Forensic
Taphonomy
Definition: history of the body after death;
postmortem changes;
Greek taphos = burial or grave;
nomos = law
Issues to be resolved
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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
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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
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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
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In addition to bones, hair and clothing are
also modified, preserved or destroyed
Human Remains
Early Postmortem Changes
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Rigor mortis
Livor mortis
Algor mortis
Ocular changes
Food in stomach
Vitreous potassium
Rigor mortis
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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
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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
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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
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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
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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
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Corneal film
Scleral discoloration
Corneal cloudiness
Corneal opacity
Exophthalmos (eyes bulging)
Endophthalmos (eyes retracting)
Food in stomach indicates time since
last meal
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Light – 1-2 hours
Medium – 3-4 hours
Heavy – 4-6 hours
Emotional state may influence rate of
emptying
Vitreous potassium
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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
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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
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Autolysis – enzymes within body break
down carbohydrates and proteins
Putrefaction – major component of
decomposition which is due to bacterial
activity
Putrefaction
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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
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Buried or not buried
Climate
Moisture
Elevation
Terrain
Protection
Insect/animal/human intervention
Interactive Autopsy
www.hbo.com/autopsy/interactive/