1. Postmortem Changes and Time of Death

2. Postmortem = after death
Necessary interdependent systems for life:
Respiratory system
Circulatory system
Central nervous system
Clinical death: All three of the above systems must be non-functioning
Legal death: Can be determined based on absence of neurological function despite lack of clinical death

3. Determination of Clinical Death
Observation for breathing
Auscultation for heart beat
Palpation for a pulse
Instrumentation
Electroencephalogram – measures brain activity
Can be misleading in cases of hypothermia due to depressed body functions
Electrocardiogram

4. Immediate Postmortem Changes

5. Immediate Postmortem Changes
Cessation of respiration
Cessation of circulation
Muscular relaxation
Loss of reflexes
Skin pallor (paleness – loss of natural color)
Dilated pupils

6. Early Postmortem Changes (not immediate)
Apparent after one or two hours:

7. Early Postmortem Changes (not immediate)
Apparent after one or two hours:
Algor mortis
Livor mortis
Rigor mortis

8. Early Postmortem Changes (not immediate)
Apparent after one or two hours:
Algor mortis – body cooling
Livor mortis – discoloration due to blood settling
Rigor mortis – stiffening of muscles

9. Algor Mortis Normal body temperature varies
Body cooling does not occur at a uniform rate
Under average conditions, the body cools at the rate of about o F per hour for the first few hours, then slower afterwards.
Skin cools more rapidly than the inside of the body – that is why the inner body core temperature should be taken at the scene.

10. Modes of Heat Loss
Conduction –
Radiation –
Convection -

11. Modes of Heat Loss Conduction – Heat transfer by items in contact
Radiation – Infrared heat transfer
Convection – Heat transfer by air movement

12. Factors Affecting Algor Mortis

13. Factors Affecting Algor Mortis
Time
Environmental temperature
Location of body – In water the temperature of a body would drop more rapidly, on the ground more slowly due to insulating effect of soil, etc.
Body type and clothing – obesity or heavy clothing slows cooling due to insulation
Humidity and air currents – body exposed to wind will cool more rapidly

14. Livor Mortis Discoloration of the skin in lower regions of the body
Usual color of lividity is red-purple
Begins immediately at death due to lack of circulation
Blood settles due to gravity
Small vessels and capillaries become congested with blood

15. Livor Mortis Not generally apparent for 1-2 hours
Fixed (or permanent) after 6-12 hours
Blood will not flow to a new region if the body is moved after livor is fixed, thus inappropriate lividity (livor mortis in an unexpected location) is an indication that the body has been moved at least 6-12 hours after death

16. Livor Mortis
Pressure can effect appearance of livor mortis, as pressure can displace blood in regions that should otherwise be darkened

17. Livor discoloration Red-purple – Normal Pink – Cyanide or cold
Cherry-red – CO or fluoro-acetate
Brown – Nitrites or methemoglobin
Note: Livor can be confused with bruises – livor can be drained, but blood from bruises cannot since the blood has infiltrated the surrounding tissues and is no longer in the capillaries

18. Livor Mortis
While livor mortis is a poor indicator of time of death, it is excellent for determining the place/position of death

19. Rigor Mortis
A post-mortem stiffening of the muscles due to lactic acid causing a cross-linkage between actin and myosin (the proteins involved in muscle contraction)

20. Rigor Mortis
ATP generally breaks this cross-linkage, but ATP is depleted shortly after death
Rigor persists until decomposition begins to break down the protein complex, thus relaxing the muscles

21. Factors Affecting Rigor
Rigor is generally noticeable at ~3 hours, but can be accelerated by:
Environmental heat
Fever in victim prior to death
Some drugs
Exercise prior to death
Can be slowed by:
Cold environment
Emaciation

22. Rigor/Algor at Average Temperatures
Body warm and flaccid: <3 hours
Warm and rigid: hours
Cold and rigid: hours
Cold and flaccid: >36 hours

23. Other time of death indicators?

24. Other time of death indicators?
Insects – various insects deposit eggs and those eggs develop and known rates
Stomach contents -

25. Other time of death indicators?
Insects – various insects deposit eggs and those eggs develop and known rates
Stomach contents – food takes approximately two hours to digest and then be emptied from the stomach under normal conditions

26. Late changes in Death Decomposition Adipocere Mummification
Skeletonization

27. Decomposition Two processes drive decomposition: Autolysis
Putrefaction

28. Decomposition Two processes drive decomposition:
Autolysis – Body’s own digestive enzymes begin to break down cellular proteins and other molecules. Begins immediately after death.
Putrefaction

29. Decomposition Two processes drive decomposition:
Autolysis – Body’s own digestive enzymes begin to break down cellular proteins and other molecules. Begins immediately after death.
Putrefaction – Decomposition driven by bacterial activity. This is the primary factor causing decomposition.

30. Putrefaction process
Green discoloration of abdomen begins at hours after death
Marbled appearance often noticeable due to intravascular hydrogen sulfide producing bacteria
Gas formation and bloating noticeable at hours – causes blisters and skin slippage, loss of hair and nails

31. Putrefaction
Liver filled with holes – why??

32. Putrefaction
Liver filled with holes – due to invasion and proliferation of gas-producing bacteria during decomposition

33. Factors affecting decomposition

34. Factors affecting decomposition
Temperature
Humidity
Body location:
Decomposition rates on land are generally twice as fast as in water, and eight times as fast as those when a body is buried due to lack of oxygen and lower temperatures

35. Alterations to normal decomposition
Adipocere – “Grave Wax”– Conversion of fats to oleic, palmitic, or stearic acids (these are waxes, not fats)
Occurs in damp, warm, anaerobic (no oxygen present) environments
Due to lack of oxygen, other decomposition changes do not occur

36. Adipocere

37. Mummification The process of desiccation of a body
Occurs in exceedingly dry conditions
Normal decomposition processes prevented due to lack of water necessary for bacterial growth