Gunshot Residue Research Articles

Optimizing the Automated Analysis of Inorganic Gunshot Residue Particles by SEM-EDX: From Synthetic Particle Standards to More Time-Efficient Settings for Daily Casework

Gunshot residues deposited on all surfaces in the nearest vicinity of the shooting incident, when revealed, can contribute to the explanation of various aspects of such an incident for forensic purposes. Examinations of gunshot residue, mainly inorganic particles, at forensic laboratories are expected to be reliable and fast. This primarily depends on the performance of the used scanning electron microscope integrated with an energy dispersive X-ray spectrometer and the automatic program searching for particles of defined characteristics. Among the milestones on the pathway towards quality assurance in examinations of gunshot particles, the invention of the synthetic gunshot residue specimen ought to be named. Such a specimen with particles of known chemical content, size, and location is now used for proficiency testing, which is a condition for a forensic laboratory to obtain accreditation in this subject matter. In this publication, the need for optimization of the procedure for the examination of a synthetic specimen, in alignment with the necessary modifications for real gunshot particles, has been addressed. The presented process of validation resulted in two procedures. The first demonstrates the full capacity of the instrument for detecting all particles present in the synthetic specimen, including the 0.5 micrometer particle at the magnification of 250×. The other procedure is the modification of the first, however aiming at 1-micrometer particles or bigger (at the magnification of 120×) and allowing the necessary backscattered signal threshold changes depending on the actual composition of gunshot residue as well as the abundance of light element debris in the case of real gunshot particles.

Effects of carbonization on gunshot residue detection in an animal model

The detection of gunshot residue (GSR) can be useful to determine if the wound has been caused by a firearm and it could help to differentiate the entry wound from the exit one. Carbonization is a good method for altering crime scenes. However, there are few studies in this specific context. The first objective of our study was to examine the persistence of GSR in wounds after carbonization. The second aim was to differentiate entry wounds from exit ones.For the experiment, bullets were fired with a 22LR on sheep limbs at contact range.The specimens were divided into four groups: two that weren't shot at (fresh and carbonized limbs) and two of shot limbs (one with carbonization and one without). Carbonization was performed in the open air using an accelerant.Wounds were analyzed using Scanning Electron Microscopy with Energy Dispersive X-ray spectrometry (SEM–EDX) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS).Lead, Antimony and Barium were observed using SEM-EDX only in the entry wounds, while lead was found in the exit ones. ICP-MS enabled the detection of these elements in the entry and exit wounds but predominantly in the entry ones. After carbonization we observed a huge decrease of GSR. With SEM-EDX most of the particles detected were only consistent with GSR. Anyway, the identification of GSR and the differentiation between entry and exit wounds were still possible with both techniques. Therefore, they are suitable for detecting GSR in carbonized gunshot wounds under the specific conditions of our experiment.

Assessing the Reliability of Firearms Expert Reports: A Critical Analysis

This critical analysis investigates the dependability of firearms expert reports, which are admissible in evidence under Section 39(1) of the Bharatiya Sakshya Adhiniyam, 2023, in criminal investigations and legal proceedings, emphasizing their function in connecting firearms to criminal activities through ballistic evidence. The research reviews advancements in firearms analysis, including trajectory reconstruction and gunshot residue testing, while also addressing concerns related to the subjective nature of these analyses and the absence of standardization across various laboratories. Through an extensive literature review, this paper identifies key issues impacting the credibility of firearms reports, such as human error, lack of proper video documentation of the search and seizure operation along with laboratory analysis of the firearms, the subjective interpretation of tool marks, absence of reliable and independent witnesses, failure to convince the court regarding the reasons on which the expert opinion is grounded, and varying methodologies. The findings indicate that although firearms expert reports play a vital role in criminal cases, elements like evidence management and the level of expertise significantly influence their reliability, highlighting the necessity for rigorous standards and quality control to maintain their evidentiary value in court.

Determination of the Perpetrator-Victim Position in a Case of Severe Traumatic Brain Injury due to a Less-Lethal Weapon Projectile, Based on Brain Injuries

Less-lethal (or non-lethal) weapons cause lethal and non-lethal injuries; this depends on many factors, including the shot distance and the modifications made to the operation of the weapon and the projectiles. This type of weapon has a similar shape to a firearm, shares the same physical and chemical operating principle and uses the combustion of a chemical substance to eject the projectile. In technical terms, the only difference is the projectile. Currently with the changes in weapons and projectiles, it is difficult to make a correlation. Just like lethal firearm projectiles and due to their operation, they leave macroscopic gunshot residues such as powder tattooing or soot deposition, only occasionally a contusion ring. In addition, there is a variety in the appearance of the entrance wounds. Therefore, it is very important to process the scene and carefully dissect the external wound and the surrounding area and, if possible, the recovery of the projectile. We present a case where a non-penetrating superficial injury to the skull produced trauma consistent with a coup contrecoup brain injury, which allows us to identify the perpetrator-victim position.

Gunshot Residue Deposition With and Without Firearm Suppressors (Silencers).

Forensic pathologists recognize the importance of estimating the range of fire for gunshot entrance wounds. Classically described ranges of fire include contact, close range, medium (or intermediate) range, and indeterminate (or distant) range. The presence or absence of gunshot residue (smoke/soot and/or gunpowder) and the characteristics of the gunshot residue are evaluated in order to estimate the range of fire. It is well known that interposed targets can block or otherwise alter gunshot residue deposition. In this preliminary study, a comparison is made between gunshot defects produced on targets using firearms with and without an attached suppressor device (so-called "silencer"). Comparisons are made at various distances from the targets, using multiple weapon/ammunition calibers.

Pathological Changes and Sodium Rhodizonate Test as Tools for Investigating Gunshot Wounds in Veterinary Forensic Pathology.

Gunshot wound morphology and gunshot residues (GSRs) evaluation have been poorly investigated in veterinary forensic pathology. The aims of the present study were to assess the gunshot wound morphology in animals and evaluate the detectability of lead deriving from GSRs using colorimetric techniques. To these aims, cadavers were divided into four different groups. Group A comprised eight animals who died from firearm-related injuries, while groups B and C included dog limbs shot using different shooting ranges; group D comprised dog limbs stabbed with a screwdriver. Morphological analysis was performed on all entry gunshot wounds. Lead residues were investigated using a Bullet Hole Testing Kit (BTK) and Rhodizonate Sodium histochemical staining (NaR-s). Gunshot wounds in group A showed an abrasion ring associated with hemorrhages and tissue necrosis. Groups B and C showed injuries related to the shooting range. NaR-s showed positive results in both animals that died from gunshot wounds and experimentally shot limbs. However, the number of positive cases and the pattern of lead distribution varied with the shooting range. Positive results by BTK were limited to close-contact shots in group B limbs. Our results suggest that both pathological examination and NaR tests represent valid tools for investigating gunshot wounds in veterinary pathology.

Intraoral gunshot injury associated with soot in the deep airways

In suicidal gunshots to the head, the oral cavity ranks among the preferred entrance sites. If the weapon’s muzzle end is located within the mouth, it is to be expected that the cartridge discharge residues are deposited on the buccal and palatal mucosa, the tongue and the pharynx, often in combination with tears of the lips due to the expanding combustion gases. Ensuing from the bullet entrance wound and any concomitant injuries, blood is released into the upper airways and subsequently aspirated into the lung periphery provided that respiration continues for at least a short time. Evidently, this impedes the detection of additional soot deposits in the trachea, bronchi and alveoli. Using the example of an intraoral gunshot with a revolver cal. 357 Magnum, the paper points out that in individual cases it may be possible to prove the presence of gunshot residues in the deep airways.

The development of screen-printed electrodes modified with gold and copper nanostructures for analysis of gunshot residue and low explosives

Due to their portability, sensitivity, and ease of use, electrochemical sensors have recently become a popular method for rapid, on-site analysis. This study presents a proof of principle for the application of modified screen-printed carbon electrodes (SPCEs) for the detection of signature metals (Pb, Sb, and Zn) commonly found in gunshot residue (GSR), as well as for the detection of nitrate/nitrite in organic GSR and low explosives. To achieve these two aims, we have examined various electrode surface modifications. For metal detection, SPCEs were modified by electrodeposition of gold to improve sensitivity. GSR samples taken from two types of cartridge cases and shooting-related surfaces were analyzed using the Au-modified SPCEs. For nitrate/nitrite analysis, further electrode surface modifications were carried out by depositing Cu(II) onto the Au-SPCEs to enhance signal through catalytic activity of the copper surfaces. Both unburned and burned forms of black powder samples, as well as burned smokeless powder, were then analyzed using the Cu/Au-SPCEs. In conclusion, due to their low cost and portability, these sensors should prove useful for rapid forensic examination.

Police vehicle contamination by inorganic gunshot residue (iGSR) in Zagreb County Police Administration (Croatia): Analysis of characteristic and indicative particles across different vehicle parts and contributory risk factors.

Inorganic gunshot residue (iGSR) analysis, crucial for linking suspects to firearm use, faces challenges from potential environmental contamination, notably in police vehicles. The present study aimed to explore the level of iGSR contamination in police vehicles from the Zagreb County Police Administration (Croatia), considering particle types and their position in vehicles, and to identify associated risk factors. From December 2021 to April 2022, 65 of 86 police vehicles (margin of error: ±6% at a 95% confidence level) were sampled with GSR stubs on the drivers' seats, back seats, and backrests and analyzed using scanning electron microscopy and energy dispersive x-ray analysis (SEM/EDX). Characteristic particles were found in 63.1% of vehicles, 33.8% on the driver's seat, and 24.6% on the back seat/backrest. Indicative particles were found in 70.77% of vehicles, with a fairly even distribution. McNemar's chi-square analysis showed no significant disparities in positive sample ratios across vehicle parts or particle types (p > 0.05). In total, 228 characteristic and 166 indicative GSR particles were identified, with no notable correlation among them (p = 0.346). Logistic regression analysis identified the transportation of individuals involved in firearms incidents as a statistically significant factor influencing the presence of characteristic particles (p = 0.030). The findings suggest a considerable prevalence of iGSR in the analyzed Police Administration unit, highlighting the need for careful contamination management in police operations to preserve evidence integrity, particularly in cases when individuals who used firearms had been transported in the vehicle.

Comparison of SEM-EDX and ICP-MS for the analysis of gunshot residues after burial: An experimental study

Gunshot residues (GSR) analysis can be valuable in a forensic context for distinguishing entry wounds from exit wounds, especially in cases when body alterations prevent macroscopic analysis. Several studies have demonstrated its usefulness in various contexts. However, few studies have examined the retention of GSR under environmental conditions particularly after burial.The primary objective of our experimental study is to investigate the retention of GSR after burial and decomposition by using two techniques: SEM-EDX and ICP-MS. Our secondary objective is to determine whether it is still possible to distinguish the entry wounds from the exit ones after 2 months of burial. For this study, we used a bovine model (cow feet), and fired with 7 mm semi-jacketed bullets. We formed several groups, including 3 control groups that hadn't been shot (buried for 2 days and 60 days and one unburied group), 3 test groups that had been shot (one unburied and two buried that were exhumed after 2 days and 60 days of burial).The results of our study show that both SEM-EDX and ICP-MS were suitable for detecting particles characteristic of GSR, after 60 days of burial. However, only SEM-EDX could differentiate easily the entry wounds from the exit ones.Our experimental study demonstrates that SEM-EDX analysis is suitable in cases where the discovery of a buried body doesn't allow the macroscopic determination of the ballistic trajectory.

Identifying Sample Provenance From SEM/EDS Automated Particle Analysis via Few-Shot Learning Coupled With Similarity Graph Clustering.

Automated particle analysis (APA) provides a vast amount of compositional data via energy-dispersive X-ray spectroscopy along with size and shape data via scanning electron microscopy for individual particles in a sample. In many instances, APA data are leveraged to support identification of the source of a sample based on the detection of particles of a specific composition. Often, the particles that provide context make up a minuscule portion of the sample. Additionally, the interpretation of complex samples can be difficult due to the diversity of compositions both in the mixture and within a particle. In this work, we demonstrate a method to compute and cluster similarity graphs that describe inter-particle relationships within a sample using a multi-modal few-shot learning neural network. As a proof-of-concept, we show that samples known to have been exposed to gunshot residue can be distinguished from samples occasionally mistaken for gunshot residue. Our workflow builds upon standard APA techniques and data processing methods to unveil additional information in a readily interpretable and quantitatively comparable format.

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.

Machine Learning and Possibility of its Application for Forensic Researches on Firearms

Role of machine learning in modern society cannot be over-estimated, especially given its steadily increasing importance in recent years. Various machine learning models are applied not only in everyday life but also in solving practical, engineering, and scientific challenges. However, the methods and capabilities of machine learning remain relatively obscure to most professionals across various fields of knowledge, including specialists in forensic firearm examination. The article discusses basic tasks that machine learning methods can facilitate and provides examples of tasks faced by forensic experts during firearm examinations that can be solved utilizing these methods. The article purpose is to familiarize professionals in the field of forensic science with be-sic capabilities of machine learning methods. The research paper demonstrates which specific types of tasks in forensic firearms examination it is advisable to apply these methods to, and what is required for this purpose. In order to achieve this goal, general scientific methods (dialectical, comparative, analysis, synthesis, induction, deduction) and special scientific methods (formal-logical, systemic-structural) have been employed. Specific expertise and skills in forensic identification methods (including ballistics, microscopic comparative analysis of traces on bullets and casings, detection and examination of gunshot residue to estimate shooting distance, etc.), principles of machine learning, and mathe-matical algorithms used to construct various models have been applied.

Voltammetric co-determination of lead and copper in gunshot residue based on iron oxide particle/spent coffee grounds-modified electrode.

A novel electrochemical sensor was developed for the detection of lead (Pb) and copper (Cu) ions using spent coffee grounds decorated with iron oxide particles (FeO/SCG). The FeO-decorated SCG was used to modify a glassy carbon electrode (GCE). FeO, SCG, and FeO/SCG were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The electrochemical properties of the modified electrode were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The electrode modifications increased theactive surface area and electron transfer and enhanced the accumulation of the target analyte. In the optimal condition, the developed sensor showed linear ranges of 1.0µg L-1-0.05mg L-1 and 0.05mg L-1-0.8mg L-1 for Pb2+ and 5.0µg L-1-0.1mg L-1 and 0.1mg L-1-0.8mg L-1 for Cu2+. The limit of detection (LOD) was 1.0µg L-1 for Pb2+ and 2.4µg L-1 for Cu2+. The developed sensor was successfully applied to determine Pb2+ and Cu2+ in bullet holes. The results were in good agreement with those obtained by inductively coupled plasma optical emission spectrometry (ICP/OES).

Investigating gunshot wounds in charred bone with XRF spectroscopy: a technical note

The analysis of traces of injuries can be difficult in cases of charred human remains since the alteration and fragmentation are high. The aim of this study is to explore the use of X-Ray Fluorescence (XRF) technique as a screening tool for detecting and analyzing gunshot residues (GSR) on cremated and highly fragmented materials, as it is a technique that allows for fast qualitative investigations without altering the sample or requiring sample preparation. The study was carried out on two steps: firstly, on completed skeletonized bones to verify if GSR survive to burning; secondly, we considered a more realistic situation, in which soft tissues were present before the shooting. To this aim, nine adult bovine ribs, four retaining soft tissue, five completely skeletonized, were subjected to a shooting test using two types of 9 mm projectiles (jacketed and unjacketed bullets). The ribs were then burnt until complete calcination in an electric furnace. The entry wound of each rib was analyzed using XRF, revealing traces of GSR. The XRF analysis showed that all samples, except for one, contain Pb and/or Sb near the lesion. Furthermore, the samples hit by unjacketed bullets had a more significant presence of Pb in macroscopic yellow areas, which persisted when moving away from the gunshot. These findings could pave the way for the use of XRF technology, mostly when a fast and immediate scan must be done on osteologic materials by a conservative method.

Prevalence of gunshot residue particles on back seats of police vehicles.

The presence of gunshot residue (GSR) in a sample can provide valuable information in forensic investigations by associating a suspect with a shooting incident. However, in order to have confidence in the integrity of the results' interpretation, the possibility of contamination by secondary transfer of GSR occurring during the transportation of a person under custody in a police vehicle should be evaluated. In order to investigate police vehicles as a source for secondary transfer of GSR particles, a total of 51 samples were collected from the rear seats of random police vehicles and used to transport arrested individuals. Results indicated that the type of upholstery of the seats plays a main role in determining the potential for secondary GSR contamination. The potential chance of coming into contact with GSR particles in police vehicles is low. GSR contamination from police vehicles is, maybe, not of a major concern but should be taken into consideration mainly when very few characteristic GSR particles are found on an analyzed sample.

A Study on the correlation of the physico-chemical properties of Gunshot Residue (GSR) particles with distance using a 9×19 mm Indian ammunition

A Study on the correlation of the physico-chemical properties of Gunshot Residue (GSR) particles with distance using a 9×19 mm Indian ammunition

IMPACTS of SUPERSONIC and SUBSONIC AMMUNITION on GUNSHOT RESIDUE DISTRIBUTION

In incidents where firearms are involved, the determination of the firing distance is one of the basic steps of the analysis aimed at determining the origin of the incident with Forensic Shot Analysis studies. Shot residues consist of partially burned and unburnt powder grains, gunpowder gas, capsule residues and inorganic and organic residues. As a result of determining the presence and density of shot residues on the target, the distance from which the shot was fired can be determined. The pattern and density of shot residues exhibit a direct correlation with the specifications of firearms and ammunition. The intended use and traits of the weapon affect the properties of the ammunition. An instance of specialised ammunition is subsonic cartridges which have lower powder burn rates and amounts compared to supersonic cartridges. To ensure accurate gunshot residue analysis, gunshot residue density and pattern from reference test-fires are necessary. The key factors affecting the GSR analysis are the type of weapon and ammunition used during test-fires, which should closely match those used in the incident. Any variation in these variables can reduce the precision of the residue analysis. In the study, an independent T-test was applied to determine whether there is a significant difference between the gunshot residue density on the target during test firing of 9×19mm diameter and type Supersonic and Subsonic cartridges with semi-automatic pistols at distances of 0cm, 15cm, 30cm, 60cm and 100cm. It was determined that a significant difference existed between supersonic and subsonic cartridges in the density and patterns of gunshot residue on the target resulting from shots fired at the mentioned distances.

Detection of gunshot residue by flash-pulse and long-pulse infrared thermography

Detection of gunshot residues (GSR) in a bullet hole area is one of the forensic investigations aiding in the reconstruction of crime scenes. Traditionally, chromogenic methods based on chemical exposure or microscopic/spectroscopic methods are used for this purpose. In this study, we explore the applicability of active excitation infrared thermography methods for GSR detection in the bullet hole area on fabric samples. A standard 9 mm full metal jacket ammunition with a nickel-plated shell and natural cotton fabric samples were used for experiments in this study. The applicability of active thermography methods based on two different light/heat excitation sources to detect the GSR was investigated. Flash-pulse and long-pulse thermography were compared through an experimental investigation. We evaluated the effectiveness of various thermographic data processing methods, including background subtraction, temperature derivative analysis, Fourier transform phase analysis, principal component analysis, and higher-order statistics for GSR evaluation. Our findings demonstrate that flash-pulse thermography and kurtosis analysis yield the highest contrast-to-noise ratio (CNR) and produce sharp, clear images of GSR, making it the optimal method for thermographic GSR detection. Our study indicates that even though the GSR particles are tiny, they can produce sufficient contrast to be detected by the thermographic methods if appropriate experimental and post-processing procedures are used. Thus, these methods could complement GSR detection as they are non-destructive and offer rapid inspection.

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.