Latent Fingermarks Enhancement in Deep Eutectic Solvent by Co-electrodepositing Silver and Copper Particles on Metallic Substrates

Non-destructive and simultaneous development and enhancement of latent fingerprints on stainless steel based on the electrochromic effect of electrodeposited manganese oxides

Latent fingerprints, as one of the most frequently encountered traces in crime scene investigation and also one of the largest sources of forensic evidence, can play a critical role in determining the identity of a person who may be involved in a crime. Due to the invisible characteristic of latent fingerprints, exploring efficient techniques to visualize them (especially the ones resided on metallic surfaces) while retain the biological and chemical information (e.g., touch DNA) has become a multidisciplinary research focus. Herein we reported a new and highly sensitive electrochemical interfacial strategy of simultaneously developing and enhancing latent fingerprints on stainless steel based on synchronous electrodeposition and electrochromism of manganese oxides in a neutral aqueous electrolyte. By utilizing a specially designed device for electrochemical testing and image capture, a series of electrochemical measurements, physical characterization and image analysis have been applied to evaluate the feasibility, development accuracy and enhancement efficacy of the proposed electrochemical system. The qualitative and quantitative analysis on the in situ and ex situ fingerprint images indicates that the three levels of fingerprint features can be precisely developed and effectively enhanced. Forensic DNA typing has also been performed to reveal actual impact of the proposed electrochemical system on subsequent analysis of touch DNA in fingerprint residues. The ratio of detected loci after electrochemical treatment reaches up to 98.5 %, showing non-destructive nature of this fingerprint development and enhancement technique.

A novel 3D-printed portable electroplating device enhances latent fingerprints on metal substrates

This work introduces a 3D-printed portable electroplating device for the visualization of latent fingerprints (LFPs) on metallic substrates. An electroplating solution of Ag+-Cu2+ in a deep eutectic solvent (DES) is used. The electroplating is performed by two electrodes equivalent to an anode (+) and a cathode (-). The cathode is connected to the metal surface with the magnetic or alligator clip for carrying the LFP. The anode is connected to cotton dipped in the electroplating solution. The device was optimized in terms of the electroplating solution composition, and electroplating potential, current, and time. The device produced images with good resolution, revealing LFP ridges in minute detail of more than 12 points. The device also exhibited good repeatability and images were assessed against guidelines from the Centre for Applied Science and Technology (CAST) and the International Fingerprint Research Group (IFRG). The developed device could be applied to visualize LFPs in forensic investigations.

Fingermark quality assessment, a transversal study of subjective quality scales

Fingermark detection research aims to improve the quantity and quality of fingermarks detected through the development of novel techniques. Subsequently, there is a need to evaluate these methods to determine the quality of the developed mark. Since the 1980's there has been a significant number of publications, which utilise a variety of different quality assessment methods. The introduction of common practice methods from the International Fingerprint Research Group (IFRG) aimed to implement a more standardised approach. Although these schemes are recommended as common practice, they are only guidelines. Consequentially, there is currently no universally accepted method to evaluate the enhancement techniques implemented in research. Therefore, this study aimed to collate and analyse the published protocols being used within fingermark detection research in order to better understand their application and how research is currently analysing and interpreting fingermark quality. This study comprised of manual and automatic searches of over 2000 published papers within the fingermark detection area. After thorough analysis of the articles, 396 published papers were found to have used a scale within the years spanning 1998-2022. The number of publications that report the use of a scale to assess quality for fingermark detection research has considerably increased over the last decade. However, whilst the number of publications utilising scales has increased, it is not proportional to the number of papers using the IFRG scales. The choice of scale is often institution specific and even more specific to their location. There are also numerous different adaptations of the IFRG recommended scales, as well as novel scales, which do not associate with the IFRG recommended versions being introduced the more research continues to grow. One such reason for this is investigated here, as different quality parameters are utilised within each individual scale. There is underrepresentation of these quality parameters within some of the IFRG scales, in particular the Centre for Applied Science and Technology (CAST) scale. This correlates to the considerable number of tailored approaches as authors are forced to add these parameters within the descriptions. Until there is an introduction of clear guidelines surrounding all areas of fingermark quality, from definition to parameters chosen within phases, the research area will continue to face such issues. This article recommends areas of potential study, whilst also recommending procedures that may be employed to alleviate some of the issues seen with fingermark quality evaluation.

Vacuum metal deposition enhancement of friction ridge detail on ballistic materials

The efficacy of Gold/Zinc and Silver/Zinc vacuum metal deposition (VMD) protocols were assessed as stand-alone methods of fingermark enhancement on ballistic brass materials. The results demonstrate the effectiveness of VMD enhancement on a large pool of donors (n = 20), with potentially identifiable marks recovered for the majority of donors, including samples aged up to two months. Of the 20 donors a subset of six donors were selected to assess the capability of VMD enhancement on brass fired cartridge cases, from which some friction ridge detail (FRD) was recovered. Lastly, an attempt to understand which fingermark components are facilitators of VMD enhancement was made. Fingermark residue was extracted from brass tiles and fired cartridge cases before analysing chromatographically (GC-MS). Although some key components were indicated, further evaluation of all fingermark components is needed to draw firm conclusions as to the role each plays in VMD enhancement.

Interpol review of fingermarks and other body impressions 2016-2019

This review paper covers the forensic-relevant literature in fingerprint and bodily impression sciences from 2016 to 2019 as a part of the 19th Interpol International Forensic Science Managers Symposium. The review papers are also available at the Interpol website at: https://www.interpol.int/content/download/14458/file/Interpol%20 Review%20 Papers%202019. pdf.

Monodisperse silica nanoparticle suspension for developing latent blood fingermarks

Traditional fingermark developing methods are unsuitable for developing and extracting latent blood fingermarks on dark surfaces at crime scene because of their ineffectiveness or tedious operation procedures. In the present work, an effective and simple method was developed to serve this purpose using a suspension of monodisperse silica nanoparticles (MSNs). A suspension of 0.1 g/mL of MSNs was prepared by dispersing MSNs ultrasonically into an ethanol solution containing 1.0% Tween 80 and then uniformly sprayed onto the latent blood fingermarks on black plastic bags. Approximately 20 s later, ethanol was sprayed to clean the superfluous developing liquid. After the ethanol had evaporated, the latent fingermarks became visible as a result of the photonic crystal effect produced by the MSNs that had adsorbed to the fingermark ridges. The developed fingermarks were then photographed using a digital camera under a white or monospectral light source, revealing fine ridges and clear fingermark details. This novel, simple and effective method uses the photonic crystal effect of MSNs to develop latent blood fingermarks without the need for surface functionalization and conjugation to dye or fluorescently label molecules. The method can detect latent blood fingermarks that have been retained on a black plastic bag surface for at least 30 d. Given the simplicity and effectiveness of the developed method, MSNs may be a useful alternative material for use in developing latent fingermarks. Further research on the topic is warranted.

Detection of Fingermarks-Applicability to Metallic Surfaces: A Literature Review

There are many different fingermark visualization techniques available, and the choice of methodology employed may be dependent on the surface type. This comprehensive review of the scientific literature evaluates the methodologies of fingermark enhancement methods that are applicable to metallic surfaces; optical, physical, chemical, and physicochemical methods are critically discussed. Methods that are currently used and those that have the potential to reduce the cost and time required to process evidence and increase the recovery rates are considered and are assessed against the Centre for Applied Science and Technology (CAST) and the International Fingerprint Research Group (IFRG) guidelines. The use of chemical imaging techniques in particular has increased the potential to recover fingermarks of sufficient quality for identification purposes. Presently, there appears to be a lack of detailed research pertaining to validation and thorough casework studies for fingermark enhancement techniques. Further studies incorporating these guidelines are recommended.