Evaluation of indanedione application methods for fingermark detection on paper : normal treatment, vacuum development and dry-transfer

Abstract

1,2-Indanedione is the most sensitive amino acid reagent currently used for developing latent fingermarks on porous substrates (D'Elia et. al 2015). Indanedione has been termed a "dual" reagent meaning that the reaction product is both coloured and photoluminescent, which facilitates improved contrast compared to the background and increased sensitivity (Patton et al. 2010). Latent fingermarks are fragile traces of evidence that must be protected. In addition, other forms of physical evidence may be present on a document, such as DNA, writing inks, printing inks, and toners. Physical factors such as heat and diffusion, along with chemical factors such as the effects of solvents, can compromise the evidence that may be present (Lennard et al, 2011). One of the most problematic sample substrates that has emerged over the years is thermal, heat-sensitive paper, which is most commonly used for sales receipts, tickets and in fax machines. Solvent-less methods such as vacuum development and dry transfer methods have become an area of research interest due to the potential for traditional methods to be destructive to fingerprints themselves or other forensic evidence. Currently the traditional method is purely lab-based; whilst the exploration into solvent-less techniques follows the green chemistry trend it also aids laboratories that don't have the potential to store and apply large amounts of solvents. Presently, the only paper that has been published on vacuum indanedione development is from Swofford et al. (2012). The advantages of using vacuum sublimation for indanedione treatment in particular includes no interference with foreign contaminants in the fingermarks (such as illicit drugs or explosives) or diffusion of ink on the document, and it does not interfere with any traces of DNA that may be present. Indanedione was also found to be the only chemical out of the seven that were tested not to interfere with forensic document examination (Swofford et al., 2012). An alternative application method that is solvent-free is referred to as "dry-transfer" (Patton et al. 2010). Patton et al. (2010) successfully developed coloured, photoluminescent fingermarks on thermal paper using the dry transfer method for indanedione. However, there seems to be no studies conducted on aged samples, as well as the inconsistencies between dry transfer methods for thermal paper and whether heat should be applied or not. Results were generated presented from a comparison of the three application methods - conventional, vacuum and dry-transfer - across a range of paper substrates and for aged fingermarks from several donors. Several proof-of-concept experiments were also conducted using vacuum indanedione treatment on a number of semi-porous and non-porous surfaces. The results overall concluded that the conventional method outperformed, both in terms of colouration and luminescence, the vacuum indanedione method and the drytransfer method; however, fingermarks of the same quality were produced in some cases. The vacuum oven method on non-porous surfaces produced some encouraging results and certainly shows promise for future work. The additional proof-of-concept work involving co-fuming indanedione and cyanoacrylate was also successful.

Date of Award	2018
Original language	English