Forensic Science Death and Decomposition

initial decay:

0-3 days - cell autolysis, skin is marbled, green and purplish staining, face is discolored

Many factors affect rigor mortis:

1) Cold temps=slower; hot temps=faster 2) weight: FAT stores more oxygen=SLOWS RIGOR 3) clothing-keeps body warm=accelerates rigor. naked=body cools fast, slows rigor. 4) illness: fever=rigor mortis faster. hypothermia=slower 5) physical activity: exercise=faster due to increase of lactic acid in muscles, hotter body temp, and decreases oxygen in muscles. 6) sun exposure: direct sunlight warms body=faster

algor mortis time

1-12 hours: body looses 1.4 degrees F per hour 12+ body looses 0.7 degrees F per hour

Black Putrefaction

10-20 days - very strong odor; parts of skin appear black, gases cause the chest and abdominal cavities to burst and collapse, fluids leak out of body cavities, eyeballs liquefy, skin sloughs off

Butyric Fermentation

20-50 days- corpse is drying out, most of the flesh is gone

Stages of Decomposition

4 stages: initial decay, putrefaction, Black Putrefaction, Butyric Fermentation, Dry Decay.

Putrefaction

4-10 days - skin blisters; odor of decaying flesh is present; corpse appears swollen due to release of carbon dioxide from the intestines

Dry Decay

50 days or more - corpse is mostly dry, no further decay due to lack of moisture

Liver Mortis time frame

Begins 2 hours after death discoloration permanent after 8 hours between 2-8 hours if skin is pressed the color will disappear.

Cause vs. Mechanism

Cause - disease, injury, stroke, heart attack Mechanism - the actual change that brought about death; loss of blood

Liver Mortis Cause

as a body decomposes, blood settles into the lower parts of the body. Hemoglobin turns purple when it spills out of the cells; this purple color is visible where the blood pools.

flies found in early stages of decomposition

blow flies, greenbottle flies, and flesh flies.

beetles found in early stages of decomp

carrion beetles

autolysis

cell breakdown

factors that affect algor mortis:

cooler/windy environments=body slows down faster excess body fat/clothing slows down algor mortis bc it keeps the heat, slowing down heat loss

Rigor mortis

death stiffness; only temporary can be useful in determining time of death

drug overdose affecting PMI

depending on the drug; some can speed up or slow down the insects development.

beetles found in late stages of decomp

ham and checkered beetles, hide beetles, skin beetles

flies found in late stages of decomp

house flies, cheese skippers

lividity indicates

if the body has been moved. gravity pulls the blood down so this reveals the position of the body within the first 8 hours

no visible rigor

indicates the body has been dead either less than 2 hours, or more than 36-48+

species succession

insects arrive at a corpse in a predictable sequence depending on the stages of decomposition. this knowledge of the sequence in which insects arrive is important bc it can help determine how long the body has been dead.

to take the temperature of a corpse

investigators insert a thermometer into the liver

dual lividity

occurs when the body is in 1 position for 2 hours after death then moved to a second position.

Factors that promote decay:

oxygen supply not restricted, humid atmosphere, warm temps, open wounds, obesity, body exposed above ground, and body on soil.

factors that delay decay:

oxygen supply restricted, dry atmosphere, cold temps, covered corpse, buried in the ground or underwater, or body hanging above ground

Lividity:

pooling of the blood in the body: provides clues as to how long the person has been dead.

Liver Mortis

roughly means death color

Algor Mortis

roughly means death heat and describes the temperature loss in a corpse.

beetles found early to late

rove beetles, clown beetles

rigor mortis time

starts within 2 hours after death (stiffness starts in head and works its way down to the legs) 12 hours body in most rigid state. Stiffness disappears after 36-48 hours

lividity impacted by

temperature. Hot=faster, cold=slower also impacted by anything impeding blood flow such as a wristband or belt

rigor mortis stiffness is caused by

the skeletal muscles being unable to relax and therefore remain contracted and hard. after death without circulation, oxygen flow accumulates in the muscle tissue. joints and muscles appear rigid. muscles begin to relax as the cells and muscle fiber begin to dissolve by autolysis.

Postmortem interval (PMI)

the time between death and the discovery of the body.

PMI factors

weather conditions, air temp, ground surface, the interfaec area between the body and the ground, and the soil under the body as well as the temp of maggot masses. also collect weather data related to daily temp and precipitation for a period of time before the body was discovered.

Most insects used in investigations are in two major orders:

Flies (Diptera) and Beetles (Coleoptera)

Changes of the eye following death

Following death, potassium accumulates inside the vitreous humor, otherwise known as ocular fluid This buildup of potassium may be used to estimate time of death Needle inserted into eyeball during autopsy and fluid removed; potassium levels are tested/analyze

Stomach and intestinal contents

In general, it takes 4-6 hours for the stomach to empty its contents into the small intestine and another 12 hours for the food to leave the small intestine It takes approximately 24 hours from when a meal was eaten until all digested food is released from the large intestines. From this, it can be concluded that: If undigested stomach contents are present, death occurred 0-2 hours after the last meal If the stomach is empty, but food is found in the SI, death occurred at least 4-6 hours after a meal. If the SI is empty and wastes are found in the LI, death probably occurred 12 or more hours after a meal

What is death?

It is defined as the "cessation", or end of life Death is a PROCESS When a cell dies, it breaks down Once enough cells begin to break down, life cannot be restarted

Manner of Death

Natural Accidental Suicide Homicide Undetermined

other factors that could affect PMI

Was the body enclosed in an area or wrapped in a material that would have prevented flies from finding the corpse and laying eggs? Were other insect species present that may have affected the development of the collected species? Were there drugs or other poisons in or on the body that might have affected the larvae's development?