Post-Mortem Examination and Viscera Collection in Poisoning

The external examination is read as a layered set of signs. The first layer is colour. Cherry-pink skin and lividity point to carbon monoxide or cyanide, both of which fix haemoglobin in a bright-red state that resists the usual blue-purple post-mortem lividity. Slate-grey or brown lividity points to methaemoglobin-forming poisons: dapsone, nitrates and nitrites, aniline dyes, older sulphonamides. Bronze pigmentation with desquamation on palms and soles is chronic arsenic.

The second layer is the smell at the body, taken on the first abdominal incision. Bitter almonds (which roughly 40 percent of the population is genetically unable to perceive) is cyanide. Garlic is the cardinal smell of aluminium phosphide, also seen in arsenic and phosphorus. Kerosene at the mouth is hydrocarbon ingestion. Alcohol points to ethanol, methanol or isopropanol. Mothballs are naphthalene. The smell record must go into the autopsy notes contemporaneously; it is the one sensory finding the analyst cannot reproduce at the bench three weeks later.

The third layer is the oral mucosa. Burns and white sloughs on the lips, tongue and oesophageal entrance indicate corrosive ingestion: sulphuric, hydrochloric or oxalic acid; sodium hydroxide or ammonia; or paraquat. Black-tarry stains paired with garlic odour are unreacted aluminium phosphide tablet residue.

The fourth layer is the pupils. Pinpoint pupils with hypersalivation, lacrimation and defecation compose the muscarinic toxidrome of organophosphate or carbamate poisoning, which dominates rural Indian autopsies. Pinpoint pupils without the cholinergic picture suggest opioids. Dilated pupils are anticholinergic (datura, atropine, tricyclics), sympathomimetic (cocaine, amphetamines), or methanol.

The fifth layer is the injection-mark survey. The cubital fossae, dorsal hand veins, groin (informally the lath area in Hindi-belt mortuary slang, with lath wale being the chronic IVDU), between the toes, and the saphenous lines are routine survey sites. Old needle-tracks with hyperpigmentation direct the toxicologist toward an opioid and benzodiazepine panel.

The standard viscera set is settled enough that any state mortuary, from Madhuban to Bhondsi to NIMHANS Bengaluru, runs the same sequence. The cavity is opened en bloc and the organs examined in situ before removal, because in poisoning the colour of the gastric serosa is itself diagnostic.

The stomach is the central organ. It is photographed in situ, surgical thread is tied at the cardia and pylorus, and the stomach is resected between the two ties and lifted out whole with contents intact onto a clean steel dish. The contents are observed before transfer: colour (yellow-green bile, blue from copper sulphate, brown-black from aluminium phosphide), smell, intact tablets, capsule shells, food particles. The whole stomach with contents is preserved in a wide-mouthed glass bottle, 250 to 500 ml, half-filled with saturated NaCl. The whole organ goes into one bottle so the contents and the wall stay together for the analyst's acid-base partitioning.

Thirty centimetres of upper jejunum, measured from the duodeno-jejunal flexure (ligament of Treitz), is tied at both ends and preserved in a separate wide-mouthed glass bottle with saturated NaCl. The jejunum-specific sample matters because absorbed poison concentrates in the jejunal wall during the absorption phase, and a high jejunal level with an empty stomach indicates the poison reached the absorption phase before death.

The liver is the metabolism organ. A 200 g chunk from the right lobe is preserved in saturated NaCl. The right lobe is hepatic-artery-predominant and less affected by post-mortem portal redistribution. The parent-to-metabolite ratio at the bench gives the analyst a clue to the time between ingestion and death.

The kidney is the excretion organ for water-soluble poisons and concentrates metals in the cortex. One whole kidney, or a 100 g chunk, is preserved in saturated NaCl. The contralateral kidney is left for histopathology.

The blood compartment is where the most common collection errors happen. The forensic blood is the peripheral femoral blood, not the cardiac blood. Thirty millilitres are drawn from the femoral vein through a small skin incision in the groin, before the cavity is opened, and split into three 10 ml vials: one with NaF 1 percent plus potassium oxalate (for ethanol, CO, cyanide), one with EDTA (for drugs and metals), one plain (as cross-check). Formalin is never used for blood. Cardiac blood is drawn separately after the cavity is opened and labelled distinctly as a back-up and a redistribution comparator.

Urine is aspirated from the bladder dome by syringe before the abdomen is opened. Volume varies; up to 50 ml. Preserved without chemical preservative if refrigerated. Vitreous humour is drawn through the lateral canthus of each eye with a 21 G needle, 1 to 2 ml per eye, pooled in a plain vial. Vitreous is anatomically isolated, resists post-mortem redistribution, and is the gold-standard cross-check for the femoral blood ethanol. Vitreous glucose and beta-hydroxybutyrate also discriminate diabetic ketoacidosis from alcohol intoxication in road-traffic deaths.

Bile is the under-appreciated sample. Thirty millilitres aspirated from the gallbladder and preserved without preservative gives the analyst a matrix in which opiates concentrate three-fold over central blood (enterohepatic recirculation) and in which aluminium phosphide can be confirmed by phosphine evolution. Bile is mandatory in any suspected opioid death and any suspected AlP death. Hair is taken from the posterior vertex, 100 mg of 3 to 6 cm length, with the root end identified and tied, sealed in a foil pouch. Hair is the long-window matrix and is covered at hair analysis for drugs and chronic poisoning.

Lung and brain are added when the history suggests inhalational poisoning (chloroform, halothane, glue sniffing, CO). Subcutaneous fat is collected in chronic lipophilic exposure (organochlorines, dioxins).

The preservative choice is driven by two questions: what bacterial decomposition does the sample undergo, and what chemical reaction does the analyte undergo with the preservative. Saturated sodium chloride (roughly 360 g/L) is the default for solid viscera because it lowers water activity below the threshold for most bacterial growth, does not react with the broad spectrum of drugs and poisons, and is cheap and available in every mortuary.

Sodium fluoride at 1 percent w/v plus potassium oxalate is the preservative for the blood vial destined for ethanol, CO and cyanide. Fluoride poisons enolase, the enzyme that would otherwise generate post-mortem ethanol from glucose by bacterial fermentation; without fluoride a body sitting overnight at ambient Indian temperature can generate 30 to 50 mg/dL of endogenous ethanol, contaminating the Section 185 Motor Vehicles Act measurement. EDTA is the anticoagulant for the drugs-and-metals vial because it chelates calcium without binding the analytes.

Formalin is never used for toxicology samples. Formaldehyde reacts with amines and aldehydes (destroying the analyte), forms methanol on storage (contaminating ethanol/methanol measurements), and irreversibly denatures cholinesterase (destroying the OP exposure marker). Histopathology samples are taken from a separate piece and labelled distinctly; toxicology and histopathology samples are never combined.

Container chemistry matters as much as preservative chemistry. Wide-mouthed glass bottles are the default. Plastic bottles (polyethylene, polypropylene) are not used for aluminium phosphide cases because phosphine gas permeates through plastic walls within hours; by the time the bottle reaches the SFSL, the phosphine has escaped and the analyst sees a false-negative. Plastic is also avoided for volatile organic compounds. Glass with a screw cap and a Teflon-lined insert is the gold standard for AlP and for volatiles. Rubber stoppers are avoided for volatiles because rubber absorbs the analyte.

Every sealed bottle carries a label: deceased's name, autopsy number, date and time, organ, preservative, volume, and the signatures of the autopsy surgeon and the receiving constable. The seal is the personal wax seal of the autopsy surgeon, impressed on a slip of cloth tied around the bottle's neck; the seal impression is recorded on the forwarding form for the analyst's verification on receipt.

The viscera collection sequence is choreographed for two reasons: to capture each sample with minimum cross-contamination, and to preserve the chain of custody on paper. The walkthrough below reflects the protocol followed at NIMHANS Bengaluru and the AIIMS forensic medicine department, with minor local variants at state mortuaries.

1. External examination and history note
   Examine the body unclothed and undisturbed under good light. Photograph the face, the lividity pattern, the pupils, the lips and oral mucosa, the conjunctivae, the nail beds, the injection-mark survey sites, and any external residue. Record the smell at the body at the moment of the first abdominal incision. Cross-reference the police inquest history and the suspected agents. Decide the viscera set for this case: standard set always, plus lung/brain if inhalational, plus subcutaneous fat if chronic lipophilic.
2. Draw femoral blood before opening the cavity
   Make a small skin incision over the femoral triangle on one side. Identify the femoral vein and draw 30 ml with a sterile syringe before the abdomen is opened. Split into three pre-labelled 10 ml vials: NaF + K-oxalate for ethanol/CO/CN, EDTA for drugs and metals, plain for cross-check. Drawing femoral blood first, with the cavity intact, prevents the artefactual rise from post-mortem redistribution and from gastric-contents contamination after the cavity is opened.
3. Aspirate urine and vitreous before evisceration
   Aspirate bladder urine through the dome with a clean syringe before the abdomen is opened. Draw vitreous humour from each eye through the lateral canthus with a 21 G needle, 1-2 ml per eye, into a pooled plain vial. Replace the lost vitreous with sterile saline injected back through the same puncture to restore eye contour for the family viewing.
4. Open thoraco-abdominal cavity en bloc and photograph in situ
   Standard Y-incision. Examine the organs in situ, with particular attention to gastric serosa colour, gastric distension, oesophageal mucosa, hepatic enlargement, renal cortex pattern. Photograph the gastric serosa before the stomach is mobilised, and again with the parietal peritoneum reflected.
5. Tie, remove, examine and preserve the stomach
   Tie surgical thread at the cardia and at the pylorus, snug. Resect the stomach between the two ties, lift out whole with contents intact, onto a clean steel dish. Open along the greater curvature in a separate clean dish, observe contents (colour, smell, particles, tablets, capsules), record findings. Preserve the whole stomach with contents in a wide-mouthed glass bottle, 250-500 ml, half-filled with saturated NaCl. Label and seal.
6. Collect intestine, liver, kidney and bile
   Resect 30 cm of upper jejunum tied at both ends, preserve in a separate glass bottle with saturated NaCl. Excise 200 g from the right lobe of the liver, preserve. Excise one whole kidney or 100 g, preserve. Aspirate 30 ml of bile from the gallbladder with a syringe, preserve in a plain glass vial without preservative.
7. Collect hair, lung, brain and subcutaneous fat if indicated
   Cut 100 mg of hair from the posterior vertex with the root end identified and tied with surgical thread. Seal in a foil pouch with the root end marked. If inhalational poisoning is suspected, collect a lobe of lung and a hemispherical chunk of brain into separate glass bottles with saturated NaCl. If chronic lipophilic exposure is suspected, collect a 50 g chunk of subcutaneous abdominal fat.
8. Seal, label, register and hand over
   Apply the autopsy surgeon's personal wax seal to each bottle's neck cloth. Label each bottle with deceased's name, autopsy number, date and time, organ/sample, preservative, volume, signatures of the surgeon and the receiving constable. Enter each bottle in the mortuary viscera register. Hand the sealed set to the investigating officer or the deputed constable, who signs the register and the police seizure memo.
9. Forward to SFSL with BNSS requisition
   The investigating officer prepares the BNSS forwarding form (the present successor to CrPC Form 65 used pre-July 2024). The form records the deceased, the FIR number, the date and place of death, the suspected agents and the history, the list of sealed bottles with seal numbers, and the requested analysis. The bottles are transported in a sealed container, either by the constable in person or through the post-mortem-vehicle escort, to the SFSL receiving counter, where the receiving register signs custody to the lab.

The chain of custody is both paper and physical. The paper trail runs through the mortuary register, the police seizure memo, the BNSS forwarding form, the SFSL receiving register and the analyst's worksheet, each signed and time-stamped. The physical trail is the unbroken seal: every bottle reaches the analyst with the autopsy surgeon's original wax seal intact, and any break is noted as a defect on the receiving register. The BSA Section 63 certificate accompanying the SFSL report incorporates the chain back to the autopsy table by reference.

Post-mortem redistribution (PMR) is a central interpretive concept in forensic toxicology, and its operational consequence is the requirement to draw femoral blood before the cavity is opened. The mechanism is passive diffusion driven by concentration gradients that re-equilibrate after circulation stops. Drugs that concentrated in solid organs during life (lung, liver, myocardium for lipophilic basic drugs) leak back into the central blood compartment, raising the cardiac blood concentration over hours to days. Drugs largely confined to plasma during life (warfarin, lithium, ethanol) are minimally affected.

The magnitudes are large enough to invert clinical interpretation. Cardiac blood tricyclic antidepressant concentrations, with Vd often above 5 L/kg, can rise three- to six-fold over peripheral concentrations within 24 to 48 hours post-mortem. A cardiac amitriptyline of 4 mg/L looks toxic-to-fatal; the corresponding femoral 0.8 mg/L is therapeutic. Same body, two samples, two opposite conclusions.

Femoral blood is preferred because the femoral vein is anatomically far from the major drug-storage organs, and the surrounding skeletal muscle is not a high-capacity drug reservoir for most agents. The SFSL report should always identify the matrix as "femoral" or "cardiac"; reports that omit the source are weaker evidence for the defence to cross-examine.

The SFSL receiving counter is the first audit point for viscera collection quality, and the analysts at Madhuban and Bhondsi see the same six errors repeatedly.

The first error is formalin. Bottles arrive listing saturated saline on the register but containing formalin in the bottle because the histopathology preservative was used at sealing. The analyst detects it by smell and by Schiff-reagent dip; the case is logged as "analyte destroyed by preservative". Recollection is not possible.

The second error is plastic for aluminium phosphide. Phosphine permeates through the plastic wall during transit. The bench test reads weakly positive or negative even when the smell at autopsy was unmistakable. The fix is glass only, marked on the forwarding form.

The third error is only cardiac blood, no femoral. The analyst can still run the panel but the interpretation is weakened by the PMR caveat, and the defence cross-examination at trial is predictable.

The fourth error is insufficient sample volume. Half-filled vials, empty urine vial because the bladder was empty and no vitreous was taken in compensation, no hair. The confirmatory steps each need a fresh aliquot, and the answer is correspondingly less certain.

The fifth error is mislabelled bottles. Bottles without the deceased's name, without the autopsy number, or with a seal impression that does not match the form. The case sits on the receiving counter until the IO clarifies.

The sixth error is broken seal. The wax seal cracked or the cloth tie missing. The analyst notes the defect and photographs the bottle; the analysis proceeds but the defence will use the record at trial to argue contamination.

The fix is procedural: a one-page laminated checklist at every dissection table, signed at sealing by both the autopsy surgeon and the receiving constable. NIMHANS Bengaluru introduced the checklist in 2019; their internal audit reported a drop in viscera rejection from 11 percent to 1.8 percent over the first two years.