Decomposition

Question 1

PM changes and TSD

Answer 1

Orderly physico-chemical
changes after death

Each change has its own time factor or rate

The longer the PMI, the less precise is the estimate of the time of death

Question 2

PM changes in eyes

Answer 2

Loss of corneal and light
reflex

Fixed (mid dilated), unreactive pupils

Decrease in eyeball tension

Feels softer within minutes
after death

Loss of glistening
reflectivity of cornea

Discoloured sclera in open
eyes (yellow/brownish)

Question 3

PM hypostasis

Answer 3

Skin discolouration
AKA: lividity, staining, cogitation and, liver mortis

Question 4

PM hypostasis continued

Answer 4

Settling of blood after death

Gravity dependent

May see pale areas where
dependent portions in contact with firm surfaces or with tight clothing

Question 5

Livor mortis colour

Answer 5

Red/purple colour

Cherry red/ pink livor seen in CO, cyanide, cold environment

Rare to see brown/ green livor

Question 6

Livor mortis modification

Answer 6

Faint/inapparent livor in anaemic/ dark skinned individuals

Question 7

Fixation time

Answer 7

Affected by temperature
Warmed= quicker
Cold= slower

Question 8

Rigor mortis

Answer 8

The progressive stiffening of the muscles of the body

Stiffening starts in the small muscles and spreads down the body

Question 9

Factors affecting right mortis

Answer 9

Environment temp

Degree of muscular activity before death

Rapid onset in children and age than in muscular young adults

Develops early and passes quickly in deaths from infections or from wasting diseases

Delayed in asphyxia deaths

Question 10

Spot checks in average temp conditions

Answer 10

Body feels warm and flaccid: <3 hrs

Body feels warm and stiff: 3-8 hrs

Body feels cold and stiff: 8-36 hrs

Body feels cold and flaccid: >36 hrs

Question 11

Cadaveric spasm

Answer 11

Muscular rigidity at the moment of death

Causes is unknown

Associated with violent deaths in intense emotions

Most commonly affects a
group of muscles only

Question 12

Pugilistic attitude

Answer 12

Typical PM body position

Caused by coagulation of muscle proteins when body is exposed to very high temperatures

Common in burning victims

Question 13

Algor mortis

Answer 13

Cooling of the body after death

Measure the core temperature (rectal or liver)

A measured rectal temperature can give some indication of the
time of death.

Question 14

Algor motos modification

Answer 14

Persons age

Body mass and surface area

Physical condition

Initial temperature

Environmental

1 degree an hour is based on a normal room
temp environment

Question 15

Body cooling

Answer 15

Body cooling is a physical process

Normally there is a temp plateau followed by linear cooling

Question 16

Late PM period

Answer 16

When the body has been out for over 24 hours

Question 17

Putrefaction

Answer 17

Environment impacts putrefaction

Begins when death occurs.

First changes affect the lower abdomen and green
discoloration of skin

Can appear as early as 24 to 36 hours

As bacteria multiplies, discoloration spreads upwards.

Bacteria causes the bloating as they produce gas. This is
seen in the face first

Decomposition fluids from nose and mouth. This is not
blood, but can be pinkish in appearance.

Question 18

Adipocere

Answer 18

Parts of the body that contains fat

Occurs a month after death

It is the product of a chemical reaction in which fats react with water and hydrogen in the presence of bacterial enzymes

Question 19

Adipocere (Sapponnification)

Answer 19

Weeks and months to form

Remains unchanged for years

A warm, moist, anaerobic environment favours adipocere formations

Question 20

Adipocere (Sapponnification)

Answer 20

Weeks and months to form

Remains unchanged for years

A warm, moist, anaerobic environment favours adipocere formations

Question 21

Skeletonization

Answer 21

Loss of tissue from the body

Extremely variable

Based on the environmental conditions and the o revende of insects and animals

Average rate is 1.5 years

Question 22

Mummification

Answer 22

Dehydration of the tissues

The body shrivels and is converted into a leathery or parchment-like mass of skin

The internal organs are often decomposed but may be preserved

Skin shrinkage may produce large artefactual splits

Question 23

Forensic entomology

Answer 23

Blowfly is the most common insect

Bluebottle the most frequent invade of dead flesh. Matures in 14-25 days (at 22°)

Beetles may arrive 3-6 months after death

Question 24

Life cycle of a blowfly

Answer 24

Adult blowfly - Egg- 1st larval instar- 2nd larval instar- 3rd larval instar- pupa- Adult blowfly

Question 25

Larval stages in blow fly cycle

Answer 25

1-2 days to start growning

4-5 days big in size

post-feeding larva 8-12 days

Pupa 18-24 days

Question 26

Fresh stage

Answer 26

Blowfly and flesh flies are first to colonise a fresh corpse

Eggs are laid around the natural provoked and any wounds (warm, moist, well protected areas)

Question 27

Bloated stage

Answer 27

Corpse begins to swell

Blowflies continue to ovipost

Maggots continue to feed

Rove beetles feed on fly larvae and eggs

Question 28

Decay stage

Answer 28

Large masses of maggots still feeding externally and internally

Silphid, histerid and muscid beetles attracted to the corpse

Question 29

Post-decay stage

Answer 29

Corpse is drying out

Reduction in number of flies

Increase in number of beetles

Question 30

Dry stage

Answer 30

Skin and bone left

Insect with the ability to digest keratin move in

Question 31

Caveat

Answer 31

Succession of different specifies in different climates differs significantly

If the indigenous species succession is not known then it is a lot more difficult to use succession as a means of PMI estimation