Advances in Fingerprint Technology.pdf

esidue and then photochemically reducing to silver and/or (2) getting
reduced to silver by some reducing agents in the latent print residue, then
silver physical development should do two things: create the necessary silver
nuclei for physical development and carry out the physical development. Like
Fuller and Thomas, they experimented with one of the classical chemical
developers. Melton and Myers, however, went further and made several Ag-
PDs using silver nitrate, several chemical developers, and several complexing
agents. Among the chemical developers used were hydroquinone, ascorbic
acid, and Elon; among the complexing agents used were di- and tetra-sodium
EDTA, potassium tartrate and bitartrate, sodium sulfite, citric acid, and
sodium citrate. The complexing agents where chosen to target either the silver
ions or the developing agent, or both. (Note: Citric acid also changes the pH
and, consequently, the reducing ability of the reducing agent used.) They
made a series of observations and recognized that silver physical development
had great potential for visualizing latent prints on paper. Although they
would have recognized this had they been aware of Morris’ pioneering work,
it is remarkable to note that these two groups were independently studying
the potential of this reagent.
Millington 19 (U.K., 1978). Millington studied the effect of light illumination
on the silver physical development process and found that it influences
the performance of such developers. It affects the stability of the reagent, the
rate of development, and generates more background development.
Hardwick 20 (U.K., 1981). Sheila Hardwick from PSDB was the first (ca. 1984)
to put the currently used Ag-PD in the police laboratory as a practical reagent
to use in casework. She distilled the work of others into one operating manual
or user’s guide. She is also among the first (ca. 1984) to suggest an acidic
wash pretreatment (using nonchlorinated acids such as maleic acid) to reduce
background development on basic paper.
Goode and Morris 13 (U.K., 1983). This report, in our opinion, should have
been published as a book. It has a wealth of information and, to this day,
remains one of the most authoritative sources for latent print visualization
methods. It has laid the foundation for other work. In their section on
physical development, Goode and Morris discuss the development, proposed
mechanisms, and use of the surfactant-stabilized silver physical developer.
Their procedure calls for prewashing with a solution containing an anionic
surfactant (Terigitol) because they claim that this improves latent print visualization
on surface-coated or plastic materials (such as pressure-sensitive
plastic tapes), both of which are nonporous. The reasoning, we hypothesize,
is that the surface area of print residue on nonporous surfaces is not as great