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Modelling Cranial Gunshot Wounds and Backspatter

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Modelling Cranial Gunshot Wounds and Backspatter MODELLING CRANIAL GUNSHOT WOUNDS AND BACKSPATTER Gemma Elizabeth Radford A thesis submitted in partial fulfillment for the degree of Master of Science At the University of Otago, Dunedin, New Zealand. December 2009 II Abstract Bloodspatter from gunshot wounds may be divided into two categories; forward spatter and backspatter. Forward spatter is ejected from the exit wound and travels in the same direction as the bullet. Backspatter on the other hand is ejected from the entrance wound and travels against the line of fire, back towards the shooter. This means it is commonly deposited on the hand of the shooter or the firearm, making it a critical piece of evidence when determining the manner of death. Despite this fact, research in this area is limited and no realistic synthetic model for studying backspatter has been documented in the literature. This project was initiated in response to this, in an attempt to create a realistic cranial model that could produce backspatter from a gunshot wound. A pig head model was developed, as it could be validated unlike a human model. This model consisted of synthetic skin, soft tissue and bone layers which completely enclosed a volume of gelatine to represent the brain. The model was tested at a firing range, along with butchered pig heads and live pigs and the results were compared. A high-speed camera was used to film each shot, in order to record key events in slow motion. The resultant wounds, the high-speed videos, and the backspatter produced were analysed and compared. The model was comparable with pigs in relation to the backspatter produced and there were also similarities between the resultant wounds. The development of this pig model has therefore laid the foundations for creating a realistic human head backspatter model in the future. It was concluded that, with further development and testing, the model could potentially be a useful tool for forensic scientists, particularly in aiding their understanding and interpretation of backspatter from gunshot fatalities. III Acknowledgements This year has been exciting and challenging and I am so happy I was given the opportunity to carry out such a novel project. It would not have been possible without the help of a number of people. Firstly I would like to thank my supervisors; Professor Jules Kieser (School of Dentistry), Dr. Michael Taylor (ESR, Christchurch) and Professor Mark Stringer (Department of Anatomy and Structural Biology). Their support and encouragement was invaluable and I feel very privileged to have had them guiding me. I would especially like to thank Jules for agreeing to supervise me and bringing out the best in me as a researcher. I would also like to thank Mr. Neil Waddell (School of Dentistry), who acted like a supervisor throughout and advised me on the technical aspects of the project. Mr. Kevan Walsh (ESR, Auckland) was also incredibly helpful. The undertaking of this project was made much easier by the help of a number of people within the University of Otago; Dr. John Schofield, Mrs. Lesley Schofield, Mr. Alistair McCullum and Mr. Dave Matthews from the Animal Welfare Office, Dr. Peter Davidson from the Injury Prevention Unit, Professor Michael Swain, Dr. Daryl Tong and Jenine Upritchard from the School of Dentistry. A number of organisations also made the experimental aspects of this project possible; The Otago Pistol club, Local Action Lighting Company, The Dunedin Police, HTRU, New World Supermarket butchery and Outram Home-kill Butchery. I also wish to show my appreciation to Nicole Bond, Rebecca Calwell, Sue Wilson and Nina Planitz who each helped out with different shooting experiments. These were long (and freezing) days so I am very grateful for all your help. IV Also within the university, I would like to thank my office mates; Darnell Kennedy, Sarah Weller and Vanda Symons - they made every day interesting and always kept me entertained. Thank you for putting up with my pig heads and bloodspattered papers in the lab! I would also like to thank the rest of the Forensic Biology group, in particular Gemma, Shelley and Francis, for supporting and encouraging me. Lastly I would like to thank my family and friends for supporting me unconditionally and always having faith in me. Mum and Dad – thank you for your advice and support. Esther, Matthew and Katherine – thanks for keeping me humble and always making me laugh! And finally to Cory, thank you for your support and for keeping me motivated when times got tough. V Table of contents Abstract............................................................................................................................. II Acknowledgements .........................................................................................................III List of Figures....................................................................................................................X List of Tables ................................................................................................................XIII List of Abbreviations ................................................................................................... XIV Chapter 1: Introduction ............................................................................... 1 1.1 Wound Ballistics ..........................................................................................................3 1.1.1 Mechanisms of Injury .................................................................................................3 1.1.2 Determinants of Injury................................................................................................6 1.1.3 Tissue Simulants .......................................................................................................10 1.1.4 Handgun Ballistics....................................................................................................12 1.2 Gunshot Wounds........................................................................................................13 1.2.1 Range ........................................................................................................................13 1.2.2 Exit Wounds..............................................................................................................18 1.2.3 Gunshot Wounds in Bone .........................................................................................19 1.3 Backspatter.................................................................................................................21 1.3.1 Significance...............................................................................................................21 1.3.2 Mechanisms of Production .......................................................................................22 1.3.3 Case-study Observations...........................................................................................24 1.3.4 Experimental Research .............................................................................................26 1.4 Summary.....................................................................................................................33 1.5 Aims and Objectives ..................................................................................................33 1.6 Experimental Approach ............................................................................................34 1.7 Experimental Design..................................................................................................34 Chapter 2: General Methods ..................................................................... 36 2.1 Testing.........................................................................................................................36 VI 2.1.1 Shooting Set-up.........................................................................................................36 2.1.2 High-speed Camera and Lighting .............................................................................38 2.1.3 Firearm and Shooting Distance.................................................................................39 2.2 Analysis of Results .....................................................................................................40 2.2.1 Entrance Wounds......................................................................................................40 2.2.2 High-speed Videos....................................................................................................40 2.2.3 Backspatter................................................................................................................40 Chapter 3: Pig Head Model ....................................................................... 42 3.1 Introduction................................................................................................................42 3.2 Aim ..............................................................................................................................42 3.3 Materials and Methods..............................................................................................42 3.3.1 Materials ...................................................................................................................42 3.3.2 Methods.....................................................................................................................46 3.4 Results .........................................................................................................................50 3.4.1 Entrance
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