Forensic Biology: What the Branch Is

In one line

Forensic biology examines material that came from a living thing, and asks what it is and whom it came from.

In the wording a student can write in an exam: forensic biology is the branch of forensic science concerned with the examination of biological material connected with an alleged offence, including blood, semen, saliva, urine, sweat, hair, tissue, bone, and material of plant and animal origin; it determines whether a stain is a body fluid and which one, whether it is of human origin, and whose it is, by grouping and by DNA profiling; and in Indian procedural law it is the branch the Explanation to section 51 of the Bharatiya Nagarik Suraksha Sanhita, 2023 has in mind when it defines examination to include blood, blood stains, semen, swabs in cases of sexual offences, sputum and sweat, hair samples and finger nail clippings by the use of modern and scientific techniques including DNA profiling.

What the branch examines

Blood, in liquid form, as a stain, and as a pattern on a surface.

Semen, on clothing, on bedding and on swabs.

Saliva, on cigarette ends, on bottle mouths, on stamps and envelopes, and in bite marks.

Urine and sweat, less often, but named in the Explanation to section 51.

Hair, human and animal.

Tissue, bone and teeth, where the body is decomposed or fragmented.

Fibres of plant origin, pollen, diatoms and wood, which sit on the boundary between biology and trace evidence.

Animal and wildlife material, in offences under the wildlife legislation.

The questions it answers, in order

The order matters and it is the same for every kind of material.

Is it a body fluid at all, and which one? A stain may be blood, or paint, or betel juice, or rust.

Is it human? A stain shown to be blood proves nothing against a man who says he slaughtered a goat.

Whose is it? Grouping narrows, profiling identifies.

And a fourth question that only some materials answer: how did it get there. Blood pattern analysis reads the shape and distribution of stains to reconstruct the event.

Why it is the most important branch today

Because profiling individualises. Fingerprints and DNA are the two disciplines that can in favourable conditions attribute material to one person, and DNA works on material that leaves no visible mark at all.

Because the material is everywhere. An offender who touches a surface leaves cells.

Because the law has caught up with it. The Explanation to section 51 of the Sanhita names DNA profiling; section 52 requires the report on a person accused of rape to describe the material taken for profiling; section 184 requires the same for the victim; and the Criminal Procedure (Identification) Act, 2022 includes biological samples and their analysis in the definition of measurements.