The ME’s 3 most important determinations: Cause, Manner, and Time of Death
Part II: Time of Death Notes
DETERMINATION OF THE TIME OF DEATH
Determining TOD is critical Both an art and a science The sooner after death the more accurate the estimate Changes death variable and unpredictable.
Physiologic TOD, Estimated TOD, Legal TOD
Always a best guess None of the methods are very accurate Body temperature Rigor mortis Livor mortis (lividity) Degree of putrefaction Stomach contents Insect activity Scene markers
BODY TEMPERATURE
Normal body temperature is 98.6F Body loses or gains heat until it equilibrates with that of the surrounding medium. The formula is: Hours since death = 98.6 - corpse core temperature / 1.5 Cold/wind/water increase heat loss Obesity, heavy clothing, warm still air, exposure to direct sunlight, and an enclosed environment slow heat loss.
RIGOR MORTIS
Spasm due to chemical reactions within the muscle cells after death. Loss of adenosine triphosphate (ATP) to adenosine diphosphate (ADP) causes the muscles to contract and stiffen. Later loss of rigidity from the putrefaction process. Rigor begins throughout the body at the same time Appears first in smaller muscles- face, neck, and hands Relaxes in same pattern General rule for rigor mortis is 12-12-12 Changes due to: activity, body temp, ambient temp, Cadaveric spasm
LIVOR MORTIS (Lividity)
Purplish—exceptions for CO (carboxyhemoglobin), Cyanide (cyanohemoglobin), Freezing Dependent areas—lying, sitting, hanging Pale support areas Gravity, then leaking into tissues Shifting vs Fixed—Onset 1/2 to 2 hours/fixed by 8 hours Mismatch of pattern and body position
THE RATE OF BODY DECAY
Time Since Death
Putrefaction—ambient temp/humidity
Internal bacteria—sepsis hastens
Water X2/BurialX4
Ultimately skeletonize
Floaters
Mummification
Adipocere-from chemical process called saponification-reaction between certain bacteria and the body’s adipose (fatty) tissues.
Stomach Contents
Stomach empties in 2-3 hours—protein, fatty meals Intestine transient @ 24 hours
INSECT ACTIVITY Forensic entomologist Insects help in two basic ways: Predictable developmental stages (blowfly); succession of insect species
Changed by body location, weather, season, night
SCENE MARKERS Includes information at the scene or from witnesses or family and friends. Missed appointments, uncollected mail or newspapers, and dated sales receipts Victim’s clothing—dressed for work, or morning jog