What sequence of latent print development techniques is used for porous materials?

The sequence of latent print development techniques for porous materials begins with 1,8-Diazafluoren-9-one (DFO), followed by Ninhydrin, and then a Physical Developer.

DFO is particularly effective for porous surfaces because it reacts with amino acids present in latent prints. This chemical enhancement is crucial because porous materials tend to absorb moisture and other substances, which may impact the visibility of latent prints. Following DFO, Ninhydrin is applied, which also reacts with amino acids and can produce a color change, making prints more visible. This step is especially beneficial for porous materials as it can further enhance any prints developed by DFO. Lastly, a Physical Developer is utilized, which is effective for resolving prints that may have been obscured due to the porous material absorbing moisture or contaminants over time.

This specific sequence is designed to maximize the potential of each reagent and to ensure successful development of latent prints on porous surfaces, making option A the correct answer. Other options listed incorporate different chemicals that may not be the most effective combination for the specific challenge posed by porous substrates.