Identification: hair examination: 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: hair examination

Sample item

A single hair found on a victim's clothes is examined under the microscope. The medulla occupies about one-fifth of the hair shaft diameter. What is the most likely origin?

AHuman, since the medullary index is below one-thirdBCannot be a hair as it has a medullaCHuman, since the medulla is always absentDAnimal, since the medullary index is above one-half

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

The answer and the reasoning

A. Human, since the medullary index is below one-third

The medullary index is the ratio of the diameter of the medulla to that of the hair shaft. In human hair it is usually less than one-third (about 0.33), whereas in many animals it is greater than one-half. A value of 0.2 therefore favours a human origin.

Option by option

A. Human, since the medullary index is below one-third (correct)
Correct. An index of about 0.2 is below the human threshold of 0.33.
B. Cannot be a hair as it has a medulla
Hairs do contain a medulla, so its presence is expected.
C. Human, since the medulla is always absent
Human hair may have a medulla, which is often thin or fragmentary but not always absent.
D. Animal, since the medullary index is above one-half
Animal hairs have an index above 0.5, which is not the case here.

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 A, Human, since the medullary index is below one-third. The medullary index is the ratio of the diameter of the medulla to that of the hair shaft.

Why is "Cannot be a hair as it has a medulla" not the answer?

Hairs do contain a medulla, so its presence is expected.

Why is "Human, since the medulla is always absent" not the answer?

Human hair may have a medulla, which is often thin or fragmentary but not always absent.

Why is "Animal, since the medullary index is above one-half" not the answer?

Animal hairs have an index above 0.5, which is not the case here.

What concept does this question test?

It tests Identification: hair examination in Forensic Medicine. In human hair it is usually less than one-third (about 0.33), whereas in many animals it is greater than one-half. A value of 0.2 therefore favours a human origin.

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: hair examination?

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.