decomposition Flashcards
define decomposition
the decay of organic matter caused by bacteria or fungal action OR the reduction of the body of a living organism to simpler forms of matter
what is very important to remember when discussing decomposition
it is highly variable
what is taphonomy
the study of the processes that affect decomposition, dispersal, erosion, burial, and re-exposure of organisms after, at and even before death
what is the carcass
the centre of a newly emerging microenvironment - also known as the cadaver or body
what is CDI and what does it demonstrate
cadaver decomposition island - the 2 way nature of decomposition
what effects can decomposition cause on vegetation
grass can appear more dull/ less green than normal above clandestine graves, and this can be visible for years - helpful for identification
what is forensic taphonomy
the study of the fate of human remains, including scientific observations of the body and the environment
what can forensic taphonomy provide
PMI estimations, a timeline of events, and answer further police enquiries
what are the 5 main stages of decomposition
- Fresh
- Bloat
- Active decay
- Advanced decay
- Skeletonization
for how long after stage does the fresh stage of decomposition last and what is it typified by
up to 72 hours after death - typified by the mortis triad
what is the bloat stage of decomposition typified by
the distention of the abdominal cavity due to the build up of gases
what peaks during the active decay stage of decomposition
insect activity
what does the process of decomposition depend on
intrinsic and extrinsic factors - making it non-linear
name 3 things that influence the rate and pattern of decomposition
- The resource quality and composition - the actual body and its size
- The physiochemical environment - weather conditions and if the body is in water or not
- The decomposer community - which bacterial and fungal species are present in the environment
what are the 3 mechanisms of decomposition
- Catalysis - enzymatic and chemical reactions transforming complex compounds into simple molecules
- Communication - physical/ mechanical breakdown of matter
- Leaching - soluble materials removed by water
what does PMI stand for in PMI estimation and what does it look at in regards to decomposition
Post-mortem interval - looks at a combination of both antemortem and post-mortem data e.g. evidence from the body, environment, habits/ actions, etc
why is PMI estimation important
it has direct bearing on legal questions of alibi, opportunity, cause of death, and helps to implicate/ eliminate suspects, potential motive and reconstruct the sequence of events
what must forensic scientists also provide with a PMI estimation
evidence of their empirical field studies, indication of reliability and the error ranges associated with their estimates
what are the two methods for PMI estimation
rate method and occurrence method
explain the rate method for PMI estimation
measures the change produced by a process which takes place at a known rate which was initiated or stopped by the death e.g. looking at chemical changes, insect lifecycles, etc.
explain the occurrence method of PMI estimation
comparing the occurrence of events which took place at known times with the occurrence of death e.g. must’ve been after a phone call - provides something that can be measured to provide statistical analysis, therefore is the most reliable
what is early PMI estimation based on and give a few examples
based on anatomical and physiological changes e.g. the mortis triad, eye changes (Viterous Humour), and gastric contents
what is Pallor mortis
when the skin pales immediately after death
why does blood gradually become acidic in the fresh stage of decomposition
due to the accumulation of carbon dioxide in the bloodstream as respiration has ceased
