Fingermark visualisation on metal surfaces: An initial investigation of the influence of surface condition on process effectiveness

Fingermark recovery from metal surfaces is an area of operational interest, both from the association of metals with weapons used in violent crime and from the increasing incidence in metal theft. This paper reports a feasibility study into the effectiveness of a range of fingermark visualisation processes in developing fingermarks on clean metals (brass, bronze and stainless steel), and on the same metals after prolonged exposure to an outdoor environment. Scanning electron microscopy (SEM) was used to investigate how the surface type and condition could influence the development of fingermarks for each of the processes used. It was found that the behaviour observed varied between each of the processes (cyanoacrylate fuming, Lumicyano?, gun blueing and carbon-based powder suspension). In some cases the chemical composition of the surface affected the development of the mark more than the surface condition, and in other cases the reverse was true. The best performing processes differed according to the surface type and condition, with cyanoacrylate fuming processes working best on brass and bronze, and powder suspensions being better on stainless steel. These preliminary results reinforce the need to take into account both surface type and condition before selection of the most effective fingermark visualisation process and demonstrate the value of techniques such as SEM in developing a fundamental understanding of the interactions between fingermarks and surfaces.     

Exposing latent fingermarks on problematic metal surfaces using time of flight secondary ion mass spectroscopy

Fingermarks are a key form of physical evidence for identifying persons of interest and linking them to the scene of a crime. Visualising latent (hidden) fingermarks can be difficult and the correct choice of techniques is essential to develop and preserve any fingermarks or other (e.g. DNA) evidence that might be present. Metal surfaces (stainless steel in particular) have proven to be challenging substrates from which to reliably obtain fingermarks. This is a great cause for concern among police forces around the globe as many of the firearms, knives and other metal weapons used in violent crime are potentially valuable sources of fingermark evidence. In this study, a highly sensitive and non-destructive surface science technique called time of flight secondary ion mass spectroscopy (ToF-SIMS) was used to image fingermarks on metal surfaces. This technique was compared to a conventional superglue based fuming technique that was accompanied by a series of contrast enhancing dyes (basic yellow 40 (BY40), crystal violet (CV) and sudan black (SB)) on three different metal surfaces. The conventional techniques showed little to no evidence of fingermarks being present on the metal surfaces after a few days. However, ToF-SIMS revealed fingermarks on the same and similar substrates with an exceptional level of detail. The ToF-SIMS images demonstrated clear ridge definition as well as detail about sweat pore position and shape. All structures were found to persist for over 26?days after deposition when the samples were stored under ambient conditions.     

A comparison of the use of vacuum metal deposition versus cyanoacrylate fuming for visualisation of fingermarks and grab impressions on fabrics

Both vacuum metal deposition (VMD) and cyanoacrylate fuming (CAF) are techniques used to visualise latent fingermarks on smooth non-porous surfaces such as plastic and glass. VMD was initially investigated in the 1970s as to its effectiveness for visualising prints on fabrics, but was abandoned when radioactive sulphur dioxide was found to be more effective. However, interest in VMD was resurrected in the 1990s when CAF was also used routinely. We now report on studies to determine whether VMD or CAF is the more effective technique for the detection of marks on fabrics. Four different fabrics, nylon, polyester, polycotton and cotton, were utilised during this study, along with 15 donors who ranged in their age and ability to leave fingermarks, from good to medium to poor, thus reflecting the general population. Once samples were collected they were kept for a determined time (1, 2, 3, 4, 5, 6, 7, 14, 21 or 28 days) and then treated using either the gold and zinc metal VMD process or standard cyanoacrylate fuming.The smoother fabrics, such as nylon, consistently produced greater ridge detail whereas duller fabrics, like cotton tended only to show empty prints and impressions of where the fabric had been touched, rather than any ridge details. The majority of fabrics did however allow the development of touch marks that could be targeted for DNA taping which potentially could lead to a DNA profile. Of the two techniques VMD was around 5 times more effective than CAF, producing a greater amount of ridge detail, palmar flexion creases and target areas on more samples and fabrics.     

Styryl dye coated metal oxide powders for the detection of latent fingermarks on non-porous surfaces

Conventional fingermark powders rely on contrast induced by absorption/reflection (e.g. black powder) or luminescence in the visible region (e.g. Blitz Green(?)). In most cases, these powders provide sufficient contrast; however, in some circumstances surface characteristics can interfere with the visualisation of powdered fingermarks. Visualisation in the near infra-red (NIR) region, however, has been shown to eliminate interferences commonly encountered in the visible region. In this study, a mixture of rhodamine 6G and the NIR laser dye styryl 11 (STaR 11) was coated onto an aluminium oxide nanopowder and then mixed with silver magnetic powder to develop and visualise fingermarks in the NIR. When compared to Blitz Green(?), it was determined that the STaR 11 magnetic powder was better suited for marks deposited on textured surfaces and for older marks, whereas Blitz Green(?) performed better on smooth glossy surfaces. The ability of the STaR 11 mixed dye formulation to be visualised in both the visible and NIR regions also provides a significant advantage over conventional luminescent fingermark powders.     

An evaluation of the effect of incorporating metal salts into 1,8 diazafluoren-9-one (DFO) formulations for fingermark enhancement

A study into the modification of 1,8-diazafluoren-9-one (DFO) formulations by the additions of metal salts into the working solution is reported. Similar additions have been found to increase the fluorescence of marks developed using other amino acid reagents including 1,2-indandione and the ninhydrin analogue 5-methylthioninhydrin. It was found that adding zinc chloride to give a 1:1 ratio of zinc ions:DFO molecules gave optimum fluorescence, and improvements in performance over the standard DFO formulation were achieved. Attempts to produce equivalent formulations with iron, nickel and palladium chlorides were unsuccessful. In a comparative trial with a 1,2-indandione-zinc formulation on brown paper and cardboard substrates, 1,2-indandione-zinc gave superior results and it was decided to focus further research on this reagent instead of DFO-zinc.     

A method for calculating the strength of evidence associated with an earwitness's claimed recognition of a familiar speaker

The present paper proposes and demonstrates a method for assessing strength of evidence when an earwitness claims to recognize the voice of a speaker who is familiar to them. The method calculates a Bayes factor that answers the question: What is the probability that the earwitness would claim to recognize the offender as the suspect if the offender was the suspect versus what is the probability that the earwitness would claim to recognize the offender as the suspect if the offender was not the suspect but some other speaker from the relevant population? By “claim” we mean a claim made by a cooperative earwitness not a claim made by an earwitness who is intentionally deceptive. Relevant data are derived from naïve listeners' responses to recordings of familiar speakers presented in a speaker lineup. The method is demonstrated under recording conditions that broadly reflect those of a real case.     

An investigation on the secondary transfer of organic gunshot residues

Gunshot residues (GSR) are an important forensic trace in firearm-related events. Currently, routine GSR analyses focus on the detection and characterisation of the inorganic components (IGSR). The increasing prevalence of heavy metal-free ammunition challenges these current protocols and there is an increasing interest in how the organic components of GSR (OGSR) can provide complementary information. Similar to the situation with IGSR, OGSR compounds originally deposited on the shooter during the firing process may further be transferred onto another individual or surface. Hence, the aim of this study was to provide additional information regarding the risk of a secondary transfer of OGSR. Two scenarios were investigated, the first one related to the arrest process and the possibilities of a secondary transfer arising between a shooter onto a non-shooter (e.g. between a police officer and a person of interest (POI)). The second scenario concerned the transfer of OGSR onto the non-shooter after handling a firearm for few minutes without discharging it. One calibre was chosen, the .40 S&W calibre, used by several Australian State police forces. A secondary transfer was observed in all cases for the two scenarios investigated, for three compounds of interest: ethylcentralite (EC), diphenylamine (DPA), N-nitrosodiphenylamine (N-nDPA). The firearm handling scenario resulted in a larger secondary transfer to that of the arrest scenario. Overall, the amounts of OGSR detected on the non-shooter were generally lower than that detected on the shooter and controls after the arrest scenario. The results of this study provide complementary knowledge about OGSR, which can be further used to improve the current practice and the interpretation of OGSR evidence. In particular, it highlights that the secondary transfer proposition must be considered during the interpretation of forensic findings, especially when small amounts of OGSR target compounds are detected.     

Developing regulatory standards for the concept of security in online dispute resolution systems

Online dispute resolution (ODR) has improved access to justice in the digital world. ODR users benefit from faster and cheaper dispute resolution mechanisms compared to traditional litigation and Alternative Dispute Resolution. There are few and quite varied regulatory systems for ODR.This research aims to develop a set of standards to measure the concept of security and to increase the consistency of security in ODR systems. An exploratory mixed method approach is used, involving a quantitative (survey) and mainly qualitative approach (face-to-face interviews) for gathering data. We identify three elements of information security, privacy, and authentication as standards for an appropriate ODR legal framework. Finally, these findings led to practical implications for policy makers and regulators.     

Scheduling of new psychoactive substance the Swiss way: A review and critical analysis

Since the introduction of the European Early Warning System in 2005, >700 new psychoactive substances (NPS) have been listed. This review article presents for the first time the Swiss narcotic law in perspective of scheduling of NPS, and compares it to the regulations of the German speaking neighbours Austria and Germany.The Swiss way is a fast and effective way for scheduling NPS, with the purpose to restrict drug trafficking and for controlling the NPS drug market: the legal basis for scheduling substances of abuse is the “Law about narcotics and psychotropic substances” (BetmG, SR 812.121), which includes the “narcotic law directory (BetmVV-EDI, SR 812.121.11) suitable for listing all controlled substances. The BetmVV-EDI, SR 812.121.11 contains seven indices, with index e specifically designed for the fast scheduling of NPS. Newly appearing NPS can either be controlled under a structure analogues definition or by listing single substances. The list of single substances is updated at least once per year, and structure analogues definitions can be implemented, in order to keep track with new developments on the NPS market. The latest version from November 30th 2018 contains ten different structure analogue definitions and 207 single substances. Requirements to list NPS are their appearance on the NPS market, suspected psychotropic effects and their suggestions by Forensic professionals. As soon as substances are newly placed, on Schedule I of the 1961 Convention or Schedule II of the 1971 Convention by the Commission on Narcotic Drugs of the World Health Organization they can easily be transferred from index e to index a-d of the BetmVV-EDI, SR 812.121.11. The Austrian law uses a structure analogue and single substances approach (introduced in 2012, one update in 2016), whereas the German NPS law (established in 2016, no update yet) only lists two structure-analogue-definitions. All three legislations have defined which core structures, kinds and sites of substitutions are regulated.     

Journey history reconstruction from the soils and sediments on footwear: An empirical approach

The value of environmental evidence for reconstructing journey histories has significant potential given the high transferability of sediments and the interaction of footwear with the ground. The importance of empirical evidence bases to underpin the collection, analysis, interpretation and presentation of forensic trace materials is increasingly acknowledged. This paper presents two experimental studies designed to address the transfer and persistence of sediments on the soles of footwear in forensically relevant scenarios, by means of quartz grain surface texture analysis, a technique which has been demonstrated to be able to distinguish between samples of mixed provenance.It was identified that there is a consistent trend of transfer and persistence of sediments from hypothetical pre-, syn- and post-crime event locations across the sole of the shoe, with sediments from ‘older’ locations likely to be retained in small proportions. Furthermore, the arch of the shoe (the area of lowest foot pressure distribution) typically (but not exclusively) retained the highest proportion of grain types from previous locations including the crime scene. A lack of chronological layering of the retained sediments was observed indicating that techniques that can identify the components of mixed provenance samples are important for analysing footwear sediment samples. It was also identified that the type of footwear appeared to have an influence on what particles were retained, with high relief soles that incorporate recessed areas being more likely to retain sediments transferred from ‘older’ locations from the journey history. In addition, the inners of footwear were found to retain sediments from multiple locations from the journey history that are less susceptible to differential loss in comparison to the outer sole. These findings provide important data that can form the basis for the effective collection, analysis and interpretation of sediments recovered from both the outer soles and inners of footwear, building on the findings of previously published studies. These data offer insights that enable inferences to be made about mixed source sediments that are identified on footwear in casework, and provide the beginnings of an empirical basis for assessing the significance of such sediment particles for a specific forensic reconstruction.     

A versatile technique for the investigation of gunshot residue patterns on fabrics and other surfaces: m-XRF

With heavy-metal-free ammunitions becoming more and more popular, it is necessary to find methods to visualize patterns of those elements in gunshot residues (GSRs) that are not accessible by chemographic coloring tests. The recently introduced millimeter-X-ray fluorescence analysis (m-XRF) spectrometer Spectro Midex M offers an easy way to record mappings of GSRs containing such elements in order to determine shooting distances as well as the general composition of these particles. A motorized stage enables samples of a maximum size of 20 x 20 cm to be investigated, like fabric, clothes, adhesive tapes (Filmolux films), and polyvinylalcohol gloves of shooter's hands. Human tissues can be measured using a Peltier-cooled specimen holder that is mounted onto the stage. As the spot size of the exiting X-rays lies in the millimeter range, which is adequate for the assessment of the residue patterns for shooting distance determination, a significant reduction in measurement time is achieved compared with mu-XRF methods. Test shots with heavy-metal-free ammunitions were performed on different target materials, like pork skin and fabric, and the elemental distributions of Ti, K, and Ga were determined. In order to show the capability of the spectrometer for conventional lead ammunitions as well, a shot series of 5-100 cm shooting distance and an adhesive tape of a shooter's hand were investigated analogously. A comparison of several methods applied in GSR investigation shows the advantages of the m-XRF method.     

Identification of Crystals Forming on Porcine Articular Cartilage: A New Method for the Estimation of the Postmortem Interval

Articular cartilage was examined to determine its decomposition sequence and its potential for assessing the postmortem interval. Scanning electron microscopy of articular cartilage from buried porcine trotters showed the presence of microcrystals on the synovial surface. These orthorhombic pyramidal or “coffin”‐shaped crystals, appeared at 3 weeks (22 days) after interment and disappeared after 6 weeks. The disappearance of these crystals was linked to decompositional changes to the integrity of the synovial joint. The formation and disappearance of these crystals was associated with a pH change at the cartilage surface. Scanning electron microscopy–energy‐dispersive X‐ray (SEM‐EDX) analysis showed that the five main elements contained within these crystals were carbon, nitrogen, oxygen, magnesium, and phosphorous. Such elemental analysis suggested the crystals may be struvite (MgNH₄PO₄6(H₂O)). Bacteria cultured from the cartilage synovial surface produced struvite crystals when grown in suitable media and were identified by DNA analysis to be Comamonas sp.     

An evaluation of the reagent NBD chloride for the production of luminescent fingerprints on paper: II. A comparison with ninhydrin

The effectiveness of the fluorogenic reagent NBD chloride has been compared with the popular colour reagent ninhydrin for the development of fingerprints on paper. NBD chloride was found to be more sensitive than ninhydrin for moderately old fingerprints (3–9 months) and never inferior to ninhydrin in all other cases. A qualitative evaluation technique was used to establish the relative efficiency of each method. This is based on the number of points of identification, assessed on a 1–4 scale, where 4 represents a courtworthy print (> 12 points) and 1 represents a print containing no identification points.     

In silico toxicity as a tool for harm reduction: A study of new psychoactive amphetamines and cathinones in the context of criminal science

The emergence of new psychoactive substances (NPS) has raised many issues in the context of law enforcement and public drug policies. In this scenario, interdisciplinary studies are crucial to the decision-making process in the field of criminal science. Unfortunately, information about how NPS affect people's health is lacking even though knowledge about the toxic potential of these substances is essential: the more information about these drugs, the greater the possibility of avoiding damage within the scope of a harm reduction policy. Traditional analytical methods may be inaccessible in the field of forensic science because they are relatively expensive and time-consuming. In this sense, less costly and faster in silico methodologies can be useful strategies. In this work, we submitted computer-calculated toxicity values of various amphetamines and cathinones to an unsupervised multivariate analysis, namely Principal Component Analysis (PCA), and to the supervised techniques Soft Independent Modeling of Class Analogy and Partial Least Square-Discriminant Analysis (SIMCA and PLS-DA) to evaluate how these two NPS groups behave. We studied how theoretical and experimental values are correlated by PLS regression. Although experimental data was available for a small amount of molecules, correlation values reproduced literature values. The in silico method efficiently provided information about the drugs. On the basis of our findings, the technical information presented here can be used in decision-making regarding harm reduction policies and help to fulfill the objectives of criminal science.