What is the main function of Small Particle Reagent in fingerprint analysis?

The main function of Small Particle Reagent (SPR) in fingerprint analysis is to adhere to fats and oils present in latent fingerprints. These components are often deposited on surfaces where fingerprints are left but are not usually visible to the naked eye. The SPR consists of small particles, typically containing a fluorochrome, that bind to these lipid materials.

When applied, SPR enhances the visibility of latent prints by creating a contrasting color against the surface, allowing for easier detection and documentation of the prints. This technique is particularly useful on challenging surfaces that are non-porous and may contain residues that are more difficult to process with other methods. The ability of SPR to selectively bind to the oily residues in fingerprints is what enables it to highlight otherwise invisible prints effectively.

In contrast, the other choices refer to different methods or aspects of fingerprint development that do not align with the primary purpose of SPR. For example, enhancing visibility of protein-based prints or providing a permanent record of prints addresses different techniques or properties unrelated to the specific adhesion characteristic of SPR.