Forensic Characteristics of Soil DIRT Forensic Characteristics of Soil

Soil- What is it? Disintegrated surface material, both natural and artificial, that lies on or near the earth’s surface.

Soil Analysis of soil includes the examination of naturally occurring rocks, minerals, vegetation, and animal matter AND the detection of manufactured objects such as glass, paint chips, asphalt, brick fragments, and cinders, whose presence may give soil characteristics that make it unique to a particular location.

Soil Most soils can be differentiated and distinguished by their overall appearance. A side-by-side visual comparison of the color and texture of soil will distinguish soils that originate from different locations.

Soil It is estimated there are distinguishable soil colors. This is why color characterization is first step in identifying soil. Low Power microscopic examination of soil will reveal the presence the plant and animal materials as well as artificial debris. 1,100

Mineral A Mineral is an inorganic, naturally occurring crystalline solid. Like other crystals in nature, color, geometric shape, density and refractive index are all used in identification. There are more than 2,200 known minerals. There are only about 40 commonly found crystals.

Rocks Rocks are composed of a combination of minerals and there are thousands of varieties on the earth’s surface. Identification of rocks is usually made of characterizing their mineral content and grain size.

Rocks and Minerals Rocks and Minerals are not only found in earth materials, but also in a variety of industrial and commercial products: Safes and Vaults (insulation) Building materials Brick Plaster Concrete

Comparing Soils Forensic laboratories utilize a Density-Gradient Tube technique: A glass tube filled from bottom to top with liquids of successively lighter densities: used to determine the density distribution of soil.

Comparing Soils In Other Words: A test tube with 6-10 layers of with different concentrations of densities where each successive layer has a lower density than the preceding one, from the bottom to the top of the tube. When soil is added to the density-gradient tube, its particles will sink to the portion of the tube that has a density of equal value: the particles will remain suspended in the liquid at this point. A comparison of soils can be obtained by treating it in a similar manner.

Density-Gradient Tube Crime Scene Courtyard Garden Sports Pitch

Collecting Soil When collecting soil from a crime scene, standard/reference soils should be collected at various intervals within a 100-yard radius of the crime scene. Soil should also be collected at all possible alibi locations

Collecting Soil The soil collected should represent what was removed from the suspect. This usually means only the top-surface layer should be collected. Only a teaspoon of soil is needed for a thorough comparative analysis Each sample should be collected separately and placed in a vial that is marked with its location