Which latent print development technique was replaced by the combination of Ninhydrin and Physical Developer for treating porous materials?

The technique that was replaced by the combination of Ninhydrin and Physical Developer for treating porous materials is Silver Nitrate. Silver Nitrate has been used in the development of latent prints on porous surfaces due to its ability to react with the salts found in perspiration. However, this method has limitations, such as its sensitivity to light and its relatively ineffective development on certain porous materials.

The combination of Ninhydrin and Physical Developer enhances the development process significantly. Ninhydrin reacts specifically with amino acids present in the sweat left behind by fingerprints, producing a visible color change (typically purple) on porous surfaces. Meanwhile, Physical Developer acts on the remaining residues or components within the fingermark, allowing for a more robust and reliable visualization of latent prints on porous materials.

This methodological advancement highlights the necessity for accurate and reliable latent print development techniques in forensic science, refining the effectiveness compared to previous methods like Silver Nitrate. The other techniques listed serve different purposes or are used on non-porous surfaces, which separates them from the specific context of this question regarding porous materials.