Roberto S.P. King

Fingerprint and inkjet-trace imaging using disulfur dinitride

Exposure of fingerprints to S(2)N(2) vapour results in the prints being visually imaged by polymeric (SN)(x) on an unprecedented range of media; in addition, the polymer forms in response to the interaction of S(2)N(2) with traces of inkjet inks, for example the minute amounts left by the contact between printed paper and an envelope.

Seeing into the infrared: A novel IR fluorescent fingerprint powder

A preliminary study demonstrates that latent fingermarks across a range of highly patterned, coloured non-porous and semi-porous substrates may be clearly developed and imaged in the near infrared following a simple dusting method using finely divided spirulina platensis powder, a naturally occurring, non-toxic algae, used widely within the food industry. Troublesome printed/multicoloured backgrounds show less interference with the fluorescence observed using this material, unlike conventional luminescent powders which fluoresce in the visible spectrum alongside the background to which they are applied. The material shows promise for use both in the field and in the laboratory.

NIR-NIR fluorescence: A new genre of fingermark visualisation techniques.

A preliminary study reveals that finely divided cuprorivaite powder may be used to efficiently develop and subsequently image latent fingermarks across a range of highly patterned, coloured non-porous and semi-porous substrates using near infrared illumination and imaging. Problematic multi-coloured backgrounds provide very little interference under the illumination conditions used, and invoked fluorescence observed, when using this material. This is the first reported example of a NIR-NIR fluorophore for use within latent fingermark visualisation and offers the potential for application at the scene and in the laboratory.

The synthesis, full characterisation and utilisation of template-free silica sodalite, a novel polymorph of silica

Empty glass: Subjecting ethylene glycol silica sodalite to heat (680 degrees C) under a nitrogen atmosphere (i) successfully removes the templating agent to give cubic silica sodalite, which, upon consequent heating under an oxygen atmosphere (ii), transforms into a rhombohedral form of the empty sodalite, in effect a novel polymorph of silica.

Visualisation of latent fingermarks on polymer banknotes using copper vacuum metal deposition: A preliminary study

The UKs recent move to polymer banknotes has seen some of the currently used fingermark enhancement techniques for currency potentially become redundant, due to the surface characteristics of the polymer substrates. Possessing a non-porous surface with some semi-porous properties, alternate processes are required for polymer banknotes. This preliminary investigation explored the recovery of fingermarks from polymer notes via vacuum metal deposition using elemental copper. The study successfully demonstrated that fresh latent fingermarks, from an individual donor, could be clearly developed and imaged in the near infrared. By varying the deposition thickness of the copper, the contrast between the fingermark minutiae and the substrate could be readily optimised. Where the deposition thickness was thin enough to be visually indistinguishable, forensic gelatin lifters could be used to lift the fingermarks. These lifts could then be treated with rubeanic acid to produce a visually distinguishable mark. The technique has shown enough promise that it could be effectively utilised on other semi- and non-porous substrates.

The recovery of latent text from thermal paper using a simple iodine treatment procedure.

Faded, or actively removed text on thermally printed paper samples may be enhanced and retrieved through the use of a simple iodine fuming procedure. The recovery of printed documentation evidence in this fashion is neither affected by prior fingerprint enhancement techniques (such as ninhydrin or DFO), nor by sample age. This method allows, for the first time, evidence to be obtained from completely faded thermal paper samples (receipts, for example) as well as allowing deliberately removed printed text (a consequence of solvent washing pre-treatment in latent fingerprint enhancement procedures) to be recovered.

The use of sulfur nitrides as fingerprint developers

Polymerization of the volatile sulfur nitride S2N2 can be brought about by interaction with latent fingerprint residues, with the resulting dark blue black polymer (SN)x visually developing the prints on a large range of media. Consideration of the technical and safety requirements of the technique allows an effective apparatus to be built and utilized with minimal risk. Observations on the diversity of media involved highlights the power of the technique, though results also indicate that no simple mechanism can account for all aspects of the interactions between the nitride, the prints and the media surfaces. This is especially apparent when prints on paper or plastic can still be imaged after washing with either water or organic solvents; likewise prints on aluminium foil can be imaged even after being heated to 500°C overnight.

Non-invasive detection and chemical mapping of trace metal residues on the skin

Residual traces of the metals copper and lead on an individuals skin may be elucidated by reaction of rubeanic acid with a gelatine lift taken from the target area in question, yielding intensely coloured reaction products. This non-invasive technique has been shown to offer promise in chemically mapping the distribution of the minute metal residues across an individuals hand deposited through touching metal items, a technique with potential forensic significance.

The use of longwave reflected UV imaging for the enhancement of cyanoacrylate developed fingermarks: A simple, safe and effective imaging tool

Longwave ultraviolet reflection (LWUVR) imaging is reported as a simple, safe and non-invasive technique that significantly aids in the visualisation of cyanoacrylate developed latent fingermarks. The process can precede traditional cyanoacrylate dye staining and often removes the necessity to use these chemical contrast reagents, saving time, cost and eliminating mess. The non-destructive nature of the process and high resolution images that are obtained, builds upon issues that surround shorter-wavelength UV imaging. It has been demonstrated that, for most samples tested (a range of non-porous and semi-porous evidence), LWUVR imaging provided superior or similar results to those obtained using the traditional BY40 dye stain. The lack of penetration depth by LWUV radiation means that only the features of the surface under observation is detected by the camera, meaning that interference that may otherwise arise from fluorescence on the reverse side of the evidence (BY40 or fluorescent inks) under conventional fluorescent dye stain imaging modes, is mitigated. A new sequential processing workflow is proposed that does not impede with the conventional and widely adopted fume>stain>fluorescence sequence, but in fact allows LWUVR imaging to be conducted in a manner that serves to benefit the sequence and, ideally, save time during the examination and treatment of evidence.

Sequential processing strategies for fingermark visualisation on uncirculated £10 (Bank of England) polymer banknotes

An investigation was undertaken to assess the relative effectiveness of five fingermark visualisation process sequences on new, uncirculated £10 polymer banknotes from the Bank of England (BoE). Each sequence was challenged with the visualisation of 64 natural fingermarks on eight banknotes, of which half were aged for 2-3days and half were aged for 12-13days (32 donors contributed in each set). The sequences investigated were; After each process was applied, fingermark development was assessed under primary viewing conditions appropriate to the technique (white light or fluorescence). All samples were also assessed under secondary viewing conditions; provided by the optical processes infrared reflection and long-wave ultraviolet reflection, and by gelatin lifting (with scanning). These additional techniques reduced the interfering effect of the complex banknote backgrounds and improved the contrast of enhanced fingermarks. Overall, with all assessment conditions considered, sequence 4 and sequence 3 visualised the most identifiable quality fingermarks (92.2% and 89.1% respectively). The most effective overall process used singularly was found to be black magnetic powder, provided that reflected infrared was used to image the results (82.8%). Further data analysis revealed that sequence 1 was the most effective sequence for fresh marks (aged 2-3days) when only primary viewing conditions within the visible part of the spectrum are considered. The need for further work which considers the sensitivity of the processes, and how they perform on BoE polymer banknotes that have become worn in circulation, is emphasised.