X-ray mapping technique: a preliminary study in discriminating gunshot residue particles from aggregates of environmental occupational origin (original) (raw)
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BioMed Research International, 2014
Chosen aspects of examinations of inorganic gunshot particles by means of scanning electron microscopy and energy dispersive X-ray spectrometry technique are presented. The research methodology of particles was worked out, which included a precise and repeatable procedure of the automatic detection and identification of particles as well as the representation of the obtained analytical data in the form of the frequencies of occurrence of particles of certain chemical or morphological class within the whole population of particles revealed in a specimen. On this basis, there were established relationships between the chemical and morphological properties of populations of particles and factors, such as the type of ammunition, the distance from the gun muzzle to the target, the type of a substrate the particles sediment on, and the time between shooting and collecting the specimens. Each of these aspects of examinations of particles revealed a great potential of being utilised in casework, while establishing various circumstances of shooting incidents leads to the reconstruction of the course of the studied incident.
2005
Automated scanning electron microscope analyses of gunshot residue samplers are being performed by many crime laboratories all over the world. Often the criminalist-technician operators of these instruments do not have adequate training for the interpretation of spectra generated by energy dispersive X-ray spectroscopy. In this case, a number of unusual particles, most of which contain phosphorus (P) and tin (Sn) were assigned by the criminalist as being “unique” to gunshot residue. Unfortunately, none of the particle spectra recorded in this case can even be assigned as “consistent,” much less “unique” to gunshot residue. Errors made by this technician are 1) missed elements, tin (Sn) and antimony (Sb), and 2) including phosphorus (P) as a gunshot element. The origin of these particles is unknown.
Spectrochimica Acta Part B: Atomic Spectroscopy, 2007
A gunshot residue sample that was collected from an object or a suspected person is automatically searched for gunshot residue relevant particles. Particle data (such as size, morphology, position on the sample for manual relocation, etc.) as well as the corresponding X-ray spectra and images are stored. According to these data, particles are classified by the analysis-software into different groups: 'gunshot residue characteristic', 'consistent with gunshot residue' and environmental particles, respectively. Potential gunshot residue particles are manually checked andif necessaryconfirmed by the operating forensic scientist.
Elemental quantification of large gunshot residues
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2015
In the present work we embarked on the evaluation of the Sb/Pb, Ba/Pb and Sb/Ba elemental ratios found in relatively large particles (of the order of 50-150 lm across) ejected in the forward direction when a gun is fired. These particles are commonly referred to as gunshot residues (GSR). The aim of this work is to compare the elemental ratios of the GSR with those found in the primer of pristine cartridges in order to check for possible correlations. To that end, the elemental concentration of gunshot residues and the respective ammunition were investigated through PIXE (Particle-Induced X-ray Emission) and micro-PIXE techniques. The ammunition consisted of a .38 SPL caliber (ogival lead type) charged in a Taurus revolver. Pristine cartridges were taken apart for the PIXE measurements. The shooting sessions were carried out in a restricted area at the Forensic Institute at Porto Alegre. Residues ejected at forward directions were collected on a microporous tape. The PIXE experiments were carried out employing 2.0 MeV proton beams with a beam spot size of 1 mm 2. For the micro-PIXE experiments, the samples were irradiated with 2.2 MeV proton beams of 2 Â 2 lm 2. The results found for the ratios of Sb/Pb, Ba/Pb and Sb/Ba do not correlate with those stemming from the analysis of the primer.
Application of proton-induced X-ray emission technique to gunshot residue analyses
1982
The proton-induced X-ray emission (PIXE) technique was applied to the identification and analysis of gunshot residues. Studies were made of the type of bullet and bullet hole identification, firearm discharge element profiles, the effect of various target backings, and hand swabbings. The discussion of the results reviews the sensitivity of the PIXE technique, its nondestructive nature, and its role in determining the distance from the gun to the victim and identifying the type of bullet used and whether a wound was made by a bullet or not. The high sensitivity of the PIXE technique, which is able to analyze samples as small as 0.1 to 1 ng, and its usefulness for detecting a variety of elements should make it particularly useful in firearms residue investigations.
A new quantitative method for gunshot residue analysis by ion beam analysis
The Analyst, 2013
Imaging and analyzing gunshot residue (GSR) particles using the scanning electron microscope equipped with an energy dispersive X-ray spectrometer (SEM-EDS) is a standard technique that can provide important forensic evidence, but the discrimination power of this technique is limited due to low sensitivity to trace elements and difficulties in obtaining quantitative results from small particles. A new, faster method using a scanning proton microbeam and Particle Induced X-ray Emission (m-PIXE), together with Elastic Backscattering Spectrometry (EBS) is presented for the non-destructive, quantitative analysis of the elemental composition of single GSR particles. In this study, the GSR particles were all Pb, Ba, Sb. The precision of the method is assessed. The grouping behaviour of different makes of ammunition is determined using multivariate analysis. The protocol correctly groups the cartridges studied here, with a confidence >99%, irrespective of the firearm or population of particles selected.
Trace element profiling of gunshot residues by PIXE and SEM-EDS: a feasibility study
X-Ray Spectrometry, 2009
A feasibility study was carried out into the use of particle-induced x-ray emission (PIXE) on the ion microprobe for the characterisation of gunshot residues (GSR). We compare these results with the conventional technique, scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDS). Samples of gunshot residue from four different sources were collected. Individual particles of GSR were analysed by SEM-EDS using a 30-keV electron beam focussed to ∼10 nm, and PIXE using a 2.5-MeV proton beam focussed to ∼4 µm. PIXE revealed trace or minor elements undetectable by SEM-EDS, thereby strengthening the discrimination between different types of GSR.