Post mortem changes can be divided into:
- Immediate changes –constitute clinical or somatic death
- Early changes –follow within 12-24 hours after death
- Late changes –follow after 24 hours after death
Immediate Changes (Somatic Death)
- Cessation of circulation
- Cessation of respiration
- Insensibility and loss of ECG rhythms
Early Changes (Cellular Death)
- Algor Mortis (cooling of body)
- Skin changes
- Eye changes
- Livor Mortis (Hypostasis) –blood gravitates to the lowest portions of the body (5-6 hours after death)
- Rigor Mortis
- Fibrinolysis and postmortem bleeding
- Chemical Changes in body fluids
- Larval infestation
- Adipocere formation
Changes in Skin
- Skin loses elasticity, becomes pale and ashy white (especially in fair skinned people). The lips darken.
- Post mortem incised wounds do not gap.
Changes in Eyes
- Loss of corneal reflex (not a reliable sign of death, as also occurs in epilepsy, narcotic poisoning)
- Clouding of cornea, which becomes opaque, wrinkled and brown
- Flaccidity of eye ball (due to loss of intraocular pressure)
- Dilated pupil due to loss of muscle tone in iris and later on constricts, as rigor mortis develops.
- Segmentation or trucking (cattle trucking) in retinal blood vessels
- Rise of potassium level in vitreous humor
- Tache noire formation –within three hours of death if eyes remain open. These are the areas of brownish black discoloration on the exposed sclera between the eye lids.
Cooling of the body, which offers a method of estimating time since death, usually up to 24 hours period.
No exact opinion can be given about the time since death but only a certain range may be given.
Temperature of the body at the moment of death is a chief factor accounting for inaccuracy.
Temperature may have increased before death:
- In asphyxia deaths
- Fat/air embolism deaths
- Aspirin poisoning deaths
- Hemorrhages into brain stem
Body temperature may rise after death due to:
- Environmental temperature
- Tetanus and strychnine poisoning
- Severe bacterial infection
Post mortem Caloricity
Retention of heat or increase in heat for the first two hours after death.
Factors involved in cooling include:
- Temperature difference between body and the environment/medium
- Mass and surface area of the cadaver
- Physique of the deceased (fatty, emaciated)
- Environment of the body (air, water, earth)
- Coverings on or around the body
- Mode of death
- Age and condition of the body
- It is known as the ‘rigidity of death’.
- Mechanism involves ATP depletion.
- Every muscle of the body is affected
- Progression is proximo-distal
- First appears in involuntary muscles (within an hour) due to less mass and less glycogen reserve
- In voluntary muscles, begins 2-4 hours after death
- Persists for about 12 hours and then begins to disappear
- Takes 12-24 hours to disappear completely
|Organ||Time taken for Rigor Mortis development|
|Eyelid muscles||3-4 hours|
|Facial muscles||4-5 hours|
|Neck muscles and trunk||5-7 hours|
|Upper limbs||6-8 hours|
Instantaneous Rigor Mortis (Cadaveric spasm)
It occurs when a person dies in an intense emotional state. Usually a few groups of muscles are involved, fixed in a state of contracture. E.g. a person shoots himself in the head, his arm may be fixed, if he is killed by some other person, there is no such observation.
- Time since death
- Body posture
- Manner of death (cadaveric spasm)
- If body is warm but no rigor –death has occurred in previous 3 hours
- If rigor is progressing but not complete –time of death is between 3-9 hours
- If rigor is fully developed –death occurred more than 9 hours before
- In exceptional cases, rigor mortis may develop even in one hour (as in instantaneous rigor mortis)
Secondary Muscle Flaccidity
- Due to putrefaction changes
- Develops in the same order as it appears
- Rigor mortis begins to disappear after 24-36 hours after death (muscles then do not respond to electrical or mechanical stimuli)
- Some rigidity may persist in the lower limb even after 3-5 days
Factors Affecting Rigor Mortis
- Mode of death
- Condition of the body
- Emotional state
- Age –children and elderly develop rigor mortis early
Conditions Simulating Rigor Mortis
1. Heat Stiffening
Especially in burning deaths or in very high temperature, protein coagulation occurs in muscles, this stiffening is known as pugilistic or boxer attitude.
2. Cold Stiffening
Solidification of fat, etc. The stiffening is not due to rigor.