Analytical and quantitative concentration of gunshot residues (Pb, Sb, Ba) to estimate entrance hole and shooting-distance using confocal laser microscopy and inductively coupled plasma atomic emission spectrometer analysis: An experimental study

Colorimetric Barium Detection of Gunshot Residues on Cadaveric Human Skin: A Pilot Application for Forensic Purposes

Introduction

In this study we microscopically investigated, for the first time ever, the colorimetric detectability of barium of gunshot residues (GSR) on cadaveric human skin with gunshot wounds.

Methods

For this purpose we used two different colorimetric techniques known in the literature, namely 0.2% sodium rhodizonate (Na-R-Ba 0.2%) and sodium rhodizonate in alcoholic environment (Na-R-Ba OH 0.2%). At the same time, we have also coupled it with scanning electron microscopy with energy dispersive X-ray (SEM/EDX) analysis and the colorimetric study for the detection of lead of GSR. These techniques were applied to 16 victims who died from gunshot injuries, as well as to a control group.

Results

SEM/EDX demonstrated the presence of lead in all cases and barium in 11 of the 16 cases. The subsequent colorimetric technique with Na-R-Ba 0.2% did not show the barium of GSR in any case, unlike the Na-R-Ba OH 0.2% technique. This latter, in fact, has demonstrated the presence of this metal in 2 cases (18%). No microscopic case of false positive was recorded.

Conclusion

The evidence obtained with Na-R-Ba OH 0.2% makes this method, applied here for the first time ever, worthy of further study. Meanwhile, although this technique can certainly be applied, it cannot be separated from the contextual colorimetric investigation for lead and the use of more sophisticated techniques.

X-ray analytic microscopy with CT-guided sample extraction to analyze potential projectile fragments in a dead serow

In forensic pathology, it is important to detect and recover as evidence residual metal particles and projectiles when evaluating potential gunshot wounds. This process can be challenging when the bullets are fragmented. This report presents our experience using multiple modalities to analyze the wound of an illegally killed Japanese serow (Capricornis crispus) found in a mountainous region without its head and hind limbs. We performed postmortem computed tomography (PMCT) and necropsy that showed a distant-range gunshot wound of the neck likely created by a centerfire rifle. A postmortem cut through the neck and absent head precluded a complete evaluation. To determine the composition of the metal-like fragments in the neck, sampling and metal analysis were performed in two ways. Samples extracted from the exposed wound surface without CT guidance were analyzed directly using inductively coupled plasma mass spectrometry (ICP-MS). Samples from the bone, muscles, and cervical cord extracted under CT guidance were analyzed using x-ray analytic microscopy (XGT-9000, HORIBA, Kyoto, Japan). In wound surface samples, silicon and iron were detected as the main components on ICP-MS, suggesting that the materials were gravel. The samples taken under CT guidance and analyzed with XGT-9000 revealed that the high-density CT areas were mainly composed of lead. Combining CT-guided sample extraction and XGT-9000 can be useful for retrieving true projectile fragments and avoiding the confusion created by erroneously sampling non-projectile surface materials.

How may analysis of an inner layer of clothing affect the scene reconstruction in a shooting incident?

Shooting distances are utilized, among other forensic input, to position shooters and victims at the crime scene. Shooting distance estimation is done, mainly under the knowledge or assumption, that no intervening object has been present between the target and the muzzle. In the analysis of clothing items of victims that have been involved in a shootout, it is assumed that most of the marks and materials are left on the outer layers of clothing. The outer layers, not the inner layers, are the first objects the bullet meets. Consequently, undergarments are often disregarded for shooting distance estimation as they are not assumed to contain sufficient information in the form of marks or materials. In light of the above, it is the standard operating procedure in some forensic laboratories not to examine underwear. In this case report, the forensic examiners started by the implementation of standard operating procedures, thus examining only the outer layers of clothing of the victims. A thorough visual examination of the various clothing items led a forensic examiner to decide to extend the standard operating procedures, and try and examine an undergarment of one of the victims as well. The interpretation of examination products led to different scene reconstruction, one that may have led to a different interpretation of evidence. In this case, simply sticking to standard operating procedures might have led to less accurate crime scene reconstruction. This case report comes to stress the importance of thorough inspection of forensic exhibits, and scientific and critical thinking about different scenarios. Moreover, it demonstrates how the case-by-case approach in shooting distance estimation may add meaningful information, and eventually-bring us even closer to the truth.

Spectroscopic (analytical) approach to gunshot residue analysis for shooting distance estimation: a systematic review

Background

The determination of the shooting distance using gunshot residue (GSR) analysis is crucial in the investigation and reconstruction of firearm-related crimes. However, the conventional chemographic method for GSR analysis is destructive and has limited sensitivity and selectivity. While the spectroscopic method has potential in GSR analysis for crime investigation, there is a current lack of consistency in the spectroscopic results obtained for shooting distance estimation via GSR analysis. Addressing such limitations will enhance the forensic capabilities of law enforcement and provide an added advantage to crime laboratories during an investigation. It will also reinforce the use of such spectroscopic data in a criminal investigation.

Main text

We obtained all peer-reviewed articles relevant to shooting distance estimation from searching Scopus, Web of Science, PubMed, and Google Scholar databases. We specifically searched the databases using the keywords “shooting distance,” “range of fire,” “gunshot residue,” “firearm discharge residue,” and “firearm-related crime” and obtained 3811 records. We further filtered these records using a combination of two basic keywords “gunshot residue” and “shooting distance estimations” yielding 108 papers. Following a careful evaluation of the titles, abstracts, and full texts, 40 original peer-reviewed articles on shooting distance estimation via GSR analysis were included in the study. The forgoing included additional sources (n = 5) we obtained from looking through the reference lists of the forensic articles we found.

Short conclusion

This paper discusses the current scope of research concerning the chemographic and spectroscopic analysis of GSR for shooting distance estimation. It also examines the challenges of these techniques and provides recommendations for future research.

Simple gunshot residue analyses for estimating firing distance: Investigation with four types of fabrics

This work presents two simple methods for estimating the firing distance from the gunshot residues (GSRs) on fabric targets. Four types of fabric targets, namely twill weave denim cotton-polyester (80/20), jersey knitting 100% cotton, plain weave cotton-polyester (80/20) and plain weave cotton-polyester (60/40), were employed. The firing tests were carried out using these white fabrics as targets at distances of 5-100 cm, respectively. In the first method, digital images of the black GSRs on fabric materials were recorded inside an illuminated box and the inverted gray intensity values were plotted against the firing distances. Since the plots of all fabrics are not significantly different, the estimation of firing distance employs the same exponential curve for all test fabrics. Although simple, the imaging method is not suitable for dark-colored materials. A chemical-based method was therefore developed as an alternative method. In the second method, a small disposable microfluidic paper-based analytical device (μPAD) was employed for detecting Pb(II) extracted from the GSRs. The μPAD method uses the measurement of the length of a narrow band of a pink color resulting from reaction between rhodizonate reagent and the Pb(II) extract. The plots indicated that the data of thick denim material are significantly different to other test fabrics which are much thinner. These three fabrics share the same estimation curve. However, it is recommended that the separate estimation curve for denim materials must be used. Both methods are suitable for short range firing distance, no further than 60 cm, since at greater distances the inverted gray intensity and the 'band-length' methods are unable to detect the GSRs.

A novel approach to detect barium in gunshot residue using a handheld device: a forensic application

The present manuscript describes an innovative handheld device for the rapid detection of barium (Ba²⁺) in Gunshot Residue (GSR) based on the use of gold nanomaterials capped with sodium malonate. The method depends on a shift in the Light Scattering Plasmon Resonance (LSPR) peak of malonate capped gold nanoparticles (AuNPs) from 526 nm to 610.5 nm, due to the carboxylate ion aggregation between the metal and the nanoparticles leading to a change in the color. Qualitative detection was realized by the change in the color, while for quantitative analysis a handheld device has been fabricated in-house. The results were then correlated with those of standard known methods such as UV-Vis Spectroscopy and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). The results showed better correlation between the fabricated device and standard methods with R² = 0.98. It shows a linearity range from 0.01 mg mL^-1 to 5 mg mL^-1 with a Limit of Detection (LOD) of 0.2 mg mL^-1. Furthermore, GSR samples were collected from cloth piece set at different range of shooting (i.e. 1 ft to 16.40 ft) using different ammunition to detect the presence of Ba²⁺ with the help of the developed device and results were found similar to those of the known methods. The hand-held device was found to be unaffected by other interfering agents (i.e. Pb²⁺, Sb³⁺, Ca²⁺, Cu²⁺, Hg²⁺, Mg²⁺, As³⁺, Cr³⁺, etc.). The results demonstrated here shows high selectivity, sensitivity and rapid method for Ba²⁺ detection in GSR, showing its greater potentiality in future.

Analysis of lead distribution in avian organs by LA-ICP-MS: Study of experimentally lead-exposed ducks and kites

Lead poisoning of wild birds by ingestion of lead ammunition occurs worldwide. Histopathological changes in organs of lead-intoxicated birds are widely known, and lead concentration of each organ is measurable using mass spectrometry. However, detailed lead localization at the suborgan level has remained elusive in lead-exposed birds. Here we investigated the detailed lead localization in organs of experimentally lead-exposed ducks and kites by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). In both the ducks and kites, lead accumulated diffusely in the liver, renal cortex, and brain. Lead accumulation was restricted to the red pulp in the spleen. With regard to species differences in lead distribution patterns, it is noteworthy that intensive lead accumulation was observed in the arterial walls only in the kites. In addition, the distribution of copper in the brain was altered in the lead-exposed ducks. Thus, the present study shows suborgan lead distribution in lead-exposed birds and its differences between avian species for the first time. These findings will provide fundamental information to understand the cellular processes of lead poisoning and the mechanisms of species differences in susceptibility to lead exposure.

A Simple and Rapid Spectrophotometric Method for Nitrite Detection in Small Sample Volumes

A simple, rapid, and environmentally-friendly spectrophotometric method for nitrite detection was developed. Detection was based on a redox reaction with iodide ions in an acidic condition. The reaction was evaluated by detecting the increase in absorbance of the colored product of iodine at 362 nm wavelength. To obtain a good spectrophotometric performance, the iodide ions concentration, hydrochloric acid concentration, and reaction time were optimized. In the optimal condition, the developed spectrophotometric method provided a linear range of 0.0625 to 4.00 mg L−1 (r = 0.9985), reaction time for 10 min, a limit of detection of 25 µg L−1, and a limit of quantitation of 85 µg L−1. This method showed good repeatability (RSD < 9.21%), high sample throughput (9 samples min−1), and good accuracy (recovery = 88 ± 2 to 99.5 ± 0.4%). The method has the potential to be used in crime scene investigations as a rapid screening test for gunshot residue detection via nitrite detection.

Gunshot residue detection in stagnant water: SEM-EDX or ICP-MS? A preliminary study

The identification of gunshot residue (GSR) on wounds enables the differentiation of entry and exit wounds. Unfortunately, studies analyzing GSR on degraded bodies have been poorly documented, and no data exist regarding GSR detection after stagnant water immersion. The aim of this preliminary experimental study was to detect GSR on wounds altered in stagnant water, using scanning electron microscopy coupled with energy-dispersive X (SEM-EDX) and inductively coupled plasma mass spectrometry (ICP-MS). Shots were performed on sheep limbs with a 22LR at a distance of 20 cm. The limbs were then submerged in stagnant water and analyzed on days 0, 6, and 14. SEM-EDX was performed on previously dehydrated wounds. For ICP-MS analysis, the wounds were rubbed with a cotton swab that was then analyzed. In the SEM studies, a higher number of particles were detected in entry wounds compared to exit wounds under every set of experimental conditions. Unfortunately, SEM-EDX failed to detect GSR particles, even on day 0. ICP-MS enabled the detection of Pb, Sb, and Ba at every stage with higher quantities on entry than in exit. These elements remained detectable following limb immersion. ICP-MS enabled differentiate entry from exit wounds, even after immersion in stagnant water. Nevertheless, when manually swabbing the wounds, quantities of matter collected is highly variable. ICP-MS is a more suitable technique than SEM-EDX for GSR identification of wounds after decomposition in stagnant water; however, standardization is needed.

Radiodense bullet wipe around osseous entrance gunshot wounds

"Bullet wipe" is the material deposited by a bullet on any surface with which it comes into contact after it is fired and may contain debris from the gun barrel, including particles of primer and metal fragments from previously fired bullets. X-ray analysis is a non-destructive method by which traces of metallic elements can be visually detected. The analysis of osseous defects for radiodense bullet wipe (RBW) assists in determining the presence or absence of perforating gunshot wounds, especially in fragmented, skeletonized remains. The aim of our current study was to determine the frequency of RBW around entrance firearms injuries that perforated bone. We prospectively analyzed entrance gunshot wounds for RBW over a three-year period using digital X-ray analysis (n = 59). We retrospectively reviewed the corresponding autopsy reports to determine the frequency of RBW by biologic sex, reported ancestry, age-at-death, location of wound, manner of death, range of fire, bullet caliber, and presence of bullet jacket. Data were analyzed by Fisher's exact test or Chi-square test with significance levels accepted at p < 0.05. RBW was present in 66% (n = 39) of examined cases. Decedent characteristics did not significantly alter RBW distribution, including biologic sex (p = 0.75), reported ancestry (p = 0.49), and age-at-death (p = 0.43). Additionally, the location of the osseous entrance gunshot wound, manner of death, range of fire, and cartridge caliber did not affect RBW detection. All cases involving non-jacketed rounds (n = 5) showed RBW (p = 0.30). To our knowledge, this study is the first to report the frequency of RBW detection from osseous entrance gunshot wounds.

Is it possible to detect lead derived from gunshot residues on decalcified human bone by means of a histochemical staining with sodium rhodizonate?

In this study we have evaluated the detectability of lead deriving from Gunshot Residues (GSR) on human bone using colorimetric techniques as well as the possible interferences of decalcification on the stainability of these particles. 22 well preserved cadavers were divided into two groups: group A enlisted 11 victims deceased because of gunshot injuries (bones and soft tissues sampled in correspondence of the entry wound of the bullet)- and group B, comprehending 11 victims deceased for natural causes (specimens sampled from intact skin areas). All the samples, after decalcification processes for bone specimens with a 14 % HCl solution, underwent standard histological procedures and were stained with hematoxylin and eosin (H&E), sodium rhodizonate (Na-R) and acidified sodium rhodizonate (Na-R-HCl 5 %). Two additional slides of soft tissues for each group were pre-treated with HCl 14 % before being stained with likewise staining. In group A, 10 samples out of 11 resulted to be negative to Na-R and Na-R-HCl 5% techniques while all the corresponding soft tissues resulted to be positive for the same staining. Additional soft tissue slides processed with 14 % HCl solution were negative in 10 cases out of 11. No sample in group B showed positivity to the staining procedures neither with nor without pre-treatment with 14 % HCl. The search for GSR residues on human bone is therefore not executable with Na-R and Na-R-HCl 5 % techniques since the essential decalcifying procedure modifies the stainability of the residues therefore adulterating the results.

Computational Approach to Identify Different Injuries by Firearms

Complications arise in the analysis of gunshot wounds to the maxillofacial region, when neither the projectile nor the gun is found at the crime scene. We simulated 5- and 15-cm firing distances at a human mandible to investigate the external morphology of entrance wounds based on fire range. The ammunition models, .40-caliber S&W, .380-caliber, and 9 × 19-mm Luger, were constructed with free-form NURBS surfaces. In a dynamic simulation, projectiles were fired against mandibular body 3D model at 5 and 15 cm. All entrance wounds presented oval aspect. Maximum diameter and von Mises stress values were 16.5 mm and 50.8 MPa, both for .40-caliber S&W fired at 5 cm. The maximum energy loss was 138.4 J for .40 S&W fired at 15 cm. In conclusion, the mandible was most affected by .40-caliber S&W and morphological differences were observable in holes caused by different incoming projectile calibers fired at different distances.

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.

The weathering and transformation process of lead in China's shooting ranges

Corroding steel-core bullets from three shooting ranges in different climate zones of China were collected. Multiple technical methods (EMPA, SEM, XRD, and ICP-OES) were applied to investigate the structure, morphology, and weathering product of this type of bullet in China to analyze the weathering mechanisms in different types of soils. A scanning electron microscope (SEM) was used to view the morphology and microstructure of corrosion layers. On the corroded lead layer surface, unevenness, micro cracks, and spallation were usually present. Around the micro cracks, many types of euhedral and subhedral crystals of the secondary products of lead were formed, most of which were composed of cerussite (PbCO3), while hydrocerussite (Pb3(CO3)2(OH)2) was predominant in the bullet collected from the humid environment. X-ray power diffraction (XRD) results show that the secondary weathering products in the three shooting range soils are clearly different. In the Fangyan shooting range, which has a neutral and semi-arid soil, the lead weathering product was mainly hydrocerussite (Pb3(CO3)2(OH)2), while no substantial amount of crystal phase of lead compound could be found in acidic, damp soils from the Fenghuang shooting range, possibly due to the enhanced dissolution and mobilization of lead compounds at lower pH and higher content of organic matter in the soil. In hot and arid environment of the Baicheng shooting range, cerussite might have undergone thermal decomposition, thus generating shannonite (Pb2O(CO3)). These results indicate that the formation of secondary Pb minerals is largely affected by the climatic zone or the soil properties, which may have implications for range management practices.

An unusual case of "dyadic-death" with a single gunshot

The terms "dyadic death" or "murder-suicide" refer to an incident where an individual commits homicide and then takes his or her own life. These events are generally committed by men within the family network, using firearms or sharp force instruments, and make up a relatively small proportion of homicides overall. Herein, we present the application of post-mortem multislice computed tomography (CT) and micro-CT analysis to an unusual case of dyadic death, where a 38-year-old man fired a single gunshot to his own right temple, killing himself and his 50-year-old wife, lying on the bed beside him. The integration of radiological, autoptic and histological data allowed us to reconstruct the trajectory of the gunshot, the most probable dynamics of the event, and to classify the incident as a "suicide-homicide", because the female victim died a few minutes later than her husband and murderer.