Forensics Unit 3 Notes

Forensic Pathology

• FORENSIC PATHOLOGY (Pathology – Study of disease) The ME determines the manner, cause, and mechanism of death and approximate time of death
• Manner: Natural Causes, Accidental, Suicidal, Homicidal, or Undetermined.
• Cause: The reason. (bludgeoning, heart attack, etc.)
• Mechanism: The specific change in the body that brought about cessation of life. (loss of blood, pulmonary arrest, etc.)
• Death: a process not an instantaneous event, irreversible cessation of circulation of blood; cessation of brain activity
• Stages to death: Stoppage and Autolysis
• Stoppage – Heart stops beating, no blood flow, no oxygen to cells, body; processes fail 
• Autolysis – Cells breakdown, cell contents spill out
• Autopsy: literally means: to see for oneself, only done for suspicious and unnatural deaths

Time of Death

• Post Mortem Interval (PMI): Time between death and when the body is found, in hours
  • 1. LIVOR MORTIS (Color of Death) 
    • blood settles to lowest part of body by gravity 
    • heart stops pumping and with lack of pressure blood seeps out of capillaries
    • normally purplish–blue color (cherry red =carbon monoxide poisoning)
    • pressure against body prevents lividity in that area,  scars also prevent lividity
    • begins in 20 minutes, noticeable after 2 hours, permanent after 8-12 hours
    • lividity occurs faster if hot and slower if cold (important to record environmental conditions)
    • Was the body moved? Does the position the body was found make sense compared to the lividity? Is there a pattern in the lividity that gives a clue to where the body was?
    • Dual Lividity: body was moved between 2 – 8 hours
    • Tardieu spots and Petechial hemorrhaging - capillaries burst and form pinpoint hemorrhaging
  • 2. RIGOR MORTIS (Stiffness of Death)
    • muscles initially relax and then contract and then relax again
    • cells without oxygen produce energy through glycolysis and produce lactic acid and calcium ions accumulate causing muscles to contract (actin and myosin bridges lock)
    • begins with small muscles and progresses to larger muscles, then rigor is lost in the same order
    • Temperature: hot - faster (clothing, fever, direct sunlight) 
    • Activity before death: aerobic exercise = faster, sleeping = slower 
    • Weight: thin = faster, obese = slower 
    • Drugs can speed (stimulants) or slow (depressants)
  • ALGOR MORTIS (Heat of Death)
    • body will cool to the temperature of its surroundings 
    • take core body temperature (normal is 98.6F or 37C) 
    • body cools on average 1.5F /hour during first 12 hours then 1F /hour after 12  hours
    • environmental factors: drugs, fever, ambient temperature, wind, body fat, and clothing
  • Stomach Contents
    • Ate 12-24 hours prior to death: Food in Large intestine, small intestine empty
    • Ate 4-6 hours prior to death: Food in Small intestine, stomach empty
    • Ate 0-2 hours prior to death: Undigested Food in stomach
  • Vitreous humor potassium
    • Level of potassium ion K+ increases as the body decays. The ocular fluid is cleanest.
  • Entomology
    • Useful for days to weeks. Examine the stages of growth of the maggots.
  • Post Mortem Hair Bands
    • Hair continues “to grow” after death Skin is actually retracting.