Modifications to the Silver Physical Developer

Abstract

The silver physical developer is currently the most successful reagent used for visualizing the water-insoluble components (e.g., lipids) of latent prints on porous surfaces. It is normally used after the amino acid visualizing reagents (e.g., ninhydrin and DFO) are used. This work found that the performance of the current formulation of silver physical developer is strongly reduced when the water used is changed from the usual distilled water to the more purified reverse osmosis/deionized (RO/DI) water. Based on numerous experiments involving the systematic variation of the component concentrations, the performance was restored and even improved by reducing the concentration of all the components (except that of the ferric salt) and by including malic acid in the formulation. These modifications resulted in a new silver physical developer formulation that performs as well as or better than the current formulation and is less expensive to make.

Relevant visualization technologies for latent fingerprints on wet objects and its challenges: a review

“…However, for standard laboratory practical purposes, the authors suggested that the order of addition was to remain as such. While investigating the modifications of PD formulation, Burow et al (2003) discovered that with the incorporation of reverse osmosis/deionized (RO/DI) water as a substitution for distilled water in the traditional formulation, the amount of surfactants needed can be subsequently reduced. This is largely because RO/DI water contains relatively less ions than that of distilled water, thus, less amount of surfactant is needed to suppress the negatively charged Ag colloids.…”

“…Despite being advantageous in visualizing aged latent fingerprints, PD is tedious since it requires pre-washing with non-chlorinated acids (e.g., maleic, malic, and dilute nitric acids) to remove the calcium carbonate (which may act as nucleation site) on papers (Burow et al 2003;Ramotowski 2012b;Kasper 2016). Apparently, this step is necessary as calcium carbonate is a common filler used in the manufacturing of papers (Ramotowski 2012b).…”

Trends in fingerprint analysis

“…One type of nanoparticle being studied for the purpose of detecting latent prints on paper is gold nanoparticles used in conjunction with cellulose interactions. Previous methods [48,37,38] have proven to be inconsistent and unreliable on paper surfaces with poor contrast, so a new method using AuNP-cellulose interactions is being studied. For the development of this method, a bifunctional compound that would bind both cellulose and the AuNPs was used to attach the AuNPs to the paper followed by an Ag-PD solution that was then added to the surface [39].…”

Chemical enhancement of footwear impressions in blood on fabric – Part 1: Protein stains

“…Initial research in the early 1970s by the British Home Office for the recovery of latent fingerprints on paper and fabrics used radioactive sulfur dioxide gas [3] with limited success, and the enhanced impressions deteriorated over time. Spedding [4] however, suggested that the radioactive sulfur reacted with lipids in the fingerprint, making it potentially suitable for articles that had been immersed in water in a manner similar to physical developer [5][6][7][8][9][10][11] and oil red O techniques [12][13][14][15][16][17][18].…”