Concept: Latent fingerprints are invisible or barely visible prints left on surfaces by the natural oils and sweat from the skin. These prints often require chemical methods to become visible. Different chemicals are used depending on the type of surface:
- Powder methods – for non-porous surfaces like glass or metal.
- Cyanoacrylate (super glue) – for plastic and smooth surfaces.
- Chemical reagents – for porous surfaces such as paper.
Step 1: Understanding porous surfaces.
Porous surfaces include materials that absorb liquids, such as:
Fingerprints on these surfaces are absorbed into the material and cannot be easily developed using normal powder techniques.
Step 2: Identifying the chemical used for development.
The chemical
Ninhydrin reacts with amino acids present in sweat residues of fingerprints. This reaction produces a deep purple color known as
Ruhemann's Purple, which makes the latent fingerprint visible. Thus, the correct answer is: