The use and understanding of forensic reports by judicial actors-The field of gunshot residue expertise as an example.

A comprehensive review was conducted on 42 closed court cases for which at least one gunshot residue (GSR) expertise had been requested. The aim of this study is to examine the use and understanding of the GSR findings by criminal justice professionals, the contribution to/relationship with other (forensic) elements of the case, and ultimately to assess the place of the GSR expertise in judicial decisions. The study shows that, in the vast majority of cases, the court appeared to interpret and use the GSR findings correctly, although some minor misuses were identified, mainly when the court incorrectly mentioned the expert's words, using the prosecutor's fallacy. In the end, a higher percentage of conviction rate (+23% points) was observed when incriminating GSR findings were obtained. Surprisingly, in half of the cases examined in which a guilty verdict was reached, GSR evidence was the only forensic evidence in the file.

Strontium in barium sulphate as a discriminating factor in the forensic analysis of tool paint by SEM/EDS.

In the context of forensic tool paint analysis, the development of analytical strategies to distinguish between different tools is of great interest in order to form a better opinion on whether or not a trace of paint seized at a crime scene originates from a tool found, for example, during a search of a house. A study was therefore conducted on the potential of using X-ray mapping to discriminate red tools that are not otherwise distinguished by standard analytical techniques (i.e. optical microscopy, infra-red spectroscopy, Raman spectroscopy). In this study, the presence of trace amounts of strontium - revealed by X-ray mapping - in the main mineral filler, namely barium sulphate, allowed the discrimination of different tools using a statistical approach. This study is one example among others of the potential of X-ray mapping for a better characterisation of tool paints in a forensic context.

External validation of the MidiCAT variant of thrombography: Comparison with calibrated automated thrombography and study of the centrifugation scheme.

Introduction: To perform Calibrated Automated Thrombography (CAT), the use of reduced plasma volumes (referred to as "MidiCAT") makes it possible to more efficiently use limited volumes of valuable biobanked plasma samples and decreases expenses for reagents. It is, however, unclear whether the MidiCAT procedure is suitable when thrombin generation (TG) is studied in the presence of added thrombomodulin (TG-TM). Moreover, a simplified centrifugation scheme would facilitate biobanking, if appropriate, for more sensitive coagulation studies. We aimed to compare the results of "MidiCAT" (halved plasma and reagent volumes) with those from regular CAT, in the absence or presence of TM, as well as to study the impact of a single-centrifugation scheme for plasma preparation before freezing. Materials and methods: Plasma samples were prepared from the citrated blood from 20 Geneva hospital diverse patients without gross coagulation abnormalities with a single- or double-centrifugation scheme. Samples were kept frozen at -80°C and thawed just before the TG assay in duplicate under two conditions: 1 pM tissue factor (TF) or 5 pM TF + TM. Results and discussion: (1) We externally validated "MidiCAT" and also extended the validation to TG-TM. Whatever the method (CAT or MidiCAT), intra-assay (assessed with duplicates) CV was below 6% (1 pM TF) or below 10% (5 pM TF + TM) for ETP. Agreement between the MidiCAT and CAT results was satisfactory; the p coefficients were above 0.95 for ETP and above 0.90 for most other parameters; biases for ETP were +10.0% (1 pM FT) and +13.5% (5 pM + TM). (2) The centrifugation scheme markedly affected the results obtained in the presence of TM, whereas the bias and limit of agreement (difference plots) were low for the no TM condition. The bias in the presence of TM was obvious, more marked with plasma samples sensitive to TM when double centrifuged: the lower the ETP-TM, the greater the relative difference between the ETP-TM of plasma samples prepared with just single centrifugation and the reference plasma samples. Thus, a single-centrifugation procedure, as is often used for plasma biobanking, is suitable for TG study only if it is not performed in the presence of TM.

Interpol review of gunshot residue 2016-2019.

This review paper covers the forensic-relevant literature in gunshot residue analysis 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%20Review%20Papers%202019.pdf.

Conduction of a round-robin test on a real sample for the identification of gunshot residues by SEM/EDX.

A round-robin test on the identification of GSR particles by SEM/EDX and involving eleven Institutes was conducted on a real sample, in order to evaluate the possibilities/limitations of using such sample to get additional information (compared to the analysis of the usual synthetic sample used within the framework of the ENFSI proficiency test) about the performances of the SEM/EDX systems. Each Institute was asked to analyse this sample following its own standard operating procedure, and by using all the systems in house, whenever available. Between each Institute, a check of the sample was performed by the organizing Institute (NICC), in order inter alia to monitor any degradation and/or contamination of the sample. A total of about 30 analyses were performed on the sample. For each particle of interest identified on the real sample, the detection effectiveness was monitored, as well as the classification allotted by each Institute. The Institutes were also asked to report some of their measurement parameters, and to send the results as they would have been communicated in their own case report. A quite good agreement was observed with regard to the classification of the particles of interest, since a broad consensus was reached for approximately 75% of these particles. A different classification risk exists for some classes, the barium/antimony classes being probably the most critical, as traces of lead may cause the particles to shift (or not) from the consistent with GSR upper-class to the characteristic of GSR upper-class; in the end, the decision to shift from one class to another strongly depends on local rules. At the end of the campaign, a survey sent to collect experience and lessons learned from this exercise showed that analysing a real sample definitively offers an added value, especially in terms of classification process (during the automatic run and when performing the manual review) of particles.

Implementation and Optimization of the Sodium-Rhodizonate Method for Chemographic Shooting Distance Estimation.

In shooting incident investigations where it is important to estimate the shooting distance, the sodium-rhodizonate coloring method has been used for the visualization of GSR patterns extensively. This publication describes the optimization of this method by the use of a heated press for the transfer of GSR traces on garments, as well as variation of a number of other important process parameters. Our final aim for this project was to prepare a formal validation of the coloring method as prerequisite for its inclusion into the scope of ISO17025-certified methods in the GSR Laboratory. A number of important factors and process parameters were identified, such as buffer composition and pH, type of textile used as a substrate and resolution of the documentation of the results. Results were tested using a synthetic proficiency test. Our optimized method has been found to be a very effective technique for visualization of macroscopic GSR traces.

Invitation letter with a standardized form is a reliable tool to exclude increased risk patients from organized fecal immunological testing-based colorectal cancer screening program.

In Europe, screening guidelines for colorectal cancer (CRC) recommend colonoscopy for high-risk patients and fecal immunological testing (FIT) for the standard-risk group. Currently, there is not any validated screening tool to exclude high-risk patients. The aim of the study is to evaluate the validity of exclusion and evaluate the follow-up of patients identified as increased risk for CRC. In this retrospective study using a prospective database, patients at increased risk were identified using the standardized form and then excluded from the FIT screening invitation. A specific questionnaire was sent to all patients at increased risk in order to confirm the reason for the exclusion and evaluate their follow-up. Among 220 695 eligible individuals, 16 693 (7.5%) were excluded after being characterized at increased risk using the standardized form. The questionnaire was sent to these 16.693 excluded patients and completed by 5076 (30.7%) patients. Validity of exclusion was confirmed in 92% of cases. Endoscopic follow-up was in agreement with guideline in 89% of persons at increased risk (inflammatory bowel disease 93%, personal history of CCR 92%, of colonic polyps 82%, family history of CRC 77%). This study suggests that the standardized form is a reliable tool to correctly exclude from the screening program 92% of patients at increased risk for CRC.

Influence of the type of fabric on the collection efficiency of gunshot residues.

Collection efficiency of gunshot residues (GSR) as a function of the type of fabric was evaluated. For this set of experiments, fabrics with differences in their sheddability were exposed to shootings. The samples were then stubbed to collect GSR following a standard procedure for SEM/EDX analysis. The results show a strong relationship between sheddability and collection efficiency, since the collection efficiency is about five-fold higher for leather compared with wool. The main factor explaining this difference is probably the rate of saturation (for instance by fibres) of the carbon tapes used to stub the fabrics. An example originating from a real case supports this hypothesis.

A study of the potential risk of gunshot residue transfer from special units of the police to arrested suspects.

The presence of gunshot residues (GSRs) on arrested suspects can help the Court to form an opinion regarding the possibility of utilization of firearms by these suspects. Since the presence of a few particles can in some cases already have a strong indicative value, the GSR experts have to evaluate in their daily work the risk of a potential contamination of these suspects during their arrest. A few studies conducted on police officers and police facilities concluded that the risk of secondary transfer on arrested suspects is quite negligible. However, the case of special force units of the police should be taken into account, since these units can be assumed to be highly contaminated by GSR due to their intensive training. The aim of this study is to evaluate this possibility of particle transfer by performing simulations of arrests by special force police units, according to both low and high contamination scenarios. The results show that secondary transfers of GSR during these simulations are in most cases not negligible, even for the low contamination scenario. This is especially apparent on the vests of the target persons, with an average of 7 GSR particles (2 PbBaSb and 5 TiZn) found on the stubs used on these materials. Of course, the major contamination levels were observed in the case of the high contamination scenario, due to the use of highly contaminated gloves by the police officers during the arrests. Some recommendations are proposed to take into account this risk of contamination and to try to minimize it, or at least to better identify it.

Primer composition and memory effect of weapons--some trends from a systematic approach in casework.

Since 2008, our laboratory has adopted a systematic approach to the examination of gunshot residues (GSR) in casework by analysing, whenever possible, the inorganic composition present in ammunition (cartridge cases and unused ammunition). By compiling the results of these analyses in a database, it is possible to observe some trends during the period of interest: on the one hand, the prevalence of primers containing lead, barium and antimony is about 50%, and even as high as 70% when including lead-barium-antimony based primers also containing tin; on the other hand, the prevalence of non-toxic primers is for the time being very low. Still using the same approach, test firings were performed with recovered weapons and litigious ammunition whenever possible in order to estimate the influence of the well known "memory effect" of the weapons on the GSR analysis results. The first results show a quite strong memory effect for the .22 and the .32 caliber, unlike the .38 caliber. This is probably due to a high prevalence of lead-barium-antimony based primers for the latter caliber.