Transcript Death and Bugs PPT

DEATH, BUGS, AND BONES
1
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
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
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
2
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 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
3
DEFINITION OF DEATH
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
4
UPON CESSATION OF LIFE
Once cell death has occurred
Autolysis—cell breakdown -begins
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
5
SUSPICIOUS DEATH
Autopsy 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 death
Mechanism of death
Time of death
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
6
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
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
7
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?
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS, CHAPTER 11
8
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?
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS, CHAPTER 11
9
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
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
10
HOW TO DETERMINE TIME OF DEATH
Livor Mortis
Rigor Mortis
Algor Mortis
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS, CHAPTER 11
11
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
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
12
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
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
13
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 throughout
After about 15 hours—

Muscle fibers begin to dissolve

Softening begins
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
14
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
15
TIME OF DEATH—RIGOR MORTIS
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
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
16
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
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
17
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 1.0 degree per hour after about 12 hours
 Heat loss is affected by the ambient temperature
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
18
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
Death occurred 12 or more
hours after a meal
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
19
TIME OF DEATH
—Stomach and
Intestinal
Contents
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
20
CHANGES OF THE EYE
During life surface of eye is wet due to blinking
Upon death the eye begins to dry out a film forms on surface
 If eye open – film forms within 2-3 hrs
 If eye closed – film forms within 24 hrs
After death potassium begins to accumulate in the vitreous humor (jelly
portion of eye) – rate of accumulation can help predict time of death
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
21
CHANGES IN THE EYE
Petechiae – 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.
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS, CHAPTER 11
22
STAGES OF DECAY
Stage
What Happens During Decomposition
Initial Decay
Corpse appears normal on outside, but decay is
beginning on inside due to bacteria
Putrefaction
Odor of decaying flesh is present and corpse appears
swollen
Black Putrefaction
Very strong odor. Parts of flesh appear black. Gases
escape and corpse collapses.
Butyric
Fermentation
Corpse is beginning to dry out. Most of flesh is gone
Dry Decay
Corpse almost dry. Further decay is slowed due to the
lack of moisture
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
23
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
24
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
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.
4th or 5th day—3rd of their 3 larva stages
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
26
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.
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
27
SPIRACLE SLITS
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
28
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
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
29
. . . . . . . . . . . . . . . . . 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
FORENSIC SCIENCE: FUNDAMENTALS & INVESTIGATIONS,
CHAPTER 11
30