Corrosives, metals, cyanide and toxic alcohols
- Finding
Corrosives, metals, cyanide and toxic alcohols leave different traces; some are found only if someone looks for them in the laboratory.
What it is
This group brings together poisons with very different forensic behaviour. Corrosives (acids and alkalis) leave visible injuries in the mouth, oesophagus and stomach. Cyanide kills within minutes and appears in fires and industrial accidents. Methanol, found in adulterated drinks, causes outbreaks with several victims; ethylene glycol leaves oxalate crystals in the kidney. Metals (arsenic, thallium, lead, mercury) can cause slow poisoning that goes unnoticed unless their analysis is requested. In Colombia, methanol poisoning from an adulterated alcoholic drink is an epidemiological alert with super-immediate notification (INS protocol, 2024).
How to tell it apart
- Pink lividity: also in carbon monoxide poisoning and in cold bodies; confirm with the laboratory.
- Methanol: at high doses death comes early and brain lesions may be absent; with long survival there is more necrosis and haemorrhage.
- Methanol versus ethanol: both are measured together; formic acid supports the diagnosis.
- Metals: routine screening of postmortem blood can detect poisonings that nobody suspected.
- Corrosives: the manner may be suicide, accident (especially in children) or assault; the scene and clothing help.
How to recognise it
- Corrosives: "dribble" injuries around the mouth and chin; necrotic, blackened or perforated oesophageal and gastric mucosa.
- Cyanide: pink lividity, congested and oedematous lungs, petechiae; after ingestion, congested gastric mucosa.
- Methanol: cerebral oedema; with survival, necrosis and haemorrhage in the central nervous system; hepatic steatosis is common.
- Ethylene glycol: kidneys with calcium oxalate crystals in the tubules and acute kidney injury.
- Metals in chronic poisoning: weight loss, neuropathy, skin or hair changes, non-specific signs.
How it forms
- Acids: coagulative necrosis; alkalis: liquefactive necrosis, which goes deeper.
- Cyanide blocks cellular respiration; cells cannot use oxygen.
- Methanol: its metabolite, formic acid, causes acidosis and damage to the retina and basal ganglia.
- Ethylene glycol: its metabolites cause acidosis and precipitate as calcium oxalate in the kidney.
- Metals accumulate and disrupt enzymes in many organs.
Forensic clues for each group
| Poison | Clue in the body | Key sample |
|---|---|---|
| Corrosives | Burns in the mouth, oesophagus and stomach | Gastric contents and clothing |
| Cyanide | Rapid death, pink lividity | Blood in a full, closed container |
| Methanol | Cerebral oedema, basal ganglia injury | Blood, vitreous, formic acid |
| Ethylene glycol | Oxalate crystals in the kidney | Blood, urine, renal histology |
| Metals | Chronic, non-specific signs | Blood, urine, hair and nails |
Next step: what to do and document
- When several people are poisoned after drinking liquor, suspect methanol, notify the health department at once and keep the drink with chain of custody.
- With a body that smells of chemicals, or after an industrial accident, ventilate and use protection before examining it.
- Send blood, vitreous, urine and gastric contents; for volatile poisons, in full, tightly closed containers.
- If you suspect a metal or slow poisoning, say so on the request and keep hair (with roots) and nails: the laboratory does not test for them routinely.
- Keep clothing splashed with corrosive and describe the pattern.
Common mistakes
- Relying on the bitter almond odour to rule out cyanide: many people cannot smell it.
- Not requesting methanol in an "alcohol" death during an outbreak.
- Sending samples for volatiles in half-empty or open tubes.
- Attributing progressive weight loss to natural disease without considering metals when the history does not fit.
Test yourself
Think of the answer, then tap the question to see it.
Which renal histological finding points to ethylene glycol poisoning?
Calcium oxalate crystals in the renal tubules, best seen under polarised light.
Why should the bitter almond odour not be relied on to detect cyanide?
Because many people cannot smell it and it can be missed; the diagnosis comes from the laboratory.
How does the INS protocol treat a case of methanol from an adulterated alcoholic drink?
As an epidemiological alert with super-immediate notification; a single laboratory-confirmed case already counts as an outbreak.
Why can metal poisoning be missed at autopsy?
Because its signs are non-specific and the laboratory does not test for metals routinely; the test must be requested and hair and nails kept.
Connections
Educational content on forensic and legal medicine; not legal advice and no substitute for the technical guides of Colombia's National Institute of Legal Medicine and Forensic Sciences. Laws change: each page links the official text and says when it was last checked. For a real case, follow the guide in force and ask the competent authority.
Sources: Methanol-related deaths: evaluation of findings in a 111-case autopsy series (Frontiers in Neurology, 2026); The undetected murder? Evaluation and validation of a practicable and rapid inductively coupled plasma-mass spectrometry method for the detection of arsenic, lead, and thallium intoxications in postmortem blood (Drug Testing and Analysis, 2025); Accidental Deaths Due to Toxic Industrial Cyanide Inhalation: An Autopsy Case Report (Cureus, 2022); Ethylene Glycol Poisoning With Oxalate Nephropathy and Acute Kidney Injury: A Case Report and Review of the Literature (Clinical Case Reports, 2026); Protocolo de vigilancia en salud pública: intoxicaciones agudas por sustancias químicas (código 365, versión 07) (Instituto Nacional de Salud, 2024); Informe de Evento 2024 Intoxicaciones Agudas por Sustancias Químicas (Instituto Nacional de Salud, 2025).
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Representative model, for educational purposes only.