Forensic Taphonomy

Definition: history of the body after death; postmortem changes;

Greek taphos = burial or grave;

nomos = law

Issues to be resolved Identification of the deceased Assessment of the time since death Cause and manner of death Many techniques have been borrowed form

other disciplines Human remains are treated as part of a

complex environment

Perimortem interval Estimating the timing of the injury Need to distinguish between antemortem

and postmortem injuries Boundary between life and death is often

obscure This time period, then, is often ambiguous

Postmortem Interval Why is it important to know this? Estimates are also often imprecise Observations used to mark time need to be

specified Kinds of changes analyzed depend on time

scale; hours, days, years

Many processes alter the condition of human remains

In addition to bones, hair and clothing are also modified, preserved or destroyed

Human Remains

Early Postmortem Changes Rigor mortis Livor mortis Algor mortis Ocular changes Food in stomach Vitreous potassium

Rigor mortis Muscular relaxation after death is followed

by gradual onset of rigidity Cross-linking of actin and myosin Perceived earlier in smaller muscles Heat accelerates the process and cold

decelerates Other variables (see handout)

Rigor mortis

Livor Mortis Settling of the blood to lowest points of the

body due to gravity Depends on position of the body Develops when cardiac activity stops Capillary bed distension due to hydrostatic

pressure Areas where blood has settled will appear

dark blue or purple (see picture)

Livor Mortis

Petechial Hemorrhages Rupture of capillaries due to hydrostatic

pressure causes small areas of skin hemorrhaging

Dark, circular spots ranging in size from pin-point to 4-5mm

Pin-point spots in the whites of the eyes (sclera) suggests asphyxiation

Petechial hemorrhages in the sclera

Algor Mortis Refers to cooling of the body Body temperature declines until it reaches

ambient temperature If the body cools at a uniform rate then

body temperature can be used to determine time of death

Body cools by radiation, convection and conduction (see handout)

Many factors affect cooling rate Scene Clothing Victim size Activity Physical factors (e.g. closed car with sun

shining on it all day)

Glaister equation – one formula used for estimating time since death

(98.4 – Trect)/1.5 = approx hrs since death

(This equation applies to Fahrenheit scale)

Ocular changes – sequential changes

Corneal film Scleral discoloration Corneal cloudiness Corneal opacity Exophthalmos (eyes bulging) Endophthalmos (eyes retracting)

Food in stomach indicates time since last meal

Light – 1-2 hours Medium – 3-4 hours Heavy – 4-6 hours Emotional state may influence rate of

emptying

Vitreous potassium Potassium levels are normally high within cells

and lower outside The pumping mechanism that maintains this

concentration difference fails after death Results in a steady increase in potassium levels

in the vitreous fluid Collected from this site because of its accessibility 7.14 X (K+ concentration) – 39.1 = hrs since

death

Postmortem Tissue Changes Decomposition Mummification – drying of the body and

“leather-like” changed Skeletonization Adipocere – formation of a waxy substance

due to hydrogenation of body fat

Decomposition involves two major components

Autolysis – enzymes within body break down carbohydrates and proteins

Putrefaction – major component of decomposition which is due to bacterial activity

Putrefaction Gas formation and bloating Green discoloration of abdomen Marbling of blood vessels – brown-black

discoloration caused by HS2 gas Blisters and skin slippage Loss of hair and nails

Skeletonization depends on many factors

Buried or not buried Climate Moisture Elevation Terrain Protection Insect/animal/human intervention

Interactive Autopsy

www.hbo.com/autopsy/interactive/