Soil Analysis

Forensic Characteristics of Soil Soil includes any disintegrated surface material, that lies on or near the earth’s surface Value based on prevalence at crime scenes and ability to transfer between scene and criminal Most soils can be differentiated and distinguished by appearance (visual comparison)

What Is Soil? Mixture of organic and inorganic material Inorganic part contains minerals Organic part is decayed plant and animal material Three textures of soil (based on particle size) Clay (fine) – retains water Silt (medium/gritty) – may retain some water Sand (coarse/granular) – air circulates, loses water

Soil Analysis Soil is darker when wet. Color comparisons must always be made when all the samples are dried under identical laboratory conditions. There are an estimated 1,100 distinguishable soil colors. There are at least 50,000 different soil types in the United States alone. Low-power microscopic examination reveals the presence of plant and animal materials as well as artificial debris.

Soil Analysis Bulk analysis Density gradient Particle size distribution (sieve) Color Mineral analysis pH Oxygen levels Organic components

Soil comparison: Density Gradient tube used to compare soil samples 1.0 g/ml 1.5 g/ml

Finding gravesites Altered soil profiles can indicate land was disturbed Discoloration Excess soil may be mounded above a new grave Older gravesites tend to sink as loose soil is compacted and body decomposes More easily detected from above due to shadowing Acidic areas reduce decomposition due to fewer microorganisms (more preserved) Coarse/sandy soils cause bodies to mummify

SOIL