of Death The Manner of Death

o The manner of death can be • Natural, the most common• Accidental • Suicidal • Homicidal • Undetermined

o Sometimes the manner of death is difficult to determine

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Cause and Cause and Mechanism of Death Mechanism of Death

o Cause of the death is the reason for the death

o Mechanism of death is the specific change in the body that brought about the cessation of life

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Time of Death—Livor Mortis 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 bodyo Red blood cells turn bluish-purple

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Time of Death—Livor Mortis Time of Death—Livor Mortis

o Lividity begins about two hours after deatho Discoloration becomes permanent after eight

hourso Ambient temperature affects the speed of

decomposition o Lividity can determine the position of the

body during the first eight hours

Forensic Science: Fundamentals & Investigations, Chapter 11 9

Time of Death—Rigor Mortis 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 throughouto After about 15 hours—

• Muscle fibers begin to dissolve• Softening begins

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Time of Death—Rigor Mortis 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 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

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Time of Death—Rigor Mortis Time of Death—Rigor Mortis

Factors affecting rigor mortis:o Ambient temperature o Weight of the body o Type of clothing, or lack of it o General health of person at time of death o Level of physical activity at time of death o Sun exposure

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Time of Death—Algor MortisTime 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

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Time of DeathTime of Death—Stomach and Intestinal Contents —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

Death occurred at least four to six hours after a

mealSmall intestine is empty;

waste found in large intestine

Death occurred 12 or more hours after a meal

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Time of DeathTime of Death

—Stomach and Intestinal Contents

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Time of DeathTime of Death—Stages of Decomposition —Stages of Decomposition

Choose: A. Within 2 days. B. After 4 days. C. Within 6-10 days.

1. Fluids begin to leak from body openings as cell membranes rupture

2. Discoloration of the face

3. The skin sloughs off

4. The skin blisters

5. Green and purplish staining from blood decomposition

6. The corpse bloats

7. Eyeballs and other tissues liquefy

8. The abdomen swells

9. Marbling appearance on the skin

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Time of Death—Insects 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

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Time of DeathTime of Death—Blowfly Life Cycle—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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Time of DeathTime of Death—Blowfly Life Cycle—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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Time of Death—Insects 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

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. . . . . . . . . . . . . . . . . Summary . . . . . . . . . . . . . . . . . Summary

o Several definitions of deatho 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