Presentation on theme: "Method for determining"— Presentation transcript:
1 Method for determining Time of DeathMethod for determining
2 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
3 Factors that affect rate of rigor mortis Environmental 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 warmIllness – fever vs. hypothermiaLevel of activity before death – high activity, fasterSun exposure – Direct sunlight, warmer, faster
4 Livor Mortis “Death Color” results in the settling of blood in areas of the body closest to the ground (begins immediately on 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
5 Lividity Pooling of blood Can provide time of death Can reveal the position of a corpse during the first 8 hoursFace down?On back?Standing?Reveal if the body has been moved
6 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).
7 Predictable Pattern of Decay FreshBody is intact, decay inside bodyLasts until body becomes bloatedBlow flies (Calliphoridae) and Fresh flies (Sarcophagidae are among first to arriveBloatedBody becomes visibly inflated due to the production of gases from bacteria that begin to putrefy the bodyHouse flies (Muscidae) now join other fliesDecaySkin breaks and body deflatesSmells BADMost maggots have finished development
8 Pictures of Process Fresh Bloat Decay Pigs used because have similar fat content to humanDecay
9 Butyric FermentationAll 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 activityThe reduction in soft food makes the body less palatable to the mouth-hooks of maggots, and more suitable for the chewing mouthparts of beetles.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.The surface of the body that is in contact with the ground becomes covered with mould as the body ferments.Insect activityThe reduction in soft food makes the body less palatable to the mouth-hooks of maggots, and more suitable for the chewing mouthparts of beetles. Beetles feed on the skin and ligaments. Many of these beetles are larvae. They hatch from eggs, laid by adults, which fed on the body in earlier stages of decay.
10 Newton’s Law of Cooling Newton’s Law of Cooling describes the cooling of a warmer object to the cooler temperature of the EnvironmentT(t)=Te+(To-Te)e-ktTo 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
12 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
13 Carbon Dating Carbon-14 is an isotope of carbon Isotopes 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 aliveOnce 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.Isotope -- same number of protons different number of neutrons
14 Half -life -- the amount of time for 1/2 of the sample to decay
15 EntomologyForensic Entomology is the study of insects and their relation to a criminal investigation, commonly used to estimate the time of death.
16 Of Maggots and Murder Flies are among first to colonize carcass Usually arrive within 10 minutesAs carcass decays, conditions changeDrierTemperature dropsTissues break down
17 Order of Insect Appearance BlowfliesOther fliesTiny Wasps (lay eggs on maggots)…live as parasites in maggotsBeetles and Mites (when body is drier)
18 Blowfly Development Egg (8 hours) Larva 1 (aka “instar 1”) Pre-pupaEarly and late pupaAdultChanges in size, color, mobility and external physical changes enable a scientist to determine when the blowflies arrived at the body.
19 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
20 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
21 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
22 Presence of Macromolecules can be detected LipidsProteinsSimple carbohydratesComplex carbohydrates
23 Lipids Function as long-term energy storage Important 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 fatsSudan Red is a fat-soluble dye that stains lipids red. Using Sudan red can show the amount and location of lipids
25 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.
27 Monosaccharides and Disaccharides Monosaccharides are simple sugars such as glucose and fructose that function as energy source in cells during cellular respirationDisaccharides are composed of two monosaccharides togetherSucrose (table sugar) is an example of a disaccharide
28 Other Carbohydrates -- starch Lugol’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