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Analysis and Collection of Soil Samples

Written by: Kathy Steck-Flynn

Back in the nineteenth century Edmund Locard developed the theory known as the "Locard's Exchange Principle." The theory in short states that when ever someone comes in contact with another object or person there is a minute exchange of particles that, in theory, can be traced back to a victim or suspect (Block 1999). In a crime context, that evidence can confirm or disprove a hypothesis of involvement between a suspect and a victim.

Locard described these particles as dust or dirt but today it is understood to include all soil borne trace evidence. Trace evidence can include blood, hair, fibre, dirt, glass particles and any other minute particles at a crime scene.

It would be nice to think that this forward thinker, Locard, moved beyond his Principle to developed the idea of soil analysis but he didn't. His mentor and friend Hans Gross published articles almost simultaneously with Sir Arthur Conan Doyle, the author of the Sherlock Holmes Fictions, regarding soil analysis (Block, 1999)( Nickel & Fischer, 1999) To Edmund Locard's great disappointment both Arthur Conan Doyle and Hans Gross beat him to the punch on the evaluation of soil as a forensic tool. However, Locard's zeal for the use of trace evidence in forensic investigations led to a life long study of the classification and identification of soil samples (Block, 1999).

Since its dawn in the late 1800's the analysis of soil has grown into a multidisciplinary field of forensic study. Modern analysis of soil may involve geologists, entomologists, toxicologists, biologists, botanists and a myriad of other experts.
Soil may be understood as just that: soil. As such it has a value in forensic studies. However, soil may also be understood as a repository for non soil contaminants which can yield valuable information about crimes. In forensic analysis materials can be grouped in several ways and each lab has its own way of subdividing these groups (Chayko & Gulliver 1999). In general soil borne materials can be considered organic or inorganic. Both types are found in soil. Further refining of these classifications where soil is concerned is to break the groups into mineral, biological or synthetic matter.

Soil is considered trace evidence. Soil is made up of disintegrated surface material which can be organic, mineral or synthetic. The ratio of the mineral content compared to other matter in the soil can be very site specific. The ratios of mineral,

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