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