Which technique is best for enhancing prints found on porous surfaces?

Ninhydrin is recognized as the most effective technique for enhancing fingerprints found on porous surfaces, such as paper or cardboard. This chemical reacts with amino acids present in the sweat and other residues left by the friction ridge skin of fingers. When ninhydrin is applied to a porous surface, it undergoes a chemical reaction that produces a purple-blue compound, known as Ruhemann's purple, which makes the latent prints visible.

This technique is especially suitable for porous materials because it penetrates the substrate and binds with the amino acids, leading to a clear and permanent enhancement of the prints. Other methods, while useful for different surfaces, are not as effective on porous materials. For instance, superglue (cyanoacrylate) fuming is typically used on non-porous surfaces like metal or glass, and the fuming gun method is also not designed for porous substrates. Magnetic application is primarily used with ferromagnetic powders, which are more suited for non-porous surfaces as well. Thus, ninhydrin stands out in its specific applicability to porous surfaces for revealing latent fingerprints.