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
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Forensic Science: Fundamentals & Investigations, Chapter 11

2. 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. 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:
Food is still present in the stomach.
The stomach is empty but food is found in the small intestine.
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.
Fluids begin to leak from body openings as cell membranes rupture.
Discoloration of the face.
The skin sloughs off.
The skin blisters.
Green and purplish staining from blood decomposition.
The corpse bloats.
Eyeballs and other tissues liquefy.
The abdomen swells.
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.
Forensic Science: Fundamentals & Investigations, Chapter 11

12. Time of Death—Insects
Blowfly eggs can be found in the moist, warm areas of a corpse within 8 hours after death.
They will have progressed to the 1st of their 3 larva stages (illustration of one shown above) within 20 hours.
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
By the 8th or 12th day the larvae will migrate away from the corpse to a dry place.
Becoming pupa and immobile within days, they will change from white to dark brown.
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
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.
Forensic Science: Fundamentals & Investigations, Chapter 11