Soil and Glass Analysis

Objectives You will understand: How to analyze and present data mathematically using graphs. Why soils can be used as class evidence. When soils can be used as circumstantial evidence.

Objectives, continued You will understand: The difference between physical and chemical properties. How glass can be used as evidence. How individual evidence differs from class evidence. The nature of glass. How to use the properties of reflection, refraction, and refractive index to classify glass fragments. Objectives, continued

Objectives, continued You will be able to: Identify a soil’s common constituents. Determine the origin of a soil sample. Interpret a topographic map. Understand the concept of spectrophotometry and its applications.

Objectives, continued You will be able to: Make density measurements on very small particles. Use logic to reconstruct events. Use technology and mathematics to improve investigations and communications. Identify questions and concepts that guide scientific investigations. Objectives, continued

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. Kendall/Hunt Publishing Company

Forensic Geology The legal application of earth and soil science Characterization of earthen materials that have been transferred between objects or locations and the analysis of possible origin or sources Petrology-branch of geology that studies the origin, composition, distribution and structure of rocks.

Forensic Geologist Tools Binocular microscopes Petrographic microscopes X-ray diffraction Scanning electron microscopes Microchemical analysis

Forensic Geology History 1887–1893—Sir Arthur Conan Doyle wrote about scientific ideas and techniques for solving crimes in his writings of Sherlock Holmes. This included information about soil and its composition which had never actually been used. 1893—An Austrian criminal investigator, Hans Gross, wrote that there should be a study of “dust, dirt on shoes and spots on cloth.” He observed, “Dirt on shoes can often tell us more about where the wearer of those shoes had last been than toilsome inquiries.”

Forensic Geology History, continued 1904—Georg Popp, a German forensic scientist, presented the first example of earth materials used as evidence in a criminal case, the strangulation of Eva Disch. 1910—Edmond Locard, a forensic geologist, was most interested in the fact that dust was transferred from the crime scene to the criminal. This helped to establish his principle of transfer.

Soil Definitions: naturally deposited materials that cover the earth’s surface and are capable of supporting plant growth; complex mix of different sized mineral grains from the weathering of rock and from organic matter from the decay of organisms; forensic definition includes anything mixed in with the soil (glass, paint, metal, concrete, other man-made products, vegetation and animal material) The Earth

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. Kendall/Hunt Publishing Company

Soil, continued Formation Living matter—plants, animals, microorganisms Climate Parent materials Topography—slope and land form Time

Soil Profile: 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 (bedrock) makes up the R horizon. Kendall/Hunt Publishing Company

Kendall/Hunt Publishing Company

Soil Texture Triangle

Example using Soil Triangle Find percentages for each soil type: Sand = 1.5 cm/4.5 cm = 0.3333 x 100 = 33.33% Silt = 2 cm /4.5 cm= 0.4444 x 100 = 44.44% Clay = 1 cm/4.5cm = 0.2222 x 100 = 22.22% Data: Sand = 1.5 cm Silt = 2 cm Clay = 1 cm Total cm = 4.5 cm Must find % if not given

Use % to find intersections Sand = 33.33% Silt = 44.44% Clay = 22.22% Soil Type = Loam

Chemistry of the Soil The pH scale shows how acidic or basic something is. Kendall/Hunt Publishing Company

Chemistry of the Soil An important chemical property of soil is whether it is acidic or basic (alkaline). Materials that make up a soil are not the only factors that affect its pH level. 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. Kendall/Hunt Publishing Company

Soil composition continued Nutrients—macro Nutrients—micro Nitrogen Phosphorus Potassium Calcium Magnesium Sulfur Manganese Iron Boron Copper Zinc Molybdenum Chlorine

Soil Comparisons May establish a relationship or link to the crime, the victim, or the suspect(s) Physical properties—density, magnetism, particle size, mineralogy, color Chemical properties—pH, trace elements

Probative Value of Soil Types of earth material are virtually unlimited. They have a wide distribution and change over short distances. As a result, the statistical probability of a given sample having properties the same as another is very small. Probative value of soil can be excellent. More than 70,000 kinds of soils have been identified in the United States.

Soil Evidence Class characteristics—the type of soil may have similar characteristics at the primary and/or secondary crime scene, on the suspect or on the victim Individual characteristics—only if the soil has an unusual or specialized ingredient such as pollen, seeds, vegetation, or fragments

Increasing Probative Value Rare or unusual minerals Rocks Fossils Manufactured particles

Minerals Naturally occurring crystals More than 2,000 have been identified. Twenty or so are commonly found in soils; most soil samples contain only three to five. Characteristics for identification—size, density, color, luster, fracture, streak, magnetism

Rocks Aggregates of minerals Types Natural—like granite Man-made—like concrete Formation Igneous Sedimentary Metamorphic

Fossils Remains of plants and animals May help geologists to determine the age of rocks Some are scarce and can be used to identify regions or locations

In order to present credible evidence in Soil Collection 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). Kendall/Hunt Publishing Company

looking at samples macroscopically X-ray diffraction 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. Explain how each of the following is useful in the examination of soil samples: looking at samples macroscopically X-ray diffraction Kendall/Hunt Publishing Company

Sand Sand is the term applied to natural particles with a grain diameter between 1/16 mm and 2 mm. Its color and contents are dependent upon the parent rock and surrounding plant and animal life. (The photo on the right shows color differences in sand from six locations around the world.)

Sand Characteristics Composition is based on the material of the source; also gives the sand its color Texture is determined by the way the source was transported Shape Grain size Sorting/Settling

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. Kendall/Hunt Publishing Company

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. Kendall/Hunt Publishing Company

Mineral Composition of Sand —Skeletal and Precipitate Sand Skeletal sand gives off bubbles when mixed with an acid. Oolite formation is not a result of weathering but an example of depositions. Kendall/Hunt Publishing Company

Sand Types Continental sands—formed from weathered continental rock, usually granite Ocean floor sands—formed from volcanic material, usually basalt Carbonate sands—composed of various forms of calcium carbonate Tufa sands—formed when calcium ions from underground springs precipitate with carbonate ions in the salt water of a salt lake

Sand Evidence “In every grain of sand is a story of earth. ” Sand Evidence “In every grain of sand is a story of earth.” —Rachel Carson Class characteristics—the type of sand may have similar characteristics to the primary and/or secondary crime scene, on the suspect or on the victim Individual characteristics—only if the sand has an unusual ingredient or contaminant

Birefringence Refractive Index-measurement of the bending of light If the light is divided into 2 different rays is called double refractions and the numerical difference between the refractive indices is called birefringence. Can see different colors using crossed polarized lenses. Isotropic substances do not exhibit birefringence (ex. Table salt, glass, liquids) Anisotropic material exhibit birefringence (ex. Sodium nitrate, cellophane, quartz, hair, some fibers)

Forensic Geology in the News A nine-year-old’s body was found in a wooded area along a river in Lincoln County, South Dakota. A forensic geologist collected soil samples from the fenders of a suspect’s truck and from the area where the body was found. Both soils contained grains of a blue mineral that turned out to be gahnite, a rare mineral that had never been reported in South Dakota. As a result, the soil tied the suspect to the crime.

Coors case

GLASS

Introduction and History of Glass Egypt circa 2500 B.C.—The earliest known human-made glass objects (beads) 1st Century B.C.—glass blowing begins 13th Century—specialized glass production was an art, a science, and a state secret in the republic of Venice

Introduction and History of Glass 14th Century—glass-making spreads through Europe The industrial revolution applies mass production to many types of glass Analysis of glass found at a crime scene can yield trace evidence

Characteristics of Glass Hard, brittle, amorphous material Amorphous because its atoms are arranged randomly Due to its irregular atomic structure, it produces a variety of fracture patterns when broken Has numerous uses and thousands of compositions Glass Regular crystal

Characteristics of Glass Usually transparent Primarily composed of silica, with various amounts of elemental oxides Exhibits conchoidal fracture

Physical Characteristics Density—mass divided by volume Refractive index (RI)—the measure of light bending due to a change in velocity when traveling from one medium to another Fractures Color Thickness Fluorescence Markings—striations, dimples, etc.

Composition of Glass (continued) Made by melting the following ingredients at extremely high temperatures Sand The primary ingredient Also known as silica or silicon dioxide (SiO2) Lime or calcium oxide (CaO) is added to prevent the glass from becoming soluble in water Sodium oxide (Na2O) is added to reduce the melting point of silica or sand

Composition of Glass (continued) Three categories of substances found in all glass Formers Makes up the bulk of the glass Examples: silicon dioxide (SiO2) in the form of sand, boron trioxide (B2O3), and phosphorus pentoxide (P2O5) Fluxes Change formers’ melting points Examples: sodium carbonate (Na2CO3) and potassium carbonate (K2CO3) Stabilizers Strengthen the glass and make it resistant to water Calcium carbonate (CaCO3) is the most frequently used

Composition of Glass (continued) The raw materials for making glass are all oxides The composition of a sample can be expressed in percentage of different oxides Example: the approximate composition of window or bottle glass is Silica (SiO2) – 73.6 % Soda (Na2O) – 16.0 % Lime (CaO) – 5.2 % Potash (K2O) – 0.6 % Magnesia (MgO) – 3.6 % Alumina (Al2O3) – 1.0

Common Types Soda-lime—used in plate and window glass, glass containers, and electric lightbulbs Soda-lead—fine tableware and art objects Borosilicate—heat-resistant, like Pyrex Silica—used in chemical ware Tempered—used in side & rear windows of cars Laminated—used in the windshield of most cars

Obsidian is a natural form of glass that is created by volcanoes Types of Glass Obsidian is a natural form of glass that is created by volcanoes Soda-lime glass The most basic, common, inexpensive glass – also the easiest to make Used for manufacturing windows and bottle glass

Types of Glass (continued) Leaded glass Contains lead oxide which makes it denser Sparkles as light passes through it (light waves are bent) Used for manufacturing fine glassware and art glass Is commonly called crystal

Types of Glass (continued) Tempered glass Stronger than ordinary glass Strengthened by introducing stress through rapid heating and cooling of its surface When broken, this glass does not shatter, but fragments or breaks into small squares Used in the side and rear windows of automobiles

Types of Glass (continued) Laminated glass Constructed by bonding two ordinary sheets of glass together with a plastic film Also used by automobile manufactures

2 Useful Physical Characteristics Density Density = Mass/Volume Mass measured in grams Volume measured in mL Refractive Index (RI) Measure of light bending when traveling from one medium to another Becke Line Snell’s Law

Density Type of Glass Density window 2.46–2.49 headlight 2.47–2.63 Pyrex 2.23–2.36 lead glass 2.9–5.9 porcelain 2.3–2.5

Methods of Comparison: Density and Measurements Density comparison A method of matching glass fragments Density (D) is calculated by dividing the mass (M) of a substance by its volume (V) D = M / V

Methods of Comparison: Density and Measurements (continued) Density comparison (continued) Example A solid is weighed on a balance against known standard gram weights to determine its mass The solid’s volume is then determined from the volume of water it displaces Measured by filling a cylinder with a known volume of water (v1), adding the object, and measuring the new water level (v2) The difference (v2 – v1) in milliliters is equal to the volume of the solid Density can now be calculated from the equation in grams per milliliter

Methods of Comparison: Density and Measurements (continued) Flotation comparison A sample of glass is dropped into and sinks to the bottom of a liquid containing an exact volume of a dense liquid, such as bromobenzene (d = 1.52 g/mL) A denser liquid, such as bromoform (d = 2.89 g/mL), is added one drop at a time until the piece of glass rises up from the bottom and attains neutral buoyancy Neutral buoyancy occurs when an object has the exact same density as the surrounding fluid, and neither sinks nor floats, but is suspended in one place beneath the surface of the fluid

Refraction

Normal line is perpendicular to the glass surface Refractive Index When a beam of light moves from one medium into another, there is a change in its speed change, and therefore, direction Refractive Index—a tool used to study how light bends as it passes from one substance to another Normal line is perpendicular to the glass surface

Refractive Index Liquid RI Glass Water 1.333 Vitreous silica 1.458 Olive oil 1.467 Headlight 1.47–1.49 Glycerin 1.473 Window 1.51–1.52 Castor oil 1.482 Bottle Clove oil 1.543 Optical 1.52–1.53 Bromobenzene 1.560 Quartz 1.544–1.553 Bromoform 1.597 Lead 1.56–1.61 Cinnamon oil 1.619 Diamond 2.419

Bends light toward the normal line Refractive Index When a beam of light moves from less dense medium (air) into a more dense medium (water): Its speed slows, and Bends light toward the normal line Forensic Science: Fundamentals & Investigations, Chapter 14

And bends light away from the normal line Refractive Index When a beam of light moves from a more dense medium (glass) into a less denser medium (air): Its speed increases And bends light away from the normal line

Determination of Refractive Index Immersion method—lower fragments into liquids whose refractive index is different Match point—when the refractive index of the glass is equal to that of the liquid Becke line—a halo-like glow that appears around an object immersed in a liquid. It disappears when the refractive index of the liquid matches the refractive index of the object (the match point).

Application of Refractive Index to Forensics Immersion method—used when glass fragments found at the crime scene are small

Application of Refractive Index to Forensics Place the glass fragment into different liquids of known refractive indexes The glass fragment will seem to disappear when placed in a liquid of the same refractive index

Application of Refractive Index to Forensics Becke Line—a halo-like effect appearing at the edges of a glass fragment when the refractive index of the glass and liquid are different If the line is inside the glass perimeter, the glass index is higher than the index of the liquid If the line is outside the glass perimeter, the glass index is lower

The Becke Line The Becke line is a “halo” that can be seen on the inside of the glass on the left, indicating that the glass has a higher refractive index than the liquid medium. The Becke line as seen on the right is outside the glass perimeter, the glass index is lower

Determination of Refractive Index, continued The refractive index of a high-boiling liquid, usually a silicone oil, changes with temperature. This occurs in an apparatus called a hot stage which is attached to a microscope. Increasing the temperature allows the disappearance of the Becke line to be observed. At match point, temperature is noted and refractive index of the liquid is read from a calibration chart.

Fracture Patterns in Broken Glass Being an amorphous solid, glass will not break into regular pieces with straight line fractures Fracture patterns provide clues about the direction, rate, and sequence of the impacts

Fracture Patterns Radial fracture lines radiate out from the origin of the impact; they begin on the opposite side of the force. Concentric fracture lines are circular lines around the point of impact; they begin on the same side as the force. 3R rule—Radial cracks form a right angle on the reverse side of the force.

Glass Fracture Patterns (continued) Types of fractures Radial Produced first Always form on the side of the glass opposite to where the impact originated Look like spider webs that spread outward from the impact hole Always terminate into an existing fracture

Glass Fracture Patterns (continued) Types of fractures (continued) Concentric Form next Encircle the bullet hole Always start on the same side as that of the destructive force

Why Radial and Concentric Fractures Form Glass after an impact shows radial fractures (red) and concentric circle fractures (blue)

Why Radial and Concentric Fractures Form Impacted glass is compressed on the side it is hit. It will stretch on the opposite side of the glass, and the tension there will radiate breaks in the glass outward from the point of impact. Then fractures form in the shape of concentric circles on the same side of the impact.

Why Radial and Concentric Fractures Form

Fracture lines: Radial and Concentric • Radial fracture lines occur first extending outward from the break point, produced when the opposite side of impact fails first • Concentric fracture lines form a circle about the break point and are produced by the side of impact failing first

Sequencing A high-velocity projectile always leaves a wider hole at the exit side of the glass. Cracks terminate at intersections with others. This can be used to determine the order in which the fractures occurred.

Determine the order of projectiles when dealing with more than one. 2 1 3

Glass Fracture Patterns (continued) Determining the direction from which a bullet was fired Compare the size of the entrance hole to the size of the exit hole Exit holes Always larger, regardless of the type of material that was shot A larger piece of glass is knocked out of the surface where the bullet is leaving because glass is elastic and bows outward when struck

Glass Fracture Patterns (continued) Entrance holes The bullet makes a very small hole when it enters The glass always blows back in the direction of the impact because of its elasticity The glass snaps back violently after being stressed and can blow shattered glass back several meters Most of the shattered glass lands on the impacted side of the glass, instead of by the exit hole

Path of a Bullet Passing through Window Glass perpendicular to the glass shot from the left shot from the right The angles at which bullets enter window glass help locate the position of the shooter Bits of the glass can fly backward (backscatter), creating trace evidence

Investigation/Analysis includes Comparing Glass Investigation/Analysis includes Finding Measuring Comparing

Glass as Evidence Class characteristics: physical and chemical properties such as refractive index, density, color, chemical composition Individual characteristics: if the fragments can fit together like pieces of a puzzle, the source can be considered unique

Comparing Glass (continued) Class Characteristics (Density and Refractive Index) The general composition of glass is relatively uniform and offers no individualization Trace elements in glass may prove to be distinctive and measureable characteristics The physical properties of density and refractive index are used most successfully for characterizing glass particles, but only as a class characteristic This data (density and refractivity) gives analysts the opportunity to compare and exclude different sources of data

Comparing Glass (continued) Individual Characteristics Only occurs when the suspect and crime scene fragments are assembled and physically fitted together Comparisons of this type require piecing together irregular edges of broken glass as well as matching all irregularities and striations on the broken surfaces Most glass evidence is either too fragmentary or minute to permit a comparison of this type

Considerations for Collection The collector must consider that fragments within a questioned sample may have multiple origins. If possible, the collector should attempt an initial separation based on physical properties. The collector must consider the possibility that there may be a physical match to a known sample (e.g., a piece of glass to a fractured vehicle headlamp). When an attempt to make a physical match is made at the site of collection, the collector should take precautions to avoid mixing of the known and questioned samples. Any glass samples collected should be documented, marked (if necessary), packaged, and labeled. —Forensic Science Communications

Collecting the Sample The glass sample should consist of the largest amount that can be practically collected from each broken object and packaged separately. The sample should be removed from the structure (e.g., window frame, light assembly). The inside and outside surfaces of the known sample should be labeled if a determination of direction of breakage or reconstruction of the pane is desired. When multiple broken glass sources are identified, it is necessary to sample all sources. A sample should be collected from various locations throughout the broken portion of the object in order to be as representative as possible. The sample should be collected with consideration being given to the presence of other types of evidence on that sample (e.g., fibers, blood). —Forensic Science Communications