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Soil, a crucial surface material found on Earth, can be both natural and artificial, playing a vital role in forensic investigations. It consists of elements like rocks, minerals, and organic matter, which vary greatly in appearance, color, and texture. The Gradient Tube Technique aids in analyzing soil specimens by layering substances of different densities. Accurate collection and preservation techniques, including sampling from crime scenes and alibi locations, ensure integrity for forensic evidence. Understanding how soil characteristics can differ helps in linking suspects to scenes effectively.
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4.4 Notes Characteristics of Soil Pg. 111-115
Soil • any disintegrated surface material, both natural and artificial, that lies on or near the earth’s surface. • Naturally occurring rocks, minerals, vegetation, animal matter • Manufactured objects
Critical as evidence • prevalence at a crime scene • transferability between the scene and the criminal
Soils differentiated by: • gross appearance • color (dried), texture • plant and animal materials • artificial debris • minerals and rocks present
Mineral • naturally occurring crystal, approx. 2200 but only 40 are most common • Rocks are characterized by mineral content and grain size
Gradient Tube Technique • Used to compare soil specimens • This test is useful when used in combination of other tests • Fill a tube with liquids of different densities • Layer on bottom is most dense, each subsequent layer is of decreasing density • Add soil samples • Particles of same density will be suspended in the match point density
Collection and Preservation • Standard/reference soils collected at various intervals within 100 yd radius • Samples collected at the alibi locations • Need 1-2 T of soil for a sample • Specimens packaged in individual containers • Objects with soil are collected • Samples of soil are collected under car fenders and frame • need to keep in lump form
