EQ: How is soil analyzed in forensic science?

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

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

                                                                                                                                                                                      

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

What is the first step in the

examination of soil?

Side-by-side comparison of color and texture

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

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

Made of a combination of minerals

Characterized by their mineral content and grain size

Rocks

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

Which magnification

allows you to see naturally occuring

crystalline solids?High Magnification

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

Many soils from different areas yield similar densities

What is the main issue with the use of

Density Gradient tubes?

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

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

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

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

4 CORNERS!!!!

a. Rocksb. Mineralsc. Soild. crystals

a. clayb. siltc. loamd. sand

a. clayb. siltc. soild. sand

a. Rocksb. Mineralsc. vegetationd. brick

a. 10b. 100c. 2200d. 1100

a. sizeb. Colorc. Geometric shaped. Density

a. Massb. Densityc. Volumed. Length

a. Differentiationb. Colorc. Variationd. Density

a. 10b. 100c. 2200d. 1100