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Soil

Soil. Soil. Why is investigating soil found on or near a suspect or victim important? Location Link Suspect Trace Evidence. Definition. Soil—considered any material (natural and artificial) that lies on or near the Earth’s surface

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Soil

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  1. Soil

  2. Soil • Why is investigating soil found on or near a suspect or victim important? • Location • Link Suspect • Trace Evidence

  3. Definition • Soil—considered any material (natural and artificial) that lies on or near the Earth’s surface • Soil evidence is useful only as support or for generating leads

  4. Examination of Soil • Look for trace evidence • Describe and compare the physical and chemical properties of each sample • Many times 2 soil samples are easily matched on visual inspection alone, however, several tests must be performed to 100% confirm a match • Soil must be dried first before colors are compared • There are nearly 1100 distinguishable soil colors

  5. Soil Tests • Gross Examination • UV Comparison • Microscopic Observation • Density Gradient Columns

  6. INTERACTIVE With a partner (seated next to you) or alone… ---Develop a Mnemonic to remember the 4 types of test— (Example: Please Excuse My Dear Aunt Sally)

  7. Gross Examination • Color • Texture • Shapes • Foreign Objects bsapp.com

  8. UV-Observations • Note the shape, size, number, and identity (if possible) of any material that fluoresces • Compare Samples bsapp.com

  9. Aragonite, a mineral which fluoresces green under UV light, occurs naturally in Mexico. bsapp.com

  10. Calcite (red) and willemite (green) under UV light. Calcite occurs all over the world, however Willemite is rarely found outside of New Jersey.

  11. Microscopic Observation • Color • Texture • Shapes • Foreign Objects bsapp.com

  12. Naked Eye bsapp.com

  13. Microscopic x10 bsapp.com

  14. Microscopic x40 (Cotton Fiber) bsapp.com

  15. Naked Eye bsapp.com

  16. Microscopic x40 (Minerals) bsapp.com

  17. Naked Eye bsapp.com

  18. Final Comparison • Any and all foreign objects found should be investigated separately • If all previous comparisons are similar between two samples they likely originate from the same area • As final comparison density gradient columns may be utilized bsapp.com

  19. Density Gradient Tubes • Assemble two identical density columns with varying levels of liquids in them • Drop equal amounts of soil samples (a control and unknown) in the columns • Allow the samples to disperse throughout the columns for comparison • If the two samples are of the same origin, then they will produce nearly identical gradient tubes bsapp.com

  20. bsapp.com

  21. Assessment • Case of the _________??

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