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Forensic Pathology

Forensic Pathology. April 6, 2009. Definition of Death. A person is dead if: He has suffered irreversible cessation of circulatory and respiratory functions Or, he as suffered irreversible cessation of all functions of the entire brain, including the brain stem Brain death:

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Forensic Pathology

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  1. Forensic Pathology • April 6, 2009

  2. Definition of Death • A person is dead if: • He has suffered irreversible cessation of circulatory and respiratory functions • Or, he as suffered irreversible cessation of all functions of the entire brain, including the brain stem • Brain death: • Coma and cerebral unresponsiveness, Apnea, Dilated pupils, Absent cephalic (brainstem)reflexes, Electrocerebral silence

  3. Reversibility of Death • Dependent upon capability of tissues to recover from anoxia • Resistance of organs variable • CNS has high sensitivity • Approx. 4-6 min. between loss of oxygen and irreversible brain damage • With cutting edge techniques may be 15-16 minutes • Age and temperature cause variability--up to 30 min.

  4. Brain Death • Physical characteristics: • Grayish appearance, marked swelling, herniation, anoxic damage, liquefaction • Brain death changes become apparent 12-16 hrs. after end of cerebral circulation • Persistent Vegetative State (PVS) • Different from brain death • Total permanent and total destruction of frontal lobe

  5. Postmortem Changes • Once dead, bodily functions cease and body begins to break down • Circulation stops, chemical composition of body fluids changes, digestion ends, natural bacteria in gut takes over, animals begin to feed on body • Happens in particular order--“postmortem clock”

  6. Algor Mortis • Body cools to ambient temperature • Cools at rate of 1.5o F to 2o F per hour • Skin cools fastest, and isn’t used in body temp determination • Body core temps used--rectum, liver, brain • Rate of cooling changes with clothing, body fat, air currents, immersion in water, size

  7. Ocular Changes • Eyes show some of the earliest postmortem changes • Settling of rbc’s in capillaries • Thin film on cornea within 2-3 minutes, cloudiness within 2-3 hours • If open, exposed areas develop tache noire (black spot) • Intraocular fluid--dries up in about 4 days

  8. Vitreous Potassium • Potassium levels in the eye much higher than potassium levels in the blood • Due to the sodium-potassium pump • After death pump no longer works, so potassium diffuses out • Known rate: (7.14 x K+ concentration) - 39.1 = hours since death

  9. Livor Mortis • Purplish-blue discoloration due to settling of blood by gravitational forces within capillaries • May be evident as early as 20 min. after death • Fixed after 8-12 hours

  10. Rigor Mortis • Right after death, muscles flaccid • Fibers in muscles bind together • Takes energy to relax • Rule of thumb: takes 12 hours to appear fully, lasts 12 hours, takes 12 hours to disappear • Variable: previous exercise, convulsions, electrocution, heat

  11. Cadaveric Spasm • Sometimes rigor mortis hits without muscle flaccidity • Occurs in deaths preceded by great excitement or tension • Drowning, murder • Clenched fist holding object

  12. Stomach Contents • Stomach empties at known rate • Digestive processes cease after death • Solid food empties slower that liquid • Starchy and fatty foods empty more slowly • Light meals: 1 1/2-2 hours • Heavy meals: 3-4 hours • Liquid: 1/2 hour

  13. Decomposition • Disintegration of body tissues • During life, biochemical process preserve integrity of cellular membranes and organelles • After death, cell enzymes leak out and microorganisms no longer killed • Autolysis--self dissolution by body enzymes • Putrefaction--decomposition changes produced by action of bacteria and microorganisms • Anthropophagy--destruction of body by predators

  14. Autolytic Changes • First changes occur in organs rich in enzymes • Pancreas, stomach, liver • Digestive juices present at death begin to eat away at organs • Mucosal lining no longer produced

  15. Putrefaction • Dependent upon temperature and prior health of individual • Gasses produced: methane, CO2, Hydrogen, Ammonia • Environment--body exposed to air decomposes more rapidly than in water, which is more rapid than in soil • 1 week in air=2 weeks in water=8 weeks in soil

  16. Stages of Decomposition • Early decomposition begins after 24-30 hours • Greenish discoloration of abdomen • Breakdown of hemoglobin by bacteria

  17. Stages Cont. • Bloat--after about 3 days • Dark discoloration of face • Purging of fluids from nose and mouth

  18. Marbling

  19. Skin Slippage & Discoloration

  20. Mummification • If environment dry, tissues won’t decompose as readily • Skin becomes leathery, shrunken and dark • Can last in this state a long, long time

  21. Adipocere • Waxy fat (grave wax)--helps preserve the body • In high humidity and temperature, body fats turn into clay-like, gray substance • Bacterial enzymes convert unsaturated fats into saturated solid fats • Takes from 3-6 months to develop

  22. Skeletonization • Once all soft tissue removed, only skeleton remains • Rate of skeletonization depends on climate • Temperate areas: 1 1/2 years • In hot and humid areas: as little as 10 days

  23. Any Questions?

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