Forensic Soil Analysis Forensic Definition of Soil Any

Forensic Soil Analysis

Forensic Definition of Soil Any disintegrated surface material, natural or artificial that lies on or near the Earth’s surface. Natural= rocks, minerals, vegetation, animal matter Manufactured= glass, paint, asphalt, brick fragments, cinders

Soil The value of soil as evidence rests with its prevalence at crime scenes and its transferability between the scene and the criminal. Most soils can be differentiated by their appearance and color. The first step in examination of soil is a side-byside examination of color and texture.

Soil Types-Texture People describe soil types in all kinds of ways such as heavy, light, sandy, clay, loam, poor or good. Soil scientists describe soil types by how much sand, silt and clay are present. This is called texture.

What is the first step in the examination of soil? Side-by-side comparison of color and texture

Comparison Microscope Soil appears different when wet, therefore samples are dried in the same manner in the lab 1, 100 distinguishable soil colors Low power magnification offers presence of plant and animal debris High magnification can classify minerals and rocks

Mineral Naturally occurring crystalline solid UNIQUE COLOR GEOMETRIC SHAPE DENSITY REFRACTIVE INDEX 2200 exist, but only 20 are common and found readily at the surface

Rocks Made of a combination of minerals Characterized by their mineral content and grain size

Mineral Analysis Rocks and minerals are used to manufacture a wide variety of industrial and commercial products; safe insulation, brick, plaster and concrete blocks for example.

Which magnification allows you to see naturally occuring crystalline solids? High Magnification

Density Gradient Tubes These tubes are typically filled with layers of liquids that have different density values. 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.

What is the main issue with the use of Density Gradient tubes? Many soils from different areas yield similar densities

Variations in Soil Crime Scene Ultimate value depends on its variation at the crime scene If the soil is indistinguishable for miles surrounding the crime scene, it will have limited value in associating soil found on the suspect with that particular site. Variations in soil composition must be made every 10 -100 yards from the crime site.

Collection of Soil Standard/reference soils are to be collected at various intervals within a 100 -yard radius of the crime scene, as well as the site of the crime, for comparison to the questioned soil. Soil found on the suspect, such as adhering to a shoe or garments, must not be removed. Instead, each object should be individually wrapped in paper, and transmitted to the laboratory.

Collection Soil must be collected at all alibi locations that the suspect claims For Standard/ Reference samples: In most cases, only a tablespoon or two of the top layer of soil is collected, placed in individual plastic containers, and labeled according to location.

Where all the locations soil should be collected? Crime scene, 100 yds radius of crime scene, alibi locations, any object or clothing of interest that