Forensic Imaging

At the microscopic level, printing on a substrate exhibits imperfections that can be used as a unique identifier for labels, documents and other printed items. In previous work, we have demonstrated using these minute imperfections around a simple forensic mark such as a single printed character for robust authentication of the character with a low cost (and mobile) system. This approach allows for product authentication even when there is only minimal printing (e.g. on a small label or medallion), supporting a variety of secure document workflows. In this paper, we present an investigation on the influence that the substrate type has on the imperfections of the printing process that are used to derive the character "signature". We also make a comparison between two printing processes, dry electro photographic process (laser) and (thermal) inkjet. Understanding the sensitivity of this approach is important so that we know the limitations of the approach for document forensics

ToScA North America (6 – 8 June 2017, The University of Texas, Austin, TX) Program

ToScA North America will address key areas of science, including Multi-modal Imaging, Geosciences, Forensics, Increasing Contrast, Educational Outreach, Data, Materials Science and Medical and Biological Science.University of Texas High-Resolution X-ray CT Facility (UTCT); Jackson School of Geosciences, The University of Texas at Austin; Natural History Museum (London); Royal Microscopical Society (Oxford, UK)Geological Science

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

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

Raman imaging for determining the sequence of blue pen ink crossings

This manuscript presents a preliminary investigation on the applicability of Raman imaging for non-destructive and rapid analysis of blue crossing ink lines. The MCRmethod was used to facilitate visualization of the distribution of inks of the same colour and the most predominant Raman signature at the crossing was used to interpret theorder of application of inks. Different pen ink types, different times separating the application of the two ink lines and different paper substrates were used. From the 90 Raman images examined, the correct order of application was determined in more than 60 % by direct observation. The remainder cases were not as clear due to the uneven distribution of inks and the empty spaces similar to a net-like pattern observed at the crossing. This pattern was possibly caused by physical impediments (the first ink applied acting as a physical barrier) or chemical impediments (the two inks did not stick). Such impediments were more strongly observed in the crossings involving the U. Eye pen ink, causing the complete skipping of this ink line. Moreover, most crossings showed some mixing between the two inks and it was more accentuated when the times separating the application of the inks were shorter, since the ink was fresher. The use of white or certificate papers did not seem to influence in the inks distribution nor determining the order of the inks. Although this study provided useful insights regarding crossing ink lines, future statistic studies may be helpful for more objective examinations

Production of artificial fingermarks. Part II – The use of a modified inkjet printer for the deposition of synthetic secretions

This study is the second part of a larger body of research dedicated to the production of synthetic secretions and the use of an inkjet printer to deposit realistic artificial fingermarks. An artificial emulsion combining eccrine and sebaceous compounds, which was described and tested in the first part of this research, was used as it showed a promising compatibility with common detection techniques. An inkjet printer was modified to print the emulsion on two different substrates: paper (porous) and acetate (non-porous). After optimisation of the printing parameters, multiple fingermarks were printed and processed with a range of standalone detection techniques: 1,2-indanedione-zinc, ninhydrin, Oil Red O, and physical developer on paper, and cyanoacrylate fuming, rhodamine 6G, gold/zinc vacuum metal deposition, and silver black powder on acetate. The detection techniques were also applied in sequence, which is considered one of the biggest advantages of the emulsion over simpler amino acid mixtures that are usable with amino acid reagents only. Natural fingermarks deposited by a single donor were processed with the same techniques for comparison. The effect of water immersion was also investigated, where fingermarks printed on paper were immersed in water for 15 min, before being processed with 1,2-indanedione-zinc and Oil Red O. The results showed that realistic-looking fingermarks could be printed on paper and that printing on acetate was also possible albeit of lower quality due to the nature of the substrate. The artificial fingermarks were successfully enhanced by all the detection techniques tested, at the notable exception of physical developer. The results obtained were very similar to what is generally observed with real fingermarks, and it was observed that the impact of water immersion on the artificial fingermarks was comparable as well. These findings open new perspectives for the development of multi-target quality control test strips or for the standardisation of proficiency testing and interlaboratory collaborative exercises where ground truth is crucial to guarantee comparable results and objective assessment

Metal-Organic Frameworks for fingermark detection — A feasibility study

© 2018 Elsevier B.V. Metal-Organic Frameworks (MOFs) are porous crystalline structures, currently used as sensors, separation membranes, and as catalysts. Due to their physicochemical and optical properties, they have been recently proposed for fingermark detection. This study further explored their potential for fingermark detection. Natural fingermarks, as well as charged and protein-enriched marks, were used to test the efficiency of the technique. Various parameters, such as precursor concentration, pH, immersion time and detection protocols, were investigated and optimised. The performance of the optimised MOF-based method was then compared to that of routinely used techniques. The results obtained indicated that MOFs can effectively detect fingermarks, especially protein-rich marks such as marks contaminated with body fluids. However, after comparison and evaluation against benchmark techniques, results were judged to be inferior to those from currently employed detection methods. However, with further research and optimisation MOFs may be promising as an alternative to current powder suspension techniques

Visualising the past – an evaluation of processes and sequences for fingermark recovery from old documents

This study aimed to collect data on the effectiveness of most of the fingermark visualisation reagents currently used on porous surfaces on fingermarks aged for up to 90 years, significantly extending the timescales for which such information exists. A limited subset of the variables associated with processing of old fingermarks was explored, with a focus on the use of 1,8 diazafluoren-9-one (DFO), 1,2-indandione, ninhydrin, and physical developer. These techniques were used in sequence on batches of cheques between 11 and 32 years old, and on documents dating from the 1920s and 1940s. The potential for applying a physical developer enhancement process (blue toning) as the final step in the sequence was also explored. The benefits of using processing sequences on porous items were clearly demonstrated, with all processes in the sequence adding value in terms of additional marks found on the cheques up to 32 years old. In addition, physical developer was found to be capable of developing fingermarks up to 90 years old, whereas the amino acid reagents appear less effective on documents of 70 years and older. An experimental physical developer formulation with reduced environmental impact was found to be as effective as the existing process in these experiments. Blue toning was found to visualise an additional 10-25% of marks, and its wider use after silver-based deposition processes is recommended based on the evidence from this study.Peer reviewedFinal Accepted Versio

Interactions between latent fingermarks, deposition surfaces and development agents

This thesis was submitted for the degree of Master of Philosophy and awarded by Brunel University.Fingerprints have provided a crucial source of forensic evidence for well over a century. Their power lies in an inherent ability for human identification and individualisation, which is based on two fundamental properties: uniqueness and lifelong permanence. Latent fingermarks represent by far the most evidentially common and challenging form of deposition, whereby an invisible copy of the unique friction ridge fingertip pattern is left as an amalgamated secretory residue on any surface that is touched. Dry powder dusting, the first and most iconic method for visualising or developing these deposits, was developed in the latter part of the 19th Century. In the period since, a great number of additional techniques, utilising physical, chemical and optical interactions in isolation or combined, have been devised for the same purpose. By selecting the correct technique in the correct order, it is now possible to extract significant print details from an unprecedented variety of surfaces. In the UK, such operational choices are recommended via Home Office issued protocol tables, which offer an optimum guide based on substrate type, substrate properties and fingermark conditions. Development technique specificity has improved in the last half-century alongside increased biochemical understanding of residue composition, however, the shear variety of potential deposition substrates that exist within a heavily industrialised world inevitably causes disparities in efficiency, even within single protocol classifications. These effects are compounded by the enormous potential for pre- and post-deposition residue composition variation, relating to donor factors (age, sex, diet, lifestyle, etc.) and time dependant changes (environmental, biological, etc.) respectively. As a result, routine technique application can cause sub-optimal development. This research utilises high resolution imaging and analysis techniques to demonstrate how subtle surface chemistry and topography features can selectively influence routine technique efficiency within a single protocol classification (smooth, nonporous plastics). Titanium dioxide, a widely used white pigment, has been shown as prevalent in a range of polymers following SEM and EDX analysis, either in a patchy or ubiquitous distribution. SEM analysis demonstrates a strong interaction between the pigment and carbon powder suspension, which causes detrimental overdevelopment effects in off-ridge areas. ToF-SIMS mapping of a Formica substrate places a significant amount of patchy distributed titanium dioxide in the top 30nm of the surface. Mapping also indicated the presence of an aluminosilicate pigment coating; however, it’s involvement in the possible surface potential or surface energy interaction mechanism is unknown The effects of linear surface features, which have previously been implicated in off-ridge cyanoacrylate overdevelopment on two operationally relevant polymers, were also analysed by creating a silicon wafer model for micro-FTIR analysis. Fingermark residues, including hydroxyl groups, have been shown to migrate significant distances along induced scratches in the model substrate over a 48hr period. It is likely that observed overdevelopment along large valley-like features (uPVC) and scratches (polyethylene) in the operationally relevant polymers is caused by a similar migration of residues.This work is funded by the UK Home Office project 7121939