Enantioselective anti-L-amino acid antibodies conjugated to gold nanoparticles are shown to facilitate the detection of latent fingermarks by interacting with amino acids present in friction ridge secretions. This antibody-based system is particularly effective for the enhancement of aged and dried fingermarks on non-porous surfaces, an area unexploited by current techniques.
Nanoparticles (NPs) have been used in numerous fields such as medicine, imaging, and electronics to cite just a few. In forensic science, NPs have been researched specifically for the detection of fingermarks. Their small size, surface functionalization ability, and luminescence properties can potentially lead to better resolution, increased sensitivity, and selectivity. This paper offers an extensive review of the various NP types investigated over the past three decades. NPs are sorted into seven categories, namely metal, metal oxide, quantum dots (QDs), carbon dots (C‐dots), silica (SiO2), and upconverters NPs (UCNPs) as well as a miscellaneous section. Each type is discussed in details from a critical viewpoint. The most promising NP types are also identified.
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Forensic Chemistry and Trace Evidence > Fingermarks and Other Marks
The primary aims of fingermark detection research are to improve the quality and increase the rate of detection of identifiable impressions. This is usually performed through the development of new methods and technologies to provide alternatives to or improve current procedures. While research of this nature is important to pursue, it fails to address the underlying question related to the factors that affect the detection of a latent fingermark. There has been significant research that has examined the differences between techniques, donors and fingermark age, as well as the composition of latent fingermarks. However, they tend not to focus on determining how these factors influence the quality of the developed mark. This study involved the development and evaluation of over 14,000 natural fingermarks deposited on a variety of surfaces to examine the effect of substrate, age, donor variability (both inter- and intra-), depletions and type of finger on fingermark development. Fingermarks were deposited on four substrates (two non-porous and two porous) and developed with either indanedione-zinc (IND-Zn) or cyanoacrylate followed by rhodamine 6G staining (CA+R6G). Three independent assessors graded each mark on the quality of development using an absolute scale proposed by the UK Centre for Applied Science and Technology (CAST). The data generated from these assessments were then analysed for trends or other useful insights. The results from this work reaffirm that individual substrate characteristics (and the choice of development technique) play a significant role in determining the number and quality of marks developed. It was found that fingermarks were more likely to be detected on porous substrates and to also be of a higher quality than on non-porous. The effect of fingermark donor variability was also explored, with significant differences observed between donors and within donors. This research shows that current detection techniques do not detect all available fingermarks, reinforcing the need for further research into the fundamentals of fingermark detection in order to gain a better understanding of the techniques currently used. The study has identified considerations for the development of novel techniques and how we need to account for variability when designing fingermark research experiments.
In current casework, most post-cyanoacrylate stains rely on luminescence emission in the visible region (400-700 nm). While traditional stains such as rhodamine 6G work well under most circumstances, some surfaces may generate background luminescence under the same conditions. Detection in the near infrared region (NIR >700 nm) has shown to be effective in minimising the interferences from such surfaces. The laser dye styryl 11 generated strongly luminescent fingermarks when applied after cyanoacrylate fuming on all surfaces tested.When compared to rhodamine 6G the dye was superior only when viewed in the NIR. Styryl 11 was subsequently combined with rhodamine 6G and the mixed stain formulation (named StaR 11 by the authors) induced stronger luminescence compared to styryl 11 alone with an ability to visualise in both the visible and near infrared regions. Reliable and consistent results were obtained when using either styryl 11 alone or the STaR 11 mixture. The enhancement achieved did not otherwise vary depending on the source of the fingermark secretions. With visualisation possible in both the visible and NIR regions, the styryl 11/rhodamine 6G mixture showed significant potential as a post-cyanoacrylate stain.
KEYWORDS:Forensic science, latent fingermarks, cyanoacrylate stain, near-infrared, styryl 11, rhodamine 6G.
Current Cyanoacrylate Enhancement StainsCyanoacrylate fuming is one of the most effective routine techniques for developing latent fingermarks on non-porous surfaces (1). The cyanoacrylate ester selectively polymerises on fingerprint secretions to form a hard white poly-cyanoacrylate deposit. To aid in the visualisation of cyanoacrylate-developed fingermarks, luminescent stains are commonly used to increase the contrast between the substrate and the fingermark. In order for a luminescent cyanoacrylate stain to be considered effective, it must permeate the cyanoacrylate deposit without altering or damaging it, produce sufficient luminescence under optimal visualisation conditions and produce minimal background staining. The post cyanoacrylate stains currently used in casework produce a luminescence emission at different wavelengths of the visible region (e.g. Ardrox 970-P10, Rhodamine 6G and Basic Yellow 40) (1). However, when viewing luminescent stains in the visible region, there is potential for the substrate to interfere with the luminescence emission from treated fingermarks. This is most common on brightly coloured or multicoloured surfaces or surfaces that have significant contrast (e.g. black text on a white background or a barcode). While background interferences can be reduced by using digital enhancement software, such processing can bring into question the integrity of the evidence. In some cases, a visible stain (rather than a luminescent stain) may produce better results. It would however be beneficial to have a multi-purpose luminescent stain that could be used to enhance cyanoacrylate developed fingermarks on all surfaces regardless of background colour or pattern.
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