Postmortem changes or Forensic traphonomy is the interdisciplinary study and interpretation of postmortem processes of human remains in the dispositional context, i.e., the history of a body following death. A knowledge of the signs of death help to differentiate death from suspended animation. The changes which take place may be helpful in estimation of the approximate time of death. The signs of death appear in the following order.
(I) Immediate (somatic death).
(1) Insensibility and loss of voluntary power.
(2) Cessation of respiration.
(3) Cessation of circulation.
(II) Early (cellular death).
(4) Pallor and loss of elasticity of skin.
(5) Changes in the eye.
(6) Primary flaccidity of muscles.
(7) Cooling of the body.
(8) Postmortem lividity.
(9) Rigor mortis.
(III) Late (decomposition and decay).
(11) Adipocere formation.
Insensibility and Loss of Movement: This is the earliest sign of death, but it can lead to error if precautions are not taken. They are found in cases of prolonged fainting attack, vagal inhibitory phenomenon, epilepsy, trance, catalepsy, narcosis, electrocution, etc.
Cessation of Respiration: This must be complete and continuous. The stethoscope is placed over the upper portions of the lungs and larynx where the faintest breath-sounds can be heard. Complete stoppage of respiration for more than 4 to 5 minutes usually causes death. Respiration may stop for a very short period without death occurring (1) as a purely voluntary act, (2) Cheyne-Stokes breathing, (3) drowning, and (4) newborn infants.
Cessation of Circulation: The stethoscope is placed over the precordial area where the heartbeat can be heard readily. Under normal conditions, stoppage of heartbeat for more than 4 to 5 minutes is irrecoverable and is accepted as evidence of death.
SUSPENDED ANIMATION (apparent death):
In this condition signs of life are not found, as the functions are interrupted for some time, or are reduced to minimum. However, life continues and resuscitation is successful in such cases. The metabolic rate is so reduced that the requirement of individual cell for oxygen is satisfied through the use of oxygen dissolved in the body fluids. In freezing of the body, or in severe drug poisoning of the brain, the activity of brain can completely stop and in some cases start again. Suspended animation may be produced voluntarily. Practitioners of yoga can pass into a trance, death-like in character. Involuntary suspension of animation lasting from a few seconds to half-an-hour or more may be found in newborn infants, drowning, electrocution, sunstroke, cholera, narcotic poisoning, after anaesthesia, shock, hypothermia, cerebral concussion, insanity, etc. The patient can be resuscitated by cardiac massage or electric stimulator and artificial respiration.
CASE: (1) A physician was called to examine an elderly man at his home. The doctor saw the man lying in bed motionless, quickly checked the man’s heart beat and pulse and declared the man dead. In the autopsy room, while the body was being placed on the table, the doctor heard a gurgling sound and noticed a slight swallowing movement. The man was rushed to a hospital and lived for two more months.
(2) Two doctors, both experienced physicians, were driving behind an omnibus which ran over a child. They went to the scene and found the child lying under the front wheel of the bus; she was black in the face and appeared to be dead. Of this they were quite certain. It was impossible to extricate the child until the vehicle was reversed to set her free, a step which the driver took only after considerable persuasion. As soon as she was released, the child immediately showed signs of life. She was taken to an adjoining shop, and a few minutes later, she was found about to be given a drink. This the doctors forbade as they felt sure that rupture of viscera had occurred. The child was taken to hospital and after a day, made a complete and uneventful recovery.
(3) A man aged 83 years attempted suicide by smothering. He was certified to be dead and was taken to the mortuary. His relatives had come with wreaths. The undertakers also arrived, but were surprised to see the “dead man” seated on top of the coffin and complaining of hunger. He subsequently walked home unaided. All postmortem changes are dependent on ambient temperature. High temperature accelerates the changes.
CHANGES IN THE SKIN : Skin becomes pale and ashy-white and loses elasticity within a few minutes of death. The lips appear brownish, dry and hard due to drying.
CHANGES IN THE EYE : (1) Loss of Corneal Reflex : This is found in all cases of deep insensibility, and therefore not a reliable sign of death.
(2) Opacity of the Cornea : This may occur in certain diseases (cholera, wasting diseases) before death. The opacity is due to drying and is delayed for about two hours if the lids are closed after death. If the eyelids are open for a few hours after death, a film of cell debris and mucus forms two yellow triangles on the sclera at each side of the iris, which become brown and then black called “tache noir” within 3 to 4 hours, upon which dust settles and the surface becomes wrinkled (artefact).
(3) Flaccidity of the Eyeball : The eyes look sunken and become softer within minutes due to reduction of intraocular tension. During life, the intraocular tension varies between 14 to 25 gm; soon after death it is less than 12 gm; within half an hour it is less than 3 gm., and becomes nil at the end of two hours.
(4) Pupils Soon after death, pupils are slightly dilated, because of the relaxation of muscles of the iris. Later, they are constricted with the onset of rigor mortis of the constrictor muscles and evaporation of fluid. As such, their state after death is not an indication of their antemortem appearance. Occasionally, rigor mortis may affect ciliary muscles of iris unequally, so that one pupil is larger than the other. If different segments of the same iris are unequally affected, the pupil may be irregularly oval or have an eccentric position in the iris. The pupils react to atropine and eserine for about an hour after death, but they do not react to strong light. The shape of the pupil cannot be changed by pressure during life, but after death, if pressure
is applied by fingers on two or more sides of the eyeball, the pupil may become oval, triangular or polygonal.
(5) Retinal Vessels Fragmentation or segmentation (trucking or shunting) of the blood columns (kevorkian sign) in the retinal vessels appear within minutes after death, and persists for about an hour. This occurs all over the body due to loss of blood pressure but it can be seen only in retina by ophthalmoscope. The retina is pale for the first two hours. At about six hours, the disk outline is hazy and becomes blurred in 7 to 10 hours. These changes are of little practical value.
(6) Chemical Changes: A steady rise in the potassium values occur in the vitreous humour after death up to 100 hours.
Changes in postmortem lividity occur when putrefaction sets in. In early stages, there is haemolysis of blood and diffusion of blood pigment into the surrounding tissues, where it may undergo secondary changes, e.g., sulphhaemoglobin formation. The capillary endothelium and the surrounding cells show lytic changes. Microscopically, the cellular outlines are obscured and the capillaries are not identifiable. A contused area shows similar putrefactive changes and it becomes impossible to determine whether the pigment in a stained putrefied area originated from an intravascular (hypostasis) or/and extravascular localised collection of blood (contusion). There is diffusion of blood-stained fluid in the chest or abdominal cavities. As decomposition progresses, the lividity becomes dusky in colour and turns brown, green and back before finally disappearing with destruction of the blood.
Medicolegal Importance: (1) It is a sign of death. (2) Its extent helps in estimating the time of death, which is unreliable. (3) It indicates the posture of the body at the time of death. (4) It may indicate the moving of the body to another position some time after death. (5) Sometimes, the colour may indicate the cause of death.
COLOUR MARKINGS ON DEAD BODY:Various types of colour markings may be seen on the skin or in the internal organs of dead body.
(A) ANTEMORTEM ORIGIN: (1) Trauma:Bruises and traumatic asphyxia. (2) Asphyxia: Cyanosis. (3) Inflammation: Congestion in organs or the skin. (4) Emboli: Fat embolism. (5) Physical: Exposure to severe cold, and heat.
(B) POSTMORTEM ORIGIN: (1) Hypostasis. (2) Putrefaction. (3) Poisoning: CO, HCN, nitrites, chlorate, etc.
(C) ARTIFICIAL: Paint, grease, dust, mud, coal, blood, semen, etc.
The cause of the colouration can be determined by the patterns of colour distribution, shape, relationship of clothing, etc.
After death, the muscles of the body pass through three stages: (1) Primary relaxation or flaccidity. (2) Rigor mortis or cadaveric rigidity. (3) Secondary flaccidity.
Primary Flaccidity: During this stage, death is only somatic and it lasts for one to two hours. All the muscles of the body begin to relax soon after death. The lower jaw falls, eyelids loose tension, and joints are flexible. Body flattens over areas which are in contact with the surface on which it rests (contact flattening). Muscles are relaxed as long as the ATP content remains sufficiently high to permit the splitting of the actin-myosin cross- bridges. Muscular irritability and response to mechanical or electrical stimuli persist. Peristalsis may occur in the bowel, and ciliary movements and movements of white cells may continue. Discharges of the dying motor neurons may stimulate small groups of muscle cells and lead to focal twitching, although these decrease with time. Anaerobic chemical processes may continue in the tissue cells, e.g., the liver cells may dehydrogenate ethyl alcohol to acetic acid, and complex chemical changes may occur in the muscles. Pupils react to atropine or physostigmine. Loss of muscle tone in the sphincters may result in emptying of bladder. Muscle protoplasm is slightly alkaline.
Mechanism : The mechanism of cadaveric spasm is obscure but possibly may be neurogenic and not the same chemical process as true rigor. The persistence of contraction after death may be due to the failure of the chemical processes required for active muscular relaxation to occur during molecular death. Adrenocortical exhaustion which impairs resynthesis of ATP may be a possible cause. It differs only in the speed of onset and the circumstances in which it occurs.
Medicolegal importance. (1) Occasionally, in case of suicide, the weapon, e.g., pistol or knife is seen firmly grasped in the victims hand which is a strong presumptive evidence of suicide. Attempts may be made to simulate this condition in order to conceal murder. But, ordinary rigor does not produce the same firm grip of a weapon, and the weapon may be placed in the hand in a way which could not have been used by a suicide. (2) If the deceased dies due to assault, some part of clothing, e.g., button of his assailant or some hair may be firmly grasped in the hands. (3) In case of drowning, material such as grass, weeds or leaves may be found firmly grasped in the hands, which indicates that the victim was alive on entering the water.
Case : (1) Tidy (1882) mentioned the soldier at Balaclava whose body remained in position on his horse for some time after he had been killed by a shell.
(2) Tidy also cited the incident at Sedan, described by Rossbach (1870), when six soldiers were killed by a shell. The head of one preserved his laughing expression, present at the moment of death. The body of another, who also had his head blown off, remained in a sitting posture, with a cup still in his hand.
(3) Tidy (1882) described two lovers who, after taking cyanide were found folded in each other’s arms, their bodies stiffened in this position.
(4) Spilsbury (1944) recorded the case of a woman found dead, seated bolt upright in her bath; she held a sponge in her hand which was raised half way to her face. Death was due to cerebral haemorrhage.
Mechanical excitability of skeletal muscle:
(1)Tendon reaction or Zasko’s phenomenon:
Striking the lower third of the quadriceps femoris muscle about 10 cm. above the patella with a reflex hammer causes an upward movement of the patella because of contraction of the whole muscle. This can be seen up to 1 to 2 hours after death.
(2) Idiomuscular contraction or bulge:
Striking at the biceps brachii muscle with the back of a knife causes a muscular bulge at the point of contact due to local contraction of the muscle. In the second phase lasting for 4 to 5 hours a strong and typically reversible idiomuscular pad develops. In the last phase, a weak idiomuscular pad develops between 8 to 12 hours, which may persist up to 24 hours.
Secondary Relaxation : Flaccidity following rigor mortis is caused by the action of the alkaline liquids produced by putrefaction. Another view is that rigidity disappears due to solution of myosin by excess of acid produced during rigor mortis. A third view is that enzymes are developed in dead muscle which dissolve myosin by a process of autodigestion.