Death, Bugs, and Bones 1 - PowerPoint Presentation

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Death, Bugs, and Bones

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Death: Meaning, Manner,

Mechanism, Cause, and Time

By the end of this chapter you will be able to:

Discuss the definition of death

Distinguish between four manners of death: natural, accidental, suicidal, and homicidalDistinguish between cause, manner, and mechanisms of deathExplain the development of rigor, algor, and livor mortis following death

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All Rights Reserved South-Western / Cengage Learning © 2012, 2009

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Death: Meaning, Manner,

Mechanism, Cause, and Time

By the end of this chapter you will be able to:

Estimate the time of death

Describe the stages of decomposition of a corpseUse 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

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Definition of Death

Cessation, or end, of lifeIrreversible cessation of blood circulationCessation of all brain activityExperts do not agree on a single definition

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Cell death

Once cell death has occurredAutolysis—cell breakdown – beginsIf enough cells die the body cannot restart itself and death will occur

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Suspicious DeathAutopsy will be conducted if the death is suspicious or was the result of crime.

During the autopsy the pathologist will try to determine:Manner of death

Cause of deathMechanism of deathTime of death

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The Manner of Death

The manner of death can be

Natural, the most common

Accidental

Suicidal

Homicidal Undetermined Sometimes the manner of death is difficult to determine

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How should death be determined?

A man with a heart condition is attacked and dies from a heart attack during the assault. Accidental or Homicide?

An elderly woman dies after being kept from receiving proper health care by her son. Natural death or Homicide?

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Both would be considered homicidal, because death resulted during the act of a crime for the man and due to negligence for the woman.

Could you convince a jury that it was due to homicide?

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Cause and

Mechanism of Death

Cause of the death

is the reason for the death

Mechanism of death

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

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How to determine Time of death

Livor MortisRigor Mortis

Algor Mortis

Will give a range for time of death, but will not give the exact time.

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Time of Death—Livor Mortis

The Leaden-Color of Death

Lividity

—

With decomposition, blood seeps down and settles in the lower parts of a body

Red blood cells turn bluish-purple The discoloration is due to the pooling of blood -

lividity

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Time of Death—Livor Mortis

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

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Time of Death—Rigor Mortis

The Rigidity of Death

Without oxygen in the blood—

Calcium accumulates in the muscles

Muscles stiffen

Starts in the head and expands throughoutAfter about 15 hours— Muscle fibers begin to dissolveSoftening begins

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Time of Death—Rigor Mortis

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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

Just over 12 hours

No visible signs of rigor

Less than 2 hours

or more than 48 hours ago

Stiffness generally disappears

After 36 hours

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Time of Death—Rigor Mortis

Factors affecting rigor mortis:

Ambient temperature

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

The Chill of Death

Body heat falls after death About 1.5 degrees Fahrenheit per hour immediately after death

Slowing to less than 1.0ºF per hour after about 12 hoursHeat loss is affected by the ambient temperatureCorpse temperature is measured by a thermometer inserted into the liverTime of death is expressed as a range of time

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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 found in small intestine

Death occurred at least four to six hours after a meal

Small intestine is empty; waste found in large intestine

Death occurred 12 or more hours after a meal

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Time of Death

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—

Stomach and Intestinal Contents

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Changes of the EyeDuring life surface of eye is wet due to blinking

Upon death the eye begins to dry out a film forms on surfaceIf eye open – film forms within 2-3 hrs

If eye closed – film forms within 24 hrsAfter death potassium begins to accumulate in the vitreous humor – rate of accumulation can help predict time of death

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Changes in the EyePetechiae

- red splotches in the whites of the eye and under the lids of the eye

due to the breaking of capullaries

. Usually seen

on victims of strangulation.

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Stages of Decay

Stage

What Happens During

Decomposition

Initial

Decay < 2 daysCorpse appears normal on outside, but decay is beginning on inside due to bacteriaSkin begins to look marbledFace becomes discolored

Putrefaction 3-5 daysOdor of decaying flesh is present Corpse appears swollen due to production of CO2Skin begins to blisterBlack Putrefaction6-10 DaysVery strong odor. Parts of flesh appear black. Body continues to bloat until bursting & gases escape and corpse collapses.Fluids begin to leak out.

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Stages of decayForensic Science: Fundamentals & Investigations, Chapter 11

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Stage

What Happens

During Decomposition

Butyric Fermentation

> 11 daysCorpse is beginning to dry out. Most of flesh is goneDry Decay>11 daysCorpse almost dry. Further decay is slowed due to the lack of moisture

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Time of Death

—Stages of Decomposition

Choose:

A

.

Within 2 days.

B. After 4 days. C. Within 6-10 days. Fluids begin to leak from body openings as cell membranes ruptureDiscoloration of the faceThe skin sloughs offThe skin blistersGreen and purplish staining from blood decompositionThe corpse bloatsEyeballs and other tissues liquefyThe abdomen swellsMarbling appearance on the skin

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https://www.youtube.com/watch?v=OFJrow7yaec

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Time of Death—Insects

Forensic entomologist

Collects insect evidence from on, above, and below 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

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Time of Death

—Blowfly Life Cycle

<8 hours after death—blowfly eggs can be found in the moist, warm areas of a corpse

Within 20 hours—1

st

of their 3 larva stages

4th or 5th day—3rd of their 3 larva stages

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Time of Death

—Blowfly Life Cycle

8 to 12 days—larvae migrates to a dry place

18 to 24 days— Early pupa; immobile; changes from light brown to dark brown

By the 21

st

-24th day the pupa cases will split open and adult blowflies will emerge.

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Spiracle Slits

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Time of Death—Insects

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

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

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

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