1. Human Decompsition
“There is a brief but very informative biography of an individual contained within the skeleton, if you know how to read it…”
—Clyde Snow, Forensic Anthropologist

2. Introduction
Death of individual body cells is a slow process that does not occur at the exact moment the heart or brain stops.
A single definition of death is something experts still debate.

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The Pathologist
Determines the time of death. This can be done most accurately if the body is found within the first 24 hours of death
Uses certain indicators such as algor, livor and rigor mortis.
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Rigor Mortis
Skeletal muscles partially contract
Joints stiffen, lock in place
Onset is 10 minutes to 3 hours
Rapid cooling can delay it
Lasts up to hours
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Living muscle cells use oxygen to burn glycogen
After death no oxygen— body makes lactic and pyruvic acids
pH falls as acidity increases
Acid promotes a reaction between actin and myosin which work together to contract the muscle
Muscle shortens until all ATP and acetylcholine is used up
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6. End of Rigor Mortis
The muscles relax when the body starts to decompose and the fibers begin to break down
Autolysis- Digestive enzymes are released as the cells begin to disintegrate, destroying the muscle fibers
Meat is more tender after rigor mortis has passed (Aged Beef?)

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Rigor Mortis
The rigidity of skeletal muscles after death.
Temperature Stiffness Approximate Time
of body of body Since Death
Warm
Cold
Not stiff
Stiff
0 to 3 hrs
Dead between 3 and 8 hrs
Dead 8 to 30 hours
Dead more than 30 hours
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8. Livor Mortis
Livor mortis is the settling of blood, resulting in a reddish or purplish color pattern.
Lividity can indicate the position of the body after death. When lividity becomes fixed, then the distribution of the pattern will not change even if the body’s position is altered.
Lividity usually becomes fixed between 10 and 15 hours after death.

9. Livor Mortis 2
Soon after death, blood is still in vessels, so pressure on an area pushes the blood out
As time goes on blood vessels break down as do blood cells and hemoglobin break down pigment moves out into the tissues
Contact pallor is caused by pressure or constrictive clothing prevents blood from pooling locally

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Livor Mortis
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11. Livor Mortis 3
After death cells release enzyme (fibrinolysins) that prevents clotting
Blood in body stays liquid after death
Permanently won’t clot minutes after death

12. Algor Mortis
Algor mortis is the cooling rate of the body after death. At a crime scene, the body temperature is obtained through:
Rectal temperature
Liver temperature
Glaister equation:
98.4°F - internal temperature/1.5 = hours elapsed since death
Generally the body cools 1 to 1.5 degrees Fahrenheit per hour until it reaches the surrounding temperature.
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13. Algor Mortis 2 Body cools by Radiation
(the higher the body temperature the more heat lost)
Conduction depends on surface contact
faster if in water because enhanced contact
Convection
Wind cools faster

14. Effects that Influence Algor Mortis
Temperature of the surrounding environment
Type of clothing on the body
Clothing Insulates body from heat loss
Wetness of the clothing
Air movement
Layers of clothing
Size of the individual
Obesity:Fat insulates, temperature falls more slowly
Ratio of surface area to volume: Children, thin people cool faster
In water? Cooling is faster since water is a better conductor of heat than air

15. Determining Long Post Mortem Intervals
Decomposition occurs in stages
Initial Decay (0-3 days)
Autolysis--body’s own enzymes destroys
tissue
Begins immediately
Putrefaction (4-10 days)
Bacteria in gut leak out
Anaerobic conditions
Bloat from hydrogen sulfide, methane, cadaverine, putrescine released
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16. Determining Long Post Mortem Intervals
Black Putrefaction (10-20 days)
Body collapses
Liquid seeps into the soil
Butyric Fermentation (20-50 days)
Cheesy smell from butyric acid
Maggots leave
Beetles arrive
Dry decay (beyond 50 days)
Hair is consumed by moths and mites
Bones are left
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17. Volatile Fatty Acid Analysis Results from the Body Farm
Depends on temperature
The hotter, the faster the reactions proceed
Depends on whether body was buried or not
Decay is faster on the surface
More insect activity
Warmer—2 feet down is fairly constant 50-55o F
Decay is slower in acid soil
Pine forests have very acid soil
Decay is slower if the body is sprayed with insecticide
Accumulated Degree Days (sum average daily temp)
Decay is linear in Accumulated Degree Days

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Adiopocere
Adipocere is a wax-like substance formed by the hydrolysis of fat to fatty acids and soaps in presence of bacterial enzymes.
It is resistant to bacteria and slows further decomposition.
Formation begins within a month of death, and in the absence of air it can last for centuries.
Formation can occur in embalmed or untreated corpses.
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Adipocere
Adipocere is formed under the following conditions:
On bodies are not exposed to insects
In a moist, airless environment (bottom of a lake, wet ground)
Prominent on cheeks, buttocks, stomach, breasts (areas with lots of fat)
An exposed, infested body (with insects), or a body in a warm environment is unlikely to form deposits of adipocere.
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Otzi
5300 year old body
Found by hikers in Austrian Alps
Otzi is primarily now adipocere
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Adipocere- Grave Wax
Over a timescale of centuries, adipocere in sealed airtight containers (such as lead-lined coffins used by the Romans) can turn into “body liquor" - a brown/orange fatty liquid that may be highly infectious.
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