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 – T rect )/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 HS 2 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