What should be used to process paper for the presence of latent prints?

• A. Iodine fuming
• B. Silver nitrate
• C. Ninhydrin
• D. Fluorescent dyes

Answer: (C)

Focusing on porous surfaces like paper, the method that best reveals latent fingerprints is ninhydrin. It reacts with the amino acids left behind by fingerprint residue, forming Ruhemann’s purple, a distinct and long-lasting coloration that penetrates the paper fibers. This makes the impression readily visible and durable, which is why ninhydrin is the standard choice for processing paper.

Iodine fuming can also be used on paper and other porous materials, but the prints it produces are typically temporary and can fade or develop background staining, so it’s less reliable for long-term documentation. Silver nitrate works on some paper surfaces by reacting with chlorides in sweat and developing under light, but the resulting prints can be fragile and highly sensitive to light exposure, which can compromise readability. Fluorescent dyes are useful for enhancing prints on difficult backgrounds or when using alternate light sources, but they’re typically supplementary to the primary development method on plain paper rather than the standard first choice.