The Spatial Distribution of Post-blast Condensed Phase Explosive Residues Nadia Abdul-Karim Submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy at University College London 2015 1 Declaration I, Nadia Abdul-Karim, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis. 2015. 2 Abstract During bomb scene investigation the collection of trace explosive residue is a principal forensic task which allows the cause of the explosion to be determined. However the optimum locations around a detonation from where these undetonated trace residues should be sampled has not been determined scientifically. Crime scene investigation guides describe several methods for collecting and analysing explosive residues, but literature regarding the most efficacious areas to sample from is relatively scarce. In this thesis, analysis of the spatial distribution patterns of post-blast explosive residues from detonation and simulation experiments with 0.5 kg, 1 kg and 2 kg aluminised ammonium nitrate and RDX composition charges are the primary original contributions to the literature. Residue samples were collected by swabbing sample sites positioned around the explosive charges and condensed phase particles were collected onto smaller sample sites in order to ascertain the physical morphology of the residues. Both organic and inorganic residues ultimately decreased in concentration nonlinearly with increasing distance from the charge centre. However, the distribution trends between different explosive analytes varied, suggesting the dispersal mechanisms or factors which affected the distribution for each were different. The post-blast particles had varying morphologies at different distances from the detonation and also exhibited different features based on the explosive type. Computational simulations of residue distributions compared well to the experimental results; substantiating the capability of numerical methods to be used as a forensic investigation aid. The key findings from this thesis have provided empirical evidence which validates the current forensic practice of concentrating trace evidence collection near the central region of a detonation area during bomb scene investigation. The findings also imply that surfaces which are downwind of the detonation should be focused on for residue sampling and that microscopic examination of items in the vicinity of a detonation may allow identification of the explosive used based on particle morphology, prior to any chemical analyses. Furthermore, having demonstrated the reliability and capability of simulation techniques to model explosive residue distribution, these can now be developed and validated through further tests which also assess the detonations of further explosives under different conditions. 3 Table of contents Declaration……………………………………………………………………………………………………………...…...2 Abstract………………………………………………………………………………………………………………...….….3 Table of contents…………………………………………………………………………………………………...….….4 List of Figures………………………………………………………………………………………………………....……8 List of Tables ………………………………………………………………………………………………………..…….17 Acknowledgments……………………………………………………………………………………………….……..19 Presentations and Publications…………………………………………………………………………….……..20 Thesis outline……………………………………………………………………………………………………….….…21 Chapter 1: INTRODUCTION…………………………………………………………………………..…….….22 1.1 Background Information………………………………………………………………………………. …..23 1.1.1 Explosives…………………………………………………………………………….…….…………...23 1.1.2 Chemical Aspects of Explosion ……………………………………………….…………….…..25 1.1.3 Physical Aspects of Explosion………………………………………………….………………..27 Chapter 2: LITERATURE REVIEW……………………………………………………………..….…………30 2.1 Introduction……………………………………………………………………………………………..………..30 2.2 Explosive Residue Formation…………………………………………………………………….……….30 2.2.1 Factors Affecting Undetonated Residue Formation…………………..………..……….31 2.3 Explosive Residue Distribution…………………………………………………………………....……..32 2.3.1 Theoretical Studies…………………………….……………………………………………..………32 2.3.2 Experimental Research……………………..……………………………………………..………..37 2.4 Forensic Crime Scene Procedures…………………………………………………………….…………48 2.4.1 Post-blast Investigations…………………………………………………………………………..48 2.4.2 Explosive Residue Evidence………………………………………………………………………49 2.5 Technical Information.…………………………………………………………..…………….…………….51 2.5.1 Diagnostic Techniques during Firing……………………..………..…………………..…….51 2.5.2 Laboratory Analysis Techniques……………………………………..……..…………………..52 2.5.3 Computational Simulation………………………………………………..…………………….….54 2.6 Summary ……………………………………………………………………………………………………..……55 2.7 Aims and Objectives…………………………………………………………………………………………. 56 Chapter 3: MATERIALS AND METHODS……………………….………………………………………….. 57 3.1 Explosive Charges………………………………………………………………………………………….…..57 4 3.2 Experimental Designs………………………….…………………………………………………..…………59 3.2.1 Charge Positioning ………………………………………………………………………………59 3.2.2 Residue Sampling Sites…………………………………………………………………………60 3.2.3 Blast Pressure Measurements……………………………………………………………… 64 3.2.4 High Speed Imaging………………………………………………………………………….… 65 3.2.5 Meteorological Conditions…………………………………………………………….......... 65 3.3 Sample Collection ………………………………………………………………………………………………65 3.3.1 Residue Collection from Unconfined and Confined Firings ……………….……65 3.3.2 Particle Collection………………………………………………………………………….……. 66 3.4 Residue Analysis ……………………………………………………………………………………….………67 3.41 Swab Extraction Procedure…………………………………………………………….……..67 3.4.2 Ion Chromatography: NH4+ and NO3- Ions…………………………………………….68 3.4.3 Inductively Coupled Plasma–Atomic Emission Spectroscopy: Aluminium. 72 3.4.4 High Performance Liquid Chromatography – Mass Spectrometry: RDX…..72 3.5 Particle Analysis………………………………………………………………………………………………...78 3.5.1 Morphology and Elemental Composition (SEM-EDX) …………………………….78 3.5.2 Chemical Identity………………………………………………………………………………….79 3.6 Simulation…………………………………………………………………………………………………………80 CHAPTER 4: STUDIES WITH 0.5 KG ALAN AND PE4 CHARGES..……………………………….84 4.1 Introduction ……………………………………………………………………………………………………...84 4.2 Results from 0.5 kg AlAN Firings…………………………………………………………………………84 4.2.1 Inorganic Post-blast Residue Results…………………………………………………….84 4.2.2 Blast Overpressure……………………………………………………………………………….95 4.2.3 Fireball………………………………………………………………………………………………..98 4.2.4 Meteorological Conditions…………………………………………………………………..103 4.3 Results from 0.5 kg PE4 Firings…………………………………………………………………………107 4.3.1 Organic Post-blast Residue Results………………………………………………………107 4.3.2 Blast Overpressure……………………………………………………………………………..110 4.3.3 Fireball………………………………………………………………………………………………114 4.3.4 Meteorological Conditions………………………………………………………………….117 4.4 Results Summary……………………………………………………………………………………………..119 4.5 Discussion……………………………………………………………………………………………………….120 Summary………………………………………………………………………………………………………………130 5 CHAPTER 5: COMPLEMENTARY STUDIES WITH LARGER CHARGES……………………..132 5.1 Introduction……………………………………………………………………………………………………132 5.2 Unconfined AlAN Firings………………………………………………………………………………….132 5.2.1 Inorganic Post-blast Residue Results…………………………………………………...132 5.2.2 Fireball………………………………………………………………………………………………141 5.2.3 Meteorological Conditions………………………………………………………………….145 5.3 Unconfined RDX Firings……………………………………………………………………………………148 5.3.1 Organic Post-blast Residue Results……………………………………………………….148 5.3.2 Fireball ………………………………………………………………………………………………151 5.3.3 Meteorological Conditions…………………………………………………………………..159 5.4 Confined RDX Firings ………………………………………………………………………………………160 5.4.1 Organic Post-blast Residue Results …………………………………………………….160 5.4.2 Fireball ………………………………………………………………………………………………164 5.4.3 Meteorological Conditions ………………………………………………………………….165 5.5 Results Summary……………………………………………………………………………………………. 166 5.6 Discussion……………………………………………………………………………………………………… 168 Summary……………………………………………………………………………………………………………... 176 CHAPTER 6: MORPHOLOGICAL AND CHEMICAL ASSESSMENT OF POST-BLAST PARTICLES AND SIMULATION STUDIES OF PARTICLE DISTRIBUTION…………………177 6.1 Introduction…………………………………………………………………………………………………….177 6.2 Aluminised Ammonium Nitrate Particles…………………..……………………………………...177 6.2.1 Morphology and Elemental Composition……………………………………….……177 6.2.2 Chemical Identity……………………………………………………………………………….185 6.2.3 AlAN Particle Summary…………………………………………………………………….. 188 6.3 RDX Particles…………………………………………………………………………………………………..190 6.3.1 Morphology and Elemental Composition…………………………………………….190 6.3.2 Chemical Identity………………………………………………………………………………. 194 6.3.3 RDX Particle Summary………………………………………………………………………. 197 6.4 Simulation Studies …………………………………………………………………………………………..198 6.4.1 Imaging Comparisons………………………………………………………………………… 200 6.4.2 Residue Distribution Trends……………………………………………………………….204 6.4.3 Particle Counts: Experiment vs. Simulation…………………………………………. 205 6.4.4 Simulation Summary ………………………………………………………………………….209 6 6.5 Discussion……………………………………………………………………………………………………… 210 Summary…………………………………………………………………………………………………………….. 217 CHAPTER 7: SUMMARY AND CONCLUSIONS…………………………………………………………218 7.1 Summary ………………………………………………………………………………………………………..218 7.2 Key Conclusions and Contributions to the Field ………………………………………………..220 7.3 Future Research Areas …………………………………………………………………………………….221 References ……………………………………………………………………………………………………………….223 Appendix A: RDX Method Development …………………………………………………………………….236 Appendix B: Blast Over-pressure Data Tables……………………………………………………………. 243 Appendix C: