Post Mortem Changes

Question 1

early post mortem changes -

Answer 1

temperature

degradation

hypostasis (colour change)

rigor mortis (stiffening)

Question 2

late post mortem changes - 4

Answer 2

decomposition and autolysis

mummification

adipocere

skeltonization

Question 3

post mortem changes

Answer 3

confirm death

• indisputable evidence, resuscitation is futile
• allows estimate of time of death
• produce confusing artefacts destroy evidence of identity, injury and disease
• have specific forensic uses

Question 4

sequence of post mortem changes

Answer 4

hours : algor mortis, livor mortis, rigor motris

days : wks: putrefaction

mths : skeletonisation, mummification

Question 5

algor mortis

Answer 5

chill of death useful indicator of post mortem interval (PMI) in first 24 hrsonly in temperate and cool climatesrequires a core body temp: rectal (not in sexual abuse cases), liver (subcostal stab)loss of heat from the body due to conduction, convection and radiationlittle heat lost by evaporationexternal surface cools quicker than internal organs rapid cooling initially until body temp is equal to atmospheric temp

Question 6

rate of cooling depends on

Answer 6

body sizeenvironmental temperature

drafts and humidity clothing and coverings

flooring immersion

Question 7

effect of body size on cooling

Answer 7

larger SA = greater heat lossobese individual will cool quicker

Question 8

effect of environmental temperature on cooling

Answer 8

day to night fluctuations

sunny vs overcast timed heating in a house

Question 9

effect of drafts and humidity on cooling

Answer 9

body found outdoors or indoors near an open window will cool quicker than a body found near a heat source or in the sun

Question 10

effect of clothing and coverings on cooling

Answer 10

body in multiple layers of clothing and under bedding will cool slower

Question 11

effect of flooring on cooling

Answer 11

person on a tiled floor will cool more rapidly than someone on a carpet

Question 12

effect of immersion on cooling

Answer 12

body cools quicker in water than in air

Question 13

body temp at time of death

Answer 13

normal = 37Clower body temp: hypothermia, cardiac failure, haemorrhage higher body temp: heatstroke, fever, exercise, drugs

Question 14

hessenge’s normogram

Answer 14

based on mathematical cooling model allows for correction for: body weight, clothing, drafts, immersion

assumptions: normal body temp at death, no variation in ambient temp

Question 15

exclusions to using hessenge’s normogram

Answer 15

nearby strong heat source

nearby cooling source

surface between body a strong conductor of heat abnormal body temp at death body moved between death and temp reading

Question 16

livor mortis

Answer 16

darkening of death pink/purple skin discolouration can be seen prior to death gravitational pooling of blood in blood vessels due to cessation of circulation

• forms horizontal fluid level evident within internal organscompression of tissues prevents formation –> contact pallor where blood cannot pool

Question 17

livor mortis and indication of PMI

Answer 17

variable interval prior to visibility may appear before death development delayed and intensity affected by natural disease, blood loss and poisoning may not be evident in all but some cases

Question 18

liver mortis timescale

Answer 18

<6hrs: incompletely formed, blanching, unfixed (can shift if body is moved - 1y pattern fades and 2y pattern develops)

10-24hrs: well established, partially fixed, blanching to finger pressure (1y pattern fixed enough to remain, 2y pattern also develops - dual distribution)

> 24 hrs: full established, fixed (1y pattern persists, no 2y pattern develops regardless of any movement)

Question 19

rigor mortis

Answer 19

stiffening of death decrease in ATP post mortem means actin-myosin bonds can’t break –> rigor mortis

Ca build up PM promotes actin-myosin cross bridging rigor suspended by decompositiondoesnt develop until ATP reserve is completed (within hours after death)

Question 20

sequence of onset of rigor mortis

Answer 20

develops in all muscles

smaller muscles usually become completely involved sooner than large ones

not necessarily constant or symmetrical

Question 21

rate of development of rigor mortis

Answer 21

onset and development dependent on :

• body temp at time of death (hyperthermia increases onset)
• ambient temp : (occurs sooner in warmer temps)
• muscle activity prior to death: in times of high intensity exercise, quicker onset

disappearance :

• decomposition
• breaking : if a limb is forcibly stretched out during autopsy, rigor doesn’t redevelop in these areas

Question 22

rigor mortis timescale

Answer 22

warm and w/o rigor: <3hrs PM

warm and w/ rigor: 3-8 hrs

cold and w/ rigor: 8-36 hrs

cold and w/o rigor: >36 hrs

Question 23

later changes of decomposition

Answer 23

indisputable signs of death

resuscitation attempts futile

autolysis and putrefaction

Question 24

define autolysis

Answer 24

enzymatic breakdown of cells/tissues

Question 25

define putrefaction

Answer 25

bacterial breakdown of cells/tissues

Question 26

what are the 5 types of decompositon

Answer 26

maceration

wet putrefaction

skeletonisation

adipocere

mummification

Question 27

what is maceration

Answer 27

sterile autolysis of foetus that has died in uterono exposure to maternal or environmental bacteria

Question 28

wet putrefaction

Answer 28

enzymatic and bacterial

Question 29

adipocere

Answer 29

saponification of soft tissues

requires wet conditions

Question 30

mummification

Answer 30

desiccation of soft tissues

requires cool, dry conditions

Question 31

putrefactive bacteria

Answer 31

temperature dependent (optimal at 21-38C) mainly commensal bacteria from GI and resp

pathogenic bacteria: organ/tissue infection, septicaemia

Question 32

sequence of putrefaction

Answer 32

1. green discolouration of lower abdomen - overgrowth of colonic bacteria (2 days)
2. green-black discolouration and swelling of face and neck - gas production from bacteria (3-4 days)
3. red-brown purge fluid from nose and mouth
4. gas production causes diffuse swelling of the body, most noticeable in the abdomen (methane, hydrogen, hydrogen sulphide, ammonia ptomaines)
5. skin slippage and blistering, hair slippage from scalp (days to a week)
6. marbling - breakdown of Hb in blood vessles, prominence of blood vessels on skin (days to a week)

Question 33

rate of putrefaction is hastened by

Answer 33

slow initial cooling (clothing, bedding, obesity)

warm environment

high humidity

fever at time of death

infection

wound/tissue disruption

Question 34

rate of putrefaction is delayed by

Answer 34

rapid initial cooling (prompt refrigeration immersion in cold water
low body mass)

cold environment

dry conditions

hypothermia at time of death

blood loss

embalming

burial

Question 35

mummification

Answer 35

takes months - years

desiccation of tissues in dry conditions (can be warm or cool)

skin dries, shrinks and becomes leathery

internal organs may decompose or be preserves

more common in infants

Question 36

adipocere

Answer 36

saponification - grave waxmoist conditions (submerged or water logged area)

transformation of body fat to oleic, palmitic and stearic acis by hydrolysis

• predominates in fatty tissues appears yellow/white/brown and waxy
• rare
• caused by clostridium welchii (anaerobic)
• released FA inhibit other bacteria weeks to months affords some preservation of tissues