Transcript death ppt
Death: Meaning, Manner, Mechanism, Cause and Time Chapter 11 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 2 Determine Time of Death —Livor Mortis livor mortis: • Process when body decomposes and blood seeps down and settles into lower parts of body. Lividity : • pooling or settling of blood in tissues after death. • Begins 2 hours after death becomes permanent after 8. 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 Determine Time of Death —Rigor Mortis Stiffening of the skeletal muscles after death • • At death, skeletal muscles cannot relax. Without oxygen, calcium accumulates in these muscles. – • • 5 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 —Rigor Mortis • 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. 6 • Figure 11-8 in book Determine Time of Death —Rigor Mortis 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 7 death – Sun exposure Determine Time of Death —Algor Mortis 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) 8 Determine Time of Death —Algor Mortis 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? 9 • 0.78 ° C x 12 hours = 9.36 ° C Determine Time of Death —Stomach and Intestinal Contents • 4-6 hours for stomach to empty contents into small intestine 10 • 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 —Stomach and Intestinal Contents 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 11 Determine Time of Death —Stages of Decomposition • Within 2 days – – – • After 4 days – – • The skin blisters. The abdomen swells. Within 6-10 days. – – – – 12 Cell autolysis begins following death. Green and purplish staining from blood decomposition. Marbling appearance on the skin. Discoloration of the face. 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 —Insects 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. 13 – will discuss more in next unit.