What should be used to develop latent fingerprints on non-porous smooth surfaces?

To develop latent fingerprints on non-porous smooth surfaces, powder and brush techniques are the most effective method. This approach involves applying a fine powder that adheres to the oils and sweat left behind in a fingerprint, creating a visible impression. The powder typically used is chosen based on the surface material and color, as it needs to stand out against the background. A brush is employed to gently apply the powder, which ensures delicate handling of the surface while maximizing the extraction of prints.

Using water and cloth is not effective for this purpose, as it would not help reveal latent prints and could potentially damage the evidence by smudging or removing the fingerprint oils. Chemical methods are more suited for porous surfaces, such as paper or cardboard, where the prints may have penetrated the material. Heat sources could potentially damage both the surface and the latent prints, making them an impractical choice for developing fingerprints. Thus, powder and brush techniques are specifically designed to effectively visualize fingerprints on smooth, non-porous surfaces.