Investigation into the performance of physical developer formulations for visualizing latent fingerprints on paper

Abstract

Latent fingerprints deposited on commercial photocopy paper were treated using various preparations of silver-based physical developer and the results from each were compared to those obtained with the standard formulation used by the Australian Federal Police. Five redox stock solutions were prepared with altered orders of reagent addition, and a further solution prepared with exchanged iron concentrations, to test the robustness of the method. Three redox solutions were prepared with specific reagents omitted to determine the significance of the role played by each in development. One redox solution was prepared using Tween 20 as the non-ionic surfactant to assess its suitability as a replacement for Synperonic N. An acid prewash was also prepared using malic acid as an alternative to maleic acid. Results showed the method to be robust to alterations in reagent addition, but not to significant concentration changes. The presence of all components was found to be desirable for distinguishable development of fingerprint detail. It was additionally found that Tween 20 gave at least equal performance to Synperonic N on recently deposited fingerprints. Finally, the use of malic acid gave equivalent fingerprint development but higher background in comparison to maleic acid.