Analytical Techniques in Forensic Science

Rosalind Wolstenholme, Sue Jickells, Shari Forbes, Rosalind Wolstenholme, Sue Jickells, Shari Forbes

• Publisher: Wiley
• Year: 2020
• ISBN:
  9781119033820
• Edition: 1
• Topic: Medizin
• Subtopic: Gerichtsmedizin

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.

Part I
Preparing for Analysis

1
Introduction 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. T...