Forensic Science Death and Decomposition
Terms in this set (41)
roughly means death color
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.
pooling of the blood in the body: provides clues as to how long the person has been dead.
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.
lividity impacted by
temperature. Hot=faster, cold=slower
also impacted by anything impeding blood flow such as a wristband or belt
if the body has been moved. gravity pulls the blood down so this reveals the position of the body within the first 8 hours
occurs when the body is in 1 position for 2 hours after death then moved to a second position.
death stiffness; only temporary can be useful in determining time of death
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
no visible rigor
indicates the body has been dead either less than 2 hours, or more than 36-48+
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.
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
roughly means death heat and describes the temperature loss in a corpse.
to take the temperature of a corpse
investigators insert a thermometer into the liver
algor mortis time
1-12 hours: body looses 1.4 degrees F per hour
12+ body looses 0.7 degrees F per hour
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
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
Cause vs. Mechanism
Cause - disease, injury, stroke, heart attack
Mechanism - the actual change that brought about death; loss of blood
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
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
Stages of Decomposition
4 stages: initial decay, putrefaction, Black Putrefaction, Butyric Fermentation, Dry Decay.
0-3 days - cell autolysis, skin is marbled, green and purplish staining, face is discolored
4-10 days - skin blisters; odor of decaying flesh is present; corpse appears swollen due to release of carbon dioxide from the intestines
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
20-50 days- corpse is drying out, most of the flesh is gone
50 days or more - corpse is mostly dry, no further decay due to lack of moisture
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
Postmortem interval (PMI)
the time between death and the discovery of the body.
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.
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?
Most insects used in investigations are in two major orders:
Flies (Diptera) and Beetles (Coleoptera)
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.
drug overdose affecting PMI
depending on the drug; some can speed up or slow down the insects development.
flies found in early stages of decomposition
blow flies, greenbottle flies, and flesh flies.
flies found in late stages of decomp
house flies, cheese skippers
beetles found in early stages of decomp
beetles found in late stages of decomp
ham and checkered beetles, hide beetles, skin beetles
beetles found early to late
rove beetles, clown beetles