Post Mortem Changes Flashcards
Overview of post mortem changes
Somatic (clinical) death Cooling - algor mortis - chill of death - hours Hypostatic lividity - livor mortis - darkening of death - hours Rigor mortis - stiffening of death - hours Putrefaction - weeks/months Skeletonisation - months/years
Usefulness of post-mortem changes
Confirm death
- indisputable evidence
- resuscitation is futile
Allow estimate for time of death
Produce confusing artefacts
Destroy evidence of identity, injury and disease
Have specific forensic uses - position and movement
Cellular resilience to hypoxia
Brain, spinal cord - 4 mins Peripheral nerves - 5 mins Skeletal muscle - 3 hours Blood cells - 6 hours Skin - 24 hours Bone, corneas - 48 hours
PM arefacts
Collapse/falls at time of death - strike nearby objects and ground - eyebrows, nose, chin and cheeks or back of head Resuscitation - bruising to neck, face, chest - scratch abrasions to face - mask marks - needle puncture marks - gripping of arms to move or lift patient - defibrillator burns - perforation of stomach Animals - insects - fish/crabs - rats/mice - dogs Water Fire Recovery of body
Artefacts of immersion
Entry impact Washerwoman change Gooseflesh - cutis anserina Rocks and river bed - flowing water Rocks and sea bed - tidal water Undressing by water movement Fish and crabs Recovery of body
Artefacts of fire
PM burns and tissue loss Skin splits Heat fractures Extradural haematoma Falling masonry Recovery of body
Calculating post mortem interval
Alibi and opportunity Survival period + PMI No reliable method Sources of information - corporal evidence - on body - environmental and associated evidence - anamnestic evidence - habits and activities
Ways to predict post mortem interval
Rate method
- observe or measure changes which occur at known rate
- changes initiated or stopped by specific events
- lividity, rigor, cooling, putrefaction
Concurrence method
- events which occurred at known times
- watch stopped by blow, digestion of meal
Features of cooling
Useful indicator of PMI in first 24 hours
Only in temperate in cool climates
Considerable experience required
Often inaccurate
Core temp measured rectally of by subcostal stab
Serial temp measurements preferred
Avoid rectal measurement in sexual cases
Factors affecting rate of cooling
Body size Exposed surface area Environmental temperature Drafts and humidity Clothing and coverings Immersion
Temperature changes post mortem
<5 hours = plateau effect 6-12 hours = linear ish fall in temp > 18 hours - curve levels out - slight increase due to decomposition - does not reach environmental temp Heat lost by - convection - radiation - conduction - evaporation
Issues with temperature post mortem
Unknown length of plateau - 30 mins up to 5 hours
Body temperature at time of death
- reduced by hypothermia, CCF and haemorrhage
- increased by heatstroke, septicaemia, pontine haemorrhage, strangulation, struggle
Environmental temp during cooling period
Features of a Henssge Nomogram
Based on mathematical cooling method
Allows correction
- for body weight, clothing, drafts, water
- corrective factors applied to body weight
Assumes normal temperature at death
Assumes constant environmental temperature
When Henssge Nomogram cannot be used
Strong heat source nearly - radiator, gas stove Cooling source nearby - air conditioning outlet Underlying surface conducts heat - body on metal tray or cold ground Abnormal body temp. at death Body had been moved
Cooling in water
Body cools faster in water than air
- better heat conductor
- twice as fast in still water than still air
- three times as fast in flowing water than still air
Water around UK is cold
- Tay estuary in January is 6°C
Phases of muscle tone
Primary flaccidity - collapse at death Rigor mortis Secondary flaccidity - due to putrification
