forensics death investigation
Livor mortis
"death color" When red blood cells break down, they turn a bluish-purple. With decomposition, blood seeps down and settles in the lower parts of a body. The discoloration that accompanies this becomes permanent after 8 hours. Warmth accelerates the process.
Stomach & intestinal contents
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Sun exposure
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what happens when you die?
1 Blood flow to cells stops. 2 Cells run out of oxygen and begin to die. 3 As cells begin to die the tissues and organs that they make up begin to shut down.
second stage of decompostion
After 4 days: The skin blisters The abdomen swells with CO2 that is released by bacteria living in the intestines
Insects
As a corpse progresses through the stages of decomposition, other kinds of insects will arrive. Forensic entomologists can do more than just estimate the time of death with the presence of insects. If insects from another region are found on a corpse, it suggests that the corpse may have been moved and provide important evidence to determine a primary crime scene.
calculation of Algor mortis
Body heat is lost at a rate of: - 1.4 F / hour or 0.78 C / hour during the first 12 hours. - 0.7 F/ hour or 0.39 C / hour during the subsequent hours.
Why is it difficult to determine the exact time of death?
Death is a process not an instantaneous event.
Changes to the eye
Following death the surface of the eye dries out. A thin film is observed within 2-3 hrs if the eyes were open at death and 24 hrs if the eyes were closed.
hourly Stomach & intestinal contents
In general it takes 4-6 hrs for the stomach to empty its contents into the small intestine and another 12 hrs for the food to leave the small intestine. It takes approximately 24 hrs from when a meal was eaten until all undigested food is released from the large intestines. If undigested stomach contents are present, then death occurred 0-2 hrs after the last meal. If the stomach is empty but food is found in the small intestine, then death occurred at least 4-6 hrs after a meal. If the small intestine is empty and wastes are found in the large intestine, then death probably occurred 12 or more hours after a meal.
blowfly life cycle
Stage First Appears Duration (hrs) Characteristics Egg hrs after death 23 Moist areas & openings, yellow/white in color Instar 1 1.8 days 27 Black mouth hooks, think, one spiracle near anus Instar 2 2.5 days 22 Black mouth hooks, dark crop visible, 2 spiracle slits Instar 3 4-5 days 130 Black mouth hooks, crop not visible, fat body, 3 spiracle slits Pupae 18-24 days 143 Immobile, dark brown, "balloons" up Adult 21-24 days Weeks Incapable of flight for first few hours, adult fly
hourly rigor moirs
Starts w/in 2 hours of death. Starts in head & moves its way down to legs. Most rigid at 12 hrs, gradually disappears after 36 hrs.
first stage of decomposition
Within 2 day after death: Cell autolysis begins Green 7 purplish staining occurs from blood decomposition The skin takes on a marbled appearance The face becomes discolored
third stage of decomoistion
Within 6-10 days: The corpse bloats w/ gas, the chest & abdominal cavities burst & collapse Fluids begin to leak from the body openings Eyeballs & other tissues liquefy Skin sloughs off
insects first appear
Within minutes of a death, certain insects arrive to lay their eggs on the warm body, attracted by the smell of the first stages of decomposition.
Time of death
can be determined using several different methods
Natural
caused by interruption and failure of body functions resulting from age or disease. Most common.
Accidental
caused by unplanned events.
Autolysis
cell breakdown. When a cell membrane dissolves, enzymes and other cell contents spill out and digest surrounding tissues.
Autopsy
conducted by a forensic pathologist to determine the manner, cause and mechanism of the death.
Homicidal
death of one person caused by another person.
Rigor mortis
death stiffness, caused by lack of oxygen which locks muscle fibers in place.
Illness
fever or hyperthermia affects the body temperature.
Forensic entomologist
gathers information from insects to help determine the time of death.
Level of physical activity shortly before death
great physical exertion right before death causes depleted oxygen & higher body temperature.
Lividity
he pooling of blood in the body. Begins about 2 hours after death. Becomes permanent after 8 hours. If death occurred between 2-8 hrs, when flesh is pressed the color will disappear, after 8 hrs it won't. Livor mortis speeds up in hot weather & slows down in cool weather. Also affected by anything that may impede the flow of blood like belts/watches/bindings... Dual lividity can show that a body has been moved.
Suicidal
occurs when a person purposefully kills oneself.
Algor mortis
refers to temperature loss in a corpse. In death a body no longer generates warmth and begins to cool down. To find the standard temperature of a corpse, a thermometer is inserted into the liver.
Death
the cessation or end of life. OR, the irreversible cessation of the circulation of blood. Also defined as the cessation of all brain activity.
Person's weight
the more fat = the more stored oxygen which tends to slow rigor
Cause of Death
the reason someone dies (ex. Disease, injury, heart attack)
Mechanism of Death
the specific change in the body that brought about the cessation of life.
Ambient temperature
the warmer the body the faster the rigor
Type of clothing
thick clothing keeps body warmer, a warmer body experiences faster rigor.
