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