Postmortem Changes

Question 1

What factors influence the rate of body cooling?

Answer 1

• Usual body temperature in this environment
• Is the body clothed? What is the nature of the clothing?
• Natural insulation of the body – adipose layer
• Convection currents – heat transfer by movement of fluid and air around body
• Environmental temperature – remember to note difference in internal and superficial body temperature, and how long it takes before the environment affects internal body temperature

Question 2

What time period offers the best opportunity for estimating the time of death?

Answer 2

First 18 hours

Question 3

What can the length of the plateau on the sigmoidal curve of body cooling represent?

Answer 3

The length of the plateau phase of the cooling curve represents the time it takes before the body actually begins to cool, and the longer the plateau the shorter the actual time and cause of death.

Question 4

What is the accuracy of al-Alousi and Henssge calculations measuring time of death based on temperature?

Answer 4

+/- 2.5hrs

Question 5

What calculations are used to measure time of death based on body temperature?

Answer 5

al-Alousi and Henssge calculations

Question 6

How much does body temperature drop in an hour?

Answer 6

1℃

Question 7

Why cant stomach contents be used to measure the time of death?

Answer 7

Too many factors influence the rate at which the stomach empties e.g.

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

Can only tell when they last ate

Question 8

Describe rigor mortis

Answer 8

Stiffening and shortening of muscle fibres leading to rigidity of the musculature and fixation of the joints due to the reduction of adenosine triphosphate (ATP) within the muscles after death. Usually seen in smaller muscle fibres first.

Question 9

When does rigor mortis become first apparent?

Answer 9

5-7hrs after death

Question 10

When does rigor mortis become fully established?

Answer 10

8-12 hrs following death

Question 11

When does rigor mortis usuually dissipate and why?

Answer 11

Dissipates in line with ensuing decomposition and frequently absent by 36 hours after death - body returns to a flaccid state

Question 12

Is rigor mortis useful when trying to determine time of death?

Answer 12

Susceptible to biological variability

Only of any potential use in the first couple of days after death

Question 13

What factor can affect the development of rigorous mortis?

Answer 13

Environmental/ambient temperature
Muscle bulk of individual
Seizures before death cause rigor mortis closer to time of death

Question 14

What is cadaveric spasm?

Answer 14

Cadaveric spasm is a rare form of muscular stiffening that occurs at the moment of death, persists into the period of rigor mortis and can be mistaken for rigor mortis. The cause is unknown, but is usually associated with violent deaths happening under extremely physical circumstances with intense emotion. Typically only affects certain groups of muscles. “Instant rigor mortis”

Question 15

Name another test for time of death that is being currently investigated

Answer 15

Measurement of the level of potassium ions in the vitreous humour of the eye

Question 16

Describe the process of decomposition and putrefaction

Answer 16

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

Question 17

What variables influence putrefaction?

Answer 17

ambient temperature
humidity
“cleanliness” of the environment
breakages in skin

Question 18

When are usually the first signs of putrefaction?

Answer 18

2-3 days: greenish discolouration of the abdominal skin

Question 19

What visible signs of putrefaction are seen following a week after death?

Answer 19

1 week: blister formation and tissue swelling, including gas formation in body cavities. Vascular “marbling” can be seen due to putrefaction of the superficial veins in the skin

Question 20

What causes vascular marbling?

Answer 20

Is due to putrefaction of pooled blood in superficial veins in the skin, usually seen 1 week into putrefaction.

Question 21

When does post mortem hypostasis become apparent?

Answer 21

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 22

When does post mortem hypostasis become fully apparent?

Answer 22

6-12 hrs later

Question 23

What are some other names for post mortem hypostasis?

Answer 23

PM lividity or PM staining

Question 24

What can analysing putrefaction be used for?

Answer 24

Certain organs are relatively resistant to putrefaction and their persistence can be valuable for identification purposes.

Question 25

What are the five stages of decomposition?

Answer 25

Fresh
Bloat
Active decay
Advanced decay
Dry remains

Question 26

What processes influence the appearance of the body following death?

Answer 26

o	Putrefaction
o	Mummification
o	Adipocere formation
o	Skeletonisation
o	Post mortem hypostasis

Question 27

Describe mummification

Answer 27

• A process of “dry” 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
• Preservation may be remarkable

Question 28

Who are more prone to mummification?

Answer 28

Infants

Question 29

Describe adipocere formation

Answer 29

• Induced by 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 damp or wet environments, e.g. bodies recovered from water

Question 30

Describe skeletonisation

Answer 30

Often referred to as the final stage of death

The condition when all of the soft tissues of the body have completely degraded

Question 31

What variables can effect skeletonisation?

Answer 31

Anything that affects the soft flesh e.g. exposure to meat-eating animals (post mortem animal predation, e.g. rats) and to dipterous larvae.

Question 32

How can we age bones?

Answer 32

Radioisotopes have been used to “age” bones, recently including strontium and polonium

Question 33

What is post mortem hypostasis?

Answer 33

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

Question 34

Describe the development of marks in post mortem hypostasis

Answer 34

Where the body surface has pressure applied there will be compression of the blood vessels, preventing ingress of blood, demonstrated by areas of “pressure pallor” within hypostasis, e.g. a body lying on its back (face up) would be expected to have areas of pallor on the upper back and the buttocks as these are the main areas upon which the body mass rests, while the mid to lower back would be red due to pooled blood.

Question 35

What information can be gathered from post mortem hypostasis?

Answer 35

Not so useful as a means of timing death, but can be a great help in ascertaining the position of the body after death and can indicate if the body has been moved after death

Question 36

Why might it be difficult to distinguish between post mortem hypostasis and other markings?

Answer 36

• May be difficult to distinguish between hypostasis and bruising
• May be difficult to distinguish between hypostasis affecting the face and “asphyxial” congestion and petechial haemorrhages where “haemorrhagic lividity” has developed in a body lying prone (face down), particularly where the head is dependent, e.g. hanging off the edge of a bed

Question 37

Why can the colour of hypostasis sometimes be useful?

Answer 37

• Usually pink/purple in colour
• “Cherry red” - indicator of carbon monoxide poisoning
• Red/brown - may be seen with methaemoglobin (caused by certain chemicals or drugs)

Question 38

Define post mortem artefacts

Answer 38

Alteration or damage to the body occurring after death which may mimic genuine processes occurring in life e.g. resuscitation, animal predation and traumatic injuries

Question 39

Describe some examples of post mortem artefacts

Answer 39

resuscitation
animal predation
traumatic injuries