Beyond the shot: Exploring secondary transfer of gunshot residue on common surfaces and the impact of hand cleaning methods

Understanding the presence, transfer dynamics and depletion of gunshot residues (GSR) on various surfaces is crucial for preserving evidence, reconstructing shooting incidents, and linking suspects to crime scenes. This study aims to explore the transfer and loss of GSR on commonly encountered surfaces such as ceramic, glass, metal, paper, and plastic, as well as the influence of different common hand cleaning methods on secondary transfer. Using scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDX) and automated detection software, we quantified highly indicative three-component characteristic particles (lead, barium, and antimony) on cups made from ceramic, glass, metal, paper, and plastic. Furthermore, we evaluated the amount of secondary transferred particles on these surfaces following various post-discharge hand cleaning methods: washing with water and soap, washing with only water, wiping with wet wipes, or using paper towels. The results demonstrate that counts of secondarily transferred GSR particles vary significantly among surfaces. Specifically, the transferred GSR count was highest on paper, followed by plastic, ceramic, metal, and glass respectively. Post-discharge hand cleaning methods, including washing with water and soap, washing with only water, cleaning with wet wipes, or with paper towel, resulted in substantial loss of GSR count on transferred surfaces. Among these methods, washing with water and soap showed the highest depletion. The empirical evidence provided by our results underscores the importance of considering surface properties, post-shooting activities, and the methods of sample collection and analysis when interpreting transferred GSR analysis. Despite challenges, these insights enhance our ability to link suspects to shooting crimes through careful consideration of the entire context.

Cranial trauma in handgun executions: Circumferential delamination defect and its relationship with contact/close-range shooting

Skeletal evidence usually constitutes the only source of information to interpret lesion patterns that help to clarify the circumstances surrounding death. The examination and interpretation of bone trauma are essential to the application and utility of anthropology as a forensic science. When discussing the effect of gunshot wounds in bone, it becomes imperative to differentiate between short and long-distance injuries based on clear, distinct, and observable signs. To contribute to the debate, our focus is directed toward the external analysis of the so-called circumferential delamination defect (CDD) as an observable proxy for close-range shooting (≤30 cm) and contact gunshot wounds in the skull. In the context of known extrajudicial killings, in which the perpetrators used short 9 × 19 FMJ ammunition in a close-range shooting, instances of CDD have been documented. Empirical evidence reinforcing the causal relationship between CDD and close-range shootings is presented. Elements' characteristics of firearm residues were also found in remains buried for up to 30 years. Primarily, this work shows that the concentrations of gunshot residues (Pb, Ba, and Sb) resemble those observed in fresh corpses with the same gunshot wound (GSW). Moreover, the correlation observed between CDD and gunshot residues, where the likelihood of CDD increases the closer to the head and the more perpendicular the shot angle is, reinforces CDD as a pivotal discriminatory factor in the skeletal evidence of short-range or contact shot. This research contributes to the field of forensic anthropology by providing fundamental insights into the etiology of CDD and its practical application.

A simple voltammetric method to evaluate the firing distance through determination of nitrocellulose

Nitrocellulose (NC) is the main component of propellants for small firearm ammunitions. Even though NC particles are ejected from gun barrels together with bullets and they are often recovered on close-to-muzzle targets, quantitative analysis of nitrocellulose for forensic purposes has been neglected so far. Moreover, although the presence of the nitroester groups makes nitrocellulose electroactive, its electrochemical determination has been poorly considered in literature. In this paper, a quantitative differential pulse voltammetric method for the analysis of nitrocellulose in targets is suggested, with the aim of estimating its concentration decay on targets with increasing the shooting distance. The presented method works in acetonitrile/ethanol/lithium perchlorate, has a LOQ of 4 mg L-1 and linearity up to 2000 mg L-1. Ammunitions loaded with a nitrocellulose/nitroglycerine-based gunpowder were discharged to draw a calibration curve for shooting distance determination in the range from 5 cm to 120 cm. The effect of possible interfering substances (water, nitroglycerine, nitroguanidine, nitrites) was evaluated, and results are compared with literature methods.

Comparison of portable and benchtop electrochemical instruments for detection of inorganic and organic gunshot residues in authentic shooter samples

Analysis of gunshot residue currently lacks effective screening methods that can be implemented in real time at the crime scene. Historically, SEM-EDS has been the standard for analysis; however, advances in technology have brought portable instrumentation to the forefront of forensic science disciplines, including the screening of GSR. This study proposes electrochemical methods with disposable screen-printed carbon electrodes for GSR screening at the laboratory and points of care due to their rapid, cost-efficient, and compact platform. GSR residues were extracted from typical aluminum/carbon adhesive collection stubs and analyzed via square-wave anodic stripping voltammetry. Benchtop and portable electrochemical instruments were compared for the assessment and classification of authentic shooter samples by monitoring a panel of inorganic and organic GSR elements and compounds including lead, antimony, copper, 2,4-dinitrotoluene, diphenylamine, nitroglycerin, and ethyl centralite. The evaluation included the assessment of figures of merit and performance measures from quality controls, nonshooter, and shooter data sets. Samples collected from the hands of 200 background individuals (nonshooters), and shooters who fired leaded ammunition (100) and lead-free ammunition (50) were analyzed by the benchtop and portable systems with accuracies of 95.7% and 96.5%, respectively. The findings indicate that electrochemical methods are fast, sensitive, and specific for the identification of inorganic and organic gunshot residues. The portable potentiostat provided results comparable with the benchtop system, serving as a proof-of-concept to transition this methodology to crime scenes for a practical and inexpensive GSR screening that could reduce backlogs, improve investigative leads, and increase the impact of gunshot residues in forensic science.

Comprehensive characterization of firing byproducts generated from small arms firing of lead-free frangible ammunition

Following the introduction of lead-free frangible ammunition in United States Air Force small arms firing ranges, Combat Arms instructors have routinely reported experiencing adverse health symptoms during live fire training exercises, including sore throat, cough, and headache. Previous studies have found that these symptoms occur despite occupational exposure limits not being exceeded. To better characterize the potential source and mechanisms for health symptoms, a comprehensive characterization of the physicochemical properties of gases and aerosols emitted during the firing of the M9 pistol and M4 rifle using lead-free frangible ammunition was completed. Weapons were fired within a sealed chamber using a remote firing mechanism. A suite of direct-reading instruments and collection-based analytical methods were used to determine the composition of the emissions. Emissions were dominated by carbon monoxide and ultrafine particles. Other prevalent gases included carbon dioxide, ammonia, formaldehyde, hydrogen cyanide, and nitric oxide when measured using Fourier-transform infrared spectroscopy. An electrical, low-pressure impactor showed that, on average, the count median diameter immediately after firing was 36 ± 4 nm (n = 10 rounds) and 32 ± 3 nm (n = 14 rounds) for the M9 pistol and M4 rifle, respectively. Analytical methods were used to determine that emitted particles were primarily composed of soot, copper, and potassium, with trace amounts of calcium, silicon, sodium, sulfur, and zinc. Results from this research confirm prior work and expand upon the characterization of emissions generated from firing lead-free frangible ammunition. By employing multiple methods to measure and analyze data we were able to quantify both total and respirable particle fractions and determine particle morphology and composition. Characterization of the emissions provides insight into potential exposure risks that may lead to the development of adverse health symptoms allowing for the development of strategies for risk mitigation.

Ten years of molecular ballistics-a review and a field guide

Molecular ballistics combines molecular biological, forensic ballistic, and wound ballistic insights and approaches in the description, collection, objective investigation, and contextualization of the complex patterns of biological evidence that are generated by gunshots at biological targets. Setting out in 2010 with two seminal publications proving the principle that DNA from backspatter collected from inside surfaces of firearms can be retreived and successfully be analyzed, molecular ballistics covered a lot of ground until today. In this review, 10 years later, we begin with a comprehensive description and brief history of the field and lay out its intersections with other forensic disciplines like wound ballistics, forensic molecular biology, blood pattern analysis, and crime scene investigation. In an application guide section, we aim to raise consciousness to backspatter traces and the inside surfaces of firearms as sources of forensic evidence. Covering crime scene practical as well as forensic genetic aspects, we introduce operational requirements and lay out possible procedures, including forensic RNA analysis, when searching for, collecting, analyzing, and contextualizing such trace material. We discuss the intricacies and rationales of ballistic model building, employing different tissue, skin, and bone simulants and the advantages of the “triple-contrast” method in molecular ballistics and give advice on how to stage experimental shootings in molecular ballistic research. Finally, we take a look at future applications and prospects of molecular ballistics.

Ear as an alternative sampling site for GSR analysis following shotgun discharge

Detection of GSR particles potentially indicates that a person fired a gun or somehow involved to a shooting event. GSR on the shooter's hand, face, and clothing may disappear within hours and with sweat secretion, washing or cleaning to remove evidences. Due to its anatomical properties, ears are relatively protected; therefore, we aimed to identify GSR particles on ears, to compare its anatomical parts of ears, and compare ears with common GSR sampling sites, based on firing frequency. A 12-gauge semi-automatic shotgun was used. In the 4-week study, one shot in the first week, two consecutive shots in second week, three shots in third week, and five shots in fourth week were fired by six participants. Samples were taken from MAE, CA, and AAECA of both ears and common GSR sampling sites. The characteristic 3-component structure (Pb/Sb/Ba) of the samples was analyzed by SEM/EDX. Right CA was the most suitable area for sampling, which might be attributed to posture of body during targeting. Right ear was the most suitable area to take samples from CA or MAE in 3-shot group. Besides, left AAECA in 1- and 2-shot groups and the left MAE in 5-shot group were the most suitable areas for GSR sampling. In conclusion, ear seems to be a valuable alternative for detection of GSR particles, due to its complex anatomical structure potentially preventing loss of GSR with daily cleaning. Findings suggested that crime scene investigation teams and criminal laboratory staff should consider ear as a valuable alternative for GSR detection.

Armed with the Facts: A Method for the Analysis of Smokeless Powders by Ambient Mass Spectrometry

The work presented here follows several others in investigating what capabilities, if any, ambient mass spectrometry might have toward the analysis of compounds commonly associated with smokeless propellant powders. This family of instrumental techniques has attracted curiosity from the field of forensic science due to its desirable properties such as rapid collection of information-rich data, combined with minimal requirements for sample mass and preparation. Experiments were conducted with a "Direct Sample Analysis" ion source integrated with a time-of-flight mass spectrometer. The ionization behaviors of nitroglycerin, methyl and ethyl centralite, akardite, diphenylamine, nitrosodiphenylamine, and nitrated diphenylamine derivatives were investigated specifically, with accurate-mass data presented for each. Diphenylamine standards were used to demonstrate the performance of this instrument, which exhibited good response linearity across 1 order of magnitude and sub-nanogram detection limits. Thirty smokeless powder extracts, recovered from ammunition potentially in circulation within Australia, were analyzed to determine whether the technique is appropriate for rapid analysis of smokeless powder particles. Results demonstrated that the technique might be applied to compare individual particles with each other or to a database. Such a capability may be of value in the examination of explosive devices containing smokeless powder, postblast residues therefrom, or muzzle discharge from a close-range shooting. However, when efforts were made to detect residues from the hands of a volunteer shooter, only some returned positive results, and a high background signal from the sample collection stub indicates that detection using this instrument is thus far insufficiently reliable.

Evaluation of the Simultaneous Analysis of Organic and Inorganic Gunshot Residues Within a Large Population Data Set Using Electrochemical Sensors*, †

The increasing demand for rapid methods to identify both inorganic and organic gunshot residues (IGSR and OGSR) makes electrochemical methods, an attractive screening tool to modernize current practice. Our research group has previously demonstrated that electrochemical screening of GSR samples delivers a simple, inexpensive, and sensitive analytical solution that is capable of detecting IGSR and OGSR in less than 10 min per sample. In this study, we expand our previous work by increasing the number of GSR markers and applying machine learning classifiers to the interpretation of a larger population data set. Utilizing bare screen-printed carbon electrodes, the detection and resolution of seven markers (IGSR; lead, antimony, and copper, and OGSR; nitroglycerin, 2,4-dinitrotoluene, diphenylamine, and ethyl centralite) was achieved with limits of detection (LODs) below 1 µg/mL. A large population data set was obtained from 395 authentic shooter samples and 350 background samples. Various statistical methods and machine learning algorithms, including critical thresholds (CT), naïve Bayes (NB), logistic regression (LR), and neural networks (NN), were utilized to calculate the performance and error rates. Neural networks proved to be the best predictor when assessing the dichotomous question of detection of GSR on the hands of shooter versus nonshooter groups. Accuracies for the studied population were 81.8 % (CT), 88.1% (NB), 94.7% (LR), and 95.4% (NN), respectively. The ability to detect both IGSR and OGSR simultaneously provides a selective testing platform for gunshot residues that can provide a powerful field-testing technique and assist with decisions in case management.

Time since last discharge of firearms and spent ammunition elements: state of the art and perspectives

The estimation of the time since last discharge of firearms or spent ammunition elements (e.g., casings) may provide crucial information in the investigation of a shooting incident and, eventually, the following trial. Herein, an exhaustive review of the methods described in the literature is reported, with the aim to evaluate their potential and limitations from a forensic perspective. This work, in particular, highlighted the fact that a number of investigations have been carried out in the field during the last century (with an especially high rate in the last 30 years), but the implementation of related procedures in forensic laboratories is still rare. The situation has been discussed and a series of propositions have been forwarded, in order to overcome challenges and facilitate the implementation of dating approaches in real casework.

Prevalence of organic gunshot residues in police vehicles

The present study investigated the organic gunshot residue (OGSR) background level of police vehicles in Switzerland. Specimens from 64 vehicles belonging to two regional police services were collected and analysed by LC-MS in positive mode. The driver's and back seats were sampled separately to monitor potential differences between locations and to assess the risks of a suspect being contaminated by OGSR during transportation to a police station. The results showed that most of the 64 vehicles were uncontaminated (44 driver's seats and 38 back seats respectively). Up to six of the seven targeted compounds were detected in a single sample, once on a driver's seat and twice on back seats. The contamination frequency generally decreased as the number of compounds detected together increased. The amounts detected were in the low ng range and less than amounts generally detected just after discharge on a shooter. Our data indicated that detecting a combination of four or more compounds on a police vehicle seat appears to be a relatively rare occurrence. The background contamination observed was most probably due to secondary transfer from police officers (e.g. through recent participation in a shooting session or firearm manipulation) or from firearms stored in the vehicles. The present results might be used as a recommendation to minimize contact of a suspect with contaminated surfaces if OGSR is implemented in routine work in parallel to IGSR analysis.

Reviewing Research Trends—A Scientometric Approach Using Gunshot Residue (GSR) Literature as an Example

The ability to manage, distil and disseminate the significant amount of information that is available from published literature is fast becoming a core and critical skill across all research domains, including that of forensic science. In this study, a simplified scientometric approach has been applied to available literature on gunshot residue (GSR) as a test evidence type aiming to evaluate publication trends and explore the interconnectivity between authors. A total of 731 publications were retrieved using the search engine ‘Scopus’ and come from 1589 known authors, of whom 401 contributed to more than one research output on this subject. Out of the total number of publications, only 35 (4.8%) were found to be Open Access (OA). The Compound Annual Growth Rate (CAGR) for years 2006 and 2016 reveals a much higher growth in publications relating to GSR (8.0%) than the benchmark annual growth rate of 3.9%. The distribution of a broad spectrum of keywords generated from the publications confirms a historical trend, in particular regarding the use of analytical techniques, in the study of gunshot residue. The results inform how relevant information extracted from a bibliometric search can be used to explore, analyse and define new research areas.

Comparison of three collection methods for the sodium rhodizonate detection of gunshot residues on hands

The aim of this study was to compare three gunshot residue (GSR) collection methods used in conjunction with chemographic detection applied by different regional Swiss police services. The specimens were collected from the hands of a shooter with either filter paper (Filter method) or adhesive foil. The adhesive foil was then either applied against photographic paper during visualisation (AF Photo method) or coated with a layer of polyvinyl alcohol (AF PVAL method). The experiments involved two conditions of the examined hands, i.e. dry and humidified. The residues were revealed using the sodium rhodizonate test (SRT). Preliminary tests assessing the possibility of conducting a confirmatory Scanning Electron Microscopy coupled to Energy Dispersive X-ray spectroscopy (SEM/EDX) analysis after the chemographic test were performed on a number of specimens by cutting positive spots and mounting them on stubs. Obtained results were compared in terms of effectiveness - number of positive spots, time requirements, quality of subsequent SEM-EDX analysis, ease of use and cost. The Filter method generally yielded a high-quality detection with both dry and humidified hands, as well as a simple, quick and efficient confirmation by SEM/EDX. The AF Photo performed well on dry hands, but not on humidified hands. The AF PVAL method performance was lower compared to the other methods in both examined conditions of the hands. The SEM/EDX analysis showed that the Filter and AF PVAL method provided satisfactory results when a sufficient carbon coating thickness was applied to the cuttings. It was also observed that the thinner the PVAL layer, the better the quality of the spectra and obtained images in SEM/EDX. Furthermore, the surface of the photographic paper did not seem to be conductive, even after the application of a thick layer of carbon. In conclusion, the Filter method gave the best overall results, but its application required slightly more time and expertise than the two other methods.

Applications of Direct Injection Soft Chemical Ionisation-Mass Spectrometry for the Detection of Pre-blast Smokeless Powder Organic Additives

Analysis of smokeless powders is of interest from forensics and security perspectives. This article reports the detection of smokeless powder organic additives (in their pre-detonation condition), namely the stabiliser diphenylamine and its derivatives 2-nitrodiphenylamine and 4-nitrodiphenylamine, and the additives (used both as stabilisers and plasticisers) methyl centralite and ethyl centralite, by means of swab sampling followed by thermal desorption and direct injection soft chemical ionisation-mass spectrometry. Investigations on the product ions resulting from the reactions of the reagent ions H₃O⁺ and O₂⁺ with additives as a function of reduced electric field are reported. The method was comprehensively evaluated in terms of linearity, sensitivity and precision. For H₃O⁺, the limits of detection (LoD) are in the range of 41-88 pg of additive, for which the accuracy varied between 1.5 and 3.2%, precision varied between 3.7 and 7.3% and linearity showed R² ≥ 0.9991. For O₂⁺, LoD are in the range of 72 to 1.4 ng, with an accuracy of between 2.8 and 4.9% and a precision between 4.5 and 8.6% and R² ≥ 0.9914. The validated methodology was applied to the analysis of commercial pre-blast gun powders from different manufacturers. Graphical Abstract.

Methods for analysis of glass in glass-containing gunshot residue (gGSR) particles

When lead, barium and antimony, or lead, barium, calcium, silicon and tin are found together in particles associated with a shooting investigation they are considered characteristic of gunshot residue (GSR). Antimony and tin are often absent from the primer of many low calibre rimfire ammunitions, which are the type most commonly used in Australia. Therefore, the likelihood of characteristic particles forming during the firing process of such rimfire ammunition is significantly less than the likelihood of these particles arising from higher calibre ammunition. The majority of rimfire ammunition examined in this research contains ground glass in the primer, which functions as a frictionator. These ammunitions produce a small number of gunshot residue particles containing glass coated with other primer components, which we refer to as glass-containing GSR (gGSR). If these particles are observed in an investigation, they have the potential to add a new dimension to gunshot residue analysis because they are not common in the environment. Furthermore, the composition of glass frictionator is stable during firing, which raises the possibility that chemical testing of the glass in gGSR may be used to identify the ammunition from which the residue was derived or to link deposits of GSR. This paper examines the application of scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS), focussed ion beam (FIB) techniques and time of flight-secondary ion mass spectrometry (ToF-SIMS) to the semi-quantitative analysis and comparisons of gGSR and frictionator extracted from unfired cartridges. SEM-EDS is effective for comparing gGSR with unfired frictionator, but the use of FIB to expose clean glass from the centre of gGSR followed by ToF-SIMS, or ToF-SIMS using ion sputtering to expose clean glass, offers more power for comparisons due to their capability for higher discrimination between frictionators from different sources.

Quantitative profile-profile relationship (QPPR) modelling: a novel machine learning approach to predict and associate chemical characteristics of unspent ammunition from gunshot residue (GSR)

Evidence association in forensic cases involving gunshot residue (GSR) remains very challenging. Herein, a new in silico approach, called quantitative profile-profile relationship (QPPR) modelling, is reported. This is based on the application of modern machine learning techniques to predict the pre-discharge chemical profiles of selected ammunition components from those of the respective post-discharge GSR. The obtained profiles can then be compared with one another and/or with other measured profiles to make evidential links during forensic investigations. In particular, the approach was optimised and successfully tested for the prediction of GC-MS profiles of smokeless powders (SLPs) from organic GSR in spent cases, for nine ammunition types. Results showed a high degree of similarity between predicted and experimentally measured profiles, after adequate combination and evaluation of fourteen machine learning techniques (median correlation of 0.982). Areas under the curve (AUCs) of 0.976 and 0.824 were observed after receiver operating characteristic (ROC) analysis of the results obtained in the comparisons between predicted-predicted and predicted-measured profiles, respectively, in the specific case that the ammunition types of interest were excluded from the training dataset (i.e., extrapolation). Furthermore, AUCs of 0.962 and 0.894 were observed in interpolation mode. These values were close to those of the comparison of the measured SLP profiles between themselves (AUC = 0.998), demonstrating excellent potential to correctly associate evidence in a number of different forensic scenarios. This work represents the first time that a quantitative approach has successfully been applied to associate a GSR to a specific ammunition.

Infrared spectroscopy and spectroscopic imaging in forensic science

Infrared spectroscopy and spectroscopic imaging, are robust, label free and inherently non-destructive methods with a high chemical specificity and sensitivity that are frequently employed in forensic science research and practices. This review aims to discuss the applications and recent developments of these methodologies in this field. Furthermore, the use of recently emerged Fourier transform infrared (FT-IR) spectroscopic imaging in transmission, external reflection and Attenuated Total Reflection (ATR) modes are summarised with relevance and potential for forensic science applications. This spectroscopic imaging approach provides the opportunity to obtain the chemical composition of fingermarks and information about possible contaminants deposited at a crime scene. Research that demonstrates the great potential of these techniques for analysis of fingerprint residues, explosive materials and counterfeit drugs will be reviewed. The implications of this research for the examination of different materials are considered, along with an outlook of possible future research avenues for the application of vibrational spectroscopic methods to the analysis of forensic samples.

Can cadaverous pollution from environmental lead misguide to false positive results in the histochemical determination of gunshot residues? Study on cadaveric skin samples

Histochemical determination of lead in gunshot residues (GSR) raises the question of possible environmental contamination by heavy metals. Authors assess the specificity of the Sodium Rhodizonate Test in the search of lead derived from environmental pollution. Sodium Rhodizonate Test and 5% HCl Sodium Rhodizonate test were applied to skin samples taken from two groups of victims, whose cause of death was not related to gunshot wounds: group A included 25 corpses found in open spaces after a long time; group B included 16 corpses exhumed after a period of 11 years. The use of these histochemical tests to skin samples from these two groups did not show metal debris histochemically similar to the lead present in GSR. These tests were confirmed to be specific in highlighting the GSR coming from gunshot, without being affected by the potential environmental contamination of the heavy metal pollutants, coming from air or soil.

The detection of gunshot residues in the nasal mucus of suspected shooters

The identification and quantification of metallic residues produced by gunshots, called gunshot residues (GSR), provide crucial elements in forensic investigations. The research has been largely focused on their collection onto the hands of suspected shooters, but the method is often burdened by risks of contamination. This research was focused on the possibility of sampling GSR trapped inside the nasal mucus of consenting shooters. Samples of the nasal mucus of "blank" control subjects and shooters were chemically analysed by Instrumental Neutron Activation Analysis (INAA), for residues of antimony (Sb) and barium (Ba), while lead (Pb) was excluded as ubiquitously environmental contaminant and due to high instrumental quantification limit (IQL) of INAA for this element. Shots were fired using two types of weapons (pistols and revolvers) and different firing sequences. The mucus was sampled at different times: immediately after the shots, after 30-60-120 and 180 min. Different amounts of Sb and Ba were detected between controls and shooters, witnessing the ability of the nasal mucus to retain GSR at concentrations significantly different even from the highest basal levels. Moreover, in order to simulate actual cases, nasal mucus from five groups of shooters was sampled after different shots with the same weapon and cartridges, immediately and after 1, 3, 12, and 24 h. The highest values were always found in the first 3 h from firing, for both weapons. Interestingly, for all the weapons, significant Sb and Ba concentrations were also found up to 12 h after firing, contrary to what occurs on hands, even though a progressive decrease was detected, with values below the detection threshold only after 24 h, thus demonstrating that GSR are persistent in nasal mucus. These first results proving that both Sb and Ba were qualitatively detectable in the nasal mucus of shooters indicate that the chemical analysis of the nasal mucus of suspected shooters may represent a promising tool in the forensic field since it is less burdened by problems related to sampling or contamination than the usual sampling on hand, providing that ammunitions employed contain Ba and Sb.

A FT-NIR spectroscopy methodology to estimate firing distance based on the direct analysis of the bullet impact surface

Fourier transform near-infrared spectroscopy is proposed as a new methodology to estimate firing distance based on the direct analysis of organic components of gunshot residues.

Analysis of ethyl and methyl centralite vibrational spectra for mapping organic gunshot residues

Detection of ethyl and methyl centralites in gunshot residues is important in forensic science due to their limited contamination from environmental sources compared to other organic residues. However, the vibrational frequencies of centralites are little explored and their frequency assignments are incomplete. Herein, we investigated vibrational frequencies of centralites based on Density functional theory (DFT) to understand their vibrations. The simulated frequencies exhibit excellent agreement with the experimental data, and the detailed assignments are comprehensively elaborated. We also demonstrate that centralite particles could be detected through Raman imaging based on their fingerprints. This work is very important for the further vibrational studies in detecting and tracing centralites in gunshot residues.

Challenging material patterning: fine lithography on coarse substrates

Precise patterning of inorganic materials is important for many technological applications. Often lithography processes are required on challenging substrates with respect to topography, flexibility, and surface adhesion. Here we show the fabrication of artificial gunshot residues (GSR) on adhesive tape samples by means of dip-pen lithography as an example for fine lithography on coarse substrates. We deposited lead-, barium-, and antimony-containing inks on SEM adhesive tape by direct writing with a fine tip. Single as well as multiple element structures with dimensions in the range of 10-75 µm were fabricated.