ABSTRACT
Most recommended methods for visualising fingermarks on paper rely on chemical developers that target and react with amino acids. Traditionally, these developers are sprayed onto paper substrates in solutions of per- and polyfluoroalkyl substances (PFAS), but now those same PFAS chemicals are undergoing phaseout or phasedown, which threatens to undermine forensic capabilities. This situation provides an opportunity to pivot towards greener approaches to fingermark visualisation. The ideal methodology would be a water-based treatment, as these provide superior safety for practitioners, combined with environmental sustainability. A major hurdle to implementing a water-based fingermark developer targeting amino acids is that water, as a universal solvent, can dissolve the eccrine components in fingermarks, as well as any optical or luminescent dyes that are created, causing the ridge detail to run or dissolve. This work circumvents this problem by delivering the amino acid developer alloxan in a hydrogel, which enables sharp fingermark ridge details to be observed despite it being a water-based treatment. Alloxan dissolved in a viscous hydrogel is shown here to react with the amino acids in fingerprint residues to form the coloured dye murexide, supported by optimisation and characterisation studies.
Subject(s)
Amino Acids , Dermatoglyphics , Hydrogels , Humans , Hydrogels/chemistry , Water , Coloring Agents , SolventsABSTRACT
With growing environmental concern and supply chain uncertainty, now is a fitting time to re-evaluate solvent-free methodologies in forensic chemistry processes. Here, this paper reviews solvent-free approaches for fingermark visualisation, including chemical fuming and vapour phase treatments, dry-transfer treatments, application of heat, and thermal paper specific treatments. After providing historical context, three objectives have been emphasised: identify feasible scenarios for implementing solvent-free methods; showcase the effectiveness of solvent-free methods relative to their nearest solution-based equivalent; and estimate the technological readiness level of each method discussed. Having reviewed the literature, dry-transfer methods of developing latent fingermarks on paper were found to be the most promising and feasible solvent-free approaches for near-term implementation. Such methods make use of standard materials and equipment commonly found in forensic laboratories, are effective at fingermark visualisation, and mitigate most of the pressing issues pertaining to environmental concern and solvent scarcity.
ABSTRACT
An inexpensive, commercially available doped strontium aluminate phosphor with long-lived afterglow has been prepared and assessed in the role of a luminescent fingerprint dusting powder. Blue, green, and aqua phosphorescence persisting for ca. 30 s was obtainable from treated fingermarks after charging the powders with the white light (400-700 nm) setting of a forensic light source. Imaging the phosphorescent afterglow enabled the elimination of background emissions encountered during latent fingermark examination. This was demonstrated by visualising fingermarks on substrates that possess inbuilt fluorescent security features and highly patterned substrate backgrounds, without any need for bespoke scientific equipment.
Subject(s)
Dermatoglyphics , Luminescence , Humans , Powders , Coloring Agents , Forensic MedicineABSTRACT
Water-based fingermark development treatments for paper have long been held back by loss of ridge detail due to diffusion. Viscous hydrogels (≥2224 cP) show promise as a green method of delivering chemical developers that inhibits diffusion, thereby preserving fingermark ridge detail. This is demonstrated here with starch and xanthan gum hydrogels applied to iodine-fumed fingermarks.
Subject(s)
Dermatoglyphics , Hydrogels , Viscosity , StarchABSTRACT
Minimising background fluorescence can enhance the visible details of treated fingerprints. Here, a 4-tpt fingerprint powder exhibiting long-lived phosphorescence is applied to this end. The powder was found to suppress background fluorescence, including on challenging surfaces, when using standard forensic equipment and eschewing specialized or bespoke imaging techniques.
