FORENSIC PATHOLOGY
TIME OF DEATH AND DECAY
Manner of Death
Natural: death as a result of age or disease; this is the most common type of deathAccidental: caused by unplanned events (i.e. car accident)Suicidal: occurs when a person purposefully kills oneselfHomicidal: death caused by another personUndetermined
Cause of Death vs. Mechanism of Death
The cause of death (COD) is the reason someone dies. Examples include heart attack, stroke, drowning, strangulation and hanging.The mechanism of death describes the specific change in the body that brought about the death. Examples include exsanguination, pulmonary arrest, and cessation of brain function.
Time of Death (TOD)
There are several factors that are used to help determine the time of deathSome of these factors include:
Livor mortisRigor mortisAlgor mortis
Livor Mortis
Means “death color”After death, blood begins to seep out of the tissues and settles in the body parts closest to the groundThe hemoglobin in the red blood cells begins to spill out of the cells and turns purpleThe pooling of blood is called lividity, and provides a clue as to how long the person has been dead
Livor Mortis (cont.)
2 HOURS: lividity begins
2-8 HOURS: lividity is present but disappears if
the skin is pressed
8 HOURS: lividity
becomes permanent
Livor Mortis (cont.)
The ambient temperature will affect the rate of livor mortis:
Heat speeds up livor mortisCool temperatures slow it down
Livor mortis is also affected by anything impeding the flow of blood such as the ground, watch, belt, etc.
Examples of Livor Mortis
Rigor MortisMeans “death stiffness”
2 HOURS: rigor begins at the head and begins
to move down
12 HOURS: peak rigor
36-48 HOURS:
rigor disappears
Rigor Mortis (cont.)
Rigor is caused by contraction of the skeletal muscle
When death occurs, calcium can no longer be kept out of the cell and the muscles contract
Skeletal muscle remains in a relaxed state in the absence of calcium. When calcium enters the cell, it triggers the contraction of the muscle. Calcium is actively pumped out of the cell to relax the muscle.
Rigor Mortis (cont.)
Eventually, the muscle cells begin to dieThis accounts for the disappearance of rigorRigor is affected by the following factors:
Ambient Air Temperature—warm weather speeds up rigorBody Weight—because fat stores oxygen, it will slow down rigorActivity Prior to Death—exercise speeds up rigor because it uses oxygen
Rigor Mortis (cont.)
Cadaveric Spasm: occurs at the moment of death if the victim was gripping something when killedThe condition relaxes within a matter of hours, then the normal pattern of rigor mortis begins
Examples of Rigor Mortis
Example of Cadaveric
Spasm
Algor Mortis
Means “death heat”When death occurs, the body can no longer maintain its internal body temperatureThe body temperature drops at a rate of .78o C every hour for the first 12 hoursAfter 12 hours, it drops .39o C every hour until it reaches the temperature of the surrounding environment
Decay
Corpses decompose in predictable ways over time and this can help determine the time of death
Initial Decay2 Days: Blood
decomposition causes green and purplish staining; skin
takes on a marbled
appearance
Putrefaction4 Days:
Skin blisters; abdomen swells
with CO2 gas released by
bacteria in the intestines; strong odor of decaying
flesh
Black Fermentation
6-8 Days: Corpse continues to bloat with CO2 gas causing the
chest and abdomen to burst; corpse collapses;
flesh appears black
Decay (cont.)
Butyric Fermentation
8-10 Days: Fluids leak out of
the body openings; eyeballs
liquefy and skin slough off
Dry DecayAfter 10 Days:
Corpse is almost dry; further decay is very slow from lack of moisture
Examples of Decay in Pig Carcass
INITIAL DECAY
PUTREFACTION
BLACK FERMENTATION
BUTYRIC FERMENTATION
Examples of Decay in Pig Carcass (cont.)
DRY DECAY
Human Decay
Marbled Skin (Initial Decay)
Skin appears black (Black
Fermentation)Skin Sloughs Off
(Butyric Fermentation)
Vitreous HumorAs red blood cells breakdown, they release potassium (K+)The K+ diffuses at a slow but constant rate into the vitreous humor, semi-fluid substance in the eyeA sample of the humor can be tested for the percentage of K+ present to determine the time of death