Forensic PathologyForensic

PathologyApril 6, 2009April 6, 2009

Definition of DeathDefinition of DeathA 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 DeathReversibility of DeathDependent 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.

Brain DeathBrain DeathPhysical 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

Postmortem ChangesPostmortem ChangesOnce 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 MortisAlgor MortisBody 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

Ocular ChangesOcular ChangesEyes 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 PotassiumVitreous PotassiumPotassium 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

Livor MortisLivor MortisPurplish-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 MortisRigor MortisRight 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 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 ContentsStomach ContentsStomach 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

DecompositionDecompositionDisintegration 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 ChangesAutolytic ChangesFirst 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

PutrefactionPutrefactionDependent 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

Stages of Decomposition

Stages of DecompositionEarly decomposition begins after

24-30 hours

Greenish discoloration of abdomen

Breakdown of hemoglobin by bacteria

Stages Cont.Stages Cont.Bloat--after about 3 days

Dark discoloration of face

Purging of fluids from nose and mouth

MarblingMarbling

Skin Slippage & Discoloration

Skin Slippage & Discoloration

MummificationMummificationIf environment dry, tissues won’t decompose as readily

Skin becomes leathery, shrunken and dark

Can last in this state a long, long time

AdipocereAdipocereWaxy 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

SkeletonizationSkeletonizationOnce 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?