time of death
DESCRIPTION
Time of Death. Method for determining. Rigor Mortis. “death stiffness” results in the shortening of muscle tissue and the stiffening of body parts in the position at death (occurs within the first 24 hrs. and disappears within 36 hrs.). - PowerPoint PPT PresentationTRANSCRIPT
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Method for determining
Time of Death
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Rigor Mortis“death stiffness”results in the shortening of muscle tissue and the
stiffening of body parts in the position at death (occurs within the first 24 hrs. and disappears within 36 hrs.).
Starts in the head and works its way down to the legs.At 12 hours the body is most rigid. Skeletal muscles cannot relax. When you are alive, muscles release Calcium to
contract. This Calcium is removed from the cells, which requires energy. In death, there is no energy, thus Calcium is not removed and the muscles remain contracted.
After 12 hours, the muscle cells begin to dissolve by autolysis
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Factors that affect rate of rigor mortisEnvironmental temperature – cooler, slowerA person’s weight – Body fat stores extra
oxygen (therefore more energy is available after death)
Type of clothing – Clothing keeps the body warm
Illness – fever vs. hypothermiaLevel of activity before death – high activity,
fasterSun exposure – Direct sunlight, warmer,
faster
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Livor Mortis“Death Color”results in the settling of blood in areas of the
body closest to the ground (begins within 2 hours after death and continues up to 12 hrs.).
Red Blood cells break down, spilling out hemoglobin. This turns purple, outside of the cell. This is visible where the blood pools.
“Lividity” – pooling of the blood. Discoloration is permanent after 8 hours.
Environmental factors affect the rate
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LividityPooling of bloodCan provide time of deathCan reveal the position of a corpse during
the first 8 hoursFace down?On back?Standing?
Reveal if the body has been moved
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Algor Mortis“Death Heat”results in the loss of heat by a body (a
general rule, beginning about an hour after death, the body loses heat by 1 to 1 1/2 degrees Fahrenheit per hour until the body reaches the environmental temperature).
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Predictable Pattern of Decay
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Pictures of ProcessFresh
Bloat
Decay
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Butyric Fermentation
All the remaining flesh is removed over this period and the body dries out.
It has a cheesy smell, caused by butyric acid, and this smell attracts a new suite of corpse organisms. .Insect activity The reduction in soft food makes the body less palatable to the mouth-hooks of maggots, and more suitable for the chewing mouthparts of beetles.
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Newton’s Law of CoolingNewton’s Law of Cooling describes the
cooling of a warmer object to the cooler temperature of the Environment
T(t)=Te+(To-Te)e-kt
To is initial temperature of object (98.6 degrees F)
Te is constant temperature of environmentT(t) is the temperature of the object at any
time t (from graph)k is a constant
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Graph of Newton’s Law of Cooling
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AnthropologyForensic Anthropology is concerned
primarily with the identification and examination of human skeletal remains.
Radiologic dating uses carbon dating techniques to determine approximate age of bones
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Carbon DatingCarbon-14 is an isotope of carbonIsotopes have the same number of protons,
different numbers of neutronsCarbon-14 dating can be used to find the ages of
once-living things because all organism absorb Carbon-14 when they are alive
Once an organism dies, its body begins to lose Carbon-14 at a fixed rate.
Scientists can measure the amount of Carbon 14 remaining in a skeleton to determine the date the person died.
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Half -life -- the amount of time for 1/2 of the sample to decay
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EntomologyForensic Entomology is the study
of insects and their relation to a criminal investigation, commonly used to estimate the time of death.
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Of Maggots and MurderFlies are among first to colonize carcassUsually arrive within 10 minutesAs carcass decays, conditions change
DrierTemperature dropsTissues break down
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Order of Insect AppearanceBlowfliesOther fliesTiny Wasps (lay eggs on maggots)…live as
parasites in maggotsBeetles and Mites (when body is drier)
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Blowfly DevelopmentEgg (8 hours)Larva 1 (aka “instar 1”)Larva 2 (aka “instar 2”)Larva 3 (aka “instar” 3)Pre-pupaEarly and late pupaAdult
Changes in size, color, mobility and external physical changes enable a scientist to determine when the blowflies arrived at the body.
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Orifices and OpeningsWhen flies arrive, search out natural
orifices (mouth, ears, nose)If larvae are found in other places (like
chest cavity), this indicates possible stab wounds or openings in that region
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Additional FactorsDrugs present at the time of death can
affect developmental rate of the maggotsCocaine speeds up developmentArsenic slows developmentInsects feed on toxins (removing them from
body) making it difficult to test for them
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Stomach ContentsThe composition of a victim’s last meal can
often provide details concerning TOD.Used for additional sources of information
as well.Prominent case study includes Nicole
Brown Simpson
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Presence of Macromolecules can be detectedLipidsProteinsSimple carbohydratesComplex carbohydrates
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LipidsFunction as long-term energy storageImportant component of the cell membraneConsist of glycerol and fatty acid “tails”“Tails” are long chains of carbon and
hydrogen and contribute to the non-polar behavior of fats
Sudan Red is a fat-soluble dye that stains lipids red. Using Sudan red can show the amount and location of lipids
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Both test tubes contain lipids
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ProteinsComplex specialized molecules composed of carbon,
oxygen, hydrogen, nitrogen, and sometimes sulferProteins have many important roles in organisms.Structural proteins such as collagen or elastin
provide supportRegulatory proteins such as enzymes control cell
processesBuiret solution is a blue liquid that changes to purple
in the presence of short chains of polypeptidesThe copper atom of the biuret solution reacts with
the peptide bonds to cause the color change.
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The purple one contains protein
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Monosaccharides and DisaccharidesMonosaccharides are simple sugars such as
glucose and fructose that function as energy source in cells during cellular respiration
Disaccharides are composed of two monosaccharides together
Sucrose (table sugar) is an example of a disaccharide
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Other Carbohydrates -- starchLugol’s solution -- an iodine solution used
to detect starchA dark blue color indicates starchLarge number of simple sugar molecules
joined by glyosidic bondsProduced by all plantsConsumed by humans
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Lipid Test:
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Protein Test
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Glucose Test
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Starch Test