Which type of prints are typically formed on surfaces by residues and are not easily visible without development?

• A. Patent prints
• B. Contaminated prints
• C. Latent prints
• D. Plastic prints

Answer: (C)

Latent prints are the ones formed on surfaces by residues and are not easily visible without development. They come from sweat and skin oils left on the friction ridges as contact occurs, so the marks are often too faint to see with the naked eye. To reveal them, investigators use development methods tailored to the surface: powders or cyanoacrylate fuming for nonporous materials, iodine or ninhydrin for porous surfaces, and other chemical reactions that enhance or visualize the residue pattern.

In contrast, patent prints are already visible because they consist of a foreign substance—like ink, blood, or dirt—that leaves a mark on the surface without any special treatment. Plastic prints are three-dimensional impressions left in soft materials such as soap, wax, or fresh plaster.