Time of Death - Welcome to Science with Mrs. Persico
Time of Death Time of Death Time of death deals with concepts concerning evidence in and around the
body that investigators use to determine PMI (Post Mortem Interval- the amount of time between when the person dies and when the body is found). Decomposition
When the death of a human body occurs it goes through several stages of decomposition. Time of death can be estimated by evaluating the stage of decomposition the
victim was found in. Death occurs after breathing stops and the heart stops pumping blood through the body. Death is a process, not an event. The
decomposition process after death has 5 stages. 1. Initial decay 2. Putrefaction 3. Black putrefaction 4. Butyric fermentation
5. Dry Decay Initial Decay 0-3 days after death The outside of the body appears fresh. Bacteria in the intestines start to feed on the intestines themselves
The bodies own digestive enzymes start to break down the organs Insects arrive Initial Decay
Initial Decay Insect Eggs Putrefaction 4-10 days after death Bacteria breaks down tissues and cells, releasing body fluid into cavities.
Bacteria also produce gases as waste products. People find these gases to be foul smelling but insects are attracted to them. Putrefaction
Pig bloated due to bacteria producing gas. Putrefaction Insects attracted to the smell of gases
Putrefaction Maggots feeding under the skin Black Putrefaction 10-20 days after death
The bloated body collapses and large volumes of fluid drain from the body attracting more insects. Flesh takes on a creamy consistency and exposed skin turns black. Insects and bacteria continue to eat flesh
Black Putrefaction Body has collapsed with black exposed flesh Black Putrefaction
This stage attracts a wide variety of insects Black Putrefaction The body has collapsed
Butyric Fermentation 20-50 days after death The remaining flesh is removed and dries out, the body produces butyric acid. The part of the body in contact with the ground gets moldy as the body ferments. The cheese fly consumes any moist flesh left as beetles feed on
skin and ligaments. Butyric Fermentation The body is now flat and dried out
Butyric Fermentation Dry Decay 50-365 days after death The body is now dry and decays very slowly Eventually the hair disappears and leaves
only the bone. Other Determinants of PMI Forensic Pathology Forensic Pathology- investigation of sudden,
unnatural, unexplained, or violent deaths. Forensic Pathologists are medical examiners and coroners. The responsibility of the Forensic Pathologist is to answer the questions Who is the
victim? What injuries are present? When did the injuries occur? Why and how were the injuries produced? and What is the cause of death? Cause of Death
If a cause of death can not be found by observation, and autopsy is performed. Autopsy- The medical dissection and examination of a body in order to determine the cause of death.
The manner of death is classified into 5 categories: Natural, homicide, suicide, accident or undetermined. Rigor Mortis
Immediately following death, Rigor Mortis occurs. Rigor Mortis -the shortening of muscle tissue and the stiffening of body parts. Rigor Mortis occurs with in the first 24 hours (peaking at 12 hours) and disappears with in
36 hours. Follows Nystens Law(1812): rigor starts in the head and progressesdownward because rigor is most noticeable in the small muscles of the face and later becomes pronounced in the larger muscles of the body.
Rigor Mortis Livor Mortis Livor Mortis- occurs when the heart stops
pumping and blood begins to settle in the parts of the body closest to the ground. The skin will appear as a dark blue or purple color in these areas. This condition occurs immediately and continues for up to 12 hours after death.
www.gary-c-king.com Livor Mortis The skin will not appear discolored in areas
where the body is restricted by either clothing or an object pressing against the body. Obtaining this information can be useful in determining if the victims position was changed after death occurred.
Algor Mortis Algor Mortis- is the postmortem changes that cause a body to lose heat. Algor Mortis is the process in which the
body temperature continually cools after death until it reaches the ambient or room temperature. Algor Mortis is measured with a thermometer.
Algor Mortis The rate of heat loss is influenced by factors such as the location and size of the body, the victims clothing, and weather conditions.
As a general rule, beginning about an hour after death, the body will lose heat at a rate of 1-1.5 degrees Fahrenheit per hour. Where do we take the temperature
for algor mortis? Ideally: temperature is measured in the rectum
Other locations are the liver or umbilicus Hours Postmordum,
120 Body Temperature (F) 100 80 60
40 20 0 Time (Hours) Livor
Body Tempature Rigor Decomposition Decomposition
Another approach for estimating time of death is determining potassium levels in ocular fluid. After death, cells within the inner surface of the eyeball release potassium into the ocular fluid. By
analyzing the amount of potassium present at various intervals, the rate at which potassium is released can give an approximation of time of death. Ocular Petechiae
Autopsy At autopsy other factors can also help to approximate time of death. For example, the amount of food in the stomach can help
to estimate when a persons last meal was eaten. Light Meal - 2 hours Medium Meal - 3-4 hours Heavy Meal - 6 or more hours Small Intestines empty every 12
hours or more Forensic Anthropology Forensic Anthropology is concerned primarily with the identification and
examination of human skeletal remains. Skeletal bones are durable and undergo an extremely slow breakdown process. Because of the resistance to decomposition, skeletal remains provide many individual characteristics.
Forensic Anthropology Examination of skeletal remains can provide information to their origin, sex, approximate age, race and skeletal injury.
For example, female skeletons differ from male skeletons in the pelvic region because of a womans capability to bear children. Dr. Bill Bass
Forensic Entomology Forensic Entomology is a study of insects and their relation to a criminal investigation. After decomposition begins, insects such as blow flies are the first to
infest the body. Their eggs are laid with in the human remains and hatch into maggot or fly larvae. The larvae are responsible for the consumption of the human organs and tissues.
Forensic Entomology The forensic entomologist can identify the specific insects present in the body and approximate how long a body has been left exposed by examining the stage of
development of the fly larvae. These determinations are not straight forward. The time required for stage development is affected by environmental influences such as geographical location, climate and weather conditions.
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