1. Estimating Time of Death
Forensics

2. Livor Mortis ”Death Color”
As body begins to decompose blood seeps down through tissues and settles in lower parts of body
Red Blood Cells Turn purplish-blue
Pooling of blood = lividity
Lividity Begins about 2 hours after death
Between 2-8 hours lividity will be present, but if the skin is pressed color will dissappear
After 8 hours lividity remains if the skin is pressed
Ambient Temperature = Temperature surrounding body
affects the rate of lividity
Higher Temperature = Increase in rate of lividity
Lower Temperature = Decrease in rate of lividity

3. Livor Mortis What else can be determined from lividity?
Position of body following death
Whether a body has been moved post mortem

4. Muscle Fibers and Contraction

5. Rigor Mortis “Death Stiffness”
Normal Muscle Contraction
Calcium released from membranes inside cell causes muscle fibers cells to contract
Active transport then removes calcium so muscle fibers can relax
This requires oxygen and an energy supply
The Rigidity of Death
Stiffness occurs because skeletal muscles are locked in a flexed position and are unable to relax.
Calcium leaks out of cell and muscle remains in a contracted position
No active transport after death
Starts within 2 hours of death
Begins with Head (Face) and neck
Peak Rigor, At 12 hours the body is at its most rigid state
At about 15 hours muscle fibers break down and soften
Stiffness gradually disappears after 36 hours
Rigor may remain for up to 48 hours

6. Rigor Mortis The body is at its most rigid state Just over 2 hours
Observation
The body is at its most rigid state
No visible signs of rigor
Stiffness generally disappears
Approx. Time Scale
Just over 2 hours
Less than 2 hours
or more than 48 hours ago
After 36 hours

7. Factors Affecting Rate of Rigor
Ambient Temperature
Cold- slows rigor
Warm- Accelerates Rigor
Clothing or Lack of Clothing
Clothes = accelerates rigor
No Clothes = slows rigor
Sun Exposure
Accelerates rigor
Activity/Exercise
Exercising or struggling = accelerates rigor
Sleep = slows rigor
Body Weight
Obese- slows rigor (fat stores oxygen)
Thin- Accelerates Rigor

8. Algor Mortis death heat
The Chill of Death
Algor Mortis-Describes temperature loss in a corpse
First 12 hours.
Temperature loss = .78 degrees Celsius (1.4 degrees Fahrenheit) per hour
After 12 hours
Temperature loss = .39 degrees Celsius (.7 degrees Fahrenheit) per hour

9. Stomach and Intestinal Contents
If undigested stomach contents are present, then death occurred 0 to 2 hours after last meal
If the stomach is empty but food is found in the small intestine, then death occurred at least 4-6 hours after last meal
If the small intestines is empty and wastes are found in large intestine, then death probably occurred 12 or more hours after last meal

10. Decomposition The rotting or break down of all tissues and organs
Bacteria and other microorganisms aid the decomposition process, just as they decompose plants and animals in the environment.
Occurs in Predictable Pattern
Can be used to help determine Time of Death

11. Stages of Decomposition
Initial Decay
Corpse appears normal from the outside, but is starting to decompose from the actions of bacteria and autolysis
Putrefecation
Odor of decaying flesh is present and the corps e appears swollen
Black Putrefecation
Very Strong odor. Parts of the flesh appear black. Gases escape and the corpse collapses
Butyric Fermentation
Corpse is beginning to try out. Most of the flesh is gone
Dry Decay
Corpse is almost dry. Further decay is very slow from lack of moisture

12. Timeline of Events during Decomposition
Within 2 days after death:
Cell Autolysis begins following death
Green and purplish staining occurs form blood decomposition
The skin takes on a marbled appearance
The Face Becomes discolored
After 4 Days:
The skin blisters
The abdomen swells with the gas carbon dioxide release by bacteria living in the intestines
Within 6-10 Days:
Corpse bloats with carbon dioxide, eventually gas causes the chest and abdominal cavities to burst and collapse
Fluids begin to leak from body openings as cell membranes rupture
Eyeball and other tissues liquefy
The Skin sloughs off

13. Factors Affecting Rate of Decomposition
Temperature
Bodies decompose fastest within degrees Celsius (70-99 degrees Fahrenheit)
Below this range rate decreases because cold temperatures slow the growth of bacteria and microorganisms
Above this range tends to dry out corpses and preserve them
Several other factors
Illness
Age
Weight
Clothing or Lack of Clothing

14. Forensic Entomology Forensic entomologist
Collects insect evidence from on, above, and below the body
Records environmental conditions
Because life cycles are affected by fluctuations in the daily environmental conditions, insects cannot provide an exact time of death, only a close estimate.
At crime lab some of the insects are raised under environmental conditions that mimic the environmental conditions at the crime scene to obtain most accurate approximation

15. Forensic Entomology
Blowflies are usually the first insects to arrive at a dead body
Usually arrive within minutes
Blowflies exhibit different life stages
Egg, larva (also known as instars), pupa, prepupa, adult

16. Egg
Soon after Death—blowfly eggs can be found in the moist, warm areas of a corpse
< 8 hrs

17. Larva Stages 1 (Instar 1)
Within 20 hours

18. Larva 2 (Instar 2)
After 2 ½ days

19. Larva Stage 3 (Instar 3)
After 4-5 days

20. Pre-Pupa
After 8-12 days

21. Pupa
After days

22. Adult
After days

23. 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