Forensic Examination and Interpretation of Tool Marks

DAVID BALDWIN Baldwin Forensic Consultancy, Formerly of Forensic Science Service Ltd, LondonJOHN BIRKETT Formerly of Forensic Science Service Ltd, LondonOWEN FACEY Staffordshire UniversityGILLEON RABEY Formerly of Forensic Science Service Ltd, London

• About the Authors xiSeries Foreword: Essentials of Forensic Science xvForeword xviiPreface xxiAbout the Companion Website xxv1 Introduction 11.1 Overview of contents 11.2 A brief history of tool marks 41.3 General aspects of marks’ comparison 71.4 Training requirements for examiners 81.5 Good forensic practice 101.6 Examination and comparison strategy 111.6.1 Analysis 111.6.2 Comparison 121.6.3 Evaluation 121.6.4 Verification 121.7 Environment and equipment 131.7.1 Basic requirements 131.7.2 Examiner’s ‘toolbox’ 141.7.3 Test mark and casting materials 141.7.4 Larger equipment 171.7.4.1 The comparator 181.8 Quality assurance 221.9 A brief summary 23References 242 Tool Manufacture 252.1 Introduction 252.2 Working with metal 282.3 Creating a tool ‘blank’ 292.3.1 Forging 302.3.2 Blanking and shearing 312.3.3 Metal cutting operations 322.4 Finishing processes 342.5 Wear, corrosion and damage 45References 513 Scene Examination 533.1 Examining and recording the scene 533.2 General preliminaries 543.2.1 Verifying the circumstances 543.2.2 Recording the scene 543.2.3 Scene to scene linking 553.2.4 Packaging 553.3 Forced entry marks—levering 563.3.1 Recovery of levering marks 583.4 Forced entry marks—other 633.4.1 Hammer-type attack 643.4.2 Gripping tool attacks 653.4.3 Motor vehicle entry 663.5 Entry by cutting 673.5.1 Padlock removal 683.5.2 Breached security systems 693.6 Theft of metal 723.7 Examination of machines 733.8 Pathology samples 743.9 Collecting suspect tools 77References 794 Initial Laboratory Examination 814.1 General preliminaries 814.1.1 Receiving items 814.1.2 Planning the examination 824.1.3 Preparing for the examination 844.1.4 Collecting the items 844.1.5 Decontamination of item packaging 844.1.6 Operating procedures 844.1.7 Recording and opening the packaging 854.1.8 Description of the item 864.1.9 Examination of the item 864.2 Mainly impressed marks 864.2.1 Levering marks 874.2.2 Impact marks 894.2.3 Gripping marks 894.2.4 The tool(s) 904.3 Mainly dynamic marks 914.3.1 Levering marks with striations 924.3.2 Cutting and stabbing marks 924.4 Saw marks 994.5 Post-mortem samples 1054.6 Alphanumeric punches 1084.7 Using tool marks for intelligence purposes 1114.7.1 Type and size of tool 1114.7.2 Scene-to-scene linking without a tool 1114.7.3 Scene-to-scene linking using a tool recovered from a scene 1124.7.4 Linking suspect’s tool(s) to previously unsuspected scenes 1124.7.5 Setting up a database 112References 1135 Detailed Laboratory Examination 1155.1 First considerations 1155.2 Presentation of material to the comparator 1165.3 Impressed marks 1195.4 Marks with striations 1235.4.1 Sliding marks 1245.4.2 Double-bladed cutting tools 1285.4.3 Stab marks (in tyres and bones) 1315.5 Saw marks 1365.5.1 Initial and final cuts 1365.5.2 Sawn ends 1375.6 Specialised marks 1395.6.1 Alphanumeric punches 1395.6.2 Drill marks 1435.6.3 Slide hammers 1445.6.4 Pipe cutters 1465.7 Other considerations 1475.7.1 Test marks made in situ 1475.7.2 Amount of detail required for comparison 1485.7.3 Use of a scanning electron microscope (SEM) 148References 1506 Interpretation and Evaluation 1516.1 Introduction 1516.1.1 Interpretation 1516.1.2 Evaluation 1536.1.3 Interpretation and evaluation 1556.1.4 Scene-to-scene linking 1576.2 Considerations as the laboratory examination progresses 1576.2.1 Eliminations and inconclusive evidence 1576.2.2 Identifications and levels of support 1586.3 Other considerations 1666.4 Verification 1706.5 After the examination 1716.6 Quality assurance 172References 1737 Manufacturing Marks: Involving Tool Mark Related Examinations 1757.1 Introduction 1757.2 Screws 1767.3 Insulated cable 1787.4 Copied coins 1797.5 Security ties/tags 181Reference 1828 Physical Fits: Involving Tool Mark Related Examinations 1838.1 Introduction 1838.2 Scene examination 1858.3 Categories of physical fit and laboratory examination 1868.3.1 Jigsaw fits 1868.3.1.1 Multiple broken pieces 1878.3.2 Physical fits requiring tool mark skills 1888.3.3 Physical fits requiring knowledge of manufacturing detail 1908.3.3.1 Broken items 1908.3.3.2 Cut items 1918.3.4 Contact ‘fits’ 1928.4 Evaluation 1939 Plastic Film Examinations 1979.1 Introduction 1979.2 The ‘blown film’ process 1999.2.1 Extrusion 1999.2.2 Bag production and construction 2019.2.2.1 Heat sealing, perforating and cutting 2019.2.2.2 Gussets 2039.2.2.3 Press seals 2039.2.2.4 Printing 2039.3 Laboratory considerations 2059.3.1 Preliminaries 2059.3.2 Equipment 2069.4 Laboratory examination and evaluation 2089.4.1 Pigmented bags 2099.4.1.1 One unknown bag versus one known bag 2099.4.1.2 Unknown bag(s) versus a roll/set of known bags 2119.4.2 Self-seal bags 2139.4.3 Wrapping film 2149.4.4 Self-adhesive tape 215References 21710 Summary 219References 220Glossary 223Index 237

“An excellent resource that would find a prominent place in an organisation’s library, a legal library and a forensic scientist’s personal library.”  (The Chartered Society of Forensic Sciences, 1 January 2015)