Natural justice and a sense of place: some examples of how soil can be used as intelligence and evidence

Forensic soil science is an increasingly important discipline, involving soils, minerals, dusts, plants and rock fragments to determine provenance i.e. to provide a chronology of their ownership, custody or location. Soil materials have been used as forensic trace evidence for many years, even in Roman times, and are often highly distinctive from one region to another. Such traces are extremely useful in a forensic context, because of their environmental specificity; their high levels of transferability; their ability to persist on items such as clothing, footwear, tools and vehicles; and their high levels of preservation after long periods of time. This resilience makes soil trace materials, frequently present at crime scenes and forensic exhibits, highly valuable forms of intelligence and evidence that can aid crime investigations and reconstructions.

Significant advances in forensic geoscience over the past decade, in the development of analytical approaches, miniaturisation and also in understanding the behaviour, transfer, persistence and preservation of sediments, soils and plant material which has widened their applicability. Evidence samples (unknown, questioned samples) can be analysed using a broad range of complementary methods that address their physical, chemical and biological components with greater precision, speed and accuracy than ever before. This now permits samples of less than 10 milligrams to be accurately characterised, and permits forensic soil science to also contribute to cold case investigations, both in providing intelligence and evidence in court. Examples will be presented of case work where soil has played a pivotal role.

Sediments/soil on footwear and vehicles can indicate where a crime may have taken place, and may provide evidence of a person being at a particular place of interest. Improved analytical capabilities, coupled with the development and availability of relevant databases, allow forensic geoscientists to help police to search for unknown objects or people, prioritise areas for investigation or search, and provide robust and reliable evidence in court. Forensic geoscience has mainly been used in the past in the context of high-impact crimes such as murder, rape, aggravated burglary and terrorism investigations, where resources allow it. However, with developments in analytical technology, and an increasing understanding of how soils and sediments are distributed within natural and anthropogenic environments, forensic soil science has more power to answer questions such as: “Where did the soil material come from?’, or “Where has this item been?” Understanding the context of a specific case is crucial to help answer such questions. In addition, being able to explain the significance of the evidence that has been analysed, and demonstrating logically and transparently how a conclusion has been reached, remains important for forensic soil science specifically and trace evidence generally.

The importance of communication of forensic science to the general public is important, in particular within the adversarial systems of justice, where the juries in court are the triers of fact. In an attempt to inform the public, I have been working with TV and through print media to show the correct methodology, where methods can be used as well as understanding and explaining the potential limitations of methods. Authors often like to create a sense of place, with soil and vegetation providing clues of where in the landscape a crime may have been committed.

The talk will cover both examples from real case work and from fiction where evidence from the earth has been of importance in helping to solve the crime and to bring about natural justice.

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