What technique is used to develop latent prints on surfaces contaminated with fatty substances?

Amido Black is an effective technique for developing latent fingerprints on surfaces that have been contaminated with fatty substances, such as oils or skin residues. This reagent reacts with proteins found in the latent print residue, enhancing the visibility of the print against the background of the surface.

When using Amido Black, the developer binds to proteins, allowing for clear contrast, thus making the latent prints more distinguishable. This makes it particularly useful in forensic science where the quality and clarity of prints are crucial for identification purposes.

In contrast, other techniques have specific use cases that may not be suitable for surfaces with fatty contaminants. For instance, Ninhydrin is primarily effective on porous surfaces where amino acids are present, while Small Particle Reagent is specifically designed for wet or heavily contaminated surfaces but might not work as well on fat-based residues. Iodine vapour is a method that can develop prints but is generally less effective on oily or fatty surfaces because it does not specifically target the protein components in latent prints.