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Chapter 15Soil and Glass Analysis and Paint too! What is Soil? Soil Material • Partly Organic – Decaying matter – Ex. Peat: 100% Organic • Partly Inorganic – Minerals – Ex. Sand: 100% Inorganic What’s in soil? • • • • • • Rocks Minerals Vegetation Animal Waste Glass Construction Debris • Asphalt How Do Soils Differ? • Color How Do Soils Differ? – 1,000 different colors Wet soils appear dark! • • • • • • • Texture Particle size pH Density Fossil types (Diatoms) Mineral and Rock Content Pesticides/Herbicides? Forensic Geology:Geo-Tracking Forensic Geology: Geo-Tracking Forensic Geology: Geo-Tracking Minerals and Rocks? Minerals =Naturally occurring crystals (2,200 known) Look at: Color, shape, density, refractive index Minerals • Fluorescence Rocks = Contain a combination of different minerals Soil and Crime • Hit and Run: - Under-fender dirt/soil deposited at impact with the victim. matching the grease on the victim with the grease under the car. • Rape: - Soil on clothing of a suspected rapist placed suspect at the crime scene. • Murder: - Soil found on murder victims used to determine the location of homicides, especially when the murder occurs in one location and the body is then moved. • Assault: - Identifying the type of rocks used as weapons led to the source of the rocks and helped locate suspects. Soil Evidence Collection Keep soil in clumps if from car Layers tell the history of the soil being added to the car Soil Evidence Collection 100 yds Collect soil at crime epicenter and at intervals up to a 100 yard radius from crime 1 or 2 tablespoons of TOP SOIL All soils packaged separately Glass • One of the oldest manufactured product • Amorphous Ingredients to make glass: 1. 2. 3. – Sand (mostly silica sand) Soda (Na2CO3)-lowers melting point Lime (CaO)-makes it water insoluble Combination of metal oxides: • Ex. Sodium, calcium, magnesium, aluminum between 1,500 and 2,500 degrees Celsius Glass Production Video Tempered or Safety Glass • Car glass • Dicing and little splintering • Stress glass by rapid heating and cooling =annealing • Glass also strong from lamination – Thin piece of plastic between glass layers Borosilicate glass • Able to withstand high temperatures 1500 F • Add boron oxides to mix Bullet-Proof Glass • http://www.youtube.com/watch?v=h5HM3y 8d0NA Glass Fracture Analysis Glass Fractures • Crime Scene Reconstruction: -Force and Direction of Impact -Type of projectile (bullet or rock) Concentric Fractures Radial Fractures Projectiles+Direction of Force Exit side of bullet is a deep crater 3R Rule =Radial cracks form a Right angle on the Reverse side of force Concentric fractures originate on the force side of glass Multiple Bullet Holes A B Which Bullet Came First? Bullet Holes • Radial fractures caused by the passage of a bullet will stop at any pre-existing fracture Mechanical Fit Analysis • Physical Fit of Edges • Look at Glass Ream Patterns Glass as Forensic Evidence Glass fragments recovered from clothing number & distribution are important a piece of glass embedded in a shoe has low probative value many small fragments from a shirt or sweater can be highly significant Glass must be classified window glass vs broken bottle glass Individualization may be possible Other Classification Methods Microscopy float glass is absolutely flat wine glasses are slightly curved bottles have microscopic defects from mold Fluorescence when excited by UV radiation, many glasses exhibit fluorescence caused by heavy metals (including tin) Fluorescence Can differentiate between float and non-float window glass Can differentiate between different samples of float glass in some cases (a) non-float glass or non-float side (b) float side Sample #1 (c) float side Sample #2 Comparative Studies FBI has a data base of from glass manufacturers of densities and refractive indexes =Used for frequency of occurrence issues If R.I.=1.5290 then found in 1/2000 specimens If R.I.=1.5180 then found in 22/2000 specimens Problem! • Most glass is uniform in its making and show no individualistic traits! Refractive Index Trace Chemical Analysis of Glass Properties of glass and soil – Physical Properties; can be measured without changing the substance, i.e., color, hardness, Refractive Index, birefringence, density, melting point, etc... Chemical Properties; the way a substance changes (reacts), i.e., combustion Density Determination D = m/V Sink or float Density Gradient Tubes Volume Displacement Method Refraction The bending that occurs when a light wave passes at an angle from one medium to another (air to glass) bending occurs because the velocity of the wave decreases Refractive Index Determination •Becke Line=Bright Halo that disappears when medium and fragment have the same refractive indexes •Medium index can be varied by adjusting temperature of stage Birefringence (a.k.a.Double Refraction) • Refraction of light in 2 directions • Sandwich between polarizing filters Paint • Where do we find painted surfaces? Paint and Locard’s Principle • Small pieces of paint are often unwittingly transferred between objects during • • • • • • vehicle accidents, burglaries, robberies, assaults, homicides, even from simple contact with freshly painted surfaces during a crime. Paint Composition Paints are opaque coatings that are typically made up of three components: Pigment: very tiny particles of organic and inorganic colored compounds that give the paint its characteristic hue. Binder: suspends the pigment particles and helps to firmly fix them to the surface. Solvent: such as water or an organic liquid, provides a consistency suitable for spreading the paint on the surface. Paints vs. Dyes • Dyes: – usually a soluble compound that binds directly to the material and does not require any medium to bind the colored material to the surface. Proper collection and preservation of paint evidence from an automobile suspected of being involved in hit-and-run incident. Paint that is foreign to the suspect automobile is observed. Procedure 1. 2. 3. 4. Scrape the foreign paint as well as all underlying layers of paint off the car’s surface using a clean knife or scalpel. The scraping must clearly show the layer structure of the paint. Obtain a control paint sample from an adjacent undamaged area of the car. Again, all layers must be included. Package each paint specimen separately in a proper container. A druggist fold or a vial makes an excellent container. Label all specimen containers. Evidence collector’s name or initials, the date, and the sampling location are to be shown. All items collected are to be described in the evidence collector’s field notes. Paint As Evidence • Individual Characteristics or Class Characteristics? Class unless…… Multilayered Paint Chip Custom Finishes Problem • A single type of car paint can be on many different models • For a given color/type of paint, batches don’t vary much in composition • Binder chemical composition may vary very slightly from batch to batch What to do? What to do? PDQ (Paint Data Query) • Law enforcement database of specific paint formulas added onto cars since 1974 Pigments and History ● Ochre is a mineral that has been sought and used by humans even before homo sapiens came into existence ● It has been used as: Body paint Artist paint Sun blocker Medicine (antiseptic and clotting agent) Possible religious symbol for blood, life, etc Pigments ~35,000 -10,000 ybp Prehistoric Cave Paintings Pigments Used Homo Sapiens Charcoal, lampblack (soot) C Pyrolucite, MnO Hematite, Fe2O3 Magnetite, Fe3O4 Limonite, Fe2O3 *H2O There is good evidence that in the cave paintings that many of the colors were a mixture of various pigments, and at some sites there is evidence that ochre was calcined (heated) to get other colors Pigments Prehistoric Cave Paintings Pigments Mineral Pigments in Use from Ancient thru Medieval Times Hematite Magnetite Limonite Goethite Malachite Azurite Cinnabar Chrysocola Lapis Lazuli Realgar Orpiment Cinnabar Verdigris (copper acetate - Ancient Greek) Van Dyke Brown (17th century peat extract) Hans Van Meegeren Traded fake paintings for genuine artwork in the 1930s Christ and the Disciples at Emmaus Supposedly an undiscovered masterpiece by Vermeer Johannes Vermeer Last Supper supposedly by Vermeer Technique • Used a synthetic phenolformaldehyde resin - known as Albertol or Ambertol dissolved in a spirit such as turpentine and/or an essential (i.e., non-fatty) oil such as oil of lilac or oil of lavender, which would then be mixed with hand-ground powder pigments. • He heated the resin transforming its chemical composition so that chemical tests would show it is really not the chemical it actually was • He painted over low value17th century paintings. He scraped away old painting “Leveling Paint” • Art Fraud analysis • Art Forger Pigments in Forensic Geology ● Because many of the pigments are minerals standard geological techniques such as microscopy, X-ray diffraction, SEM analysis, and optical spectroscopy can be used to discriminate them The organic vehicle or binders can be discriminated by Gas Chromatography – Mass Spectrometry