A preliminary investigation of a two-step, non-invasive process to determine chronological deposition order of fingerprints and printed ink on paper.

While traditional techniques have long allowed forensic investigators to positively identify fingermarks on documents of interest, understanding the chronological sequence of events that led to their deposition is still seen as a 'holy grail' for forensic examinations. By way of example, the question of whether a mark is above or below printed text is crucial. The work herein reveals that a novel application of a recently established fingermark development technique readily allows such differentiation. The process in question allies forensic gelatin lifters with RECOVER, a development system that hinges on the polymerisation of disulfur dinitride. While the latter was specifically developed in its current form for the retrieval of prints from metal surfaces exposed to extreme conditions or washing, its ability to target surface effects allows for visualisation of surface interactions on forensic gelatin lifts. Crucially, in doing so the order in which the lifted material was originally deposited is also revealed. This, therefore, permits clear elucidation of the order of deposition of printed text and fingermarks-and does so both rapidly and in a non-invasive way. This long sought-after capability has the potential to revolutionise forensic document examinations.

The importance of dark adaptation for forensic examinations; an evaluation of the Crime-lite Eye™.

Forensic practitioners are recommended to dark adapt their eyes prior to conducting evidential searches in the dark. The dark adaptation process remains poorly standardised across the discipline, with little quantified regarding the benefits of such preparative steps. Herein, we report the findings of a study that recruited 50 participants to assess the effectiveness of the Crime-lite Eye™, a darkness adaptation device developed to assist forensic practitioners both in the laboratory and in field. Participants were tasked with searching for the fluorescent signatures left by reaction of 1,8-diazafluoren-9-one (DFO) with amino acids, in a manner akin to the fluorogenic fingerprint treatment of porous evidence. Using an Epson Stylus Photo R265 inkjet printer, ink cartridges were filled with alanine solutions of various concentrations, allowing different motifs to be printed onto copy paper and subsequently developed using DFO. Participants searched for this 'evidence' both with and without dark adapted vision. On average, participants were able to locate and correctly recognise 16% more evidence once dark adapted using the Crime-lite Eye™. The increase in evidence located by participants once dark adapted suggests that crime scene officers should be dark adapting in order to visualise as much as possible. The time taken to dark adapt, 10 min on average during this study, is not excessively long, and should not significantly slow the investigation.