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Soil and Forensic Geology

Soil and Forensic Geology. What Is Soil?. Mixture of organic and inorganic material May range from 100% inorganic (sand) to nearly 100% organic (peat) Inorganic part is minerals Organic part is decayed plant and animal material and is sometimes called humus. Forensic Significance of Soil.

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Soil and Forensic Geology

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  1. Soil and Forensic Geology

  2. What Is Soil? • Mixture of organic and inorganic material • May range from 100% inorganic (sand) to nearly 100% organic (peat) • Inorganic part is minerals • Organic part is decayed plant and animal material and is sometimes called humus

  3. Forensic Significance of Soil • Soil is class evidence - cannot be individualized to a particular location • There is no classification system for soils • Soils can be easily transported • Soils within a few meters horizontally or vertically differ

  4. Forensic Analysis of Soils • Bulk analysis • Density gradient • Particle size distribution (sieving) • Inorganic components • Color (dissolve in water) • Petrography - mineral analysis; Requires a good deal of skill and practice

  5. Forensic Analysis of Soils • Organic components • Liquid chromatography • Oxygen availability • Bacterial DNA? - Future possibility

  6. Why is soil such a good source of evidence? • Large Variations of soil characteristics • Extreme Complexity of its composition • Minerals • Oxides • Organic Matter • Microorganisms • Artificial additions (concrete, asphalt, plastics) • Runoff additions (salt, fertilizers, pesticides) • Manufactured products: glass, paint, asphalt, brick, industrial products, • Complex Physical Nature • Varies due to above compositions

  7. Forensic Geologists • The forensic Geologists examinations involve the identification of: • Earth materials • Comparison of samples to determine common source • Studies that aid a criminal investigations and intelligence studies.

  8. Forensic Geology In Intelligence Work Remember the outcrop you saw behind Osama bin Laden on TV after September 11. What was the location? A geologist who has done field work in the area would be able to locate that outcrop, and that actually happened: Geologist John Shroder was able to identify the region where bin Laden had been sighted in Afghanistan in 2001 (see Geotimes, February 2002).

  9. Forensic Geologists of the Past • Starting in 1887 Sir Arthur Conan Doyle wrote The Sherlock Holmes series used soil and residues many times to link individuals to specific locations. • In 1893, Hans Gross, authored “Handbook for Examining Magistrates”. In it he suggested that the dirt on someone's shoes could tell more about where a person had last been than many other techniques used in that time.

  10. The Eva Disch Case • In October 1904 a dirty handkerchief containing bits of coal, snuff, and grains of the mineral hornblend was found at the murder scene of a seamstress named, Eva Disch. • A suspect was found who used snuff, and worked part-time at both a coal burning gas works and a quarry that had an abundance of the mineral hornblend. • The suspect also had two layers of dirt in his pant cuffs. The lower layer matched the soil at the crime scene and the upper layer, characterized by a particular type of mica particle, matched the soil found on the path to the victim's home. • When confronted with the evidence the suspect confessed. (Murray and Tedrow, 1991, p. 4)

  11. Forensic Geologists • The microscope is and will remain an important tool. • Qualifications and competence of examiners is a major problem. • Should those qualifications be regionalized? • The future will see: • Improved training of those who collect and analyze samples • Increased automated methods of examination • Improved research: • The diversity of soils • What parts of soil are transferred during various types of contacts and could their be a pattern

  12. Forensic Geologists Questions Interconnected by the following questions: • What is this material? • Where did this material come from? • Is this material unique to a crime scene or unique to circumstances under which a criminal act was committed? • What is the geologic context of a crime scene?

  13. My Husband Went hunting and never came home  • A pond with bentonite (clayish mud) in the mountains of western Colorado proved to be a really great place to camp for John Dodson.

  14. Physical Properties of Soil • Soil Texture, Structure, Compaction • is the percent of sand, silt and clay in a soil. • sand is the coarsest (0.06 - 2 mm) • silt is intermediate (0.002 - 0.06 mm) • clay is the finest (<0.002 mm)

  15. Soil Texture • The texture of a soil is determined by the percentages of particles like sand, silt, & clay that it contains.

  16. Physical Properties of Soil

  17. Soil Comparison: Simple observations using local geologists • Color of dry sample, (1,100 controls) • Texture of dry sample • Composition: • Mineralogy, mineral: crystalline solid • +2,200 minerals, • 40 commonly seen • ROCKS COMPOSION VARIES BASED ON MINERAL COMPOSITION • Mineral content • Grain size • LP Microscopy, shows animal, plant and artificial remains and their %s • Side by side comparison

  18. Minerals: • Minerals are used by various commercial and industrial companies. • Brick, shale, plaster, and concrete are all found in many indoor products, drywall insulation. • Robbery suspects often have minerals within clothing fibers. • Why???? • Locard’s Exchange Principle

  19. Locard’s Exchange Principle • The exchange of materials between two objects that occurs whenever tow objects come into contact.

  20. Physical Properties of Soil Organics • Humus: a mixture of organic material that binds nutrient mineral ions and holds water. • Detritivores like Earthworms, termites, and ants help to breakdown humus. • Humus persists in agricultural soil for about 20 years. • Humus  CO2 + H2O + nutrient + minerals

  21. Physical Properties of Soil(Organisms) • Bacterial and Protozoan colonies • Plant litter • Fungi • Animal • Most common insects, arachnids, and annelids • Materials in varying states of decomposition

  22. Physical Properties of SoilSoil Pore Spaces • Pore spaces: Occupy about 50% of a soils volume and can be filled with H2O (soil H2O) or air (soil air). • Soil air is found in larger pores. • Soil H2O is found in smaller pores (0.05mm).

  23. Physical Properties of Soil Soil Horizons • Horizontal layers of organized soil. • A soil profile is a vertical section from surface to parent material. Differentiated Instruction Alert

  24. Soil Horizon Basic

  25. Soil Horizon Basic Boreal Forest

  26. Soil Horizons

  27. Soil Horizons for Honors??

  28. Soil Collection • Various interval 100 yard radius of the CS. • Sampling Surface and Subsurface layers • Approximately 1 tablespoon per sample • Individual plastic vials On Suspect • Both soil and object are wrapped in paper • Layering effect on vehicles: occurs over time due to sedimentation • Collected separately only if jarred loose

  29. Soil Comparisons Soil nutrients, Nitrate and Phosphorus Water holding capacity Texture pH Organic Content Sieve Percent Composition Undisturbed vs. newly disturbed soil Density Leads to other chapters Crime Scene Impression Foot and tire Anthropology Botanicals Inductively coupled plasma mass spectrometry (ICPMS) (Ask Mark He can get you one) Laboratory Possibilities

  30. Soil Comparison: • Differences in soils can identify location of victims, suspects, or the crime scene. • Or Inconsistencies between them!! • Remember the DEA SA Camarena?

  31. Disturbed Soil Comparison: Newly disturbed Soil showing O-Layer:(Organic)fresh, organic topsoillayer OldUndisturbedSoil same consistent color

  32. Excavations:

  33. Lab: Investigating Soil Core Sampling

  34. Lab: Finding Your Past • Objective: Locate evidence of a past structure that is no longer in existence. • Hint: Try to remember past homes, hangouts, relatives homes . Can you think of a structure • Change the color of your house? • Relocate a structure?

  35. Lab: Finding Your Past

  36. Lab: Finding Your Past

  37. Lab: Finding Your Past

  38. Charcoal tells us what?? • Another Attempted Cremation: Like Hitler, Joseph and Magda Goebbels were cremated. The bodies of their six children remained in the bunker. They were found by Russian soldiers when Berlin fell to the Allies.

  39. Density-Gradient Tube: • Glass tubes measuring 6 to 10 millimetres in diameter and 25 to 40 centimetres in length are filled with several layers of two liquids mixed in varying proportions such that each layer has a different density. • An example is the mixture of tetrabromoethane, which has a density of 2.96 gmL-1 with ethane, with a density of 0.789 gmL-1. • The soil components then sink to the layers corresponding to their own density values and the distribution of particles can be compared between soil specimens. Sample from Crime Scene Sports Pitch College Gardens Courtyard

  40. Inductively coupled plasma mass spectrometry (ICP-MS) The coupling of ICP-MS shows many advantages over other analysis techniques. • Benefits of the ICP over other radiation sources include improvement in excitation and ionization efficiencies and the reduction or elimination of many of the chemical interferences found in flames or furnaces. • Mass spectrometry generates a large amount of information, has high throughput capabilities, high sensitivity and low limits of detection. ICP-MS is capable of multi-elemental detection which reduces analysis time and therefore increases sample throughput. ICP-MS is one of the few analytical techniques that permits the quantifying of elemental isotopic concentrations and ratios. • It can achieve very low limits of detection

  41. Inductively coupled plasma mass spectrometry (ICP-MS) An analysis of the elemental composition of the soil. • The plasma is formed by argon gas flowing through a radiofrequency field where it is kept in a state of partial ionization, i.e. the gas consists partly of electrically charged particles. This allows it to reach very high temperatures of up to approx. 10,000ºC. • The sample being analyzed is introduced into the plasma as a fine droplet aerosol. ICP-MS is the combination of an ICP with a mass spectrometer (MS). • The ions generated by the ICP are directed into the MS, which separates the ions according to their mass-to-charge ratio. Thus, ions of a selected mass-to-charge ratio can be detected and quantified.

  42. Inductively coupled plasma mass spectrometry (ICP-MS)

  43. Inductively coupled plasma mass spectrometry (ICP-MS)

  44. Inductively coupled plasma mass spectrometry (ICP-MS)

  45. Inductively coupled plasma mass spectrometry (ICP-MS)

  46. Finito’

  47. Website link: Analytical Techniques for the Comparison of Soil Samples Links: • www.channel4.co.uk/.../S/science/ images/fracture.gif • http://www.file:///C:/InetTemp/Content.IE5/QFML2789/256,1,All About Glass • http://www.adtdl.army.mil/cgi-bin/atdl.dll/fm/19-20/Ch10.htm

  48. Sewage leak do to inadequate Support

  49. Sherlock Holmes • “…observation shows me that you have been to the Post Office this morning, but deduction lets me know that you dispatched a telegram.”

  50. Sherlock Holmes • “It is simplicity itself. Observation tells me that you have a little reddish (soil) mould adhering to your instep. Just opposite the post office they have taken up the pavement and thrown up some earth. (It is) impossible to go to the post office without treading that dirt. The earth is a particular reddish color not found anywhere else in town – observation – the rest is deduction.”

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