Gunshot Residue Analysis Research Articles

Micro-CT features of intermediate gunshot wounds covered by textiles.

The analysis of gunshot residue (GSR) on the clothing and the underlying skin of the victim may play an important role in the reconstruction of the shooting incident. The aim of the present study was to test micro-computed tomography (micro-CT) for the analysis of firearm wounds experimentally produced on human skin covered by textiles. Firing trials were performed on 60 sections of human calves enveloped by a single layer of fabric (cotton or jeans or leather or nylon) and 15 controls consisting of bare calves. Experimental firings were conducted in a ballistic laboratory at three different muzzle-to-target distances (5, 15, and 30cm), using a .32 ACP pistol (Beretta Mod. 81) loaded with full-jacketed bullets coming from the same production lot (7.65 × 17mm, Browning SR). The visual inspection revealed the classic pattern of GSR distribution on the fabrics and the skin of control samples, while only a dark ring around the entrance lesion was identified on the skin beneath the fabrics. Micro-CT analysis showed the presence of radiopaque material on all entrance wounds, with a statistically significant difference between cases and controls. No differences were found among specimens covered by fabrics, with regard to the firing distance and the type of clothing. No GSR-like deposits were detected in exit wounds. Our results suggest that micro-CT analysis may be a useful screening tool for differentiating entry from exit gunshot wounds when the covering textiles are contaminated, damaged, or missing.

Surface-enhanced Raman spectroscopy for the analysis of smokeless gunpowders and macroscopic gunshot residues.

Gunshot residues (GSR) result from the discharge of a firearm being a potential piece of evidence in criminal investigations. The macroscopic GSR particles are basically formed by burned and non-burned gunpowder. Motivated by the demand of trace analysis of these samples, in this paper, the use of surface-enhanced Raman scattering (SERS) was evaluated for the analysis of gunpowders and macroscopic GSR particles. Twenty-one different smokeless gunpowders were extracted with ethanol. SERS spectra were obtained from the diluted extracts using gold nanoaggregates and an excitation wavelength of 633nm. They show mainly bands that could be assigned to the stabilizers diphenylamine and ethylcentralite present in the gunpowders. Then, macroscopic GSR particles obtained after firing two different ammunition cartridges on clothing were also measured using the same procedure. SERS allowed the detection of the particles collected with an aluminum stub from cloth targets without interferences from the adhesive carbon. The results demonstrate the great potential of SERS for the analysis of macroscopic GSR particles. Furthermore, they indicate that the grain-to-grain inhomogeneity of the gunpowders needs to be considered. Graphical Abstract SERS allows the detection of GSR particles collected with adhesive stubs from cloth targets using gold nanoaggregates and an excitation wavelength of 633 nm.

LC–MS method development and comparison of sampling materials for the analysis of organic gunshot residues

This study aimed at developing a LC–MS method to compare the efficiency of various sampling materials for the collection and subsequent analysis of organic gunshot residues (OGSR). Seven sampling materials, namely two “swab”-type and five “stub”-type collection materials, were tested. The evaluation of sampling materials was systematically carried out by first analyzing blank extracts of the materials to check for potential interferences and determining matrix effects. Based on these results, the best four materials, namely cotton buds, polyester swabs, a tape from 3M and PTFE were compared in terms of collection efficiency during shooting experiments using a set of 9mm Luger ammunition. It was found that the tape was capable of recovering the highest amounts of OGSR. As tape-lifting is the technique currently used in routine for inorganic GSR, OGSR analysis might be implemented without modifying IGSR sampling and analysis procedure.

A study into the distribution of gunshot residue particles in the random population

When considering the impact and value of gunshot residues (GSR) as forensic trace evidence, the likelihood of a suspect producing a positive GSR analysis result without having direct exposure to a firearm is a major consideration. Therefore, the random prevalence of GSR and ‘GSR-like’ residues in the wider population is a highly pertinent question when considering the probative value of such evidence. The random prevalence of GSR in two Australian jurisdictions – Victoria and South Australia – was assessed through the collection and analysis of GSR samples obtained from randomly selected members of the public. Volunteers were asked to declare any firearms use, hobbies or potential firearms exposure before allowing their hands to be sampled using aluminium GSR sample stubs coated in adhesive tape. A total of 289 samples, 120 from Victoria and 169 from South Australia were collected and analysed using scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDS). Across all samples, three ‘characteristic’ three-component Pb/Ba/Sb particles were detected from a single subject in South Australia, corresponding to an overall prevalence of 0.3%. Two-component ‘consistent’ particles were more prevalent, with Pb/Sb particles being the most frequently occurring, in 8% of samples, and in South Australia only. A number of samples, approximately 7%, showed populations of single element particles of Pb, Ba and Sb, which has the potential to generate a false positive for GSR if using a bulk analysis technique such as NAA or AAS. The prevalence of GSR or ‘GSR like’ particles in this study matches closely with similar surveys conducted in other jurisdictions. Such surveys are a useful foundation for the creation of a probabilistic method for the assessment of GSR evidence.

Review: Identification and Analysis of Inorganic Gunshot Residues on after Discharging of Some Firearms

Review: Identification and Analysis of Inorganic Gunshot Residues on after Discharging of Some Firearms

Analysis of gunshot residues as trace in nasal mucus by GFAAS

When a gun is fired, the majority of gunshot residues are deposited on the shooter's hands. But these residues disappear through contact with surfaces or washing. Therefore, the maximum time frame to find GSR on a suspect's hands is 8h. The mucus, inside of a nostril, forms a surface layer where they are trapped foreign particles. In this way, mucus inside of a gunshot suspect's nostrils could act like an adhesive medium to stick on it gaseous particles from a gunshot. In this study, the presence of GSR in nasal mucus and its residence time is examined. A new procedure for the sampling of possible gunshot residue accumulated in the nasal mucus is designed. Samples are taken with cotton swabs moistened with a solution of EDTA and, after an acid digestion, are analysed by graphite furnace atomic absorption spectrometry. In addition, samples of hands are taken for comparison purposes. GSR recovery has been successful. The concentration of GSR in nasal mucus is found to be lower than on the hands, but with a longer residence time. Thus, it is possible to expand the sampling time of a suspect also, as nasal mucus cannot be contaminated by handling weapons.

Copper Determination in Gunshot Residue by Cyclic Voltammetric and Inductive Coupled Plasma-Optical Emission Spectroscopy

Analysis of gunshot residue (GSR) is a crucial evidences for a forensic analyst in the fastest way. GSR analysis insists a suitable method provides a relatively simple, rapid and precise information on the spot at the crime scene. Therefore, the analysis of Cu(II) in GSR using cyclic voltammetry (CV) on screen printed carbon electrode (SPCE) is a better choice compared to previous alternative methods such as Inductive Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) those required a long time for analysis. SPCE is specially designed to handle with microvolumes of sample such as GSR sample. It gives advantages for identification of copper in GSR on-site preliminary test to prevent the sample loss on the process to be analyzed in the laboratory. SPCE was swabbed directly on the shooter’s arm immediately after firing and acetate buffer was dropped on SPCE before CV analysis. For ICP-OES analysis, cotton that had been soaked in 0.5 M nitric acid was swabbed on the shooter’s arm immediately after firing and kept in a tightly closed sampling tube. Gold coated SPCE that had been through nanoparticles modification exhibits excellent performance on voltammograms. The calibration was linear from 1 to 50 ppm of copper, the limit of detection for copper was 0.3 ppm and a relative standard deviation was 6.1 %. The method was successfully applied to the determination of copper in GSR. The Cu determination on SPCE was compared and validated by ICP-OES method with 94 % accuracy.

Fast Analysis of Complete Macroscopic Gunshot Residues on Substrates Using Raman Imaging.

Raman spectroscopy has emerged as a viable technique for the organic analysis of gunshot residues (GSRs), offering additional information to the well-established analysis using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX). In this article, a Raman imaging system with an electron-multiplying coupled-charged device (EMCCD) camera was used to analyze complete GSR particles from both conventional and nontoxic ammunition fired at different cloth targets. The same cloths were then stained with blood to mimic real evidence and measured. The direct analysis using Raman imaging of the GSR particles collected with the stubs used for SEM-EDX analysis (the frequent method used for GSR collection) was evaluated. Multivariate curve-resolution and chemical-mapping methods were applied to the spectroscopic data to identify and highlight the signal corresponding to the GSR particles and differentiate them from the substrates. It was confirmed that both measurement approaches (on the targets and the stubs) could be used for the identification of GSR particles, even under unfavorable conditions such as the presence of blood. The results obtained demonstrate the huge potential of Raman imaging for the fast analysis of complete GSR particles and prove its complementary usefulness in the analysis of the stubs used by the well-established SEM-EDX technique.

A new method to reduce false positives due to antimony in detection of gunshot residues

False positives due to the presence of antimony in vehicle seat fabrics are a problem in gunshot residue (GSR) analysis, in particular, when graphite furnace atomic absorption spectrometry (GFAAS) is employed. In this study, we sought to determine the reason for the prevalence of false positive results and to propose a new approach for the analysis of GSR on vehicle seats. GFAAS was used to examine adhesive tape swabs collected from 100 seats of 50 different automobiles. Characterization of seat fabrics was carried out by using Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy with energy dispersive X-ray (SEM/EDX) spectroscopy. The results of FTIR analysis indicated that all seat covers containing antimony were composed of polyester. Experimental results obtained by SEM/EDX analysis revealed that the fabrics in these seat covers contained evenly distributed antimony within the structure of polyester fibers. This study shows that the type of seat fabric should be determined by FTIR spectroscopy before elemental GSR analysis. In this way, most of the false positives caused by polyester fibers in GSR analysis can be prevented.

Preparation of a Ytterbium-tagged Gunshot Residue Standard for Quality Control in the Forensic Analysis of GSR.

Preparation of a ytterbium-tagged gunshot residue (GSR) reference standard for scanning electron microscopy and energy dispersive X-ray spectroscopic (SEM-EDS) microanalysis is reported. Two different chemical markers, ytterbium and neodymium, were evaluated by spiking the primers of 38 Special ammunition cartridges (no propellant, no projectile) and discharging them onto 12.7 mm diameter aluminum SEM pin stubs. Following SEM-EDS microanalysis, the majority of tri-component particles containing lead, barium, and antimony (PbBaSb) were successfully tagged with the chemical marker. Results demonstrate a primer spiked with 0.75% weight percent of ytterbium nitrate affords PbBaSb particles characteristic of GSR with a ytterbium inclusion efficiency of between 77% and 100%. Reproducibility of the method was verified, and durability of the ytterbium-tagged tri-component particles under repeated SEM-EDS analysis was also tested. The ytterbium-tagged PbBaSb particles impart synthetic traceability to a GSR reference standard and are suitable for analysis alongside case work samples, as a positive control for quality assurance purposes.

Multivariate optimisation of ICP OES instrumental parameters for Pb/Ba/Sb measurement in gunshot residues

Inductively coupled plasma-optical emission spectrometry (ICP OES) is a powerful analytical tool for the determination of metals. It is simple, fast and inexpensive due to its high sensitivity and versatility, and it can be used to analyse multiple elements. However, its use in forensic chemistry remains underexplored. This study aims to optimise the analysis of gunshot residues (GSRs) by ICP OES using the concentrations of Pb, Ba and Sb released during the firing of ammunition. In this study, experiments were designed using multivariate optimisation to establish the best operating conditions for ICP OES in GSR samples generated from a .38 revolver. Three variables were studied (radio frequency power, nebuliser gas flow and aspiration rate), and the interactions between those variables were investigated using a central composite design to establish the best analysis parameters. The nebuliser gas flow was the most important parameter in the optimization of the signal intensities, and the interactions between the variables were not significant. The optimum values determined for radio frequency power, nebuliser gas flow and aspiration rate were 1300W, 1.2Lmin−1, and 1.0mLmin−1, respectively. After optimisation of the parameters, the performance characteristics of the proposed method were established: linearity, detection and quantification limits, and accuracy (recovery percentage), with and without addition of an internal standard.

PREPARATION OF MOLECULARLY IMPRINTED POLYMERS FOR DIPHENYLAMINE REMOVAL FROM ORGANIC GUNSHOT RESIDUES

In order to obtain a better tool for collecting forensic evidence at the crime scene and the subsequent analysis of gunshot residue in laboratories, we propose the development of Molecularly Imprinted Polymers (MIPs) for the retention of diphenylamine (DPA), an organic compound coming from gunshot residues. This technique aims to achieve molecular recognition of a particular organic molecule, called target molecule. Once occurred recognition, this organic molecule may be removed, separated, and preconcentrated for further analysis. For this, a series of MIPs and their analogs Non Molecularly Imprinted Polymers (NIPs) following a non-covalent strategy was synthesized. This was carried out by solution radical polymerization, using 1-vinyl-2-pyrrolidone (VP) as monomer, and diphenylamine as imprinting and target molecule. The retention capacity of MIPs was studied by HPLC and UV-VIS spectroscopy, meanwhile adsorption mechanism was studied by isothermal and kinetic assays. Resin yields ranged from 25% to 100%. The results show that the variable that has more influence on DPA retention is the amount of crosslinking, wherein a greater amount of crosslinking results in higher retention of DPA, achieving values up to 90%. There is a clear difference in adsorption capacity between MIPs and NIPs, where MIPs show higher adsorption capacity reaching a double or triple retention value. Kinetic studies show that it is achieved a high retention capacity within 5 min of contact. The results show that the fundamental mechanism for molecular recognition displayed by the imprinting effect can be attributed at two processes: the pre-organization of complementary functional groups present in the polymer and the template and selective cavity formation which complement the template size. Binding factors and selectivity combined effects contributing to molecular recognition of diphenylamine (DPA) by MIPs.

Characterization of organic gunshot residues in lead-free ammunition using a new sample collection device for liquid chromatography–quadrupole time-of-flight mass spectrometry

The identification of characteristic organic gunshot residues (OGSR) provides conclusive evidence in the elucidation of elemental profiles when lead-free ammunition is fired. OGSR also prevents false negatives. Toward this aim, a quick and efficient method based on liquid chromatography–quadrupole time-of-flight mass spectrometry (LC–QTOF) was developed to detect and identify 18 gunpowder additives in gunshot residues (GSR). The unequivocal identification of target analytes was assured by using MS/MS mode. Swabs were compared with home-modified tape lift supports covered with a PTFE layer to determine the better sampling technique. The modified tape lift provided better extraction recoveries and enabled the analysis of inorganic and organic GSR simultaneously. The developed method was applied to the analysis of GSR from four different lead-free ammunitions. Diphenylamine and its nitrated degradation products and centralites were identified in all samples, providing strong evidence of GSR.

Skin permeation of organic gunshot residue: implications for sampling and analysis.

Traditional gunshot residue (GSR) analysis is based on detection of particulates formed from metals found in the primer. Recent concerns regarding the interpretation of GSR evidence has led to interest in alternatives such as the organic constituents (organic gunshot residue, OGSR) found in propellants. Previous work has shown OGSR to be detectable on hands for several hours after a firing event, and given the lipophilic nature of these compounds, it was expected that losses due to secondary transfer (an issue with GSR particulates) would be negligible. However, other loss mechanisms have been identified, specifically skin permeation and evaporation. This paper describes experimental and modeling studies used to elucidate characteristics of skin permeation of 5 compounds present in OGSR. Pharmaceutical methods were adapted to characterize skin permeation using a skin surrogate and Franz diffusion cells. The amount of compounds deposited on skin after an authentic firing event (1 and 2 shots) was experimentally determined and applied for the permeation experiments. A fully validated selected ion monitoring GC/MS method was developed for quantitative analysis, and easily accessible online tools were employed for modeling. Results showed that OGSR residues should be detectable on skin for many hours after a firing event of as few as one or two shots, with detection capability being a function of the efficacy of sampling and sample preparation and the instrumental method employed. The permeation rates of the OGSR compounds were sufficiently different to suggest the potential to develop methods to approximate time-since-deposition.

Analysis of gunshot residues produced by .38 caliber handguns using inductively coupled plasma-optical emission spectroscopy (ICP OES)

A new analytical method is proposed for the collection and quantification of gunshot residues (GSRs) from firearms using inductively coupled plasma optical emission spectrometry (ICP OES). Lead (Pb), barium (Ba) and antimony (Sb) concentrations in GSR from .38 caliber Taurus® handguns were monitored, and three important methodologies were evaluated such as: i) the collection region of the hand of the shooter; ii) tape-type versus swab collectors; and iii) GSR quantification from the right and left hands. Pb, Ba and Sb were found in four of the hand regions analyzed (palm, back, thumb and forefinger palm (TF-palm), and thumb and forefinger back (TF-back)), with their concentrations increasing as a function of the number of shots (one, three and five). Lead was found to be the most abundant species present. In terms of relative analytical sensitivity, higher concentrations of these three elements are mainly found in the back, TF-palm and TF-back regions. The effect of hand washing was also evaluated, which the TF-palm and the TF-back regions maintained sensitivity for the detection of three elements (concentrations higher than 4.56μgL−1) for only three and five shots. Among the collection devices analyzed, swab collectors (dry, moistened with EDTA, and moistened with water) presented higher sensitivity than tape-type collectors (adhesive, double-sided and adhesive-plaster). Additionally, swabs are a more economical collection device, providing a simple and fast collection method that does not require microwave digestion. Pb, Ba and Sb concentrations were also evaluated on the left and right hands. It was observed that Pb is mainly found on the right hand, whereas Ba and Sb concentrations are similar on both hands. ICP OES is therefore a powerful tool for GSR analysis, providing multielemental quantification of Pb, Ba and Sb.

Detection of gunshot residues using mass spectrometry.

In recent years, forensic scientists have become increasingly interested in the detection and interpretation of organic gunshot residues (OGSR) due to the increasing use of lead- and heavy metal-free ammunition. This has also been prompted by the identification of gunshot residue- (GSR-) like particles in environmental and occupational samples. Various techniques have been investigated for their ability to detect OGSR. Mass spectrometry (MS) coupled to a chromatographic system is a powerful tool due to its high selectivity and sensitivity. Further, modern MS instruments can detect and identify a number of explosives and additives which may require different ionization techniques. Finally, MS has been applied to the analysis of both OGSR and inorganic gunshot residue (IGSR), although the “gold standard” for analysis is scanning electron microscopy with energy dispersive X-ray microscopy (SEM-EDX). This review presents an overview of the technical attributes of currently available MS and ionization techniques and their reported applications to GSR analysis.

2013 Atomic spectrometry update—A review of advances in environmental analysis

This is the 30th annual review of the application of atomic spectrometry to the chemical analysis of environmental samples. This Update refers to papers published approximately between August 2013 and July 2014 and continues the series of Atomic Spectrometry Updates (ASUs) in environmental analysis that should be read in conjunction with other related ASUs in the series, namely: clinical and biological materials, foods and beverages, advances in atomic spectrometry and related techniques, elemental speciation,X-ray fluorescence spectrometry, and the analysis of metals, chemicals and functional materials. In the field of air analysis, highlights within this review period included: the use of 3D printing technology for the rapid prototyping of new air sampler components; single particle ICP-MS studies; use of a new triple-quadrupole ICP-MS for the analysis of radioactive species and the use of FEG-SEM and IBA for the analysis of gun-shot residues. In the field of water analysis, methods continue to be developed: for the extraction and preconcentration of elements; speciation of As, Cr, Hg and Sb forms and determination of elemental constituents in colloidal and NP fractions. Instrumental developments reported include the use of MC-ICP-MS for isotopic tracer studies and a review of XRF techniques and associated preconcentration procedures for trace element analysis. Many articles featuring the analysis of plants and soils appeared but, as usual, most focused on environmental applications rather than the advancement of atomic spectrometry. There have, however, been interesting developments, such as the almost bewildering increase in types of micro-extraction for analyte preconcentration and the resurgence of CS-AAS. Clearly LIBS is maturing rapidly, with soil analysis becoming more routine in nature. Also notable was the way the accident at the Fukishima-Daiichi nuclear power plant triggered development of analytical methods for the assessment of contamination in the surrounding area. Recent research indicates that geological applications still drives many of the instrumental and methodological advances in LA-ICP-MS. Fundamental studies continue to shed light on the processes involved and hence ways of improving the analysis of laser-produced aerosols. The preparation of NP powders for the production of matrix-matched RMs for microanalytical techniques such as LA-ICP-MS and SIMS showed great promise for addressing one of the major issues when analysing geological materials by these techniques. Steady advances in MC-ICP-MS methodology is feeding through to applications in isotope geochemistry, while new SIMS instrumentation is being directed towards probing fine growth structures in biogenic carbonates and inferring past climate conditions from their geochemistry. Feedback on this review is most welcome and the review coordinator can be contacted using the email address provided.

Editorial

Welcome to this special edition of X-ray spectrometry in forensics! The X-ray spectrometry technique scanning electron microscope energy dispersive X-ray analysis (SEM-EDS) is widely used by forensic laboratories for the examination of trace evidence. The technique is used in the international standard for gunshot residue analysis and is also used for the analysis of fibres, hair, glass and paint specimens, to name a few. The technique has gained increasing popularity since the 1970s because of its low cost, non destructive nature, ease of operation and interpretation. In this edition, we will see how complementary X-ray spectrometry methods may assist the forensic investigations of the future. In particular, Galli et al. show how portable X-ray fluorescence (XRF) devices are used in the related field of cultural heritage and how some of the advantages of portable XRF might be translated to forensic samples. On this theme, Fonseca et al. will show how XRF can be used to estimate shooting distance, and Ernst et al. outline a protocol for forensic glass analysis by using XRF. On a larger scale to tube XRF, synchrotron XRF (SXRF) has been recently used in a murder case in Japan, and Kawai gives an interesting account of the Jury's interpretation of the SXRF data from two experts, adding his own interpretation to the data, highlighting the complexity of interpretation of XRS spectra in a forensic context. Nakai et al. will show how a soil database is being constructed in Japan by using SXRF, outlining a new and useful application of the technique in forensic science. As SEM-EDS is a noteworthy force in forensics, optimisation and modification of the technique are essential to meet increasing demands from police organisations for high throughput, low cost and robust analytical techniques. Levin et al. meet these demands in the context of high throughput gunshot residue analysis by capitalising on new developments in instrumentation. Their article provides a guide, which will be useful for other forensic laboratories interested in installing silicon drift detectors. In complement to this article, French et al. use SEM-EDS to look at the possibility of secondary transfer of gunshot residue under various circumstances, putting the spotlight on the interpretation of gunshot residue evidence in the courts. It is evident from this edition that X-ray spectrometry techniques have a great range of potential and exciting new applications, which could have a significant impact on police investigations.

Is it possible to determine firearm calibre and shooting range from the examination of gunshot residue in close range gunshot wounds? An experimental study

Introduction: The aim of the study was determining the type of weapon and shooting distance depending on chemical analysis of inorganic gunshot residue from the skin gunshot wounds in experimental animals (pigs).Methods: Experimental study was conducted in order to determine components and their percentage in gunshot residue (GSR). In 60 samples, pig skin was shot by fi ring projectiles from four different weapons and from three different distances (contact wound and near contact wound from 5 cm and 10 cm). The methodology included determining the presence of inorganic material: antimony, barium, lead, nickel, zinc and copper in the skin and subcutaneous tissue using atomic absorption spectrophotometry (AAS).Results: Formula for determining weapon type was provided cutt-off points for different weapons, with 78.6% of original grouped cases being correctly classifi ed. Formula for determining weapon type was provided cutt-off points for different distances, with 58.9% of original grouped cases being correctly classified, which was slightly less reliable compared to weapon type discrimination analysis.Conclusion: The presented study showed that chemical analysis of GSR in entrance wound with AAS could be useful in determining the type of weapon, as well as the shooting distance, i.e. in our study, determiningwhether the wound is contact or near contact. This could be particularly useful in postmortally putrefi ed or charred bodies with gunshot wounds.

Optimizing FEG‐SEM combined with an SDD EDX system for automated GSR analysis

Gunshot residue (GSR) analysis by scanning electron microscopy/energy dispersive x‐ray spectrometry (SEM/EDX) is routinely performed in forensic science laboratories. At the end of 2011, a field emission gun (FEG)‐SEM was installed at the authors' laboratory for this type of examination. Following the installation of the FEG‐SEM, an extensive process was conducted, in order to determine the optimal operating parameters of this instrument for GSR analysis. Because the nature of synthetic GSR samples (such as the European Network of Forensic Science Institutes GSR2011 proficiency test sample) is significantly different from casework samples, it was decided not to use them for this purpose. Instead, a GSR casework sample, previously analyzed by tungsten‐filament SEM as part of the laboratory's routine examinations, was selected. This sample was repeatedly analyzed (more than 200 times), under different operating conditions. The main parameters that were examined for the FEG‐SEM were the electron source accelerating voltage, the backscattered electrons image acquisition time, the magnification, the backscattered electrons image resolution, and the energy‐dispersive X‐ray spectrometry acquisition time. The smallest detected feature was calculated by the software, based on the set image resolution and magnification. For each set of parameters, the detected GSR particles were recorded, in addition to the total number of detected particles and the time taken for the run. It was found that for a given smallest detected feature, the effective search conditions were higher magnification and lower number of pixels per line. The present work includes a detailed description of the optimization process and its results. The process utilized in this work is applicable for other laboratories conducting similar type of GSR analysis as well. Copyright © 2013 John Wiley & Sons, Ltd.