EQ: How is soil analyzed in forensic science?
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Transcript of EQ: How is soil analyzed in forensic science?
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EQ: How is soil analyzed in forensic science?
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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
Forensic Definition of Soil
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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 exam-ination of soil is a side-by-side examination of colorand texture.
Soil
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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.
Soil Types-Texture
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What is the first step in the
examination of soil?
Side-by-side comparison of color and texture
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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
Comparison Microscope
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Naturally occurring crystalline solid
UNIQUE COLOR GEOMETRIC SHAPE DENSITY REFRACTIVE INDEX
2200 exist, but only 20 are common and found readily at the surface surface
Mineral
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Made of a combination of minerals
Characterized by their mineral content and grain size
Rocks
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Rocks and minerals
are used to manufacture a wide variety of industrial and commercial products; safe insulation, brick, plaster and concrete blocks for example.
Mineral Analysis
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Which magnification
allows you to see naturally occuring
crystalline solids?High Magnification
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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.
Density Gradient Tubes
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Many soils from different areas yield similar densities
What is the main issue with the use of
Density Gradient tubes?
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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.
Variations in Soil Crime Scene
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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 of Soil
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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.
Collection
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Where are all the locations soil
should be collected?Crime scene, 100 yds radius of
crime scene, alibi locations, any object or clothing of interest
that contains soil
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4 CORNERS!!!!
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a. Rocksb. Mineralsc. Soild. crystals
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a. clayb. siltc. loamd. sand
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a. clayb. siltc. soild. sand
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a. Rocksb. Mineralsc. vegetationd. brick
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a. 10b. 100c. 2200d. 1100
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a. sizeb. Colorc. Geometric shaped. Density
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a. Massb. Densityc. Volumed. Length
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a. Differentiationb. Colorc. Variationd. Density
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a. 10b. 100c. 2200d. 1100