Soil Evidence

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Soil Evidence

  1. 1. TRACE EVIDENCE SOIL ANALYSIS
  2. 2. Soil <ul><li>soil or dried mud adhering to suspect’s clothing or shoes or to an automobile may link a suspect or object to the crime scene when compared to the soil there </li></ul><ul><li>soil analysis without a crime scene can also be helpful in finding the place where the crime was committed </li></ul>
  3. 3. Soil <ul><li>analysis must be made with soil dried under identical lab conditions </li></ul><ul><li>analysts look for </li></ul><ul><ul><li>physical characteristics </li></ul></ul><ul><ul><li>chemical characteristics </li></ul></ul>
  4. 4. Soil <ul><li>physical characteristics </li></ul><ul><ul><li>microscopic examination – </li></ul></ul><ul><ul><ul><li>reveals presence of plant and animal materials </li></ul></ul></ul><ul><ul><ul><li>any artificial debris </li></ul></ul></ul><ul><ul><ul><li>helps characterize minerals and rocks in earth materials </li></ul></ul></ul>
  5. 5. Soil <ul><li>physical characteristics </li></ul><ul><ul><li>color – 1,100 soil colors </li></ul></ul><ul><ul><li>soil types </li></ul></ul><ul><ul><li>magnetic particles </li></ul></ul><ul><ul><li>fluorescence </li></ul></ul>
  6. 6. Soil <ul><li>chemical characterisitics </li></ul><ul><ul><li>pH </li></ul></ul><ul><ul><li>nitrates, phosphates, potassium </li></ul></ul><ul><ul><li>carbonates, iron, chloride, copper </li></ul></ul>
  7. 7. Soil <ul><li>to determine common origin of soil samples one must consider… </li></ul><ul><ul><li>number of comparative points </li></ul></ul><ul><ul><li>frequency of occurrence </li></ul></ul>
  8. 8. Soil <ul><li>geology training helpful </li></ul><ul><li>2,200 minerals exists, only ~20 are common </li></ul><ul><li>rocks are combinations of minerals, characterized by </li></ul><ul><ul><li>mineral content </li></ul></ul><ul><ul><li>grain size – using sieve set </li></ul></ul>
  9. 9. Soil – Mineral Properties <ul><li>color </li></ul><ul><ul><li>useful but limited </li></ul></ul><ul><ul><li>many minerals appear in a variety of colors </li></ul></ul><ul><ul><li>many are white or colorless </li></ul></ul><ul><li>size </li></ul><ul><ul><li>simple labels: coarse, medium, fine grains </li></ul></ul><ul><ul><li>use of sieve set to further describe </li></ul></ul>
  10. 10. Soil – Mineral Properties <ul><li>texture </li></ul><ul><ul><li>describes crystal’s outward appearance </li></ul></ul><ul><ul><li>generally referred to as the “habit” of a crystal </li></ul></ul>
  11. 11. Soil – Mineral Properties <ul><li>texture – habits </li></ul><ul><ul><li>dendritic – has a plant like shape </li></ul></ul><ul><ul><li>as in copper </li></ul></ul>
  12. 12. Soil – Mineral Properties <ul><li>texture – habits </li></ul><ul><ul><li>bladed – appears as layers that look like the blades of knives </li></ul></ul><ul><ul><li>as in actinolite </li></ul></ul>
  13. 13. Soil – Mineral Properties <ul><li>texture – habits </li></ul><ul><ul><li>acicular – forms as pointy, needle-like masses, or radiating </li></ul></ul><ul><ul><li>as in scolecite </li></ul></ul>
  14. 14. Soil – Mineral Properties <ul><li>texture – habits </li></ul><ul><ul><li>massive – has no definite shape </li></ul></ul><ul><ul><li>as in limonite </li></ul></ul>
  15. 15. Soil – Mineral Properties <ul><li>texture – habits </li></ul><ul><ul><li>prismatic – looks like many prisms fused together (as in barite) </li></ul></ul><ul><ul><li>or a uniform cross section (as in beryl) </li></ul></ul>
  16. 16. Soil – Mineral Properties <ul><li>texture – habits </li></ul><ul><ul><li>reniform – looks like a jumble of rounded masses </li></ul></ul><ul><ul><li>as in hemitite </li></ul></ul>
  17. 17. Soil – Mineral Properties <ul><li>luster </li></ul><ul><ul><li>describes the way light is reflected off of the mineral’s surface </li></ul></ul><ul><ul><li>type and intensity vary according to </li></ul></ul><ul><ul><ul><li>mineral surface </li></ul></ul></ul><ul><ul><ul><li>amount of light absorbed </li></ul></ul></ul>
  18. 18. Soil – Mineral Properties <ul><li>luster </li></ul><ul><ul><li>vitreous </li></ul></ul><ul><ul><li>glass-like </li></ul></ul>
  19. 19. Soil – Mineral Properties <ul><li>luster </li></ul><ul><ul><li>greasy </li></ul></ul><ul><ul><li>milky </li></ul></ul>
  20. 20. Soil – Mineral Properties <ul><li>luster </li></ul><ul><ul><li>silky </li></ul></ul><ul><ul><li>satiny </li></ul></ul>
  21. 21. Soil – Mineral Properties <ul><li>luster </li></ul><ul><ul><li>pearly </li></ul></ul>
  22. 22. Soil – Mineral Properties <ul><li>luster </li></ul><ul><ul><li>metallic </li></ul></ul>
  23. 23. Soil – Mineral Properties <ul><li>luster </li></ul><ul><ul><li>dull or earthy </li></ul></ul>

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