Postmortem alterations on gunshot wounds in ribs recovered from the marine environment
Lindström, Anne-Christine Gudrun Erna
This thesis contributes to the understanding of the persistence of gunshot residue (GSR) in tissues during decomposition in a marine environment. The thesis also aims to shed light on the isotope exchange in bone when exposed to the marine environments. The first part of the thesis describes two studies that looked at the retention and distribution of GSR on fleshed and defleshed bony specimens. New and novel combinations of qualitative and quantitative data were obtained by studying bony gunshot wounds (GSWs). Fleshed and defleshed bovine ribs were shot at contact range with .22 calibre hollow point ammunition using a Stirling .22 calibre long rifle. Triplicates were placed in three habitats: submerged, intertidal and supralittoral. Decomposition was examined on 3, 10, 24 and 38 days and analysed with SEM-EDX and ICP-MS. The presence of GSR was recorded using SEM-EDX and persisted on defleshed bones over the full course of the study. On fleshed specimens, GSR persisted on intertidal and supralittoral samples but only up to ten days on submerged. Using ICP-MS for both groups GSR disappeared faster from submerged and intertidal samples compared to supralittoral samples. SEM-EDX, ICP-MS and micro-computed tomography were used to look at the composition of GSR, its distribution on bony GSWs and the effect of overlying softtissue. Entry and exit wound morphology and the distribution of GSR was examined. Greater bony destruction was associated with the presence of overlying soft tissue. In an additional study hollow point and round nose .22 calibre lead (Pb) bullets used, showed similar morphological wounding profiles prior to the marine decomposition study. On defleshed ribs, GSR was irregularly dispersed throughout the wound, with the highest concentrations at entry. In contrast, fleshed bony wounds had more evenly distributed but lower elemental abundances. Shot bone and unshot bone could be distinguished by the presence and concentration of Sb, Ba and Pb. These results highlight the potential of microscopic and analytical methods for examining suspected GSWs in highly decomposed bodies in marine habitats. The second part of the thesis aims to shed light on isotope exchange in bones exposed to a marine environment. Pulverised bone samples from bovine ribs that have been decomposing in the above-mentioned study were chemical treated with hydrogen peroxide (H2O2) and the carbon and oxygen carbonate isotope ratios were analysed with a Thermo mass spectrometer. No significant changes in these ratios were observed over time within or between each environment. However, alteration in the isotope values due to chemical treatments was noted, which highlights the importance of developing a proper standard method for this type of analysis.
Advisor: Kieser, Jules; Hoogewerff, Jurian; Duncan, Warwick; Waddell, Neil
Degree Name: Doctor of Philosophy
Degree Discipline: Sir John Walsh Research Institute, Dentistry
Publisher: University of Otago
Research Type: Thesis