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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.).
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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.). • 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
Factors that affect rate of rigor mortis • Environmental temperature – cooler, slower • A 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. hypothermia • Level of activity before death – high activity, faster • Sun exposure – Direct sunlight, warmer, faster
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
Lividity • Pooling of blood • Can provide time of death • Can reveal the position of a corpse during the first 8 hours • Face down? • On back? • Standing? • Reveal if the body has been moved
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 1/2degrees Fahrenheit per hour until the body reaches the environmental temperature).
Pictures of Process Fresh Bloat Decay
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.
Newton’s Law of Cooling • Newton’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 environment • T(t) is the temperature of the object at any time t (from graph) • k is a constant
Anthropology • Forensic 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
Carbon Dating • Carbon-14 is an isotope of carbon • Isotopes have the same number of protons, different numbers of neutrons • Carbon-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.
Half -life -- the amount of time for 1/2 of the sample to decay
Entomology • Forensic Entomology is the study of insects and their relation to a criminal investigation, commonly used to estimate the time of death.
Of Maggots and Murder • Flies are among first to colonize carcass • Usually arrive within 10 minutes • As carcass decays, conditions change • Drier • Temperature drops • Tissues break down
Order of Insect Appearance • Blowflies • Other flies • Tiny Wasps (lay eggs on maggots)…live as parasites in maggots • Beetles and Mites (when body is drier)
Blowfly Development Changes in size, color, mobility and external physical changes enable a scientist to determine when the blowflies arrived at the body. Egg (8 hours) Larva 1 (aka “instar 1”) Larva 2 (aka “instar 2”) Larva 3 (aka “instar” 3) Pre-pupa Early and late pupa Adult
Orifices and Openings • When 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
Additional Factors • Drugs present at the time of death can affect developmental rate of the maggots • Cocaine speeds up development • Arsenic slows development • Insects feed on toxins (removing them from body) making it difficult to test for them
Stomach Contents • The 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
Presence of Macromolecules can be detected • Lipids • Proteins • Simple carbohydrates • Complex carbohydrates
Lipids • Function as long-term energy storage • Important component of the cell membrane • Consist 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
Proteins • Complex specialized molecules composed of carbon, oxygen, hydrogen, nitrogen, and sometimes sulfer • Proteins have many important roles in organisms. • Structural proteins such as collagen or elastin provide support • Regulatory proteins such as enzymes control cell processes • Buiret solution is a blue liquid that changes to purple in the presence of short chains of polypeptides • The copper atom of the biuret solution reacts with the peptide bonds to cause the color change.
Monosaccharides and Disaccharides • Monosaccharides 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
Other Carbohydrates -- starch • Lugol’s solution -- an iodine solution used to detect starch • A dark blue color indicates starch • Large number of simple sugar molecules joined by glyosidic bonds • Produced by all plants • Consumed by humans
