Death: Meaning, Manner, Mechanism, Cause and Time

Chapter 11

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Death Death

• Manner of death can be natural, accidental, suicidal, homicidal, or undetermined.

• The most common manner of death is natural.

• Mechanism of Death is the specific change in the body that brought about the cessation of life

Lividity : • pooling or settling of blood in tissues after death.

• Begins 2 hours after death becomes permanent after 8.

Determine Time of Death Determine Time of Death —Livor Mortis

livor mortis: • Process when body decomposes and blood seeps down and settles into lower parts of body.

Determine Time of Death Determine Time of Death —Livor Mortis

Livor mortis can: • Determine Time of Death

•Within 2-8 hours, can press skin and color disappears•Factors affecting lividity

•Ambient temperature, anything that could impede flow of blood to area

•Reveal the position of the corpse within first 8 hours•If on back, blood will pool along backside

•Reveal if the body was moved•If moved, may show dual lividity from first position and then from second position

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Stiffening of the skeletal muscles after death

• At death, skeletal muscles cannot relax. • Without oxygen, calcium accumulates in these

muscles. – Calcium is used by the body to signal muscle

contraction, this accumulation signals the muscles to contract.

• The muscles become stiff. • Rigor mortis starts in the head and works its

way down to the legs.

Determine Time of Death Determine Time of Death —Rigor Mortis

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• 2 -6 hours postmortem (after death), rigor begins in the head

• 12 hours postmortem, rigor is complete and throughout the entire body

• 15 -36 hours postmortem, the muscle fibers begin to dissolve, and softening begins (rigor mortis starts to end).

• 36 -48 hours postmortem, rigor ends and is relaxed throughout the entire body.

• Figure 11-8 in book

Determine Time of Death Determine Time of Death —Rigor Mortis

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Factors that affect rigor mortis

– Ambient temperature • (cold = slow rigor)

– The weight of the body • (obesity = slow rigor)

– The body’s clothing or lack of it – Any illness the person had at the time of death– The level of physical activity at the time of

death – Sun exposure

Determine Time of Death Determine Time of Death —Rigor Mortis

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Cooling of the body after death

• In death a body no longer generates warmth and begins to cool down.

• To find the standard temperature of a corpse, a thermometer is inserted into the liver.

• Time of death determined by temperature calculations is expressed as a range of time.

– Normal body temperature is 98.6°F (37°C)

Determine Time of Death Determine Time of Death —Algor Mortis

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Calculations• First 12 hours after death:

– Body cools 0.78 °C (1.4 °F) per hour

• After 12 hours after death:– Body cools 0.39 °C (0.7 °F) per hour

• Example– What is the temperature loss for someone who has

been dead for 12 hours?• 0.78 ° C x 12 hours = 9.36 ° C

Determine Time of Death Determine Time of Death —Algor Mortis

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• 4-6 hours for stomach to empty contents into small intestine

• Another 12 hours for the food to leave the small intestine for the large intestine

• 24 hours for the food to leave the large intestine

Determine Time of Death Determine Time of Death —Stomach and Intestinal

Contents

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Example – Determine the time of death from the last

meal if food is found in the small intestine

Answer: Death occurred 4 - 6 hours after the last meal

Determine Time of Death Determine Time of Death —Stomach and Intestinal

Contents

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• Within 2 days– Cell autolysis begins following death. – Green and purplish staining from blood decomposition. – Marbling appearance on the skin. Discoloration of the face.

• After 4 days – The skin blisters. – The abdomen swells.

• Within 6-10 days. – The corpse bloats. – Fluids begin to leak from body openings as cell membranes

rupture. – The skin sloughs off. – Eyeballs and other tissues liquefy.

Determine Time of Death Determine Time of Death —Stages of Decomposition

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Forensic Entomology

• Within minutes of a death, certain insects arrive to lay their eggs on the warm body.

– Blowflies are a common example.

• As a corpse progresses through the stages of decomposition, other kinds of insects arrive.

– will discuss more in next unit.

Determine Time of Death Determine Time of Death —Insects