What technique can be used to enhance latent fingerprints on porous surfaces?

Ninhydrin application is an effective technique for enhancing latent fingerprints on porous surfaces. When ninhydrin is applied to a porous material, it reacts with amino acids and proteins present in the sweat that is deposited along with the fingerprint. This reaction leads to the development of a colored compound, typically a deep blue or purple, which allows the fingerprint to be visualized clearly.

The ninhydrin method is particularly useful on surfaces like paper or cardboard, where traditional fingerprint powders and brushes may not be effective due to the nature of the substrate absorbing moisture and oils. This technique greatly improves the chances of identifying and analyzing fingerprints collected from these types of materials, making it a reliable method in forensic investigations.

In contrast, methods like water vapor exposure, glove dusting, and thermal imaging may not effectively enhance latent fingerprints on porous surfaces. Water vapor exposure might not produce the necessary chemical reactions for visualization, while glove dusting typically pertains to non-porous surfaces. Thermal imaging, on the other hand, is more suited for detecting body heat rather than enhancing fingerprints, making ninhydrin the superior choice in this context.