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Estimating Time of Death Forensics 2013-1014. Livor Mortis Livor Mortis Death Color As body begins to decompose blood seeps down through tissues and settles

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Text of Estimating Time of Death Forensics 2013-1014. Livor Mortis Livor Mortis Death Color As body begins...

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Estimating Time of Death Forensics 2013-1014 Slide 2 Livor Mortis 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 Slide 3 Livor Mortis What else can be determined from lividity? Position of body following death Whether a body has been moved post mortem Slide 4 Muscle Fibers and Contraction Slide 5 Rigor Mortis 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 Slide 6 Rigor Mortis 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 Slide 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 Slide 8 Algor Mortis 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 Slide 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 Slide 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 Slide 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 Slide 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 Slide 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 Slide 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 Slide 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 Slide 16 Egg Soon after Deathblowfly eggs can be found in the moist, warm areas of a corpse < 8 hrs Slide 17 Larva Stages 1 (Instar 1) Within 20 hours Slide 18 Larva 2 (Instar 2) After 2 days Slide 19 Larva Stage 3 (Instar 3) After 4-5 days Slide 20 Pre-Pupa After 8-12 days Slide 21 Pupa After 18-24 days Slide 22 Adult After 21-24 days Slide 23 Time of DeathInsects o The insect life cycle provides scientists with a benchmark to estimate a time of death o Insect evidence cannot provide an exact time of deathfluctuating environmental conditions o Insect evidence provides a close estimate

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