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: Coma and cerebral unresponsiveness, Apnea, Dilated pupils, Absent cephalic (brainstem)reflexes, Electrocerebral silence

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 minutes Age and temperature cause variability- -up to 30 min.

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

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”

Algor Mortis Body cools to ambient temperature Cools at rate of 1.5 o F to 2 o 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

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

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) = hours since death

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

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

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

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

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

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

Putrefaction Dependent upon temperature and prior health of individual Gasses produced: methane, CO 2, 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

Stages of Decomposition Early decomposition begins after hours Greenish discoloration of abdomen Breakdown of hemoglobin by bacteria

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

Marbling

Skin Slippage & Discoloration

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

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

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

Any Questions?