Identification: developing latent prints: 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 · Identification: developing latent prints

Sample item

A latent fingerprint is suspected on a sheet of paper from a ransom note. Which reagent, reacting with amino acids in sweat, is most suitable for developing it?

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

The answer and the reasoning

B. Ninhydrin

Ninhydrin reacts with the amino acids deposited from sweat on porous surfaces such as paper and cardboard, giving a purple (Ruhemann's purple) print. Powders and cyanoacrylate fuming are used on smooth, non-porous surfaces.

Option by option

  • A. Aluminium powder dusting

    Aluminium powder is used on smooth non-porous surfaces and would clog paper.

  • B. Ninhydrin (correct)

    Ninhydrin develops prints on porous surfaces such as paper by reacting with amino acids.

  • C. Cyanoacrylate fuming

    Cyanoacrylate fuming polymerises on non-porous surfaces such as glass and plastic.

  • D. Sudan black

    Sudan black stains greasy or sticky deposits, for example on adhesive tape, and does not target amino acids.

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.

More Forensic Medicine questions

Questions about this Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is B, Ninhydrin. Ninhydrin reacts with the amino acids deposited from sweat on porous surfaces such as paper and cardboard, giving a purple (Ruhemann's purple) print.

Why is "Aluminium powder dusting" not the answer?

Aluminium powder is used on smooth non-porous surfaces and would clog paper.

Why is "Cyanoacrylate fuming" not the answer?

Cyanoacrylate fuming polymerises on non-porous surfaces such as glass and plastic.

Why is "Sudan black" not the answer?

Sudan black stains greasy or sticky deposits, for example on adhesive tape, and does not target amino acids.

What concept does this question test?

It tests Identification: developing latent prints in Forensic Medicine. Powders and cyanoacrylate fuming are used on smooth, non-porous surfaces.

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 Identification: developing latent prints?

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.