What is the main characteristic of Ninhydrin as a fingerprint reagent?

The main characteristic of Ninhydrin as a fingerprint reagent is that it serves as a general-purpose reagent for porous surfaces. Ninhydrin reacts with amino acids found in the sweat of fingerprints, leading to the formation of colored products that can be visualized. This reaction is particularly effective on porous materials such as paper and cardboard, making it an essential tool in forensic science for developing latent prints on these types of surfaces.

The effectiveness of Ninhydrin on porous substrates stems from the way sweat components are absorbed into the material, allowing the reagent to reach and react with the residues left behind from fingerprints. This versatility makes it a crucial option for investigators working with a variety of evidence types found at crime scenes.