Zadora / Martyna / Ramos Statistical Analysis in Forensic Science

Evidential Values of Multivariate Physicochemical Data
1. Auflage 2013
ISBN: 978-1-118-76317-9
Verlag: John Wiley & Sons
Format: PDF
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)

E-Book, Englisch, 336 Seiten, E-Book

A practical guide for determining the evidential value ofphysicochemical data

Microtraces of various materials (e.g. glass, paint, fibres, andpetroleum products) are routinely subjected to physicochemicalexamination by forensic experts, whose role is to evaluate suchphysicochemical data in the context of the prosecution and defencepropositions. Such examinations return various kinds ofinformation, including quantitative data. From the forensic pointof view, the most suitable way to evaluate evidence is thelikelihood ratio. This book provides a collection of recentapproaches to the determination of likelihood ratios and describessuitable software, with documentation and examples of their use inpractice. The statistical computing and graphics softwareenvironment R, pre-computed Bayesian networks using HuginResearcher and a new package, calcuLatoR, for thecomputation of likelihood ratios are all explored.

Statistical Analysis in Forensic Science will provide aninvaluable practical guide for forensic experts and practitioners,forensic statisticians, analytical chemists, andchemometricians.

Key features include:

* Description of the physicochemical analysis of forensic traceevidence.

* Detailed description of likelihood ratio models for determiningthe evidential value of multivariate physicochemicaldata.

* Detailed description of methods, such as empiricalcross-entropy plots, for assessing the performance of likelihoodratio-based methods for evidence evaluation.

* Routines written using the open-source R software, aswell as Hugin Researcher and calcuLatoR.

* Practical examples and recommendations for the use of all thesemethods in practice.

Autoren/Hrsg.

Zadora, Grzegorz

Martyna, Agnieszka

Ramos, Daniel

Aitken, C. G. G.

Aitken, Colin

Inhaltsverzeichnis

Preface xiii
1 Physicochemical data obtained in forensic sciencelaboratories 1
1.1 Introduction 1
1.2 Glass 2
1.3 Flammable liquids: ATD-GC/MS technique 8
1.4 Car paints: Py-GC/MS technique 10
1.5 Fibres and inks: MSP-DAD technique 13
References 15
2 Evaluation of evidence in the form of physicochemical data19
2.1 Introduction 19
2.2 Comparison problem 21
2.3 Classification problem 27
2.4 Likelihood ratio and Bayes' theorem 31
References 32
3 Continuous data 35
3.1 Introduction 35
3.2 Data transformations 37
3.3 Descriptive statistics 39
3.4 Hypothesis testing 59
3.5 Analysis of variance 78
3.6 Cluster analysis 85
3.7 Dimensionality reduction 92
References 105
4 Likelihood ratio models for comparison problems 107
4.1 Introduction 107
4.2 Normal between-object distribution 108
4.3 Between-object distribution modelled by kernel densityestimation 110
4.4 Examples 112
4.5 R Software 140
References 149
5 Likelihood ratio models for classification problems151
5.1 Introduction 151
5.2 Normal between-object distribution 152
5.3 Between-object distribution modelled by kernel densityestimation 155
5.4 Examples 157
5.5 R software 172
References 179
6 Performance of likelihood ratio methods 181
6.1 Introduction 181
6.2 Empirical measurement of the performance of likelihoodratios 182
6.3 Histograms and Tippett plots 183
6.4 Measuring discriminating power 186
6.5 Accuracy equals discriminating power plus calibration:Empirical cross-entropy plots 192
6.6 Comparison of the performance of different methods for LRcomputation 200
6.7 Conclusions: What to measure, and how 214
6.8 Software 215
References 216
Appendix A Probability 218
A.1 Laws of probability 218
A.2 Bayes' theorem and the likelihood ratio 222
A.3 Probability distributions for discrete data 225
A.4 Probability distributions for continuous data 227
References 227
Appendix B Matrices: An introduction to matrix algebra228
B.1 Multiplication by a constant 228
B.2 Adding matrices 229
B.3 Multiplying matrices 230
B.4 Matrix transposition 232
B.5 Determinant of a matrix 232
B.6 Matrix inversion 233
B.7 Matrix equations 235
B.8 Eigenvectors and eigenvalues 237
Reference 239
Appendix C Pool adjacent violators algorithm 240
References 243
Appendix D Introduction to R software 244
D.1 Becoming familiar with R 244
D.2 Basic mathematical operations in R 246
D.3 Data input 252
D.4 Functions in R 254
D.5 Dereferencing 255
D.6 Basic statistical functions 257
D.7 Graphics with R 258
D.8 Saving data 266
D.9 R codes used in Chapters 4 and 5 266
D.10 Evaluating the performance of LR models 289
Reference 293
Appendix E Bayesian network models 294
E.1 Introduction to Bayesian networks 294
E.2 Introduction to Hugin ResearcherTM software 296
References 308
Appendix F Introduction to calcuLatoR software 309
F.1 Introduction 309
F.2 Manual 309
Reference 314
Index 315

Über Autor(innen)

Grzegorz Zadora, Institute of Forensic Research, Krakow, Poland.
Daniel Ramos, Telecommunication Engineering, Universidad Autonoma de Madrid, Spain.