Method for determining

Time of Death

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 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

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

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

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).

Predictable Pattern of Decay

Pictures of ProcessFresh

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 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

Graph of Newton’s Law of Cooling

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

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.

Half -life -- the amount of time for 1/2 of the sample to decay

EntomologyForensic Entomology is the study

of insects and their relation to a criminal investigation, commonly used to estimate the time of death.

Of Maggots and MurderFlies are among first to colonize carcassUsually arrive within 10 minutesAs carcass decays, conditions change

DrierTemperature dropsTissues break down

Order of Insect AppearanceBlowfliesOther fliesTiny Wasps (lay eggs on maggots)…live as

parasites in maggotsBeetles and Mites (when body is drier)

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.

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

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

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

Presence of Macromolecules can be detectedLipidsProteinsSimple carbohydratesComplex carbohydrates

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

Both test tubes contain lipids

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.

The purple one contains protein

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

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

Lipid Test:

Protein Test

Glucose Test

Starch Test