Science News

Soil solves crimes

Wed, 14th Sep 2011

Amy Chesterton

The UK is a world-leader in applying geological knowledge to investigate crime.  Using the strong UK base as a starting point, a new initiative has been created to develop an international forensic geology network.  

The International Union of Geological Sciences (IUGS) has created a new group to promote and develop forensic geology across the world.  By establishing agendas and standardising protocols it is hoped that expert knowledge can be integrated across the world. Soil sample on a shoe

Forensic science is a team sport - the application of many sciences to answer questions of interest to a legal system.  Forensic geologists are a key player; they use their understanding of geological processes and environments to discover where soil samples originated.  Whatever the crime, small particles will be transferred onto perpetrators, particularly their clothing and footwear, and these trace particles can be analysed using increasingly sophisticated techniques.  

Soil is a complex mixture of material.  As well as the parent rock material, each soil sample has a unique mixture of vegetation, flora and fauna that has lived, or does still live within it.  The composition of minerals, the size and shape of sand grains and the DNA of the microbes can all be used to characterise soils.  

Colleen%20Clancy%20interviewGeological forensics is currently used about once a month in UK courts as evidence for conviction.  Comparison of samples can help to assess whether there is an association between materials found at a crime scene, and on a suspect.  But the usefulness goes beyond that.  Forensic geologists also provide police intelligence at an early stage of investigation.  When sand, soil or rock material is recovered on a suspect, analysis can eliminate or identify areas in which to find the crime scene.  Using trace evidence to search for buried items has become a vital tool for police.

Professor Lorna Dawson, the principle soil scientist at the James Hutton Institute explains, “Soils are continuous, so it’s not like DNA evidence where you actually have a match - soils will be similar or dissimilar”.  So DNA testing still leads the way, being the diagnostic test to link a person to an object or crime scene.  But soil evidence is becoming increasingly used as supportive evidence.  Plus soil can contain anything: any trace evidence such as a hair, fiber or paint fragment can also be identified, and link evidence in investigations.

The new international collaboration will allow easier comparison of different countries' soil databases, and will be used not only in criminal cases but also in verifying country and even region of origin of food products like garlic.

Click here to listen to Professor Lorna Dawson explain more...

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