Thanatology: lividity colour in methaemoglobin-forming poisons: practice question

A Forensic Medicine question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Forensic Medicine · Thanatology: lividity colour in methaemoglobin-forming poisons

Sample item

A farm labourer is found dead after drinking an unlabelled liquid. The dependent areas show chocolate-brown postmortem staining and the blood is also brown. Which type of poison is most likely?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

C. Nitrites or aniline dyes

Nitrites, aniline and chlorates oxidise haemoglobin iron to methaemoglobin, giving brown blood and chocolate-brown hypostasis. Carbon monoxide gives cherry-pink staining and cyanide a bright pink or reddish hue, while organophosphates produce no characteristic colour.

Option by option

  • A. Carbon monoxide

    Carbon monoxide produces cherry-pink lividity.

  • B. Organophosphate insecticides

    Organophosphates cause no characteristic change in the colour of lividity.

  • C. Nitrites or aniline dyes (correct)

    Correct. Methaemoglobin formers turn the blood and the lividity brown.

  • D. Cyanide salts

    Cyanide gives a bright pink-red lividity and a bitter almond odour.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is C, Nitrites or aniline dyes. Nitrites, aniline and chlorates oxidise haemoglobin iron to methaemoglobin, giving brown blood and chocolate-brown hypostasis.

Why is "Carbon monoxide" not the answer?

Carbon monoxide produces cherry-pink lividity.

Why is "Organophosphate insecticides" not the answer?

Organophosphates cause no characteristic change in the colour of lividity.

Why is "Cyanide salts" not the answer?

Cyanide gives a bright pink-red lividity and a bitter almond odour.

What concept does this question test?

It tests Thanatology: lividity colour in methaemoglobin-forming poisons in Forensic Medicine. Carbon monoxide gives cherry-pink staining and cyanide a bright pink or reddish hue, while organophosphates produce no characteristic colour.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Thanatology: lividity colour in methaemoglobin-forming poisons?

Learn postmortem changes with their timelines, and toxicology as poison, sign, test and antidote. Then use the flashcards and the other Forensic Medicine questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.