Forensic Science: Fundamentals & Investigations, Chapter 11 1 Chapter 11 Death: Manner, Mechanism, Cause, and Time By the end of this chapter you will.

Forensic Science: Fundamentals & Investigations, Chapter 11 1

Chapter 11 Death: Manner, Mechanism, Cause, and Time By the end of this chapter you will be able to:

explain the development of livor, rigor, and algor mortis following death

use evidence of these to estimate time of death 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 All Rights Reserved South-Western / Cengage Learning © 2009

Forensic Science: Fundamentals & Investigations, Chapter 11 2

Death Death

The Manner of Death The manner of death can be natural,

accidental, suicidal, homicidal, or undetermined.

Sometimes it is difficult to determine the manner of death.

The most common manner of death is natural.

Forensic Science: Fundamentals & Investigations, Chapter 11 3

Death Death

Cause and Mechanism of Death

The reason for the death is the cause of the death.

The specific change in the body that brought about the cessation of life is the mechanism of death.

Forensic Science: Fundamentals & Investigations, Chapter 11 4

Time of Death—Livor Mortis

The Leaden-Color of Death When red blood cells break down, they turn a

bluish-purple. With decomposition, blood seeps down and

settles in the lower parts of a body. The discoloration that accompanies this

becomes permanent after 8 hours. Warmth accelerates the process.

Forensic Science: Fundamentals & Investigations, Chapter 11 5

Time of Death—Rigor Mortis

The Rigidity of Death At death, skeletal muscles cannot relax. Without oxygen, calcium accumulates in these

muscles. The muscles become stiff. This starts in the head and works its way down to

the legs. After about 15 hours, the muscle fibers begin to

dissolve, and softening begins.

Forensic Science: Fundamentals & Investigations, Chapter 11 6

Time of Death—Rigor Mortis

At 12 hours after death, the body is at its most rigid state.

If a body has no visible signs of rigor, it probably has been dead less than 2 hours or more than 48.

If the body exhibits rigor only in the head and neck, the time of death is just over 2 hours.

This stiffness will have disappeared for the most part after 36 hours.

Forensic Science: Fundamentals & Investigations, Chapter 11 7

Time of Death—Rigor Mortis

Many factors affect when rigor mortis sets in and how long it lasts:

– Ambient temperature – The weight of the body – The body’s clothing or lack of it – Any illness the person had at the time of death – The level of physical activity at the time of death – Sun exposure

Forensic Science: Fundamentals & Investigations, Chapter 11 8

Time of Death—Algor Mortis

The Chill of Death In death a body no longer generates warmth and

begins to cool down. To find the standard temperature of a corpse, a

thermometer is inserted into the liver. Body heat is lost at about 1 to 1.5 degrees an

hour. Time of death determined by temperature

calculations is expressed as a range of time.

Forensic Science: Fundamentals & Investigations, Chapter 11 9

Time of Death—Stomach and Intestinal Contents

Based on these specifics, give an estimate for each of these on how much time has passed since the meal was eaten: 1. Food is still present in the stomach. 2. The stomach is empty but food is found in

the small intestine. 3. The small intestine is empty but waste is

present in the large intestine.

Forensic Science: Fundamentals & Investigations, Chapter 11 10

Time of Death—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.

Forensic Science: Fundamentals & Investigations, Chapter 11 11

Time of Death—Insects

Besides recording data about the environment at a crime scene, a forensic entomologist collects insect evidence.

Within minutes of a death, certain insects arrive to lay their eggs on the warm body. Blowflies are a common example.

As a corpse progresses through the stages of decomposition, other kinds of insects arrive.

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Time of Death—Insects

1. Blowfly eggs can be found in the moist, warm areas of a corpse within 8 hours after death.

2. They will have progressed to the 1st of their 3 larva stages (illustration of one shown above) within 20 hours.

3. By the 4th or 5th day they will have progressed to the 3rd of their 3 larva stages.

Forensic Science: Fundamentals & Investigations, Chapter 11 13

Time of Death—Insects

4. By the 8th or 12th day the larvae will migrate away from the corpse to a dry place.

5. Becoming pupa and immobile within 18-24 days, they will change from white to dark brown.

6. By the 21st-24th day the pupa cases will split open and adult blowflies (illustration of one shown above) will emerge.

Forensic Science: Fundamentals & Investigations, Chapter 11 14

Time of Death—Insects

Because scientists know how long it takes for the various stages of development at given temperatures, forensics entomologists can determine when the insects arrived.

Because life cycles are affected by fluctuations in the daily environmental conditions, insect evidence cannot provide an exact time of death.

Insect evidence, nonetheless, can yield a close estimate.

Forensic Science: Fundamentals & Investigations, Chapter 11 15

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

A body decomposes through the 3 changes of livor, rigor, and algor mortis.

Forensic scientists use evidence from these to estimate the time of death.

They also use stomach contents and insect evidence to estimate the time of death.

It is also important to remember how environmental factors can affect the estimated time of death.