Estimating Time of Death

1. Estimating Time of Death Forensics 2013-1014

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

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 Mortisdeath 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 21-37 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 18-24 days

22. Adult • After 21-24 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