POSTMORTEM EXAMINATION IN A CASE OF POISONING
Poisoning cases being invariably medicolegal in nature, if the patient dies, an inquest will have to be done, followed by post-mortem examination by a forensic pathologist. This is for the purpose of ascertaining the circumstances in which poisoning occurred, and to establish the exact cause and manner of death.
The general procedure of examination is the same as for any medicolegal autopsy, with particular attention being paid to those aspects which can afford a clue to the detection of and identification of the poison involved. The following is a summary of the important points to be noted:
· Stains or marks of vomit, faecal matter, etc., on the clothing, or on the body.
· There may be evidence of corrosion in the form of discol- caustic ingestion (acid/alkali).
· Presence of jaundice suggests a hepatotoxic poison, or one which causes haemolytic anaemia.
· Odour: Several poisons have characteristic odour which may be perceptible in the vicinity of the mouth..
· Colour of postmortem lividity*: Certain poisons impart characteristic colouration, for example—
· Carbon monoxide Cherry pink
1. Cyanide Brick red
2. Hydrogen sulphide Greenish blue
3. Phosphorus Brown
4. Nitrobenzene, aniline, potassium chloride Brownish red
· Putrefactive changes: Some poisons are said to retard the rate of decomposition of a dead body, e.g. arsenic, organo-phosphates.
· Injection marks : Especially likely in a victim who had been a drug addict in life.
Odour: It is preferable to open the cranial cavity first, since poisons impart a faint odour to the brain which may be difficult to perceive in the presence of overpowering odours from the thorax or abdomen if they have been opened earlier. Examples of such poisons include alcohol, chloroform, cresol, cyanide, and phenol.
Evidence of inflammation: Ingested poisons may cause softening, reddening, corrosion, or even perforation of the gastrointestinal tract. Sometimes the poisonous substance in the form of tablets, powder, plant parts, or fluid may still be present. There may be associated odour.
The state of the other organ systems: Liver and kidneys are invariably congested. In some cases, there is evidence (gross or microscopic) of degenerative changes or even necrosis. Brain may be congested or oedematous, particu-larly in the case of neurotoxic poisons. Petechiae in the white matter are often seen with asphyxiant poisons, which also produce pulmonary oedema with consequent froth in the airways. The heart may demonstrate petechiae or degenerative changes in the case of cardiotoxic poisons. Subendocardial haemorrhages are said to be characteristic (though not pathognomonic) of acute arsenic poisoning.
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