Latent print processing on paper commonly uses which chemical?

Latent print processing on paper commonly uses which chemical?

• A. Silver nitrate
• B. Ninhydrin
• C. Cyanoacrylate
• D. Iodine fuming

Answer: (B)

Latent print processing on paper relies on a chemical that reacts with the substances left in sweat, specifically amino acids. Ninhydrin is used because it reacts with those amino acids to produce Ruhemann's purple, a vivid and stable color that stands out against the pale background of paper. This makes prints on porous surfaces like paper much easier to see and photograph, and the resulting print remains visible for long-term documentation. Other methods have their places but aren’t as well suited for paper. Iodine fuming can reveal prints on porous materials quickly, but the results are often temporary and fade unless stabilized. Silver nitrate was historically used on paper, but it can leave background staining and isn’t as reliable for durable prints. Cyanoacrylate (super glue) fuming works best on nonporous or rough surfaces and tends to be less effective on smooth paper. So, ninhydrin is the best choice for latent prints on paper because it yields a clear, enduring color directly from the amino acids in sweat on a porous substrate.

Latent print processing on paper relies on a chemical that reacts with the substances left in sweat, specifically amino acids. Ninhydrin is used because it reacts with those amino acids to produce Ruhemann's purple, a vivid and stable color that stands out against the pale background of paper. This makes prints on porous surfaces like paper much easier to see and photograph, and the resulting print remains visible for long-term documentation.

Other methods have their places but aren’t as well suited for paper. Iodine fuming can reveal prints on porous materials quickly, but the results are often temporary and fade unless stabilized. Silver nitrate was historically used on paper, but it can leave background staining and isn’t as reliable for durable prints. Cyanoacrylate (super glue) fuming works best on nonporous or rough surfaces and tends to be less effective on smooth paper.

So, ninhydrin is the best choice for latent prints on paper because it yields a clear, enduring color directly from the amino acids in sweat on a porous substrate.