Bullets (n = 12) from four different types of ammunition were selected for this study (Action 4, n = 3; QD-PEP, n = 3; Hydra-Shok, n = 3; 7.65 Browning, n = 3) (Fig. 1). The bullets were divided into two groups according to their core materials. One group (copper group, n = 6) included the unjacketed Action 4 and QD-PEP bullets, which are composed of copper. These solid copper bullets are deformation bullets that were developed for law enforcement units. The other group (lead group, n = 6) included the Hydra-Shok and 7.65 Browning bullets, which are frequently encountered lead bullets with jackets composed of copper-zinc alloys (copper/zinc). The Hydra-Shok bullet is a semi-jacketed hollow-point (deformation) bullet, while 7.65 Browning bullets (which are also referred to as .32 ACP bullets) are full metal-jacketed bullets. From each type of ammunition, three bullets were fired into animal cadaver models at a dedicated shooting range. Sheep legs were used as a substitute for human tissue. The shootings were performed by a ballistics expert from a forensics institute. After shooting, each sheep leg was scanned by CT.
Action 4 (a), QD-PEP (b), Hydra-Shok (c), and 7.65 Browning (d) bullets were fired into animal cadaver models at a dedicated shooting range. Then, computed tomography scans of the animal cadaver models with lodged copper bullets (a, b) and lodged lead bullets (c, d) were performed
jacketed performance with cast bullets pdf download
Additionally, the distinction between copper and lead bullets was assessed in real forensic cases with fatal gunshot wounds and lodged bullets. The decedents (n = 15) underwent postmortem imaging as part of forensic judicial investigations. Ethical approval was waived by the responsible ethics committee. The bullets were removed during autopsy and identified by the forensics institute. Before the bullets were removed, the decedents underwent a CT examination using the same scanner used for the animal cadaver study. The CT scan protocol from the animal cadaver study was used. Decedents with a lodged Action 4 copper bullet (n = 3) and decedents with a lodged .22 LR lead bullet (n = 3) were selected for this study.
The difference between using CT numbers from a single energy and the DEI for the distinction between copper and lead bullets within the animal cadaver models was assessed by considering the energy level, the use of the mean and maximum CT numbers, and the ROI position (core or edge). The two groups of bullets were compared using statistical analysis, standard deviations, and data overlap. Finally, the most suitable method with the lowest standard deviations and the smallest data overlap was applied and assessed in real forensic cases.
The core-based 80/100 dual-energy index (DEI)max (a), the core-based 80/120 DEImax (b), the edge-based 100/120 DEImean (c), the edge-based 100/120 DEImax (d), the edge-based 120/140 DEImax (e), and the edge-based 120/140 DEImax (f) yielded statistically significant differences between the two groups of bullets (x-axis: Action 4 bullets, 1-3; QD-PEP bullets, 4-6; Hydra-Shok bullets, 7-9; 7.65 Browning bullets, 10-12). While large overlaps are visible for core measurements, the copper group visibly differed from the lead group in terms of the DEI calculated from edge measurements. Only the edge-based 120/140 DEImax resulted in a clear dividing line between the two groups of bullets (green dashed line). The Hydra-Shok no. 2 (bullet number 8 on the x-axis), which was separated from its jacket, yielded lower values than all other copper/zinc-jacketed lead bullets.
Some limitations of this study should be noted. First, only bullets composed of copper or lead were investigated. However, these are the most frequently encountered types of bullets [27, 28]. Other metallic components, such as steel, bismuth, and tungsten, are much less often used for the bullet core, while steel is more frequently used for the jackets of bullets. To distinguish ferromagnetic steel-jacketed bullets from non-ferromagnetic non-steel-jacketed bullets, different studies yielded contradictory results [17, 29] since the type of metal used for the core of the bullet (usually copper or lead) was not considered [18, 29]. Notably, some bullets have different core metals at the point than at the body. Second, only a small number of bullets were used in this study, consequently minimising the statistical power of the results. Additionally, the ROIs at the edges of the bullets contained only a small number of pixels (see Fig. 2). Despite the small number of bullets used in the animal cadaver study and the small number of pixels in the ROIs, the selected 120/140 DEImax was successfully applied to decedents. Third, intra-observer agreement and inter-observer agreement were not tested in this study. However, a previous study [26] reported negligible observer variabilities for ROI measurements. Fourth, inter-scanner variability was not assessed in this study. Fifth, a potential benefit of using the dual-energy technique could not be assessed since the dual-energy data do not allow ECTS reconstructions. Additionally, CT numbers above the upper limit of the ECTS had to be excluded in this study.
2ff7e9595c
Comments