Death: Meaning, Manner, Mechanism, Cause and Time

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. If these things can’t be determined from evidence, then an autopsy is performed Unnatural Deaths – Accident, Execution, Homicide, Misadventure, Being attacked by insects, reptiles, fishes, lions, tigers, bears, stingrays, or other wild animals, Adverse outcome of surgery, Suicide, Terrorism, War 2 2

Determine Time of Death —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. Livor mortis results in the settling of blood in areas of the body closest to the ground (begins immediately on death and continues up to 12 hours). 3

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 4

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. 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. 5 5

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. If the body exhibits rigor only in the head and neck, the time of death is just over 2 hours. If a body has no visible signs of rigor, it probably has been dead less than 2 hours or more than 48. 6 6

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 death Sun exposure Illness – hyperthermia will slow rigor or a fever means high temps and fast rigor 7 7

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) Celcius to Farhenheit conversion = (C x 9/5) + 32 = F Farhenheit to Celcius conversion = (F -32) x 5/9 = F 8 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? 0.78 ° C x 12 hours = 9.36 ° C 9 9

Determine Time of Death —Stomach and Intestinal Contents 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 If undigested stomach contents are present, then death occurred zero to two hours after the last meal. If the small intestine is empty and wastes are found in the large intestine, then death occurred 12 or more hours after a meal. 10 10

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 11

Determine Time of Death —Amount of Potassium in the Eye Amount of potassium in the vitreous humor increases 12 12

Determine Time of Death —Stages of Decomposition 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. Potassium level in ocular fluid – cells within inner surface of eyeball release potassium Rigor mortis – the muscles relax and then become rigid without shortening of the muscle Livor mortis – when human heart stops pumping, the blood begins to settle in the parts of the body closest to the ground. The skin will appear as a dark blue or purple color in these areas. The skin will not appear discolored in areas where the body is restricted by either clothing or an object pressing against the body. Info useful in determining if the victim’s position was changed after death. 13 13

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. 14 14

Forensic Anthropology Skeletal Detectives Used to identify and examine human remains Slow breakdown process (decades to centuries) Reveals sex, approximate age, race, and allows face reconstruction. 15 15

Autopsy-External a. Body tag • b. Weight and height • c. Clothing and valuables identified • d. Scars, tattoos, injuries, wounds, bruises recorded • e. Foreign objects noted 16 16

Autopsy-Internal a. Dissection of head and abdomen • b. Organs removed, weighed, measured and examined • c. Tissue samples examined under microscope • d. Fluid samples tested for drugs, infection 17 17