Stable Isotope Forensics

Wolfram Meier-Augenstein, PhD is Professor in Stable Isotope Forensics at the Robert Gordon University in Aberdeen, Scotland, UK. He is a registered expert advisor with the National Crime Agency (NCA, UK) and holds a Diplom-Chemiker degree, as well as a Doctorate in Bio-organic Chemistry, both awarded by the University of Heidelberg, Federal Republic of Germany. Dr. Meier-Augenstein has assisted police forces and coroners' offices around the world in murder enquiries and drug-related crime investigations.

Series Foreword xi

Foreword: Dame Sue Black xiii

Foreword: Mark Harrison xv

Foreword to the 1st Edition xvii

Book Endorsements xix

Preface to the 2nd Edition xxi

List of Abbreviations xxv

About the Companion Website xxvii

Introduction: Stable Isotope ‘Profiling’ or Chemical ‘DNA’:

A New Dawn for Forensic Chemistry? xxix

I How it Works 1

I.1 What are Stable Isotopes? 2

I.2 Natural Abundance Variation of Stable Isotopes 4

I.3 Chemically Identical and Yet Not the Same 12

I.4 Isotope Effects, Mass Discrimination and Isotopic Fractionation 15

I.4.1 Physical Chemistry Background 15

I.4.2 Fractionation Factor α and Enrichment Factor ε 17

I.4.3 Isotopic Fractionation in Rayleigh Processes 19

I.4.3.1 Isotopic Fractionation Summary 20

I.5 Stable Isotopic Distribution and Isotopic Fractionation of Light Elements in Nature 22

I.5.1 Hydrogen 22

I.5.2 Oxygen 26

I.5.3 Carbon 27

I.5.4 Nitrogen 30

I.5.5 Sulfur 32

I.5.6 Isoscapes 35

I.6 Stable Isotope Forensics in Everyday Life 40

I.6.1 “Food Forensics” 42

I.6.1.1 Authenticity and Provenance of Single-Seed Vegetable Oils 42

I.6.1.2 Authenticity and Provenance of Beverages 45

I.6.1.3 Caveats 49

I.6.2 Authenticity and Provenance of other Premium Products 53

I.6.3 Counterfeit Pharmaceuticals 54

I.6.4 Environmental Forensics 59

I.6.5 Wildlife Forensics 61

I.6.6 Anti-Doping Control 62

I.7 Summary of Part I 65

References Part I 67

II Instrumentation, Analytical Techniques and Data Quality 81

II.1 Mass Spectrometry versus Isotope Ratio Mass Spectrometry 82

II.1.1 Stability, Isotopic Linearity and Isotopic Calibration 85

II.2 Instrumentation for Stable Isotope Analysis 90

II.2.1 Dual-Inlet IRMS Systems 92

II.2.2 Continuous-Flow IRMS Systems 93

II.2.3 Bulk Material Stable Isotope Analysis 94

II.2.3.1 13C, 15N and 34S 94

II.2.3.2 2H and 18O 96

II.2.4 Compound-Specific Stable Isotope Analysis of Volatile Organic Compounds 98

II.2.4.1 Compound-Specific 13C or 15N Analysis by GC/C-IRMS 98

II.2.4.2 Compound-Specific 2H or 18O Analysis by GC/HTC-IRMS 100

II.2.4.3 Position-Specific Isotope Analysis 101

II.2.5 Compound-Specific 13C/15N Analysis of Polar, Non-Volatile Organic Compounds by LC-IRMS 101

II.2.6 Compound-Specific Isotope Analysis and Forensic Compound Identification 103

II.3 Quality Control and Quality Assurance in Continuous-Flow Isotope Ratio Mass Spectrometry 106

II.3.1 Compliance with IUPAC Guidelines is a Prerequisite not a Luxury 106

II.3.2 The Identical Treatment Principle 111

II.3.3 The Importance of Scale Normalization 112

II.3.3.1 Scale Normalization of Measured δ2H Values to VSMOW 114

II.3.3.2 Scale Normalization of Measured δ13C Values to VPDB 120

II.3.3.3 Scale Normalization of Measured δ18O Values to VSMOW 122

II.3.3.4 Scale Normalization of Measured δ15N Values to Air 126

II.3.3.5 Scale Normalization of Measured δ34S Values to VCDT 127

II.4 Points of Note for Stable Isotope Analysis 128

II.4.1 Preparing for Analysis 128

II.4.2 Generic Considerations for BSIA 131

II.4.2.1 Scale Normalization of BSIA 132

II.4.2.2 Keeping Your Powder Dry 134

II.4.2.3 Isobaric Interference 135

II.4.2.4 Ionization Quench Effect 137

II.4.3 Particular Considerations for BSIA 140

II.4.3.1 Bulk 15N Analysis of Nitrates 140

II.4.3.2 Bulk 2H Analysis of Nitrogen-Rich Compounds 141

II.4.3.3 Total δ2H versus True δ2H Values 141

II.4.3.4 Organic Compounds with Exchangeable Hydrogen and Implications for 2H Abundance Analysis 144

II.4.3.4.1 Chemical and Biochemical Considerations – Example: Hair 152

II.4.3.5 2H Analysis of Human Hair 158

II.4.3.5.1 Two-Point Equilibration with Water at Ambient Temperature 161

II.4.3.5.2 Two-Point End-Member Comparative Equilibration 166

II.4.3.5.3 On-Line Two-Point End-Member Comparative Steam Equilibration 170

II.4.4 Points of Note for CSIA 172

II.4.4.1 Scale Normalization of GC-IRMS Analyses 172

II.4.4.2 Isotope Effects in GC-IRMS during Sample Injection 175

II.4.4.3 The Chromatographic Isotope Effect in GC-IRMS 176

II.4.4.4 Derivatization of Polar Compounds for GC-IRMS 178

II.4.4.5 Compound-Specific 2H Analysis of N- or Cl-Rich Compounds 181

II.5 Statistical Analysis of Stable Isotope Data within a Forensic Context 183

II.5.1 Chemometric Analysis 183

II.5.2 Bayesian Analysis 185

II.6 Quality Control and Quality Assurance in Forensic Stable Isotope Analysis 194

II.6.1 Accreditation to ISO 17025 195

II.6.1.1 Who Assesses the Assessors? 197

II.6.2 The Forensic Isotope Ratio Mass Spectrometry Network 205

II.7 Summary of Part II 207

II.A How to Set Up a Laboratory for Continuous-Flow Isotope Ratio Mass Spectrometry 209

II.A.1 Pre-Installation Requirements 210

II.A.2 Laboratory Location 210

II.A.3 Temperature Control 211

II.A.4 Power Supply 212

II.A.5 Gas Supply 213

II.A.6 Forensic Laboratory Considerations 216

II.A.7 Finishing Touches 217

II.B Sources of International Reference Materials and Tertiary Standards 219

II.C Selected Sample Preparation Protocols 220

II.C.1 Derivatization of Amino Acids for Compound Specific Isotope Analysis by GC-IRMS 220

II.C.2 Acid Digest of Carbonate from Bio-apatite for 13C and 18O Analysis 223

II.C.3 Preparing Silver Phosphate from Bio-apatite for 18O Analysis 225

II.C.4 Two-Point Water Equilibration Protocol for Determination of Non-ex δ2H Values of Human Hair 227

II.D Internet Sources of Guidance and Policy Documents 231

References Part II 233

III Stable Isotope Forensics: Case Studies and Current Research 247

III.1 Forensic Context 248

III.1.1 Legal Context 249

III.2 Distinguishing Drugs 255

III.2.1 Natural and Semisynthetic Drugs 255

III.2.1.1 Marijuana 255

III.2.1.2 Morphine and Heroin 257

III.2.1.3 Cocaine 259

III.2.2 Synthetic Drugs 263

III.2.2.1 Amphetamines 263

III.2.2.2 Methamphetamine: Synthesis and Isotopic Signature 264

III.2.2.2.1 Two Different Synthetic Routes – Clandestine Conditions 268

III.2.2.3 MDMA: Synthesis and Isotopic Signature 270

III.2.2.3.1 Three Different Synthetic Routes – Controlled Conditions 273

III.2.2.3.2 One Synthetic Route – Variable Conditions 279

III.2.3 “Legal Highs” and “Designer Drugs” 284

III.2.3.1 Mephedrone 284

III.2.3.2 Piperazines 287

III.2.4 Excipients 291

III.2.5 Conclusions 293

III.3 Elucidating Explosives 296

III.3.1 Stable Isotope Analysis of Explosives and Precursors 297

III.3.1.1 Ammonium Nitrate (AN) 298

III.3.1.2 Hexamine, RDX, C4 and Semtex 300

III.3.1.3 Isotopic Product/Precursor Relationship 305

III.3.1.3.1 RDX and HMX 305

III.3.1.3.2 HMTD and TATP 309

III.3.1.4 Hydrogen Peroxide 315

III.3.2 Potential Pitfalls 321

III.3.3 Conclusions 323

III.4 Matching Matchsticks 324

III.4.1 13C-Bulk Isotope Analysis 325

III.4.2 18O-Bulk Isotope Analysis 326

III.4.3 2H-Bulk Isotope Analysis 328

III.4.4 Matching Matches from Fire Scenes 330

III.4.5 Conclusions 331

III.5 Provenancing People 333

III.5.1 Stable Isotope Abundance Variation in Human Tissue 336

III.5.1.1 Hair and Nails 338

III.5.1.1.1 Characteristics of Hair 340

III.5.1.1.2 Characteristics of Nails 342

III.5.1.1.3 Diagenetic Changes of Keratin 342

III.5.1.1.4 2H Isotopic Record in Hair and Nail 343

III.5.1.1.5 18O Isotopic Record in Hair and Nail 345

III.5.1.1.6 13C Isotopic Record in Hair and Nail 346

III.5.1.1.7 15N Isotopic Record in Hair and Nail 347

III.5.1.2 Bone and Teeth 350

III.5.1.2.1 Chemical Composition of Bone and Teeth 351

III.5.1.2.2 Static versus Remodelling Tissue Compartments 352

III.5.1.2.3 Diagenetic Changes of Bone and Teeth Mineral 354

III.5.1.2.4 Diagenetic Changes of Type I Collagen 356

III.5.1.2.5 18O Isotopic Record in Carbonate and Phosphate from Bio-apatite 357

III.5.1.2.6 13C Isotopic Record in Carbonate from Bio-apatite 363

III.5.1.2.7 Isotopic Record in Type I Collagen 364

III.5.1.3 Trophic Level Shift Effect on Stable Isotope Abundance Values in Human Tissue 365

III.5.2 Case Examples 370

III.5.2.1 The Skull from the Sea 371

III.5.2.2 A Human Life Recorded in Hair 375

III.5.2.3 Found in Newfoundland 379

III.5.2.4 The Case of “The Scissor Sisters” 384

III.5.2.5 Too Short a Life 390

III.5.2.6 Saltair Sally 393

III.5.2.7 A Tale of Two Cultures 394

III.5.3 Conclusions and Caveats 397

III.6 Stable Isotope Forensics of Other Physical Evidence 401

III.6.1 Microbial Isotope Forensics 402

III.6.2 Toxins and Poisons 404

III.6.3 Paper, Plastic (Bags) and Parcel Tape 404

III.6.3.1 Paper 404

III.6.3.2 Plastic and Plastic Bags 407

III.6.3.3 Parcel Tape 408

III.6.4 Conclusions 412

III.7 Evaluative Interpretation of Forensic Stable Isotope Data 413

III.7.1 Not Scale Referenced δ-Values 415

III.7.2 Unresolved Contradictory Data 418

III.7.2.1 Example: “Geographic Provenance of a Murder Victim” 418

III.7.2.2 Example: “Manslaughter due to Negligence” 420

III.7.3 Foregone Conclusions 422

III.7.4 Logical Fallacies 424

III.7.5 Untested Assumptions 426

III.7.6 Conclusion 428

III.8 Summary of Part III 430

III.A An Abridged List of Forensic Stable Isotope Laboratories Worldwide 432

References Part III 434

Recommended Reading 453

Author’s Biography 459

Acknowledgements 461

Index 463