Which technique is primarily used for enhanced visibility of latent prints on plastic surfaces?

The technique primarily used for enhanced visibility of latent prints on plastic surfaces is superglue fuming. This method involves heating cyanoacrylate, commonly known as superglue, to produce vapors that adhere to the moisture and oils in latent prints. When the vapors condense, they form a visible white residue that enhances the contrast of the prints against the surface of the plastic. This makes superglue fuming particularly effective for developing prints on non-porous surfaces such as plastics, metals, and glass where other methods may not yield satisfactory results.

Other techniques like powder dusting are more suited for use on porous surfaces or when the latent prints are fresh, as they rely on an electrostatic or adhesive bond to lift the print. Ninhydrin is effective on porous surfaces like paper and cardboard, as it reacts with amino acids in sweat, producing a colored reaction but is not ideal for plastic. Iodine fuming can also visualize prints but typically produces transient results that need to be stabilized with a chemical fixative to retain visibility. Thus, superglue fuming stands out as the most effective method for enhancing latent prints on plastic surfaces.