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Real Life CSI: Soil Fighting Crime

Footprint in the sand When was the last time you cleaned your shoes? Could the mud collected in the tread tell us where you were last week? It happens in CSI, but it is also happening closer to home in the real world. Soil really is fighting crime!

A research project, based at the Macaulay Institute in Scotland and funded by the EPSRC Crime Initiative, is developing analytical methods to help police gain valuable clues from soil. Soil particles stick to clothing, shoes, tyres and spades, and can be used to link a suspect, through examination of muddy pieces of evidence, to a crime scene.

Soil is made of mineral grains, organic material, and living and dead organisms. These components differ in a unique manner depending on where the soil is from and what it is used for. The complex nature of soil makes it a powerful piece of evidence, giving clues as to its origin. Something as simple as soil colour, or the size and shape of mineral grains, can be used to compare soil samples. Mineral particles provide clues as to the underlying stones and geology on which the soil was formed, while the organic matter gives clues as to what type of plants grew on the soil thus indicating likely land use.

However, soil evidence is not new. Arthur Conan Doyles' fictional character, Sherlock Holmes, used soil in a murder novel over a century ago. Modern ways of looking at soil make the clues that it hides far more accessible than they used to be. Analytical techniques can build up a detailed soil fingerprint of a sample, describing its mineral, organic, and living components. The information can be used to predict where an unknown soil evidence sample is likely to have come from, and point the police investigation in the right direction. Researchers at the Macaulay Institute and National Soils Research Institute are linking modern analytical methods to soils databases and geographical 'smart maps', in the development of powerful tools. These tools have the potential to provide the police with detailed information from tiny traces of soil. To find out more, visit http://www.macaulay.ac.uk/soilfit.

Remember, the next time you walk down a muddy path your shoes are picking up a recorded history of where you have been?.

By L M Macdonald