CMA 1 Flashcards
define taphonomy
The study of the processes by which organic remains change after death
environmental taphonomic factors
abiotic + biotic
cultural taphonomic factors
mortuary activities, cultural modifications
ante mortem
before death
peri-mortem
period at or around death
Post-mortem
from death to recovery
post-recovery
from recovery to analysis
two stages of decomp
- Autolysis
- Putrefaction
6 stages of decomp
- Fresh
- Bloating
- Putrefaction
- Black putrefaction
- Buytric Fermentation
- Dry Decay
Autolysis
> cellular self-destruction
caused by lack of oxygen
Build up of CO = decreased pH
Releases nutrient rich fluid
colder = slower
Putrefaction
> Caused by autolysis = anaerobic environment
Release of carbohydrates feeds bacteria
produces gases + aromatic compounds
Order of Putrefaction
- Intestines, stomach, digestive tract, heart + blood
- Air passages and lungs
- Kidneys and bladder
- Brain + nervous tissue
- Skeletal muscles
- connective tissue + skin
- bones
bone diagenesis
bacteria eliminate collagen from within the bone
biotic factors
> insect activity
Animal scavenging
Human interaction/intervention
affect of insects on decomp
> as no. of insects increase so does temp
Larval mass = further tissue exposure = more insects
more consumption > more access > more eggs
Effect of animal scavenging on decomp.
> increase if they scavenge the body
decrease if they scavenge insects
order of scavenging
- Face and neck
- Thorax
- Upper extremities
- Lower extremities
- Trunk
evidence of rodent scavenging
parallel striations
effect of clothing type on decomp.
> man-made fibres insulate
natural allow air flow
wrappings (plastic) will increase decomp.
high humidity low temp
slow decomp
high humidity high temp.
rapid decomp
low humidity low temp.
freeze drying = no decomp.
low humidity high temp.
dehydration/mummification = no decomp.
rainfall/ground water on decomp.
adipocere formation (saponification): waxy substance from hydrolysis of fat - protects body from decomp.
livor mortis
settling of RBC according to gravity = indicates body position
Algor mortis
Change in body temp to match environment temp - can be used to measure PMI
Rigor Mortis
Gradual stiffening of muscles after death due to build of ATP - can be used to measure PMI but not accurate
marbling
> caused by sulfhaemoglobin through vascular system
progressive decolouration of body
bloating
> production of gases (volatile organic compounds) = cadaverine and putrescine
eventually will purge through body cavities along with fluids
Saponification
> hydrolysis of body fats
Adipocere formation
requires water
forms anaerobic environment
dehydration - mummification
> removes water access for bacteria, slowing and stopping decomp.
high temp. low humidity
sand burials
dehydration - freezing
> removes access to water = arrests decomp
arctic expeditions
dissolution
dissolving body in acid or lyme
resomation
alkaline hydrolysis (type of dissolution)
maceration
controlled putrefaction = leaves only skeleton
promession
freeze-dried to produce a powder
mushroom burial
mushroom suit
Methods of detecting deposition sites
- Aerial Photography
- Thermal Imaging
- Ground Penetrating Radar
- Resistivity
- Magnetometry
- Scent dogs
decomp gases
putrescine + cadaverine
ground penetrating radar
> can be problems with clay soils
good for penetrating concrete or paved layers
Resistivity
> requires some level of moisture
ploughing and paving cause problems
dry soil and frozen ground problematic
magnetometry
> useful in less disturbed soils
problematic in urban areas (power lines)
water detection
> ground penetrating radar
only viable in fresh water environments
scent dogs
Methods for determining PMI
- Potassium conc. of vitreous humour
- Algor mortis (body temp)
- Livor mortis
- Rigor mortis
- last meal
- entomology
Radiocarbon dating
> N14 forms C14
plants + animals take up C14 during life
At death, C14 decreases at known rate = PMI
total body score
Head & neck + Torso + limbs
Accumulated degree days
> measurement of thermal units required for growth and development of insects to adult stage
mixed assemblage causes
> mass fatality events
mass graves
ossuary
sorting steps
- sort bone/tooth from other debris
- Sort human from non-human
- Inventory bones by type or side
- Examine morphology
- determine age/sex/ethnicity
- Consistency of size, length, robusticity, joint surface congruency
- evidence of duplication
Imaging of commingled remains
> radiography
computed tomography
SWGANTH guidelines for commingled remains
1.Visual pair matching
2.Articulation
3.process of elimination
4.Osteometric Comparison
5. Taphonomy (not primary technique)
Determining how many individuals present
> MNI (minimum)
MLNI (most-likely)
MaxNI (maximum)
MNI calc.
Max left or right of any single element (ignore pairs)
Grand minimum total calc.
L+R-P
MLNI calc.
(L+1)(R+1)/(P+1) - 1
which quantification method to use?
> MNI underestimates until majority of remains uncovered
MLNI overestimates but generally more accurate
Use of forensic entomology
> Estimating PMI
Body transfer
Confirm cadaver presence
DNA
Detect Drugs
Necrophages
> First species feeding on corpse tissue (blowflies, beetles, clown beetles)
Omnivores
> feed on the corpse and associated maggots
large populations of omnivores may slow decomp.
ants, wasps and beetles
Predators of necrophages
> Beetles and wasps
Incidental bugs
> hoverflies, spiders etc. - use the corpse as as an extension of their natural habitat.
Bug stages
1.Eggs
2. 1st Instar
3. 2nd Instar
4. 3rd Instar
5. Pupa
6. Adult
common colonizers of exposed bodies
> calliphoridae (blowflies)
Development Threshold Temperature (DTT)
> Optimum temperature outside which development stops
lower temp slows and halts development
high temp. denatures and kills
Effective/Base Temperature
Temp. threshold below which development will not occur
Degree Days
The portion of thermal units insects use to grow and develop over one stage.
Accumulated Degree Days
Degree days for stages added together to give the full life cycle
ADD/H calculation
Time x (temp. - ET) = ADD/H
