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An in-depth text that explores the interface between analytical chemistry and trace evidence
Analytical Techniques in Forensic Science is a comprehensive guide written in accessible terms that examines the interface between analytical chemistry and trace evidence in forensic science. With contributions from noted experts on the topic, the text features a detailed introduction analysis in forensic science and then subsequent chapters explore the laboratory techniques grouped by shared operating principles. For each technique, the authors incorporate specific theory, application to forensic analytics, interpretation, forensic specific developments, and illustrative case studies.
Forensic techniques covered include UV-Vis and vibrational spectroscopy, mass spectrometry and gas and liquid chromatography. The applications reviewed include evidence types such as fibers, paint, drugs and explosives. The authors highlight data collection, subsequent analysis, what information has been obtained and what this means in the context of a case. The text shows how analytical chemistry and trace evidence can problem solve the nature of much of forensic analysis. This important text:
- Puts the focus on trace evidence and analytical science
- Contains case studies that illustrate theory in practice
- Includes contributions from experts on the topics of instrumentation, theory, and case examples
- Explores novel and future applications for analytical techniques
Written for undergraduate and graduate students in forensic chemistry and forensic practitioners and researchers, Analytical Techniques in Forensic Science offers a text that bridges the gap between introductory textbooks and professional level literature.
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Table of Contents
Cover
Analytical Techniques in Forensic Science
Copyright
List of Contributors
Preface
Acknowledgements
Part I: Preparing for Analysis
1 Introduction to Forensic Science
1.1 Forensic Science
1.2 The Forensic Process
1.3 Judicial Systems
1.4 The Role of Analytical Chemistry in Forensic Science
References
2 Analytical Methodology and Experimental Design
2.1 Scientific Method
2.2 What Do We Mean by Analysis?
2.3 The Stages of Analysis
2.4 Analysis Development
3 Presumptive Testing
3.1 Introduction
3.2 Drugs
3.3 Firearms Discharge Residue
3.4 Explosives
3.5 Ethanol (Ethyl Alcohol)
3.6 Ignitable Liquid Residues
3.7 Non‐Chemical Presumptive Tests
References
4 Sample Preparation
4.1 Sample Preparation
4.2 Extraction
4.3 Sample Preparation for Inorganic Analyses
4.4 DNA Profiling
4.5 Conclusion
References
Part II: Spectroscopic and Spectrometric Techniques
5 The Electromagnetic Spectrum
Reference
6 Ultraviolet–Visible and Fluorescence Spectroscopy
6.1 Forensic Introduction
6.2 Theory
6.3 Instrumentation
6.4 Application to Analyte
6.5 Interpretation and Law
6.6 Case Studies
6.7 Forensic Developments
References
7 Infrared Spectroscopy
7.1 Introduction
7.2 Theory of the Technique
7.3 Application to Analyte
7.4 Interpretation and Law
7.5 Case Studies – Discrimination of Acrylic Fibres
7.6 Forensic Developments
References
8 Raman Spectroscopy
8.1 Forensic Introduction
8.2 Theory
8.3 Application to Analyte
8.4 Interpretation and Law
8.5 Case Studies
8.6 Forensic Developments
References
9 Scanning Electron Microscopy
9.1 Introduction
9.2 Theory of the Technique
9.3 Application to Analyte(s)
9.4 Interpretation and Law
9.5 Case Study
References
10 Mass Spectrometry
10.1 Introduction
10.2 Theory of the Technique
10.3 Application to Analytes
10.4 Interpretation and Law
10.5 Case Studies
10.6 Forensic Developments
References
11 Isotope Ratio Mass Spectrometry
11.1 Forensic Introduction
11.2 Basis of the Technique
11.3 Introduction to the Isotope Ratio Mass Spectrometer
11.4 Interpretation
11.5 Case Studies
11.6 Applications in Forensic Science
11.7 Future of IRMS and Stable Isotopic Comparisons
References
Part III: Chromatographic Techniques
12 Chromatographic Separation and Theory
12.1 Introduction
12.2 Chromatography
12.3 The Separation Process
12.4 Separation Theory
12.5 Practical Applications of Chromatographic Theory
12.6 Conclusion
References
13 Gas Chromatography
13.1 Introduction
13.2 Gas Chromatography Components
13.3 Application to Analyte
13.4 Interpretation and Law
13.5 Case Studies
13.6 Forensic Developments
References
14 High Performance Liquid Chromatography and Ultra‐High Performance Liquid Chromatography Including Liquid Chromatography–Mass Spectrometry
14.1 Introduction
14.2 Components of an HPLC instrument and their Optimisation
14.3 Related Techniques
14.4 Chromatography Theory
14.5 Detection
14.6 Coupling of Liquid Chromatography to Mass Spectrometry
14.7 Types of Analytes
14.8 Accreditation and Method Validation
14.9 Interpretation of Results in the Forensic and Legal Context
14.10 Case Studies
14.11 Forensic Developments
14.12 Conclusion
References
15 Capillary and Microchip Electrophoresis
15.1 Capillary Electrophoresis: Introduction
15.2 Microchip‐Capillary Electrophoresis
15.3 Detection Systems
15.4 CE and ME in Forensic Analysis
15.5 Case Study: Lab‐on‐a‐Chip Screening of Methamphetamine and Pseudoephedrine in Clandestine Laboratory Samples
15.6 Conclusions
Acknowledgements
References
Index
End User License Agreement
List of Tables
Chapter 1
Table 1.1 Selected evidence types and common sources for them. The focus here...
Table 1.2 Example of a verbal scale of support. In this example, verbal stren...
Chapter 3
Table 3.1 Common presumptive colour tests for drugs (Cole 2003; Johns et al. ...
Table 3.2 Common presumptive microcrystal tests for drugs.
Table 3.3 Common presumptive colour tests for firearm discharge residue.
Table 3.4 Common presumptive colour tests for explosives.
Chapter 4
Table 4.1 Solid‐phase extraction stationary phases, interaction mechanisms wi...
Table 4.2 Commercially available SPME fibres.
Chapter 6
Table 6.1 Common UV‐Vis solvent cut‐off wavelengths.
Table 6.2
λ
max
values for common chromophores.
Table 6.3 Rules for
α
,
β
‐unsaturated ketones and aldehyde absorption....
Table 6.4 Solvent corrections for
α
,
β
‐unsaturated ketones.
Chapter 7
Table 7.1 Common mid‐infrared spectral bands.
Chapter 8
Table 8.1 Features of the excitation wavelength regions for Raman spectroscop...
Chapter 9
Table 9.1 Elemental composition of GSR versus types of ammunition (Michalska ...
Table 9.2 Classification scheme of GSR particles.
Table 9.3 Type and number of particles identified during case examination.
Table 9.4 Mean elemental composition of glass fragments found in debris colle...
Table 9.5 Results of likelihood ratio (LR) calculations within a classificati...
Chapter 10
Table 10.1 Modes of ionisation and their categories.
Table 10.2 Common EI fragments.
Chapter 11
Table 11.1 International isotopic primary reference materials
Chapter 12
Table 12.1 Terms associated with column chromatography.
Chapter 14
Table 14.1 Reported differences between HPLC and UHPLC.
Table 14.2 Mobile phase modifiers typically used in HPLC.
Table 14.3 Substances and their concentrations detected in a case involving p...
Table 14.4 Substances and their concentrations detected by LC‐MS/MS in a case...
Table 14.5 Substances and their concentrations detected by UHPLC‐MS/MS in a c...
Chapter 15
Table 15.1 Applications of CE and ME in forensic analysis.
Table 15.2 Preparation procedures used for sample types determined using the ...
Table 15.3 A comparison of analyses of clandestine laboratory samples by LOC ...
List of Illustrations
Chapter 1
Figure 1.1 Forensic process flow chart. Once the forensic examiners of the c...
Chapter 2
Figure 2.1 Full factorial designs for
n
variables where
n
= 1, 2, or 3.
Figure 2.2 Model effect plots: (a) depicting the overall main effect of Fact...
Figure 2.3 Simple response surface design, full grid, for two linear effects...
Figure 2.4 Model plot for a two‐variable response surface model. Squares rep...
Chapter 4
Figure 4.1 Simplified decision tree scheme for chemical analysis in forensic...
Figure 4.2 Pyraclostrobin.
Figure 4.3 Stages of SPE. and represent analytes. and represent inte...
Figure 4.4 Vacuum manifold showing SPE cartridges inserted into the top plat...
Figure 4.5 Representation of the structure of silica showing silanol groups ...
Figure 4.6 Solid‐phase microextraction. The process is shown for the extract...
Chapter 5
Figure 5.1 Electromagnetic radiation. The classical model describes two perp...
Figure 5.2 The electromagnetic spectrum.
Chapter 6
Figure 6.1 Typical electronic transitions for organic molecules.
Figure 6.2 Absorption spectra of 1,2,4,5‐tetrazine: (a) vapour; (b) hexane s...
Figure 6.3 Energy level diagram for fluorescence.
Figure 6.4 Schematic of a double beam UV‐Vis spectrometer.
Figure 6.5 Schematic of a fluorescence spectrometer with detector at 90° to ...
Figure 6.6 Idealised absorption (dashed line) and emission (solid line) spec...
Figure 6.7 Excitation–emission matrix spectra of nylon 361 (N361) cloths pre...
Figure 6.8 Hypercube of a blood stain, with two spatial (
x,
y) and one wavele...
Figure 6.9 Absorbance spectrum (a) and associated first‐order derivative spe...
Chapter 7
Figure 7.1 Stretching and bending molecular vibrations.
Figure 7.2 Layout of a Michelson interferometer.
Figure 7.3 A micro‐ATR accessory.
Figure 7.4 Reflection–absorption spectroscopy.
Figure 7.5 Infrared spectra for a polyethylene storage bag. (a) absorbance a...
Figure 7.6 Infrared spectra of undyed acrylic fibres: (a) polyacrylonitrile;...
Chapter 8
Figure 8.1 Energy level diagram for Raman scattering.
Figure 8.2 Stokes and anti‐Stokes scattering for cyclohexane. To show the we...
Figure 8.3 Modes of vibration for a triatomic molecule.
Figure 8.4 Raman and IR active vibrations for CO
2
.
Figure 8.5 Schematic of a dispersive Raman system with a CCD detector
Figure 8.6 Normal Raman (NR) and surface‐enhanced Raman spectra (SERS) of Ac...
Figure 8.7 Characteristic Raman frequencies. (Note, there is no significance...
Chapter 9
Figure 9.1 Diagram of a scanning electron microscope: (a) electron gun, (b) ...
Figure 9.2 Schematic showing selected electron interactions in an atom used ...
Figure 9.3 Naming convention for X‐rays generated by specific electron jumps...
Figure 9.4 An illustration of the difference in X‐ray intensity reaching a d...
Figure 9.5 Diagram of a scintillator/photomultiplier detector used for measu...
Figure 9.6 Diagram of an energy dispersive X‐ray detector: (a) atmospheric t...
Figure 9.7 Illustration of resolution, i.e. capability to distinguish three ...
Figure 9.8 The morphology of three‐component PbSbBa particles found on the s...
Figure 9.9 Type of glass fragment preparation: (a) embedded technique; (c) n...
Figure 9.10 Examples of SEM‐EDX spectra: (a) silica glass used in inside bul...
Figure 9.11 (a, b) Professional SEM stub used for seizing of GSR particles; ...
Figure 9.12 Filament of car bulb (evidence 1) observed under SEM‐EDX with me...
Chapter 10
Figure 10.1 Aston's first mass spectrometer. The coils in the background mak...
Figure 10.2 Atlas MAT CH‐5 magnetic sector mass spectrometer coupled to a ga...
Figure 10.3 The main components of a mass spectrometer. The inlet provides a...
Figure 10.4 Schematic diagram of an EI source. The main body of the EI sourc...
Figure 10.5 Example EI spectra of butanone. Note the last two peaks furthest...
Figure 10.6 Schematic diagram of a chemical ionisation source. The analyte (...
Figure 10.7 Schematic diagram of the ESI process. Droplets are formed by the...
Figure 10.8 Schematic diagram of the MALDI process. The analyte and matrix (...
Figure 10.9 Schematic diagram of the DESI ion source and process.
Figure 10.10 Schematic diagram of a quadrupole mass filter. Resonant ions wi...
Figure 10.11 Schematic diagram of a TOF mass analyser following production o...
Figure 10.12 Cutaway picture of the partial cross‐section of an Orbitrap ele...
Figure 10.13 Schematic diagram of a continuous electron multiplier. When the...
Figure 10.14 (a) Plot of ion abundance versus time. When coupled to a chroma...
Figure 10.15 (a) Full scan TIC chromatogram. A full scan GC‐MS run has been ...
Figure 10.16 Full scan (a) versus selected ion monitoring (SIM) (b) spectra....
Figure 10.17 (a) Full scan TIC chromatogram and (b) SIM TIC chromatogram. A ...
Figure 10.18 A full scan LC‐MS analysis has been performed on a solution con...
Chapter 11
Figure 11.1 Elemental configurations of carbon, showing stable isotope (
13
C)...
Figure 11.2 Carbon isotopic abundance ranges for naturally occurring materia...
Figure 11.3 Oxygen isotopic abundance ranges for naturally occurring materia...
Figure 11.4 Effect of a range of factors on
δ
2
H and
δ
18
O values of...
Figure 11.5 Global distribution of modern
δ
13
C value ranges in carbon d...
Figure 11.6 Schematic of an IRMS instrument showing different measurement op...
Figure 11.7 Typical output for a sample measured using IRMS. The square peak...
Chapter 12
Figure 12.1 Thin layer chromatography (TLC). (a) TLC plate spotted with samp...
Figure 12.2 The process of chromatographic separation illustrated for a HPLC...
Figure 12.3 Sample chromatogram illustrating some important parameters in ch...
Figure 12.4 GC chromatograms of electronic cigarette aerosols showing band b...
Figure 12.5 Contributions to eddy dispersion. (a) Flow of eluent around a pa...
Figure 12.6 Band broadening due to longitudinal diffusion in the chromatogra...
Figure 12.7 Mass dispersion in porous, silica particles. The channels/pores ...
Figure 12.8 Graphical representation of Eq. (12.17) showing how changing (a)...
Figure 12.9 van Deemter plot for a GC separation showing the change in plate...
Figure 12.10 van Deemter plot (plate height,
H
, vs. mobile phase velocity,
u
...
Figure 12.11 Theoretical Knox curves plotted for HPLC with particle sizes 1....
Chapter 13
Figure 13.1 Schematic of the components of a GC‐MS instrument.
Figure 13.2 Vaporising injector for gas chromatography.
Figure 13.3 Gas chromatography inlet liners (a) untapered split liner; (b) t...
Figure 13.4 (a) Sharp, Gaussian peak shape expected and (b) shark‐fin shaped...
Figure 13.5 Schematic of the carrier flow of sample through a split injector...
Figure 13.6 Schematic of the carrier flow of sample through a splitless inje...
Figure 13.7 Direction of flow through a gas sampling valve. (a) At the point...
Figure 13.8 Distribution of volatile compounds from the liquid sample into t...
Figure 13.9 Schematic of dynamic headspace sampling using ‘purge‐and‐trap’....
Figure 13.10 Sample collection options including (a) sorbent tube containing...
Figure 13.11 Configuration of a pyrolysis GC‐MS system.
Figure 13.12 Schematic of a wall‐coated open tubular (WCOT) column and a sup...
Figure 13.13 Comparison of a low and high isothermal analysis compared with ...
Figure 13.14 Schematic of a flame ionisation detector.
Figure 13.15 Total ion chromatogram showing TMS derivatised sterols analysed...
Figure 13.16 (a) The chromatogram of a gasoline standard analysed using GC‐M...
Figure 13.17 A chromatogram showing co‐elution of peaks (in highlighted sect...
Figure 13.18 Schematic of the components of a GCxGC‐TOFMS system including t...
Figure 13.19 Example first dimension (a) and second dimension (b) chromatogr...
Figure 13.20 Example of an older model Griffin 450 portable GC‐MS instrument...
Chapter 14
Figure 14.1 Interactions between stationary phase (C
8
), drug analytes (morph...
Figure 14.2 A typical chromatogram resulting from the analysis of spiked mob...
Figure 14.3 Typical features of an HPLC instrument: mobile phase, typically ...
Figure 14.4 Typical pumps and connections used in HPLC. (a) Binary pumps. Tw...
Figure 14.5 The 6‐port valve used to inject samples. There are two settings ...
Figure 14.6 An example of method development for the analysis of oxazepam gl...
Figure 14.7 An example of the optimisation of chromatography for isohumulone...
Figure 14.8 Typical detectors used traditionally in HPLC analyses. (a) UV de...
Figure 14.9 The differences between the
A
term in (a) the van Deemter theory...
Figure 14.10 Distinction between a total ion chromatogram a) and extracted i...
Figure 14.11 Three pairs of total ion chromatograms and MRM chromatograms fo...
Chapter 15
Figure 15.1 Schematic diagram of a capillary electrophoresis system. A few n...
Figure 15.2 Electropherogram of amphetamine, methamphetamine, 3,4‐methylened...
Figure 15.3 Electrokinetic injection procedures in ME: (a) floating and (b) ...
Figure 15.4 Gated injection scheme using a cross injection design. (a) Image...
Figure 15.5 Decision tree for processing of samples from a clandestine labor...
Figure 15.6 Electropherogram of a standard mixture of ephedrine, pseudoephed...
Guide
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Analytical Techniques in Forensic Science
Edited by
Rosalind WolstenholmeSheffield Hallam UniversitySheffield, UK
Sue JickellsRetired Analytical Chemist, formerly University of East Anglia and King's CollegeLondon
Shari ForbesUniversité du Québec á Trois‐Riviéres QuébecCanada
This edition first published 2021
© 2021 John Wiley & Sons Ltd
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions.
The right of Rosalind Wolstenholme, Sue Jickells and Shari Forbes to be identified as the authors of the editorial material in this work has been asserted in accordance with law.
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In view of ongoing research, equipment modifications, changes in governmental regulations, and the constant flow of information relating to the use of experimental reagents, equipment, and devices, the reader is urged to review and evaluate the information provided in the package insert or instructions for each chemical, piece of equipment, reagent, or device for, among other things, any changes in the instructions or indication of usage and for added warnings and precautions. While the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.
Library of Congress Cataloging‐in‐Publication Data
Names: Wolstenholme, Rosalind, editor. | Jickells, Sue, editor. | Forbes,
Shari, editor.
Title: Analytical techniques in forensic science / edited by Dr. Rosalind
Wolstenholme, Dr. Sue Jickells, Prof. Shari Forbes.
Description: First edition. | Hoboken, NJ : Wiley, 2021. | Includes
bibliographical references and index.
Identifiers: LCCN 2020022864 (print) | LCCN 2020022865 (ebook) | ISBN
9781119978282 (hardback) | ISBN 9781119033813 (adobe pdf) | ISBN
9781119033820 (epub)
Subjects: MESH: Forensic Sciences–methods | Chemistry Techniques,
Analytical
Classification: LCC RA1051 (print) | LCC RA1051 (ebook) | NLM W 700 |
DDC 614/.1–dc23
LC record available at https://lccn.loc.gov/2020022864
LC ebook record available at https://lccn.loc.gov/2020022865
Cover Design: Wiley
Cover Image: © Forensic science graph ‐ CReative
Commons ‐ source MDPI, https://doi.org/10.3390/separations3030026
List of Contributors
Sarah Benson
AFP (Australian Federal Police)
Canberra
Australia
Lucas Blanes
Oswaldo Cruz Foundation
Rio De Janeiro
Brazil
Alan Brailsford
King's College London
London
UK
Nerida Cole
Swinburne University of Technology
Melbourne
Australia
Wendell Karlos Tomazelli Coltro
Universidade Federal de Goiás
Goiás
Brazil
Philip Doble
University of Technology Sydney
Sydney
Australia
Shari Forbes
Université du Québec à Trois‐Rivières
Québec
Canada
Ellen Flávia Moreira Gabriel
Universidade Federal de Goiás
Goiás
Brazil
Sue Jickells
Retired Analytical Chemist, formerly University of East Anglia
and
King's College London
UK
Tim Jickells
University of East Anglia
Norwich
UK
Kylie Jones
AFP (Australian Federal Police)
Canberra
Australia
Aleksandra Michalska
Institute of Forensic Research
Kraków
Poland
Robson Oliveira dos Santos
University of Santa Cruz do Sul
Santa Cruz do Sul
Brazil
Mark Parkin
Eurofins Forensic Services
London
UK
Luke N. Rodda
Office of the Chief Medical Examiner
San Francisco
USA
and
University of California
San Francisco
USA
Claude Roux
University of Technology Sydney
Sydney
Australia
Renata Mayumi Saito
Brazilian Navy Technology Center in São Paulo
São Paulo
Brazil
Barbara Stuart
University of Technology Sydney
Sydney
Australia
Sophie Turfus
University of Huddersfield
Huddersfield
UK
Rosalind Wolstenholme
Sheffield Hallam University
Sheffield
UK
Florian Wulfert
Sheffield Hallam University
Sheffield
UK
Grzegorz Zadora
Institute of Forensic Research
Kraków
Poland
and
University of Silesia in Katowice
Katowice
Poland
Preface
Forensic science is a fascinating and important subject. It provides vital information in many criminal and civil cases and allows courts to address the questions: what has happened and who is responsible? There are three main stages in the forensic science process: crime scene examination, where evidence is collected and preserved; laboratory examination of recovered evidence to determine if there are any associations between pieces of evidence; and court reporting, where the scientist presents their findings to the court. Scene examination and court reporting are well represented in forensic textbooks. However, as university lecturers interested in forensic chemistry, we saw a need for a textbook that combines analytical theory and forensic application. That is to say, for a book that looks at the interface between analytical chemistry and (primarily) trace evidence, where trace evidence means materials found in small quantities such as paint chips, fibres, and firearm discharge residue. We hope to provide the depth of technique theory and application required for students on science based forensic science undergraduate and postgraduate courses, bridging the gap between introductory and advanced texts. We also hope the book will serve as a resource for forensic scientists who may wish to broaden their knowledge of analytical forensic science or for analytical scientists who wish to apply their knowledge in a forensic context.
Sheffield, November 2019
Rosalind Wolstenholme
Sue Jickells
Shari Forbes
Acknowledgements
This textbook has been a long time in the making. One of us has had two children, one has retired, and one has moved continent, twice! I am very grateful to my co‐authors and all contributors for agreeing to be involved and for their incredible patience throughout the process and while we dealt with unexpected delays, including skydiving accidents!
Very many thanks are due to Sue who, as my MSc tutor, was the first to put it into my head that I could read for a PhD. She was my first thought when I considered this project and soon realised that I couldn't do it on my own. Sue has always been enthusiastic about the book and what we could do with it. We have managed more than one ice cream on the North Norfolk coast while editing the book and I hope there will be more. I am also grateful that when I asked Sue if she would like to be involved in the book, she had the good sense to bring in Shari. As well as her immensely valuable editorial contribution, Shari has been our pacemaker, keeping us going by consistently meeting the deadlines we set ourselves in our regular conference calls. I am eternally thankful that you both stuck with the book and me.
Thanks are due to friends and colleagues who have commented on various chapters and to my elder sister who is my word processing guru and provided invaluable help with formatting in an emergency. Thanks also to the rest of my family for support at various times along the way.
Finally, my love and gratitude go to my husband, Matthew Roberts, who has been involved in many one‐sided book related conversations and got the children breakfast during early morning conference calls to the other side of the world, and my love always to my children, Francesca and Bronwen. They have not known a time when I wasn't fretting in one way or another about ‘the book’. I can finally give them the weekend away in a camper van that I have been promising they could have when the book was completed!
Rosalind Wolstenholme
Thanks go to all the analytical chemists that I've worked with through my career. You have all taught me/forced me to learn more about analysis. Thanks also to Roz and Shari for the journey of this book. It was tough at times but you both made it much more enjoyable. What will I do with all the extra time?
Sue Jickells
Thank you to Roz and Sue for inviting me to join this journey, even before they knew me that well. It was a rewarding (and at times challenging!) experience and I am glad we got through it together. I appreciate having the opportunity to work with you as colleagues and to know you better as friends. Thanks to all my other colleagues who I called on to help with the book, whether it was writing a chapter, editing, or reviewing content. Your efforts were greatly appreciated.
Shari Forbes
Part IPreparing for Analysis
1Introduction to Forensic Science
Sue Jickells, Rosalind Wolstenholme, and Shari Forbes
1.1 Forensic Science
Forensic science is typically defined as the application of science to the law; both criminal and civil law. Most people tend to associate forensic science with the investigation of crimes such as burglary; arson; possession of illegal drugs; drug trafficking; drink and drug driving offences; and attacks against the person including murder and sexual assault. However, forensic science is applied to the investigation of a far wider range of potential prosecutions including war crimes; fraud; medical incidents; doping offences in sport; environmental pollution incidents; road traffic accidents; maritime and aviation incidents; industrial incidents; and issues relating to food authenticity.
Potential scenarios which may result in prosecution through criminal or civil justice systems and which require some sort of forensic examination are almost limitless. (Note that, unless otherwise stated, the terms civil justice, civil law etc. will be used to describe the processes of being sued rather than meaning constitution based legal systems.)
Similarly, different countries have different judicial systems and different systems for investigating cases that may result in prosecution. Hence, it is difficult to discuss all possible types of scenarios, authorities and personnel involved in investigation and the processes to be used. Thus, the discussions which follow are based on some of the major types of crime prosecuted under the major types of criminal judicial system and how such crimes would be investigated, emphasising the analytical chemistry techniques associated with such investigations.
It is the job of those working in the field of forensic science to consider whether there is evidence that can provide information about a particular incident or situation. The Oxford Dictionary defines ‘evidence’ as ‘Information drawn from personal testimony, a document, or a material object, used to establish facts in a legal investigation or admissible as testimony in a law court’ and ‘The available body of facts or information indicating whether a belief or proposition is true or valid’ (https://en.oxforddictionaries.com/definition/evidence). When we use the term ‘evidence’ in this book, it implies these definitions. We have deliberately included both definitions because not all evidence that a scientist finds through their investigations will result in judicial proceedings. The evidence may have intelligence or investigative value proving, for example, that a suspect could not have committed a crime and hence no prosecution is brought against them. It might also be that the evidence obtained is sufficient in civil cases to persuade parties to make a settlement out of court or, in criminal cases, for a suspect to enter a ‘guilty’ plea such that there is no requirement for evidence obtained by a forensic scientist to be presented in court.
Evidence may be obtained through analysis, which is defined as ‘Detailed examination of the elements or structure of something’ (https://en.oxforddictionaries.com/definition/analysis). Such analysis could be as simple as visual examination, for example, identifying flakes of paint on a car involved in a fatal ‘hit and run’ incident. In some cases, the shape of the paint flake may provide sufficient evidence of provenance; fitting exactly the piece of paint missing from a car suspected of being involved in the incident (termed a physical fit). What if there is no physical fit but the surface colour of the paint flake appears to be similar to the colour of the suspect car? More in depth evidence is required, which entails a more sophisticated analysis to provide chemical information about the paint. This, together with information about the colours of the layers present and their thicknesses, will provide evidence as to whether or not the paint flake may originate from the suspect car.
This book is concerned with the analytical techniques used to provide information about the nature of the sample being investigated, with emphasis on techniques that provide information about the chemical nature of samples, or techniques that involve measuring a chemical property of the sample to provide evidence. These analytical techniques are used exceedingly widely in other fields but we concentrate on forensic science in this book because, as analytical chemists involved in the teaching of forensic science, we believe that a forensic scientist using such techniques should have a good understanding of them. This includes how the techniques work, the nature of the information obtained, as well as what this means in terms of interpreting the information provided through analysis and coming to a conclusion about evidential value. Sophisticated and complex instrumentation is often used as part of these analytical techniques and discussion of such instrumentation forms one of the main elements of this book. Table 1.1 gives some examples of common types of evidence that might be received in a forensic laboratory and analytical techniques appropriate for use in their examination.
Table 1.1 Selected evidence types and common sources for them. The focus here is on trace evidence.
Evidence types
Common sources
Fibres
Garments, furnishings
Hairs
Human hair (head, facial, etc.), animal hair
Paint
Cars, door and window frames, walls
Glass
Windows, car windscreens, drinking glasses, bottles
Documents
Notes, cheques, wills
Firearm discharge residue/explosives
Firearms, spent ammunition, improvised devices
Note the distinction between interpreting information obtained through analysis and coming to a conclusion about evidential value as a result. A good example of this is analysis of ethanol in blood, associated with driving under the influence of alcohol. Interpretation of data resulting from analysis provides a quantitative result giving the concentration of ethanol in blood but this information alone is not sufficient. A decision has then to be made as to whether this value is above or below the legal restriction when driving, taking into account the precision of the analytical method, resulting in a conclusion about the evidential value.
You might have noticed that we use the term ‘forensic scientist’ in the previous paragraph. What defines a forensic scientist? In this book we are using it to refer to a scientist who works in an organisation whose primary business is forensic science and where the expectation is that analyses will result in evidence that may be presented in court. We recognise that there will be many more scientists where the results from their analyses may result in evidence presented in court but where the primary business of the organisation for which they work is not forensic science. An example of this would be an analytical chemist analysing blood or urine samples in a hospital to identify and quantify drugs for diagnostic and treatment purposes. From time to time, analysis may identify a sample that indicates that something illegal has taken place and this may result in legal proceedings. Such an analyst is far more likely to refer to themselves as an analytical chemist, or in this specific case as a toxicologist, rather than a forensic scientist (or, in this case, a forensic toxicologist). Thus, although the emphasis in this book is on the use of analytical techniques used in forensic science, we hope that analytical chemists working in other areas will find this text useful because, they too, should have a good understanding of the analytical techniques that they use.
Many of the chemical analytical techniques used in forensic science cannot be used ‘at scene’, i.e. where the sample to be investigated originated. This is generally because the techniques are too complex to bring to scenes; the nature of the scene may not be an appropriate environment in which to carry out the analysis; or the instrumentation used is not portable. Hence it is common practice to bring the sample to a specialist laboratory for analysis. A scientist working in a forensic laboratory needs to have knowledge of what has happened to the sample before it came into their possession because this can have important implications for analysis and in interpretation of analytical results. Such information may include the environment from which the sample came; how long it was in this environment; who collected the sample and how; how was it packaged and transported from the point of collection to the forensic laboratory; and how and where it has been stored since it was received. It is not our intention to cover in detail the steps that take place before a sample is analysed in a forensic science laboratory – other authors have already covered this aspect thoroughly (Gardner 2011; Horswell 2016) – but we will give a brief overview here to give context to the content of individual chapters in this book and context to the place of analytical evidence in an investigation. We will also give a brief overview of the basic principles that allow forensic investigations to be carried out, the forensic issues and questions pre and post laboratory analysis, and the judicial systems within which forensic science operates.
1.2 The Forensic Process
A simplified flow chart showing the stages in a forensic investigation is given in Figure 1.1. The specific personnel and protocols will vary according to jurisdiction but the basic process will remain the same.
Figure 1.1 Forensic process flow chart. Once the forensic examiners of the crime scene have recovered the evidence a decision will be made about which items to send for further analysis. This should be done in conjunction with the police and the forensic laboratory scientists. After the laboratory analysis the forensic scientist will write a report and may have to go to court to defend their findings.
The usual starting point for an investigation involving forensic science is where there is the suspicion that a possible offence has been committed or there are suspicious circumstances requiring investigation. Depending on the circumstances, the police may or may not be involved in the investigation. If it is obvious that a crime has been committed, or there are suspicious circumstances resulting in harm or loss of life, the police will be involved early in the investigation and will take a coordinating role.
The scene must be managed so that the police and specialist investigators can do their job but also so that they do not contaminate or destroy potential evidence (see Section 1.2.1). It is usual in most jurisdictions to employ specialist investigators. These may have different titles in different jurisdictions and depending on the nature of the potential incident they are investigating. Most police forces in the UK employ crime scene investigators whose role it is to examine crime scenes. They will evaluate the evidence at the scene, taking into account possible information from victims, suspects and eyewitnesses, and carry out analyses at the scene which will aid the police in their investigations. Where more specialised analysis is required, crime scene investigators will collect samples and package them for transport to specialist forensic science providers, usually working in what are referred to as ‘forensic science laboratories’. In the UK, these laboratories are generally operated independently of the police authorities but in some countries and jurisdictions, the police may have direct responsibility for crime scene investigation and forensic laboratories. Whatever system is in place, there should be close cooperation between the crime scene investigators and forensic laboratories because in many jurisdictions, the scientist working in a forensic laboratory is unlikely to have visited the scene and hence needs information about the nature of the crime suspected to have taken place, the origin of samples and the conditions to which the sample may have been exposed before collection. Was the sample exposed to strong sunlight; was it subject to rain or covered with water; could animals have had access to it, etc.? Scene investigators must record this information and make it available to the analyst.
Depending on circumstances, the police will call in other specialists to help with investigation at the scene. Such specialists may include photographers, fingerprint recovery experts, forensic pathologists, road traffic incident investigators, arson investigators, firearms and ballistics experts, and blood pattern analysts. The role of all these specialists is to investigate the scene and to provide expert opinion to the police (and, ultimately, to the courts) on what has taken place and evidence to support judicial proceedings.
1.2.1 Forensic Principles and the Crime Scene
There are four main types of physical evidence that may be recovered from a crime scene: chemical (e.g. drugs and alcohol); biological (e.g. DNA and pollen); trace (e.g. glass and fibres); and pattern (e.g. fingermarks and tool marks). Table 1.1 gives some common sources of trace evidence. The primary focus of this text, in terms of physical evidence type, is trace evidence, which is simply anything of investigative or evidential value that is found in minute quantities. In order to provide context for the discussion of trace evidence we give a short summary of the basic principles and issues in forensic science and crime scene examination. To be able to correctly interpret their results, the forensic scientist must understand these principles to understand how the evidence came to be at the scene and how it came to be in the form in which it was received in the laboratory.
For any forensic discipline that relies on crime scene examination there is one principle without which the examinations would not be possible. This is Locard's Exchange Principle. This states that wherever contact occurs between two objects a transfer from one to the other will take place, commonly stated as ‘every contact leaves a trace’ (Kirk 1953). This may be a transfer of material or of form (i.e. an indentation). The transfer can occur from only one of the contacting objects to the other (one‐way transfer) or from both to the other (two‐way transfer), these are both types of direct transfer. If transfer did not occur there would be no trace evidence, no fingermarks, no trace DNA and a much lower chance of associating a perpetrator with their crime.
However, it must be noted that transfer is not always of practical use. The amount transferred may be too small to be detected or may occur in such a way as to make interpretation impossible, e.g. transfer of a ubiquitous fibre such as blue denim. There is also a third kind of transfer, which is indirect transfer. Indirect transfer is when transfer occurs independently of the ‘crime’ event, i.e. from a to b and then from b to c. The possibility of indirect transfer and, therefore, no connection to the event, must always be considered when interpreting results. For example, person X's trouser fibre could be transferred from their trousers (a) to a seat cushion (b) on sitting on a chair and then consequently transferred to person Y's trousers (c) when they sat on the same chair. This example could even be extended further by the fibre being transferred again to another chair or other object (d). A forensic examiner must weigh up the likelihood of consecutive transfer in the relevant scenario.
A further transfer related issue is that of legitimate access. Transfer may have occurred as a result of normal everyday activities by a person who would normally have access to the scene. For example, at a domestic burglary the homeowner or any person the homeowner has allowed into their home relatively recently would be deemed as having legitimate access. The evidential value (see Section 1.2.3.2) of any evidence associated with a person with legitimate access generally would be low. A perpetrator could exploit this as an explanation for the presence of trace evidence associated with them at a crime scene, which is especially difficult to manage for offences where the perpetrator is often known to the victim, e.g. sexual assault. In some cases, the forensic investigation may be able to corroborate or refute a version of events.
Once the exchange principle is accepted it swiftly follows that contamination is a serious problem. The aim of a crime scene examination is to secure, record and recover evidence so that as much information as possible can be gained to accurately reconstruct the events that took place. In most cases a crime scene does not appear clean and fresh with no previous transfer and is not transfer free once the crime has occurred. Contamination occurs when transfer not related to the ‘crime’ takes place, either by accident or intentionally. It can occur at the scene or at some later date. The scene of crime examiner should not be the source of any contamination, hence the use of suit, gloves, boots and mask and the importance of correct packaging to maintain integrity. Integrity is the preservation of evidence in its state at the time of the crime or more probably at the time of its recovery from the crime scene. Packaging preserves evidence by preventing the addition and loss of material and supplies the chain of custody to identify the keeper of the evidence at all times. An overview of packaging and chain of custody issues follows.
As noted in Section 1.1, most forensic scientists will not visit the scene and so rely on those examining the crime scene not to contaminate samples or to destroy potential evidence. The aim is that the sample analysed in the laboratory resembles the sample as it was at the scene with nothing added or taken away or changed in any other way, i.e. it retains its integrity. Packaging is imperative in protecting samples between recovery at the scene and the point at which the sample is opened for analysis. Scene investigators must use the appropriate packaging and samples must be transported to the laboratory under suitable conditions, including keeping appropriate samples cool and preventing cross‐contamination from other samples that may be transported together. In some investigations, the ‘scene’ may extend beyond the initial place where the potential crime was discovered. This applies to post‐mortem examinations (PMEs) where the body may contain potential evidence and is classed as a scene itself. The body must be packaged appropriately for transport for PME and samples taken at PME should be collected in suitable containers, with preservative added if appropriate. They should be stored under conditions that prevent any further changes taking place.
In some instances, there may be no ‘scene’ to be investigated. Examples include foods investigated for their authenticity or for suspected contamination. These may be samples on the shelves of supermarkets or seized from a shipping container at importation. It will be sufficient for the investigator to note the place of seizure without a photographic record. Similarly, for a sportsperson providing a urine sample to be analysed for potential evidence of a doping offence, the place where the sample is collected is not important in terms of subsequent analysis, although the nature of the collection process is important. (For example, was there an opportunity for the sample to be substituted or adulterated? Was a clean sample vessel used?) In environmental pollution incidents, the first sign that an incident has taken place may be dead wildlife. This may be remote from the original source of the pollution and analysis may be required to identify the cause of death, which may then lead investigators to the source.
The chain of custody supports correct packaging by documenting the history of real evidence (see Section 1.3.4) from the time of collection to the time it is used in court. The chain refers to the paper trail created as the evidence is transferred from one person to another. It ensures that the evidence is in the direct control of the responsible person at all times to ensure the authenticity (and therefore competency) of the evidence.
When evidence is collected at a crime scene, the officer will initiate the chain of custody by photographing in situ, collecting, packaging, sealing and appropriately labelling the evidence. The evidence may be placed in storage by the custodian or may be delivered to the laboratory for analysis. Each of these, and subsequent, transactions must be appropriately documented chronologically on the chain of custody form. A person will sign for the evidence at the time it is received and will sign again when it is handed over to the next person. Each time a forensic scientist examines the evidence, they must also maintain the chain of custody by ensuring that the affixed seals have not been disturbed, and by documenting the condition of the evidence at the time it was received. The form provides a detailed history of the custody of the evidence allowing for any of the custodians to be called as an expert witness to testify about the condition, analyses and storage of the evidence.
If a gap is identified in the chain of custody, even when accidental, this can raise questions in court about the authenticity and integrity of the sample. At the very least it can prevent a case going to court or mean that the evidence is deemed inadmissible, and in the worst case scenario it can result in an acquittal or a guilty verdict being overturned upon appeal. Maintaining the chain of custody is an essential responsibility of any forensic scientist to ensure that the evidence is not adulterated or tampered with in a manner that could affect its probative value.
The chain of custody and correct packaging (and storage) should ensure continuity (i.e. that the piece of evidence recovered is the same one as that examined) and ensure that the integrity of the evidence is preserved at all times. The forensic examiner must be able to assess whether or not an item received in the laboratory is correctly packaged, which they can begin to do with an understanding of the principles and issues outlined above. However, as there are many methods, which vary between and within different countries, the reader is directed to Horswell (2016) and Gardner (2011) for more in depth discussion.
In addition to recovering items of interest from the scene the examiner must also recover control samples. Whatever type of evidence is recovered or may be recovered from the suspect, the relevant reference samples must also be collected. For example, in an assault scenario if blue fibres have been recovered from the victim that are not from the victim's clothing or possessions, blue fibres should be collected from any suspects' clothing and homes.
While preserving and recovering material from the ‘crime’ scene, an examiner must also make contemporaneous notes. These are a record of everything that they have done at the scene, including the time at which it was done, and any other important observations, who was at the scene, transient details, e.g. lights on or off, windows open or closed, phone ringing, etc. Contemporaneous notes also include scene sketches and photographic logs. Some types of analysis may be carried out at the scene. For example, fingerprint evidence will be sought; the scene may be examined with light sources to detect body fluids; and suspected traces of body fluids may be tested in order to make decisions about which samples to collect from the scene and send for more specialised testing. Again, these must be noted and form part of the case documentation. Contemporaneous notes are important in providing evidence of what was done and form part of the chain of custody by noting how items were recovered. They also act as an aide memoire to examiners who carry out hundreds of examinations a year and may not be called to give evidence on a particular scene until months or years later. (Contemporaneous notes/record keeping for the laboratory forensic scientist are discussed in Chapter 2.4.1.)
The issue of contamination is also central in determining the viability of a scene examination. The time immediately after the crime is committed, in the context of evidence recovery, is called the ‘golden hour’. In this time the maximum amount of evidence is available that retains its integrity and may ultimately be used in court. As time passes the chance of contamination and loss of material increases, particularly if there is lots of activity at the scene, so the chances of recovering evidentially valuable evidence decreases. Once the scene examination is complete and the scene is returned to normal use, the chance for evidence recovery is ended and any further examination would be subject to questions about its viability. It should be noted that the potential for evidence recovery is the same no matter what the severity of the offence, burglars are no more or less likely to leave hairs and fibres, shoe marks etc. than murderers (assuming the same time at a scene and the same level of activity). Whether the evidence is recovered or not will depend, not least, on factors such as the severity of the offence, local policing priorities and budget. Maximising recovery during the golden hour is also important to mitigate against the effects of attrition, in which at each stage of an investigation the material that is taken forward diminishes. This could be due to one of many reasons, inconclusive analysis, inadmissibility and, not least, budgetary constraints. The laboratory forensic scientist should always remember that they may not be asked to examine all the evidence recovered and it may be advisable to discuss the selection of items submitted with the investigative team. To maximise evidential value, i.e. the ability of the evidence to assist in proving or disproving a hypothesis, consideration of the issues discussed above, such as the possibility of contamination or indirect transfer, the integrity and potential evidential value, will assist in selecting the most appropriate items for examination.
One measure of evidential value is the type of characteristics available for examination. Class characteristics are those that are held by a group of items, e.g. all the glass produced from a particular batch of raw materials or all the shoe soles made from a particular shoe sole mould. Individual characteristics are those that are held only by a single item, e.g. a glass car windscreen that has been scratched by windscreen wipers and the impact of debris or a shoe sole that has been worn down by the wearer's gait and has been scratched by contact with the ground. Clearly, individual characteristics have greater evidential value than class characteristics. A still higher evidential value is gained through a physical or jigsaw fit. In this case, two items fit together in such a way that it is apparent that they were originally one object. Evidential value is discussed at further length in Section 1.2.3.2.
Finally, the forensic scientist and the investigative team should always remember that ‘absence of evidence is not evidence of absence’, i.e. just because you didn't find it doesn't mean it wasn't there. There may be any number of reasons why evidence may not be discovered, recovered or detected, which will need to be conveyed to the trier of fact.
1.2.2 Preparatory Issues in Laboratory Analysis
Before beginning an examination in the laboratory, the analyst should take into account case circumstances and they should ask themselves questions such as: What is the purpose of this analysis? What do I hope to show as a result? What evidence may be available from this analysis which may support, or rule out, a prosecution? What evidence may be available from analysis to indicate whether hypothesis A is more likely to be correct than hypothesis B? Allied to these questions are others such as: What technique or combination of techniques that I have available to me will best provide answers to the above questions? (See also Chapter 2.)
Once a strategy has been decided upon the scientist can begin to look at the items submitted. They must first check that the paperwork for the item(s) to be examined is in order, the chain of custody is intact and the packaging is appropriate and has not been compromised. The laboratory should have systems in place for ensuring that the examination environment is clean and there is no opportunity for contamination, such as procedures for cleaning down benchtops, procedures for keeping evidence from different sources apart and installation of air conditioning systems with filters to prevent particles from moving from one laboratory to another.
Examination, whether at a crime scene or in the laboratory, starts with the least destructive or least invasive methods of analysis before progressing to more destructive ones and should start with examination in situ. Non‐destructive testing is very important in forensic examination to preserve the integrity of the sample but also to ensure that wherever possible the sample is available for re‐examination by either legal team. If a test is not repeatable and/or its results are called into question it may lead to a reduction in evidential value or the evidence not being admitted in court.
Visual examination is the starting point, possibly allied with smell and hearing, depending on case circumstances. Depending on the item being examined, the scientist may need to record details of the item as a whole then look for and recover further evidence using tweezers for easily visible evidence followed by other techniques such as tape lifting or similar and swabbing. An example of this would be in a garment examination whereby the condition, colour, shape, size, label details, etc. of the garment would be recorded along with sketches and photographs. Then any trace evidence such as hairs, fibres, glass, paint, etc. would be recovered, packaged and recorded, including where on the garment they were recovered from as this may be important to the case, e.g. in an assault case the position of fibre transfer may indicate where contact has taken place and may support or refute a version of events. The garment may then be tape lifted to recover any evidence not immediately visible and swabs may be taken to test for the presence of body fluids and hence DNA. In this scenario, the original item, the garment, may now be of less interest than the evidence recovered from it in the laboratory.
If not already employed, the visual examination may be followed by investigation using specialist light sources or may proceed directly to physical or chemical analysis or both. Analysis may also involve microscopy to reveal evidence not visible to the naked eye. For most samples, a combination of analyses will be applied. This is because each examination may reveal additional, useful, information; and may highlight additional analyses to be carried out or may indicate that further analysis will not be useful or necessary.
The analyst also needs to think about the nature of the sample and whether it needs to be prepared in some way before analysis can be carried out. For example, if the sample to be examined is urine which may (or may not) contain traces of a drug, there are no analytical techniques which can identify, unequivocally, what drug is present and at what concentration without separating the drug in some way from the urine matrix. Note the use of the word ‘unequivocally’. Further discussion of confirmation of the identity of a particular substance can be found in Chapter 3
