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Title: Classification of barrel rifling transitions for the forensic identification of firearms
Author: Bolton-King, Rachel Sarah
Awarding Body: Nottingham Trent University
Current Institution: Nottingham Trent University
Date of Award: 2012
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This thesis investigates the shape of transitions located between adjacent lands and grooves of rifled internal pistol barrel surfaces. The variations in the transition structure, which arise from gun design and manufacturing processes, are extracted by microscopically imaging the physical cross-sections of cast barrel bores. This approach was informed by a preliminary study, which examined the suitability of a number of different image measurement modalities. The analysis of the resultant curvilinear image structures is undertaken using a numerical pattern recognition method specifically developed for this application. The hypothesis that transition shape is a basis for discrimination and identification is robustly supported by this work. Binarised transition images are processed with fast Fourier transform on which principal component analysis (PCA) is performed. One-way analysis of variance (ANOVA, a = 0.05) concludes significant differentiation between 11 barrel manufacturers when calculating weighted Euclidean distance (WED) between any trio of land transitions and an average land transition for each barrel in the database. The quantitative PCA method is also applied to illustrate the high consistency in transition profile for hammer forged SIG Sauer 9x19 mm pistols manufactured in the same and different batches using one-way ANOVA (a = 0.01) and that wear in the barrel may be located towards the chamber throat after a significant period of use. Forged and cut methods of rifling utilised during the barrel manufacturing process are also demonstrated to be differentiated by comparing the mean and standard deviation of matching WED datasets; higher values infer the broach cut method, which produces more variable land transition geometries within the barrel. The use of curvilinear transition geometries as an additional class characteristic, combined with the proposed method is a promising novel approach for the classification, identification and evaluation of firearm manufacturers. This significant outcome shows the future potential for previously unexploited surface features to be utilised for identification by practitioners in the field of firearms and toolmark examination.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available