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FM13.13 | Metallic Poisons (Arsenic, Lead, Mercury, Copper, Iron) — SDL Guide (Part 2)

Clinical Examination, Documentation and Analytical Methods

The forensic examination of a patient with suspected metallic poisoning must systematically search for the pathognomonic signs described above and document them contemporaneously for medicolegal purposes.

Clinical examination priorities:
- Nails: inspect for Mees' lines (arsenic) — use hand lens if available; document distance from nail fold and width of each band
- Gingiva: Burton's line (lead — blue-black gingival margin); mercury gingivostomatitis
- Skin: rain-drop pigmentation, arsenical keratosis of palms/soles (arsenic); pallor from anaemia (lead, arsenic, copper)
- Neurological: wrist drop/foot drop (lead); tremor/erethism (mercury); peripheral numbness/stockings-gloves pattern (arsenic, mercury)
- Urine: colour (haemoglobinuria in copper — port-wine; vin rosé in deferoxamine-treated iron; dark in mercury nephritis)
- Blood film (if available): basophilic stippling (lead)

Investigations to order and document:
- Blood metal levels (whole blood for lead; serum for arsenic, mercury, copper)
- Urine metal levels (arsenic — 24-h urine; mercury — spot urine creatinine ratio)
- Hair and nail analysis (arsenic — historical exposure; Mees' lines are clinical but nail clippings for AAS are the forensic standard)
- Blood count and film (basophilic stippling, haemolytic anaemia)
- LFT, RFT, ABG (multi-organ assessment)
- Nerve conduction studies (if available, for lead/arsenic neuropathy)

Forensic sampling:
For post-mortem: blood (femoral), liver, kidney, stomach contents (if undigested), hair, and nail clippings should all be collected and preserved separately in clean, sealed containers. Arsenic distributes to all tissues; hair and nail archiving allows temporal reconstruction of exposure episodes.

Pathognomonic Signs of Metallic Poisoning

Medicolegal Inference and Treatment Framework

The treatment framework for metallic poisons is unified by the principle of chelation, but with metal-specific modifications:

Metal	First-line chelator	Route	Key note
Arsenic	Dimercaprol (BAL)	IM	DMSA (oral) for mild/chronic
Lead	Ca-EDTA	IV	DMSA (oral) for blood lead 25–44 µg/dL
Mercury	Dimercaprol (BAL)	IM	DMSA for organic mercury; support renal
Copper	D-penicillamine	Oral	Gastric potassium ferrocyanide lavage
Iron	Deferoxamine	IV/IM	Vin rosé urine confirms working

General principles across all metals:
- Decontamination first (gastric lavage if early ingestion, within 1–2 hours)
- Supportive care (fluids, cardiac monitoring, renal support)
- Chelation (metal-specific as above)
- Enhanced elimination: haemodialysis for severe arsenic, lead, mercury nephrotoxicity; aids removal of small metal-chelate complexes; forced diuresis for iron-deferoxamine

Medicolegal inference:

For chronic arsenic poisoning: key questions for the MLR — who had access to the food/drink? Was the source identifiable (well water, pesticide, herbal product)? Can the Mees' lines timing be correlated with the victim's social history?

For occupational lead/mercury: report must distinguish occupational disease (a civil/compensation matter) from criminal exposure. Document workplace, duration of exposure, PPE use, and employer compliance with occupational safety regulations.

Relevant statutes:
- IPC §328: causing hurt by poison — administering a poison with intent to hurt
- IPC §302/304: if death results
- Factories Act 1948 and occupational safety regulations (relevant to lead/mercury workplace exposure)
- Environmental Protection Act 1986 (arsenic/mercury contamination of water supplies)

Analytical confirmation — key tests:
- Marsh test (arsenic): classic qualitative test; now supplemented by AAS/ICP-MS
- Reinsch test (arsenic, mercury, antimony): metal deposits on copper strip from acidified solution
- Spectrometric analysis (all metals): AAS and ICP-MS are the current gold standard for quantitative metal levels in biological specimens

Chelation Therapy for Metallic Poisons