The autopsy procedure always begins with external examination of the clothing as well as the body followed by internal examination. In developed countries with resources available, blood, urine, bile, and vitreous should be routinely be collected and analyzed. However, this is not feasible in resource-scarce settings. As such, in our context, toxicological analysis is carried out in
- Suspicious deaths when no cause of death is found
- Suspected poisoning from circumstantial evidence
- Routine toxicological analysis in Air crash (Captain and Co-pilot),
- Drivers in road traffic accidents
- Surgical and anesthetic deaths
Scene of death
Details regarding the scene should be documented, including scene disturbance, position of deceased, any vomitus as well as presence of container or spilled poison. Any poison or drug containers, vomitus or spilled poison present at the scene should be collected and sent to Forensic Science Laboratory for analysis.
If the ingestion of poison was witnessed by anyone, details regarding substance ingested, symptoms after ingestion, as well as treatment and procedures should be documented. In addition, the access to the substance should also be documented, especially if the poisoning was a result of an overdose of prescribed medicine.
Some heavy metals can mimic natural diseases, especially on chronic exposure. Chronic arsenic poisoning can mimic cholera or gastro-enteritis; similiarly, chronic thallium poisoning can mimic peripheral neuropathy. It is therefore important to deduce relevant occupational and exposure history. Lack of anatomical evidence of these diseases can preclude a suspicion of heavy metal poisoning.
If the deceased was admitted in hospital and received treatment, vomitus as well as first gastric lavage should be collected and analyzed. Where blood has been drawn, it may be sent for toxicological analysis, following death.
Any abnormal odor associated with the body should be noted. Kerosene like smell is associated with organophosphorus poisoning, garlicky smell is seen in Phosphorus containing poisons like aluminum phosphide and arsenic, and cyanide poisoning presents with a bitter almond smell. Clothes should be examined for stains, which should be collected for analysis.
External examination should include examination for patchy alopecia as seen in chronic arsenic poisoning, Mees’ line seen in nails in heavy metal poisoning, skin pigmentation in heavy metal poisoning, Icterus indicates hepatotoxic poisons and also a sign of multi organ failure when the patient had been hospitalized for long duration.
Examination should try to determine the route of administration by examining for chemical burns, puncture marks etc. In case of puncture marks, skin surrounding the puncture mark should be excised and collected for analysis.
Examination of post-mortem hypostasis may demonstrate color changes depending on the poisoning. For example, cherry red discoloration of lividity indicates carbon monoxide poisoning. Similarly, a bright red coloration may indicate cyanide poisoning while a yellowish-brown discoloration indicates phosphorus poisoning.
Internal examination of the deceased is extremely important to rule out natural disease processes and to correlate with the development of clinical features. Blood and muscle tissue appear cherry red in carbon monoxide poisoning. Examination of tongue, esophagus and stomach could reveal abnormal smell, stain, congestion, mucosal edema, erosion as well ulceration and perforation.
Heart should be examined for signs of myocardial infarction, even if the coronary arteries are patent. Some drugs, cocaine in particular, cause severe vasospasm resulting in myocardial infarction and arrhythmias. Lungs generally appear to show evidence of generalized edema. However, in inhaled poisons, lung parenchyma may demonstrate injuries, including contusions, hemorrhage and erosions. Liver may appear enlarged and yellowish, with signs of hepatitis. Kidneys may show signs of glomerulonephritis as well as other focal hemorrhages.
Diagnosis of the cause of death in a case of poisoning requires demonstration of poison or metabolites in the body beyond the median lethal dose. While it may be possible to correlate and perhaps even diagnose, based on physical characteristics of poison as well as the symptomatology, it is highly recommended that samples be collected for toxicological investigations to provide an objective analysis.
SAMPLES TO BE COLLECTED
The samples to be collected depend on the type of investigation and specifically, the mode of administration, the site of metabolism, distribution and excretion of the drugs. Currently in our context, the samples to be collected for toxicological analysis include:
- Stomach with its entire content (Preserved in saturated solution of sodium chloride).
- Part of liver (estimated 200-300gm) (Preserved in saturated solution of sodium chloride).
- Half of each kidney (Preserved in saturated solution of sodium chloride).
- In case of suspected alcohol intoxication and carbon monoxide poisoning, at least 10ml of blood is collected (preserved in sodium fluoride for alcohol analysis and for carbon monoxide poisoning blood sample is sealed with paraffin without any preservatives).
Depending on the nature of poisoning, additional samples can be collected, including 25-30cm of proximal small intestine, 2-3 cm of skin tissue, muscles etc., lung tissue, hair, bone and nails as well target organ tissue including lungs, heart, brain, pancreas, etc.