Postmortem Changes

Question 1

Death

Answer 1

the irreversible failure of the CV system

Question 2

What happens after death?

Answer 2

• failure of O2 delivery to the tissues resulting in cellular death
• energy production ceases and the body cools
• circulating blood becomes stagnant and settles under the effects of gravity
• the usual body defences fail and it can no longer inhibit the proliferation of bacteria- putrefaction ensues

Question 3

How long after death is body temperature relevant?

Answer 3

up to 12 hours

Question 4

What factors influence the rate of body cooling?

Answer 4

• clothes?
• nature of clothing
• usual temp
• natural insulation of body
• convection currents
• environmental temp
• length of plateau of cooling curve

Question 5

What is the rule of thumb when it comes to body cooling?

Answer 5

1 degree per hour

Question 6

How accurate can body temp be in time of death?

Answer 6

no better than +/- 2.5 hours

Question 7

Why can the rate at which the stomach empties not be used as an indication of TOD?

Answer 7

Too many influencing factors:

• nature/amount of food
• solids vs liquids
• stress
• certain medication

Question 8

What is rigor mortis?

Answer 8

stiffening and shortening of muscle fibres leading to rigidity of the musculature and fixation of the joints

Question 9

What causes rigor mortis?

Answer 9

the reduction of ATP within the muscles after death

Question 10

Describe the timeline of rigor mortis

Answer 10

• becomes apparent 5-7 hours after death
• usually fully established 8-12 hours after death
• dissipates in line with ensuing decomposition and frequently absent by 36 hours after death

Question 11

What will affect the development of rigor?

Answer 11

ambient temperature

Question 12

What causes putrefaction?

Answer 12

the action of bacterial micro-organisms; process begins at death but takes a period of time to become detectable

Question 13

What variables should be considered with putrefaction?

Answer 13

• ambient temp
• humidity
• cleanliness of the environment

Question 14

Describe the timeline of putrefaction

Answer 14

• 2-3 day: greenish discolouration of the abdominal skin

- 1 week: blister formation and tissue swelling, including gas formation in body cavities, Vascular marbling can be seen

Question 15

Mummification

Answer 15

• a process of fry decomposition with desiccation of the body and a relative lack of bacterial involvement.
• body essentially dries out the facial features and hands/feet may become rigid

Question 16

What induces adipocere formation?

Answer 16

the alteration of fatty tissue within the body into a greasy/waxy or brittle material which frequently remains attached to the bony skeleton and may retain the body structure to some extent. tends to occur in wet environments

Question 17

What variables exist in skeletonisation?

Answer 17

exposure to meat eating animals and to dipterous larvae

Question 18

Post mortem hypostasis/PM lividity/PM staining

Answer 18

represents the pooling of stagnant blood in dependent regions of the body under the influence of gravity

Question 19

Describe the timeline of PM hypostasis.

Answer 19

begins as soon as the circulation of blood ceases but takes time to become visible usually about 1-2 hours and fully established by 6-12 hours

Question 20

What is pressure pallor?

Answer 20

where the body surface has pressure applied there will be compression of the blood vessel preventing ingress of blood

Question 21

What can the colour of hypostasis tell us?

Answer 21

• pink/purple= normal
• cherry red= carbon monoxide poisoning
• red/brown=methaemoglobin

Question 22

PM artefacts

Answer 22

alteration or damage to body occurring after death which may mimic genuine processes occurring in life

Question 23

What are examples of PM artefact?

Answer 23

• CPR
• animal predation
• traumatic injury