Chapter 12 Soil Examination By the end of this chapter you will be able to: Identify the different minerals in sand Analyze sand found in different Hawaiian beaches Recognize various soil types Discuss soil horizons Explain the chemistry of soils Describe the collection and examination of soil evidence All Rights Reserved South-Western / Cengage Learning © 2012, 2009 Forensic Science: Fundamentals & Investigations, Chapter 12

Introduction Factors affecting soil and sand Temperature Rainfall Chemicals and minerals in the soil Soil and sand physical and chemical characteristics vary by location Soil and sand analyses help link: Suspects to crime scenes Locating burial sites Forensic Science: Fundamentals & Investigations, Chapter 12

History of Forensic Soil Examination Dr. Hans Gross— Criminal Investigation (1893) One of the first to recognize the importance of physical evidence like soil Georg Popp First to use soil evidence to solve a crime Linked soil samples found on a suspect with samples found at the crime scene (coal on handkerchief) . Forensic Science: Fundamentals & Investigations, Chapter 12

Sand & Soil Analyze for mineral content. Gross Examination Use microscopic examination.

Sand—Weathering Breaking down rock into sand with wind and water forces Old sands are more around. Forensic Science: Fundamentals & Investigations, Chapter 12

Mineral Composition of Sand Quartz Sand may contain minerals: Quartz feldspars micas iron compounds Sand can contain organic materials Coral Seashells Mica Forensic Science: Fundamentals & Investigations, Chapter 12

Composition of Hawaiian Sand Unlike the sand on a typical continental beach, the sands of Hawaii's beaches contain very little quartz. This is because there is almost no quartz present in the dark basaltic lavas of the Hawaiian volcanoes.  See the following slides for different minerals found in the sand. Forensic Science: Fundamentals & Investigations, Chapter 12

Biogenic Sand Sea Shells & Coral Forensic Science: Fundamentals & Investigations, Chapter 12

Magnetite iron bearing mineral (a form of iron oxide) that is magnetic. opaque, very small and very black and are attracted by a magnet. Forensic Science: Fundamentals & Investigations, Chapter 12

Olivine A yellow-green mineral, translucent. Forensic Science: Fundamentals & Investigations, Chapter 12

Basalt Fragments Small pieces of lava rocks Dark gray to black and are opaque Forensic Science: Fundamentals & Investigations, Chapter 12

Soil Composition Soil is top layer of Earth’s crust It is composed of Minerals Decaying organisms Water Air All in varying amounts Forensic Science: Fundamentals & Investigations, Chapter 12

Soil Texture/Types The 3 main grain sizes in soil are Sand (L) Silt (M) –sediments in riverbeds Clay (S) Loam – all three sand, silt, and clay combined. (best for agriculture) Peat – decaying organic material Chalk – alkaline soil with mineral (poor for agriculture) Forensic Science: Fundamentals & Investigations, Chapter 12

Soil Profiles 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

Chemistry of the Soil The pH scale measures the acidity or basicity of a solution Forensic Science: Fundamentals & Investigations, Chapter 12

Chemistry of the Soil Acidic or basic (alkaline)—the pH scale What affects the pH level? Materials that make up a soil Rainfall Pollution Fertilizer The pH value of a soil sample helps scientists match it to other samples Forensic Science: Fundamentals & Investigations, Chapter 12

Soil Collection —Chain of Custody A chain of custody log is essential Bag, identify, seal, and sign Each subsequent user opens bag on a “new” side Return contents to original bag evidence bag, seal it in another bag, and sign the evidence log Forensic Science: Fundamentals & Investigations, Chapter 12

Analysis Obtain some soil samples from your teacher and try to match sample with crime scene.