Death: Manner, Mechanism, and Cause

Introduction

Death of individual body cells is a slow process, not instantaneous.
Experts still debate a single definition of death.
Establishing the postmortem interval (PMI) is of great forensic importance.
- PMI is the time between death and body discovery.
- The longer the PMI, the less accurate the estimate.

Manner of Death (MOD)

Official terms for the manner of death include:
- Natural death
- Accidental death
- Suicidal death
- Homicidal death
- Undetermined death

Natural Death

Most common manner of death.
Interruption/failure of body functions due to age or disease.
Examples: Heart disease, stroke, cancer.

Accidental Death

Unplanned events.
Examples: Car accident, falling from a ladder, factory accident.

Suicidal Death

The person purposely kills themself.
Examples: Hanging, gunshot, poison, overdose.

Homicidal Death

Death of one person caused by another.

Undetermined Death

Listed as the official cause when the cause cannot be determined.
Occurs when there is no strong evidence or contradictory evidence.
May occur when only part of the body is found.
Example: Differentiating between suicide and accidental death.

Postmortem Interval (PMI)

The time between death and body discovery.
To estimate the postmortem interval (PMI) forensic scientists use:
- Livor mortis
- Algor mortis
- Rigor mortis
- Stomach and intestinal contents
- Stages of decomposition

Cause of Death (COD)

The mechanism of death describes the specific change in the body that brought about the cessation of life.
- Cause of death: shooting
- Mechanism of death: blood loss
- Cause of death: heart attack
- Mechanism of death: heart stopping or pulmonary arrest

Autopsy

A medical examination to determine the cause and manner of death.
Clinical autopsies are done for medical research study purposes, and foul play is not considered.
Forensic autopsies are performed when foul play is suspected.
- External examination
- Internal examination
Family members can request an autopsy for about 3,000.

Body Changes After Death

Death is a process and not a singular event.
The following processes occur from seconds to hours later in a series of 2 stages:
1. Stoppage:
  - Heart stops beating, no blood pumped.
  - No delivery of oxygen, breathing stops.
  - Cell death.
  - Switch from cellular respiration to anaerobic respiration.
2. Autolysis (Cell-Self Digestion):
  - Cellular enzymes released into the cell; rupture membrane.
  - Brain dies within 3-7 minutes without oxygen (almost always irreversible).
  - All other cells & organs begin to die off (up to 15 hours to donate).
  - Muscles relax; bladder and bowels release.

Livor Mortis

Means “death color.”
Red blood cells break down and spill out contents.
- Blood seeps down and settles in lower parts of the body.
Turns the body purple (lividity).
Color change starts 2 hours after death.
Becomes permanent after 8 hours.
Hotter temperatures cause color change to happen faster.
Press on the skin and discoloration disappears.
Can reveal TOD (time of death), position of corpse, and if they have been moved.

Rigor Mortis

Means “death stiffness”.
Temporary.
No oxygen causes calcium to build up in muscles.
Muscles become stiff and cannot relax.
Starts at the head and works its way down the body.
Starts within 2 hours after death.
Most rigid at 12 hours.
Softening begins at 15 hours.
Stiffness disappears after 36 hours.

Progression of Rigor Mortis

Time After Death	Event	Appearance	Circumstances
2 to 6 hours	Rigor begins	Body becomes stiff and stiffness moves through body.	Stiffness begins in small muscles, such as those of the face, and progresses to larger muscle groups.
12 hours	Rigor complete	Peak rigor is exhibited.	Entire body is rigid.
15 to 36 hours	Slow loss of rigor	Rigor is uneven.	Rigor is slowly lost first in smaller muscles and later in larger muscles.
36 to 48 hours	Rigor absent	Muscles relaxed.	Many variables may extend rigor beyond the normal 36 hours.

Factors Affecting Rigor Mortis

Temperature
Body weight
Clothing
Illness
Sun exposure
Level of activity before death

Factors Affecting Rigor	Event	Effect	Circumstances
Temperature	Cold temperature	Inhibits rigor	Slower onset and slower progression of rigor
	Warm temperature	Accelerates rigor	Faster onset and faster progression of rigor
Activity before death	Anaerobic exercise	Accelerates rigor	Lack of oxygen to muscle, buildup of lactic acid, and higher body temperature accelerates rigor.
	Sleep	Slows rigor	Fully oxygenated muscles exhibit rigor more slowly.
Body mass	Obese	Slows rigor	Fat stores oxygen.
	Thin	Accelerates rigor	Body loses oxygen quickly.

Algor Mortis

Means “death heat”.
The body no longer generates heat and begins to cool down.
Body loses 1.4^{\circ}F every hour for the first 12 hours.
Body loses 0.7^{\circ}F every hour after 12 hours until it matches the surrounding temperature.
To find the temperature of a corpse, a thermometer is inserted into the liver.
Helps determine the time of death - average body temp is 98^{\circ}F.

Factors Affecting the Rate of Heat Loss

Body surface area to mass ratio: thin bodies lose heat faster.
Body position: an extended body has a greater surface area and loses more heat.
Clothing: heavy clothing insulates the body and slows heat loss.
Colder environment: heat loss is faster in cooler environments.
Submerged bodies: heat loss is faster if the water is cooler than the body because water is a good conductor of heat.
- Warmer water than body temperature slows heat loss.

Stomach and Intestinal Contents

The stomach empties into the small intestines within 2-6 hours.
Food leaves the small intestine 12 hours later.
Waste is released through the rectum after 24 hours.

Stages of Decomposition

At the Moment of Death

The heart stops.
The skin gets tight and grey in color.
All the muscles relax.
The bladder and bowels empty.

Days 0-3 (Initial Decay)

The corpse appears normal on the outside, but the body is breaking down due to autolysis (cell death).
The temperature begins dropping.
Flies land and lay eggs, which hatch into maggots.
After 24 hours, the face is harder to recognize.
The abdomen becomes blue-green after 3 days.
Rodents and pet cats can eat the face of the body; dogs tend to guard the owner’s body.

Days 4-10 (Putrefaction)

The corpse appears bloated and swollen.
Days 5-6: the abdomen greatly swells, and skin blisters.
Skin is marble-colored and may be leaking fluids.
The body begins to smell.
Skin slips & hair and nails fall off at days 4-7.

Days 10-20 (Active Decay)

AKA Black Putrefaction.
The body has a very strong odor.
Flesh is black-colored, and the skin has ruptured - seeping fluids and gases.
Most of the body mass disappears due to insect activity- the greatest amount of maggots is at this time.
Ends when maggots migrate away from the body to pupate.
Creates an “island” in the ground (vegetation disappears).

Days 20-50

The body is drying out, and most of the flesh is gone.

Days 50+

Mostly skeletal remains, only bones, cartilage, and dry skin.
Vegetation starts to grow back.

Estimating Postmortem Interval

To estimate a postmortem interval, evidence is compiled from the body, the environment, the autopsy findings, and the person’s social contacts, if necessary.
A PMI is never precise because of the many environmental variables and other factors that influence what happens to a body after death.