4. TDI Flashcards
What are methods of establishing TDI?
Insects Carbon dating Decomposition/ADD/total body score Pollen Botany
Process of carbon dating
Cosmic rays enter earths atmosphere and collide with an atom = neutron
Neutron collides with nitrogen atom to make nitrogen-14 become a carbon-14
Plants absorb carbon dioxide and incorporate c-14 through photosynthesis
Animals/people eat plants and take in c-14
After death and burial, wood and bones lose c-14 as it changes to n-13 by beta decay with a half life of 5730yrs
Problems with carbon dating in recent years?
1955-1963 saw a rise in C-14 in the atmosphere due to nuclear testing
Past 60yrs has seen artificially high c-14 level so bodies will contain large amounts of it (useful to differentiate archaeological from forensic)
Levels now dropping as c-14 soaked up by oceans etc
Issues with carbon dating
Relies on the fact c-14 is dropping and amount of radiocarbon in people depends on when their tissues were formed
Requires knowledge of tissue formation
Soft tissue needed to predict time of death (nails, hair, blood)
Will only be useful for next 10/20yrs while levels still returning to normal
Process of total body score
Take each decompositional change, order and score each stage
Score different areas (head/neck, torso, limbs)
Combine = total body score
Process of ADD
Max and Min temp of day divided by 2
One degree day is accumulated for each 24hr period where the average temp is above ‘threshold’
Process of palynology
Pollen is sticky and seasonal
Therefore can look at layers of pollen to estimate the number of seasons that a body has been exposed for
Can be found in nose and lungs
Amino acids
Fresh bone may yield as many as 16 amino acids
Will reduce to 7 after 100 years or more
*not hugely accurate
Bone flourescence
UV fluorescence of bone reduces over time
Loss of 20% intensity in first 15yrs
Loss of fluorescence begins around medullary cavity at 3-80yrs PMI
*some suggest bones can stay fluorescent for up to 350yrs, so tests aren’t accurate
