To develop latent fingerprints found on plastic surfaces, which technique is considered the best?

Developing latent fingerprints on plastic surfaces is most effectively achieved through the use of cyanoacrylate fuming, also known as super glue fuming. When cyanoacrylate fumes are applied to a plastic surface, they adhere to the moisture and oils present in the latent print, causing a solidified polymer to form around the fingerprint. This process results in a visible print that stands out against the plastic background.

The technique has proven particularly effective on non-porous surfaces, such as plastic, because the fumes can penetrate the micro pores and build a robust contrast that makes the print detectable. The application of heat can enhance the fuming process, allowing for better development of the latent prints.

While the other methods listed may also be used for developing fingerprints, they are less suitable for plastic surfaces. For instance, ninhydrin is commonly used on porous materials like paper and cardboard, and magnetic powders are typically applied to flat or slightly tactile surfaces for enhancing prints, not designed for non-porous substrates. Therefore, cyanoacrylate fuming stands out as the most appropriate choice for this particular scenario.