Chapter 7: Forensic Taphonomy
A forensic taphonomist will be tasked with everything from identification of remains, estimation of postmortem interval (PMI), investigation of circumstances surrounding death, and identification of clues leading to the perpetrator
Intrinsic factors → factors associated with the nature of the body itself. Things such as body mass, sex, age, physical state at the time of death, and substances in the body
Extrinsic factors → fall into one of two categories: either depositional context or human behavior.
Depositional context are things such as environmental factors that affect decomposition, such as water, soil, temperature, oxygen, and local flora and fauna.
Human behavior includes the cause and manner of death, when, where, and how a body is deposited, and treatment of the body after death.
Forensic Tamphonomy → the use of taphonomic models, approaches, and analyses in forensic contexts to estimate the time since death, reconstruct the circumstances before and after decomposition, and discriminate the products of human behavior from those created by natural processes
Algor Mortis
This term refers to the post-mortem cooling of the body, which occurs as the body temperature gradually equilibrates to the ambient temperature.
The rate of cooling can be influenced by various factors such as the environmental temperature, clothing, the individual's body composition, and the presence of any surrounding environmental conditions.
A body tends to cool at a rate of 1 C per hour.
not the most accurate to determine time of death
A dead body experiences an “initial temperature plateau” before cooling.
a phenomenon in which the body maintains temperature for about three hours after death and then begins to cool at 1 C per hour thereafter
Henssge equation and nomogram → a diagram that uses scales to represent the relationship between three or more variable quantities. There is one scale for each variable in an equation; the idea is that each scale has a known relationship to the other scales, so if you know the value of one or more scale, you can use that information to find the unknown value on another scale.
Decomposition: Autolysis & Putrefaction
Autolysis is the breakdown of tissue from the inside out
One of the earliest internal changes that occur after death is the self-digestion and degradation of the cells and organs by intracellular enzymes
present first in those organs that are rich in digestive enzymes: the pancreas, stomach, liver, and small intestines
After death, the enzymes escape their physical confines and move into the surrounding tissues.
Loss of membrane integrity leads to lysosomes releasing their hydrolytic enzymes which escape into the surrounding cytoplasm.
Primarily this is due to the lack of oxygen supply after death, along with a decrease in cytoplasmic pH, which results in the loss of cell membrane structure
The presence of these enzymes causes denaturation of molecules and the remaining cellular membrane. They have the capacity to break down almost all macromolecules in the body, including carbohydrates, lipids, proteins, and nucleic acids.
Putrefaction is the breakdown of tissues form the outside in
The breakdown of tissue by microorganism
Process begins in the large inestine with the action of bacteria and other microorganisms, which leads to the fermentation of undigested food and the production of gases that contribute to bloating.
The results of putrefaction are the liquidation of soft tissues
Body Decomposition Breakdown
Protein breakdown — Bacterial enzymes degrade body proteins through proteolysis into proteoses, peptones, and polypeptides.
Exoenzyme action — Bacterial exoenzymes denature proteins and release free amino acids.
Deamination — Amino acids lose their amine groups.
Decarboxylation — Amino acids lose their carboxyl groups.
Putrescine — Produced from decarboxylation of ornithine.
Cadaverine — Produced from decarboxylation of lysine.
Sulfur‑containing amino acids — Cysteine, cystine, and methionine undergo desulfhydration.
Desulfhydration products — Generates hydrogen sulfide, sulfides, ammonia, thiols, and pyruvic acid.
Odor compounds — These gases and chemicals create the characteristic smell of active putrefaction.
The decomposition of the body can take place at different rates dependent upon the action of bacteria, the amount of moisture present in the tissues, and the ambient temperature
Proteolysis first presents in the soft tissues, such as the epithelial tissues. It then moves to the brain, liver, and kidneys during the very early stages of decomposition.
Keratin and collagen rich tissues will survive for long periods after death since these tissues are highly resistant to both autolysis and putrefaction
Type I collagen proteins are found in the hard tissues of the body, such as bone and tooth enamel
Keratin is a secondary protein characterized by a rigid structure of extensive disulfide bonds and cross-linkages. This structure prevents common proteolytic enzymes from digesting it.
Hemolysis → Bacteria and enzymes attacking the blood and breaking down the hemoglobin
Anaerobic microorganisms are dominant within a body after death. These microorganisms will invade surrounding tissues, and begin anaerobic degradation of fatty acids through hydrogenation.
Marbling → the decomposition of blood by microorganisms within blood vessels.
External Putrefaction
Eventually, the bacterial putrefaction present internally will become obvious on the external surfaces of the body
The fluid formed from liquefied tissues will begin to purge from bodily orifices, and the skin will begin to blister and slough.
Putrefaction causes the build-up of various gasses which are trapped within the bodily cavities. These gasses will be most apparent in the abdominal region and the scrotum.
Ocular Changes
As a result of autolysis, the cornea may demonstrate a cloudy appearance.
If the eyelids are open after death, then air and other substances have unfettered access to the conjunctiva.
This results in discoloration of the whites of the eyes called tache noire de la sclerotique (often abbreviated simply as tache noire)
Livor Mortis
Once the heart stops beating, the blood will have no way of moving throughout the body. As circulation stops, the blood will tend to gravitate to the most dependent parts of the body.
Livor Mortis → the settling of blood according to gravity, resulting in discoloration (reddish purple coloration) that is present in all dependent parts of the body that allow for floor flood
also occurs with the internal organs and clean to discoloration on lighter organs (e.g., lungs and heart)
Rigor Mortis
The Skeletal Muscles
Skeletal muscles are made of long, thin bundles of fibers which work together to cause muscle contraction.
Sarcomeres (which make up the muscles) are made up of several strands of protein: Actin (called “I-bands”), myosin (called “M-bands” or “A-bands”), troponin, and tropomyosin.
Actin filaments are long and thin and line up on either side of the myosin filaments
The actin filaments are attached to protein structures at either end of the sarcomere called z-bands or z-lines (or sometimes z-disc).
Studded all along the actin filaments are myosin-binding sites—areas on each “bead” that are super, super attractive to the protein myosin:
Calcium loves troponin, which causes a conformational change that ultimately exposes the myosin-binding sites on the actin filaments, allowing for muscle contraction to occur.
Muscle relaxation occurs when the bond between calcium and troponin is broken along with the bond between actin and moysin
ATP comes in, breaks the bond between actin and myosin, breaks the bond between troponin and calcium, and then everything goes back to the way it was, relaxing the muscle.
Actin is blocked from myosin by troponin and tropomyosin
Nerve signals flood the sarcomere with calcium
Calcium binds to troponin, revealing the actin-binding sites
Myosin binds to actin, pulling the actin filaments toward the center of the sarcomere
Actin pulls the z-lines to the center, causing contraction of the sarcomere as a whole
A bunch of sarcomeres contract at once, causing full muscle contraction
ATP will break the bond between actin and myosin, allowing muscles to relax
Rigor Mortis
Cccurs as ATP levels decrease post-mortem, leading to a permanent connection between actin and myosin, resulting in muscle stiffness until decomposition begins.
Rigor mortis is first observed in small muscles groups (e.g. the eyelids, the fingers, and the lower jaw) and eventually becomes apparent in the larger muscle gorups, until every muscle is fully contracted and the body is in a fully stiffened state
As muscle fibers decompose, rigor mortis passes until the body is again flaccid
12-12-12 Rule → the general rule of rigor mortis and how long it lasts
takes 12 hours for rigor mortis to fully appear in the body
full rigor mortis lasts for about 12 hours
it takes 12 hours for rigor to disappear from the body completely
Cadaveric Spasm (instantaneous rigor) → the phenomomenon when rigor moris is immediately initiated at the moment of death, often observed in cases involving dramatic or violent deaths, where the body exhibits stiffness without the typical progression seen in post-mortem rigor mortis.
must used physical force or heat to “break” rigor mortis
Forensic Taphonomy: Entomological Pests and Bed Bugs
Bed bugs are classified as insects within the order Hemiptera.
They are widely regarded as annoying pests that frequently infest human dwellings, with a primary focus on bedrooms.
Their feeding habits involve consuming blood from sleeping animals, including humans.
While bed bugs are generally detested by those experiencing an infestation, they are not currently known to spread or transmit any diseases.
Anatomy and Histological Structure of Skeletal Muscle
Skeletal muscles are composed of fibers that are long, thin, and arranged in bundles.
These muscle fibers function in a coordinated manner to produce muscle contraction.
Under microscopic examination, skeletal muscle exhibits a distinct striped pattern known as striation.
The pattern of striation is created by a sequence of basic structural units referred to as sarcomeres.
The comprehensive structure of skeletal muscle includes several specific components:
Bone: The attachment point for the muscle.
Tendon: The connective tissue that joins the muscle to the bone.
Epimysium: The outermost layer of connective tissue surrounding the entire muscle.
Perimysium: The connective tissue that groups muscle fibers into bundles called fascicles.
Endomysium: The layer of connective tissue that surrounds individual muscle fibers.
Fascicle: A bundle of skeletal muscle fibers.
Sarcolemma: The cell membrane of a muscle fiber.
Myofibril: The elongated contractile threads found in striated muscle cells.
Nuclei: The multiple nuclei located within the muscle fibers.
Blood Vessels: Integrated within the muscle structure to provide nutrients and oxygen.
Postmortem Scavenging and Predation
Following death, internal microorganisms begin to consume the body.
External animals also act as scavengers of bodily remains, as a dead organism serves as a primary source of nutrition.
Various types of scavengers include:
Insects (such as ants).
Carnivores.
Birds (specifically turkey vultures).
Scavenging activities can create postmortem predation artifacts on the body.
These artifacts can be deceptive in a forensic context because they often closely resemble injuries sustained antemortem (before death) or perimortem (at the time of death).
Mummification and Bacterial Decomposition
Natural mummification occurs when flesh remains preserved on the bones long after death.
A notable example is a natural mummy from the year located at the Museum of the Mummies in Guanajuato, Mexico, which still possesses visible flesh.
Decomposition rates can vary across different parts of the same body:
Extremities (such as hands and feet) may become mummified while the torso simultaneously undergoes putrefaction.
This differential preservation is caused by the distribution of bacteria within the body.
The abdomen contains a relatively large population of bacteria, facilitating rapid putrefaction.
The hands and feet have a relatively small presence of bacteria, allowing for mummification rather than total decay.
Aidpocere
Also commonly known as “grave wax”
The result of anaerobic enviorment where bacteria will produce a waxy cast of tissue containing palmitic, oleic, and stearic fatty acids (so this is a byproduct of lipid degradation under anaerobic conditions).
Skeletonization and Long-Term Preservation
Skeletonization is the stage of decomposition where the body lacks almost all soft tissue, leaving the bones clearly visible.
Once a body has reached the state of skeletonization, the bones have the potential to last for a very long period.
Archeological digs frequently uncover skeletons that have remained preserved in the environment for extensive durations.
Rule of Thumb of Body Decomposition
One week in air = Two weeks in water = Eight weeks in soil