Forensic DNA Transfer

Forensic DNA Transfer provides a guide to the recognition and current understanding of DNA transfer in forensic criminal investigations. Increased improvements in technology mean that it is now routinely possible to obtain DNA profiles from non-visible deposits. How or when the DNA in question was deposited may be an issue in the context of the case, especially if the donor of the DNA is not in dispute. A DNA profile alone cannot reveal when or how that DNA was deposited at a crime scene, nor can it reveal the body matter from which it originated. Issues of transfer associated with activities may be debated—which the traditional discrimination purpose of DNA profiling cannot address.DNA may be everywhere and anywhere—in homes, at workplaces, during transport, and on personal items including clothing. DNA from a person may be on an object they have never contacted or in a room they have never entered. Concepts discussed in the book include non-self DNA on hands through day-to-day activities, the prevalence of background DNA in the environment and perhaps on the exhibit, the persistence of any DNA transferred, and that a DNA result will depend on these variables as well as recovery techniques. Since DNA may be transferred to an exhibit: (a) during the commission of a crime, (b) before the crime, and/or (c) after the crime through handling, examination, and testing, this book covers various transfer pathways and sources of DNA. Documented cases of inadvertent transfer of DNA resulting in wrongful convictions or the misdirection of criminal investigations are discussed—with an emphasis on contamination mitigation throughout the entire process.Forensic DNA Transfer examines the additional complexity resulting from non-visible deposits of DNA that impact on sampling and testing regimes. The changing understanding of the composition of purported'touch DNA'deposits from the skin, including extracellular DNA transported via body secretions, is described. Further, the newer focus on interpreting DNA evidence—using activity level propositions and the rationale and associated issues—is also discussed. This book provides a guide to the recognition and current understanding of DNA transfer in forensic criminal investigations. Cover 1 Half Title 2 Title Page 4 Copyright Page 5 Table of Contents 6 Preface 12 Acknowledgements 17 About the Author 18 Chapter 1 Transfer of Matter 22 1.0 Introduction 22 1.1 Principles of Transfer 23 1.2 Transfer of Visible Trace Material 25 1.2.1 Early Experimental Data and Application to Crimes 25 1.2.2 Transfer of Debris 27 1.3 Transfer of Non-visible Trace Material 30 1.4 Transfer of Visible and Non-visible Biological Deposits 30 1.5 Technology Enhancements and Limitations 34 1.5.1 Increasing Technology 34 1.5.2 Context 37 1.6 Changing Forensic Science Landscape 39 1.6.1 Forensic Science Practice 39 1.6.2 Forensic Science Literature 41 References 43 Chapter 2 DNA 46 2.0 Introduction 46 2.1 Meaning of DNA 48 2.2 Where DNA Is Found 49 2.3 Association of Biological Matter to a DNA Profile 54 2.3.1 Body or Somatic Origin 54 2.3.2 Source Attribution 55 2.3.3 Association Error 58 2.3.4 Transfer Association Error 59 2.4 The Scientific Method 61 2.5 The Likelihood Ratio 61 2.5.1 Origin 61 2.5.2 Formulation 62 2.5.3 Transposition of the Conditional 64 2.6 Hierarchy of Propositions 67 2.6.1 Definitions 67 2.6.2 Investigative and Evaluative Opinions and Reporting 71 2.7 Relevance of DNA to Criminal Investigation 71 2.7.1 Ignoring Context 71 2.7.2 Undermining DNA Evidence 73 2.8 Relevance of DNA Transfer to Criminal Investigation 74 References 76 Chapter 3 TRACE DNA 80 3.0 Introduction 80 3.1 Definition of ‘Trace DNA’ versus ‘Touch DNA’ 83 3.2 Trace DNA Transfer 87 3.2.1 History 87 3.2.2 Terminology of DNA Transfer 89 3.3 Speculative Recovery of Trace DNA 98 3.3.1 Recognition and Preservation 98 3.3.2 Relocation of DNA 100 3.3.3 Collecting Trace DNA Deposits – Sampling and Testing Rationale 108 3.4 Trace DNA Quantities 111 3.5 No Relevant Deposit Detected 111 3.6 Context of Trace DNA 116 References 117 Chapter 4 Trace DNA Sources 122 4.0 Introduction 122 4.1 Skin Contact 124 4.1.1 Human Skin 124 4.1.2 Self-DNA from the Hands 124 4.1.3 ‘Self-DNA’ from Skin from the Body 127 4.2 Non-self DNA on Skin from the Body 127 4.2.1 Non-self DNA on Hands 127 4.2.2 Non-self DNA from Areas of the Body 135 4.3 Shedder Status 136 4.4 ‘Wearer’ or ‘User’ DNA on Clothing or Other Personal Items 139 4.4.1 ‘Wearer’ DNA on Clothing 140 4.5 Background DNA 142 4.5.1 Definitions 142 4.5.2 Analysis of Background DNA 143 4.5.3 Homes and Offices 144 4.5.4 Motor Vehicles 144 4.5.5 Controls 145 4.6 Persistence of DNA 146 4.6.1 Introduction 146 4.6.2 Persistence and Time of Deposit for DNA from Different Body Sources 146 4.6.3 Persistence of DNA After Use 148 4.6.4 Persistence of DNA after Cleaning/Washing 151 4.7 Priority-based Recovery, Detection and Analysis 152 4.7.1 Principles 152 References 153 Chapter 5 Medical Exhibits 158 5.0 Introduction 158 5.1 Sexual Assault Investigation Kits 160 5.1.0 Introduction 160 5.1.1 Female Genital Medical Samples: Vaginal and Vulval Swabs 162 5.1.2 Spermatozoa Presence and Persistence in the Vagina 162 5.1.3 Post-mortem Medical Samples 167 5.1.4 Y-STR Profiling 167 5.1.5 Persistence of Male DNA in the Vaginal Cavity 168 5.1.6 Background Levels of Male DNA in the Vagina 170 5.1.7 Vulval Swabs 171 5.2 Rectal and Oral Cavities 172 5.3 Male Intimate Swabs – Penile Swabs 173 5.3.1 Sampling Rationale 173 5.3.2 Activity-level Propositions 174 5.4 Fingernails 177 5.4.1 Collection, Transfer and Persistence 177 5.4.2 Association Fallacies 180 5.5 Areas of Skin 182 5.6 Abandoned Material 182 References 185 Chapter 6 Clothing and Implements 188 6.0 Introduction 188 6.1 Clothing 190 6.1.1 ‘Wearer’ and ‘Toucher’ DNA 190 6.1.2 Location of DNA on Clothing 191 6.1.3 ‘Touching’ a Garment by a Person of Interest 199 6.1.4 Clothing on Flooring 205 6.1.5 Washing of Clothing 205 6.1.6 Fabric Gloves 207 6.2 Knives 210 6.2.1 Direct Transfer of DNA to Knives 210 6.2.2 Indirect Transfer of DNA to Knives 213 6.3 Firearms 215 6.3.1 DNA on Firearms 215 6.3.2 Levels of DNA Transfer 220 6.4 Equipment and Implements 221 6.4.1 Persistence of DNA on Equipment and Implements 221 6.5 Communal Items and Spaces 222 6.5.1 Direct and Indirect Transfer of DNA 222 6.5.2 Public Spaces 222 6.5.3 Office and Work Spaces 223 References 225 Chapter 7 Inadvertent DNA Transfer 229 7.0 Introduction 229 7.1 Importance of Quality Procedures, Documentation and Contamination Mitigation 231 7.2 Personal Protection Equipment 238 7.3 Crime Scene 241 7.3.1 Collection of Exhibits 241 7.3.2 Photographs and Video Recordings 242 7.4 The Mortuary 246 7.5 Medical Examination 246 7.6 Packaging, Handling and Storage 247 7.6.1 Handling 247 7.6.2 Packages or Exhibit Bags 248 7.6.3 Storage Facilities 250 7.7 Police and Other Laboratories 256 7.7.1 Police and Other Laboratories Prior to Submission to Forensic Biology Laboratory 256 7.7.2 Fingerprint Laboratories 257 7.8 The Forensic Biology Laboratory 258 7.8.1 Surfaces, Tools and Equipment 258 7.8.2 Cold Cases 261 7.8.3 Control Samples 262 7.9 Staff DNA Elimination Databases 264 7.9.1 Forensic Laboratories 264 7.9.2 Police Staff Contamination 266 References 268 Appendix A: Principles of Forensic DNA Transfer 272 Appendix B: Flawed Logic and Forensic DNA Transfer 277 Glossary of Terminology 286 Index 292 forensic,science;,forensic,biology;,secondary,transfer;,DNA,transfer;,trace,DNA;,presumptive,test;,forensic,DNA;,mtDNA;,DNA,profile;,forensic,serology;,forensic,genetics;,likleihood,ratios forensic science,forensic biology,secondary transfer,DNA transfer,trace DNA,presumptive test,forensic DNA,mtDNA,DNA profile,forensic serology,forensic genetics,likleihood ratios