Identification: bite mark evidence: 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: bite mark evidence

Sample item

A forensic dentist wishes to recover the assailant's saliva for DNA from a suspected bite mark on the victim's skin before any cleaning. Which technique is recommended?

AScraping the skin surface into a culture mediumBDouble swab technique with a moistened swab followed by a dry swabCCleaning with spirit followed by a tape liftDSingle dry swab rubbed over the bite mark

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

The answer and the reasoning

B. Double swab technique with a moistened swab followed by a dry swab

The double swab technique uses a swab moistened with distilled water to loosen and collect dried saliva, followed by a dry swab to pick up the remaining moisture. Both swabs are air dried and packaged separately for DNA typing. Photography with a scale is done before and after swabbing.

Option by option

A. Scraping the skin surface into a culture medium
Scraping into culture medium would destroy the pattern and is not a recognised method for DNA recovery.
B. Double swab technique with a moistened swab followed by a dry swab (correct)
A moist swab followed by a dry swab is the accepted method for recovering dried saliva.
C. Cleaning with spirit followed by a tape lift
Cleaning with spirit would remove or degrade the saliva that is the evidence.
D. Single dry swab rubbed over the bite mark
A single dry swab recovers little dried saliva and is less efficient.

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.

Questions about this Forensic Medicine question

What is the answer to this Forensic Medicine question?

The best answer is B, Double swab technique with a moistened swab followed by a dry swab. The double swab technique uses a swab moistened with distilled water to loosen and collect dried saliva, followed by a dry swab to pick up the remaining moisture.

Why is "Scraping the skin surface into a culture medium" not the answer?

Scraping into culture medium would destroy the pattern and is not a recognised method for DNA recovery.

Why is "Cleaning with spirit followed by a tape lift" not the answer?

Cleaning with spirit would remove or degrade the saliva that is the evidence.

Why is "Single dry swab rubbed over the bite mark" not the answer?

A single dry swab recovers little dried saliva and is less efficient.

What concept does this question test?

It tests Identification: bite mark evidence in Forensic Medicine. Both swabs are air dried and packaged separately for DNA typing. Photography with a scale is done before and after swabbing.

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: bite mark evidence?

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.