ASIS Professional Certified Investigator Practice Exam 2025 – Complete Study Guide

Ninhydrin is the method used to develop purple-colored latent fingerprints on paper. This chemical reacts with amino acids present in the sweat and oils left behind in fingerprints. When ninhydrin is applied to the surface of the paper, it reacts with these compounds to produce a purple or blue color, making the fingerprints visible. This process is particularly effective on porous surfaces like paper, where the latent prints can be more challenging to reveal compared to non-porous surfaces.

The effectiveness of ninhydrin lies in its ability to penetrate the porous material and react with the organic substances within the latent fingerprints. The resulting color change is a clear indicator that fingerprints are present, aiding investigators in their work.

While other methods such as iodine fuming and cyanoacrylate fuming are useful for developing fingerprints on various surfaces, they do not produce the characteristic purple color associated with ninhydrin use on paper. Laser enhancement also serves a different function, primarily in improving visibility of latent prints on various surfaces but without yielding the specific chemical reaction that produces colored prints.