Thanatology: lividity in cold exposure: 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 in cold exposure

Sample item

A 30-year-old homeless man is found dead on a winter morning in an open field after a night of sub-zero temperatures. The dependent areas show bright pink-red post-mortem staining. There was no fire, no vehicle and no enclosed space nearby. What is the most likely explanation for the colour?

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

The answer and the reasoning

B. Cold slows the dissociation of oxygen from haemoglobin, so oxyhaemoglobin persists in the capillaries

In bodies exposed to cold, tissue oxygen consumption stops and low temperature keeps oxygen bound to haemoglobin, so lividity looks pink or bright red. This can mimic carbon monoxide or cyanide staining, which is why circumstances and toxicology matter. Methaemoglobin gives a chocolate-brown colour.

Option by option

  • A. Cyanmethaemoglobin formed from inhaled cyanide

    Cyanide can give pink lividity, but nothing in the circumstances suggests exposure.

  • B. Cold slows the dissociation of oxygen from haemoglobin, so oxyhaemoglobin persists in the capillaries (correct)

    Correct. Retained oxyhaemoglobin in a cold body gives a bright pink lividity without any poison.

  • C. Methaemoglobin formed by nitrite exposure

    Methaemoglobin produces a brownish, not bright pink, discolouration.

  • D. Carboxyhaemoglobin formed from inhaled carbon monoxide

    Carbon monoxide gives a similar colour, but there was no exposure source here and it would need confirmation on spectroscopy.

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 B, Cold slows the dissociation of oxygen from haemoglobin, so oxyhaemoglobin persists in the capillaries. In bodies exposed to cold, tissue oxygen consumption stops and low temperature keeps oxygen bound to haemoglobin, so lividity looks pink or bright red.

Why is "Cyanmethaemoglobin formed from inhaled cyanide" not the answer?

Cyanide can give pink lividity, but nothing in the circumstances suggests exposure.

Why is "Methaemoglobin formed by nitrite exposure" not the answer?

Methaemoglobin produces a brownish, not bright pink, discolouration.

Why is "Carboxyhaemoglobin formed from inhaled carbon monoxide" not the answer?

Carbon monoxide gives a similar colour, but there was no exposure source here and it would need confirmation on spectroscopy.

What concept does this question test?

It tests Thanatology: lividity in cold exposure in Forensic Medicine. This can mimic carbon monoxide or cyanide staining, which is why circumstances and toxicology matter. Methaemoglobin gives a chocolate-brown 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 in cold exposure?

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.