Particle Analysis for the Detection of Gunshot Residue. I: Scanning Electron Microscopy/Energy Dispersive X-Ray Characterization of Hand Deposits from Firing

Abstract

Several methods of bulk elemental analysis, such as fiameless atomic absorption, flame emission spectroscopy, neutron activation analysis, and photoluminescence spectroscopy, can reliably and quantitatively determine the amounts of antimony and barium (antimony and lead in the case of photoluminescence) removed from the hand. The information thus furnished, however, in most cases is not sufficient to constitute presumptive evidence of the presence of gunshot residue. Many analyses are inconclusive because the amounts of antimony and barium (lead) are less than certain “thresholds” considered necessary because these elements are not unique to gunshot residue. Firings from .22 caliber weapons, unless the cartridge is known to be a Federal brand, are not usually analyzed because domestic rimfire primers, except Federal, do not contain antimony. Understandably, there has been great interest in alternative analysis methods capable of furnishing additional information of potentially higher specificity for gunshot residue.

Variation of the chemical contents and morphology of gunshot residue in the surroundings of the shooting pistol as a potential contribution to a shooting incidence reconstruction

“…The following assumptions were made in order to simplify the calculations: all particles were of spherical shape (that remains in agreement with the observation that as much as 70% of metallic particles are of spherical shape, see e.g. [3]), they revealed homogenous chemical content and the density of particles composed of more than one element was an average value of densities of the constituting elements. Therefore, similarly as in article [21], for each location studied and each of the chemical class of particles parameter j, being a reciprocal value of multiplication of the particle diameter and its density was calculated:…”

“…For the purpose of proving that a person was present in a close vicinity of a firing gun, GSR ought to be characterised by both, the specific element content being related mainly to the composition of the primer mixture and their morphology of molten and suddenly cooled droplets of metals revealing sizes in the range from submicrometers to several micrometers. The most popular method simultaneously providing information on the two features is scanning electron microscopy combined with energy dispersive Xray spectrometry (SEM-EDX) [2][3][4][5][6]. Automation of the analytical process of GSR examinations with this method was successfully solved helping an operator in the arduous process of location and chemical classification of particles [7].…”

Distribution and properties of gunshot residue originating from a Luger 9mm ammunition in the vicinity of the shooting gun

“…The following assumptions were made in order to simplify the calculations: all particles were of the spherical shape (that remains in agreement with the observation that as much as 70% of metallic particles are of the spherical shape, see, e.g. [3]), they revealed a homogenous chemical content and the density of particles composed of more than one element was an average value of the densities of the constituting elements.…”

“…A classification scheme of metallic particles introduced by Wolten et al [3][4][5], later modified by Wallace and McQuillan [6] was widely accepted by gunshot residue examiners and used for more than two decades. According to the scheme three-component particles containing lead, antimony and barium are unique primer residues.…”

Tiro-aztarnen identifikazioa, auzitegi-laborategien erronka

“…Partikula ez-organikoen analisirako erabili izan diren teknika analitikoak aktibazio neutroniko bidezko analisia (NAA) [20], xurgapen atomikoko espektroskopia (AAS) [21,22], foto-luminiszentzia [23,24], akoplamendu induktibozko plasma-emisio atomikoko espektrometria (ICP-AES) [25], akoplamendu induktibozko plasma-masa espektrometria (ICPMS) [26,27], ekorketa bidezko mikroskopia elektronikoa (SEM) [28] eta teknika elektrokimikoak dira [29].…”