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 hrs
only in temperate and cool climates
requires a core body temp: rectal (not in sexual abuse cases), liver (subcostal stab)
loss of heat from the body due to conduction, convection and radiation
little heat lost by evaporation
external 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 size
environmental temperature
drafts and humidity 
clothing and coverings
flooring 
immersion

Question 7

effect of body size on cooling

Answer 7

larger SA = greater heat loss

obese 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 = 37C
lower 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 organs
compression 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 decomposition
doesnt 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 utero | no 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 wax moist 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