PMI - late postmortem period and influencing factors

What is decomposition

• its a continuous process

• starts from the moment of clinical death

• dependent on many variables

Divide decomposition into 5 categories

• fresh

• bloat

• active decay

• advanced decay

• skeletonisation

What happens during bloat stage

• uncontrolled activity of internal bacteria

• build up of gas and pressure in intestines and abdomen

• discolouration

• blisters, marbling

What happens during active decay

• maggots hatch and destroy integrity of the body

• bacterial action continues

• temperature rises due to maggot mass - accelerates bacterial and enzymatic action

What happens during advanced decay

• gases still released

• decomposition fluids leach into surroundings

• maggots retreat, beetles more active

• bacterial action reduced

what happens during Skeletonisation

• decomposition slows down

• gradual exposure of the bones

• some tendons and ligaments still visile

• disarticulation

• scavangers can take away small bones

What is important to keep in mind about the 5 stages?

• decomposition is not always linear

• dependent on intrinsic and extrinsic factors

• stages can be extended, paused, overlapped or skipped

• progression and sequence is always being researched

Explain influencing factors

The rate of decomposition = the speed at which a body transforms from a fresh whole body to complete skeletonisation

Combination of:

• Extrinsic factors (external/environment)

• Intrinsic factors (internal/individual)

What regulated decomposition?

Name extrinsic factors

• temperature

• access by instincts

• moisture/ humidity/rainfall

• sun/shade

• coffins

• submersion in water - decomposition rate slows by half in water

• hanging above ground - maggots may fall off or be washed away by rain

Name intrinsic factors

• body size, smaller = faster decomposition

• clothing/covering

• trauma - scents of blood attract insects quickly

• burning

• disease

• drugs - morphine slows decomposition

What does ADD/ADH stand for?

accumulated degree days/hours

How is ADD/ADH calculated?

• sum of daily temperature varations at the cs or recovery site

• accumlation of thermal energy ( degrees Celsius) over time (days)

• reflects cumulative heat exposure to the body

• base temperature needs to be selected