1. Human Decomposition Taphonomy~
Study of the transition of animal remains postmortem (after death)
Stages of decay are not discrete, described from 2-8 stages but 5 stages most common
Five stages of decay~
Fresh, bloat, active decay, advanced decay, putrid/dry remains
Also referred to as:
autolysis, putrefaction, diagenesis
Fresh (autolysis), bloat (putrefaction), decay (putrefaction & carnivore/scavenging activities), dry (diagenesis)
Recycling of tissues to simplest building blocks (organic molecules of carbohydrates, proteins, lipids, nucleic acids)

2. Stages of decay Rate of decay varies according to: Fresh~
Temperature & relative humidity (season, geography, elevation, etc.)
Corpse/carcass condition (intact, dismembered, burned, etc.)
Corpse/carcass size & biomass
Presence of clothing, physical barriers, etc.
Placement of corpse/carcass (terrestrial, aquatic, buried, hung, indoors, shade-vs-sunlit areas, etc.)
Availability to insects, vertebrate scavengers, bacteria, fungi
Fresh~
Cells begin dying ~3-7 mins PM due to lack of O2 (brain cells die 1st, epithelium can survive up to 24 hrs PM)
Corpse appears normal externally, yet cellular death & microbial activities are occurring internally

3. Fresh stage (cont.) Fresh (cont.)~
Decay initiated by ‘autolysis’ (self-digestion by lysosomal enzymes)
As cells die, [CO2] increases in blood, pH decreases, & cellular byproducts accumulate….causing more cell death
Autolysis externally observable ~few days PM w/ skin blistering, slippage, or ‘gloving’
Rate of tissue degradation in liver (i.e., breakdown of DNA) used as a PM indicator since high [enzyme] in organ leads to linear correlation btw degree of degradation & PMI

4. Fresh stage (cont.) Fresh (cont.)~
Algor mortis- body temperature acclimates to ambient temp
Livor mortis- blood pools in vessels due to gravity, causes discoloration of skin (reddish-purple coloring)
Observable ~ mins PM as blotches, then spreads & deepens in color w/ ~10-12 hrs PM
RBC’s decay & diffuse across vessels into surrounding tissues
Helps indicates initial position of body PM (‘pressure pallor’)
Rigor mortis- stiffening of muscles/joints due to binding of actin & myosin filaments (skeletal muscle) & cytoplasm ‘gelling’ w/ decreased pH
Rigor begins ~3-4 hrs PM, peaks ~12 hrs, & reverses over next ~36-48 hrs as individual cells decay and myosin heads detach from actin filaments
Prolonged due to low ambient temps
Can break rigor by ‘forcefully’ pulling on limbs

5. Bloat stage Bloat stage~
Marked by beginning of ‘putrefaction’, decay of soft tissues by bacteria, fungi, protozoa
Anaerobic bacteria in intestines remain active, breaking down cells (catabolism) & releasing by-products including gases, liquids, & simple molecules
Anaerobic fermentation by intestinal bacteria releases volatile fatty acids (butyric acid) as by-products
Accumulated gases (hydrogen sulfide, carbon dioxide, methane, ammonia, sulfur dioxide, hydrogen) cause abdomen to expand, tongue to protrude, fluids to ooze out of mouth, nostrils, rectum
Odor of decay now able to be detected

6. Bloat stage (cont.) Bloat (cont.)~
A greenish discoloration forms due to breakdown of pooled blood (sulfhaemoglobin causes greenish hue)
Bloat stage relatively short, though slight distension can be seen during cooler temps of winter
Purging of gases & fluids from rectum marks beginning of ‘active decay’ stage

7. Active decay Active decay~
Abdomen, etc. no longer distended (or only slightly so); greenish discoloration becomes yellow-brown-blackish w/ time
Breakdown of skeletal muscle releases amino acids, bacteria then use to make more fatty acids
Aerobic & anaerobic bacteria flourish, insect activity dominate w/ fly larvae consuming majority of soft tissue
‘Black putrefaction’ refers to darkening of skin due to continued tissue breakdown
Typically appears first in head region as colonization of fly larvae (Calliphoridae) in area accelerates decay
Escaping gases produce a very strong odor, NH3 most noticeable

8. Advanced decay Advanced decay~
Marked by mass migration of fly larvae away from corpse to pupate
Remains now resemble a ‘collapsed’ corpse/carcass that includes remaining portions of internal organs, bone, tendons, ligaments, & limited amount of muscle, skin
Adipocere (a waxy, fatty substance formed by glycerol & fatty acids) will be present, but ranges from crumbly (rapid decay) to soft, paste-like (slower decay)
Produces a ‘cheesy’ odor associated with the remains
Mold, fungi, & other microbes become apparent on drying surfaces
Surfaces of skin, hide, bone; on clothing, soil surface, etc.
Insect activity still very important, though species change as ‘food’ & ‘habitat’ resources vary

9. Putrid/dry remains Putrid/dry remains~
Dry or nearly dried remains including bone, tendons, ligaments, hair (hide), nails (hooves, horns), & sinew (shreds of dried tissues attached to bone, hides)
Putrid remains tend to have layer of adipocere present (i.e., soil surface, adipocere, bones etc.)
Dry remains typically include sun bleached bone & mummified tissues (if remain) resting on ‘dried soils’ devoid of adipocere
Remains have now become ‘skeletalized’
Table 1.2 inaccurate regarding timing of insects and descriptions of stage.

10. Generalized decay rates in LA (for a small-normal sized adult*)
During warmer months in LA (March-October)~
Fresh: day 1
Bloat: days 2-3
Active decay: days 4-7
Advanced decay: days 8-10
Putrid/dry remains: days 11+
High-heat index of July, August will accelerate decay, cold fronts will decrease rate, etc.
*Exposed, nude corpse, laying in a terrestrial environment (grasses, sparse forest, etc.)

11. Aquatic environments Aquatic environments~
Remains decay ~2x slower than terrestrial habitats due to cooler temps, low [O2], & inhibition of insect activity
6 stages of decomposition in freshwater ecosystems:
Submerged fresh~ carcass sinks to bottom of pond, etc.
Early floating~ carcass floats to surface as gases accumulate in abdomen; flies begin to lay eggs on exposed flesh
Floating decay~ ‘active decay’ w/ fly larvae feeding on exposed flesh
Bloated deterioration~ carcass still floating though fly larvae have consumed exposed skeletal muscle; limbs begin to disarticulate, body fluids leak from orifices
Floating remains~ disarticulated limbs, skin, internal organs, fatty tissues, etc. ‘float’ as a mass; exposed remains now have little/no insects associated w/ it
Sunken remains~ bones, bits of skin, etc. sink to bottom of pond

12. Aquatic environments (cont.)
Marine ecosystems~
Crustaceans, fish, gastropods, & echinoderms (starfish) main decomposers of carrion
Recovery of human remains rare & limited research on forensic taphonomy in marine environments
Burned bodies~
A ‘complete’ burn extremely difficult to achieve
Typically, flies will still oviposit on the non-burned tissues (bloating of carcass exposes ‘fresh tissues’)
Dismembered, buried, wrapped, etc. all will alter decay~
Text pg 29: case-by-case scenario for ‘exposure to sunlight’