Chapter 12 Soil Examination GMA Manson Murders Charles Manson- Dr. Baden Decomposition

Introduction *Factors such as temperature, rainfall, and the chemicals and minerals in the soil influence the production of soil. *Soil from different locations can have different physical and chemical characteristics. Because of this, soil analysis has been helpful in such things as linking suspects to crime scenes and locating burial sites. Forensic Science: Fundamentals & Investigations, Chapter 12

History of Forensic Soil Examination Dr. Hans Gross is believed to be one of the first to recognize the importance of physical evidence. His Criminal Investigation, written in 1893, had ground breaking material in this science. Georg Popp is credited with being the first to use soil evidence to solve a crime. He linked soil samples found on a suspect with samples found at the crime scene. Forensic Science: Fundamentals & Investigations, Chapter 12

Soil Composition *Any disintegrated surface material, both natural and artificial that lies on or near the earth’s surface Rocks –combo of minerals (40 common minerals can be found) Forensic Science: Fundamentals & Investigations, Chapter 12

Soil Composition Soil is part of the top layer of Earth’s crust. It contains minerals, decaying organisms, water, and air in varying amounts. *Soil texture describes the size of the mineral particles that make up soil. *The 3 main grain sizes are sand, silt, and clay. *The 3 subcategories of soil are loam, peat, and chalk. Forensic Science: Fundamentals & Investigations, Chapter 12

Soil Profiles (don’t copy) Soils are formed in layers (horizons): Humus, the O horizon, is made of decaying organic matter. Topsoil, the A horizon, is a mixture of humus and minerals. Sand and silt makes up the E horizon. Subsoil, the B horizon, is made of clay and minerals. Broken rock, the C horizon, has very little humus present. Solid rock makes up the R horizon. Forensic Science: Fundamentals & Investigations, Chapter 12

Forensic Science: Fundamentals & Investigations, Chapter 12

Chemistry of the Soil *The pH scale shows how acidic or basic something is. Forensic Science: Fundamentals & Investigations, Chapter 12

Chemistry of the Soil Rainfall can change the pH value of a soil. Pollution and fertilizer also can change the pH value of soil. *The pH value of a soil sample can help a forensic scientist match it to other samples. * Beside pH , other chemical tests can be run –like reactions with certain chemicals (ex. HCl- Carbonates bubbles) Forensic Science: Fundamentals & Investigations, Chapter 12

Sand **The action of wind and water on rocks forms sand. This may take millions of years. **Because water acts as a buffer, water produces sand more slowly than wind. Wind-blown sand becomes rounded more quickly because the grains strike each other directly without a buffer. Forensic Science: Fundamentals & Investigations, Chapter 12

Mineral Composition of Sand Sand from different locations contains different combinations of minerals. *The most common mineral found in sand is quartz. *Other than quartz, mineral content of sand can include: feldspars micas iron compounds *Sand also can be made of organic material such as coral and seashells. Forensic Science: Fundamentals & Investigations, Chapter 12

Mineral Composition of Sand —*Continental and Volcanic Sand *Note that the identifying feature of continental sand is quartz; whereas there is no quartz in volcanic sand but has volcanic ash Forensic Science: Fundamentals & Investigations, Chapter 12

Mineral Composition of Sand —*Skeletal and Precipitate Sand *Skeletal sand (shells) gives off bubbles when mixed with an acid. Oolite or Precipitate (CaCO3)formation is not a result of weathering but an example of depositions. Forensic Science: Fundamentals & Investigations, Chapter 12

Other soil types (in book) Clay Small particles, poor drainage Sticky feel Silt Medium sized particles, good drainage, easily farmed Crumbly, slippery like flour Peat Decaying organic material, retains water Compressible Loam Sand,silt, clay mix, best for ag. Loose Chalk Below top soil, bad for ag. Basic soil w/mineral stones Forensic Science: Fundamentals & Investigations, Chapter 12

Soil Collection (don’t copy) In order to present credible evidence in court, a chain of custody log is essential. A person bags the evidence, marks it for identification, seals it, and signs it across the sealed edge (above, left). It is signed over to a technician in a lab for analysis who opens it, but not on the sealed edge. After analysis, the technician puts it back into the evidence bag, seals it in another bag, and signs the evidence log (above, right). Forensic Science: Fundamentals & Investigations, Chapter 12

Soil Examination *The presence of soil unique to a certain area can show that a suspect or victim must have been in that area. Layers of soil or sand taken from shoes or the wheels of vehicles can show a suspect was present at a series of locations. *Soil is class evidence Forensic Science: Fundamentals & Investigations, Chapter 12

Testing Soil Done by forensic geologist No two places have precisely the same soil *Test: side by side comparison (macroscopic) Microscope (both low and high power) Look at color (1100 colors possible), fluorescence, pH, chemical reactions Find density with density-gradient tube Forensic Science: Fundamentals & Investigations, Chapter 12

FBI old video Forensic Science: Fundamentals & Investigations, Chapter 12