Forensic Glass Examination PDF

**GLASS.** Glass is a hard (non-crystalline), amorphous material made by melting sand (silicon dioxide), lime (calcium oxide) and sodium oxide at a very high temperature. - Amorphous. Because its atoms are arranged in random fashion. - Main component of glass: chemical silicon dioxide (silica...

**GLASS.** Glass is a hard (non-crystalline), amorphous material made by melting sand (silicon dioxide), lime (calcium oxide) and sodium oxide at a very high temperature. - Amorphous. Because its atoms are arranged in random fashion. - Main component of glass: chemical silicon dioxide (silica) SiO2. **[Characteristics of glass:]** 1. Hard, amorphous solid 2. Usually, transparent 3. Primarily composed of silica with various amounts of elemental oxides. 4. Brittle 5. Exhibits conchoidal fracture. **[Types of glass:]** 1. Soda lime. Used in plate & window glass, glass containers, electric light bulbs. - Most common. (Approximately 90% of all produced glass is soda lime glass) - Cheap to make. - Used mostly glass items that do not have to be heated. - Great for glass recycling. Because it can be resoftened & remelted several times. 2. Soda lead. Fine table ware and art objects. - Density is much higher than soda lime glass. - High refractive index, making it brilliant and sparkling. This is why lead glass is often used in decorative items. 3. Borosilicate. Heat resistant, like Pyrex. - Primarily made of silica (SiO2) and boron trioxide (B2O3) - Extremely resistant to chemicals and temperature changes. - Can be heated and will not crack. - Used for cooking and laboratory glass (Pyrex, kimax) 4. Silica /Fused silica/. Used in chemical ware, windows for the space shuttle. - Glass made from pure silica (sand) - Strongest & most thermally stable for of glass known. 5. Tempered. Used in the side windows of cars, mobile phone screens. - 4 to 5 times stronger & safer than annealed or untreated glass. - When broken, tempered glass shatters into small, regular, pebble-like pieces that are less sharp and less likely to cause serious injury. 6. Laminated glass. Used in the windshield of most cars. - 2 sheets of tempered glass are bonded together with 1.52 mm thick Polyvinyl Butyral (PVB). - Well known for safety & security. \+ Colored glass /Tinted glass/. Tinted with metallic salts during manufacturing proc. (Oxide glass - Colored) \+ Wire mesh glass. The glass is inlaid with a grid/mesh of thin metal wire. - When wired glass breaks, the wire holds the pieces of broken glass together. - wired glass is often weaker than non-wired (unwired) glass. **Glass as forensic evidence:** - Broken/Shattered glass found at a crime scene is an important piece of evidence. - The different types of glass, each have unique properties that can be measured & compared. - Glass fragments can scatter up to nine feet or more from the point of impact, and may become lodged in the suspect\'s clothing, shoes, or hair. This can provide crucial evidence linking a suspect to the crime scene. - When a window or glass object is shattered by a projectile, such as a bullet, forensic experts analyze the breakage pattern to deduce the nature of the projectile and the angle of impact. - In some cases, investigators can identify the type of object used to break the glass based on the fracture pattern and characteristics of the impact. - The presence of glass fragments on a suspect are linking them to crime scene. **[Handling of crime scene glass samples:]** - Identify and photograph any glass samples before moving them. - Collect the samples using rubber tip forceps/plastic forceps. - Collect the largest fragments that can be reasonably collected. - If multiple window panes are involved, show their relative position in a diagram. - Look for trace evidence embedded in glass. (Hair, fiber, blood....) - Glass pieces should not be transported in glass vials. **[Collection of glass samples:]** - Glass fragments should be packaged in boxes to avoid further breakage. - If evidence has to be examined, it should be taken whole and each of them individually wrapped in paper and boxed. - For transportation, place them in sandwich layer of cotton padding in a wooden box. - If glass fragments pieced together, must be collect all fragments. - Submit glass evidence along with a control sample of each type of glass from the crime scene. Class characteristics: - Physical & chemical properties - Refractive index - Density - Color - Chemical composition. **FORENSIC EXAMINATION OF GLASS.** - Compare physical & chemical characteristics. - Optical properties: color & refractive index. - Non-Optical properties: surface wear, thickness, hardness, dirt, density - Chemical properties: additives/trace elements. Goals in examining glass evidence: - Determine the types of glass at the scene. - Determine how the glass was fractured. - Use physical characteristics to classify it. - Individualize the glass to a source. **[Forensic examination of glass: ]** 1. Physical characteristics - Color - Thickness - Fluorescence - Design or patterns - Markings- striations, dimples... - Density - Refractive index 2. Physical matching. - Perform physical matching of the larger pieces collected from the crime scene. - Count the total no. of glass pieces and segregate the pieces based on phy. characteristics. - Matching should be perform in a manner that the pieces join with each other in smooth manner rather than by force. - Avoid further breakage. 3. Refractive Index study. The refractive index of glass is a measure of how much it bends light. - Immersion method. When a transparent object, such as glass, is immersed in a liquid of same refractive index, it will be invisible because of the optical homogeneity of the system. - The Becke line. - When a glass fragment is submerged in a liquid with a similar refractive index, the boundary between the glass and the liquid becomes difficult to see, and a Becke line appears. - The Becke line is a bright halo or outline that appears around the edge of the glass fragment when viewed under a microscope. This line is due to the differences in refractive index between the glass and the surrounding liquid. - Observation: 1. If the Becke line does not appear, it indicates that RI of the glass & the liquid **same**. 2. If the Becke line appears **inside** the glass fragments, it indicates that RI of the glass is **higher** than the liquid. 3. If the Becke line appears **outside** the glass fragments, it indicates that RI of the glass is **lower** than the liquid. - Hot stage. - 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 the match point (no Becke line), the temperature is noted, and the refractive index of the liquid is read from a calibration chart. - Place the glass in the oil on the microscope, and then heating is done to look for the refractive index of the sample. 4\. Density study. Density = mass / volume. Unit: g/mL - Bromoform (very high density -- 2.89 g/cc) - Methylene iodide (high density -- 2.28 g/cc) - Bromobenzene (1.5 g/cc) - Nitrobenzene (1.2 g/cc) - Benzene (low -- 0.876 g/cc) - Xylene (low density -- 0.864 g/cc) - Direct method. - The density of the glass sample can be measure directly by determining mass and volume usually by displacement method. - 1\. Weigh the glass piece using weighing balance. - 2\. In a measuring cylinder, take 10ml of water. - 3\. Place the glass piece in water in cylinder. And record the new volume of water (Vfinal) after placing the glass piece in the cylinder. - 4\. Using density formula calculate the density of glass piece. Vdisplaced ​= Vfinal​ − Vinitial​ \-\-\-- Density = mass / Vdisplaced - Suspension method. - 1\. Weigh the glass piece using weighing balance. - 2\. In beaker, take 10 ml of water. Weigh the beaker along with water then make the weigh 0. - 3\. Tie the glass piece using string then suspend the glass piece in the beaker without touching the walls of the beaker. - 4\. Calculate the density: W1 / W1 -- W2 (W1: weigh of the glass, W2: WG after suspension) - Flotation method. - Gradient column method. - In the process we add glass sample into different densities liquids columns to determine the glass density. 5\. Fracture study & Sequencing a. Fracture patterns are unique. Forensic scientists can analyze these unique patterns to identify the origin of the break and the conditions under which it occurred. b. By examining fracture patterns, investigators can get valuable information about the object that was used to break the glass. c. Fracture examinations can reveal the direction from which the breaking force was applied. d. Fracture examinations can help establish the sequence of multiple impacts. - Radial fracture. - Fracture forming a pattern like a spider-web. - It originates on the opposite side of the force. - Always the first fracture to appear on glass. - Concentric fracture. - Fracture forming a series of broken circles. - It originates on the same side as force. - Secondary fracture as they always appear after radial fractures. - Cone fracture. - High projectile (like bullet) penetrates the glass, it makes a round crater shaped hole. - Surrounded by radial & concentric cracks. - Fracture by heat. - Fracture caused by excessive heat form V-shape. - Heat causes the glass to break into small fragments rather than larger pieces. - The fragments typically fall on the side where the heat was applied. **Rib marks.** Rib marks are stress marks found on the broken edges of glass, visible on one side of the fractured pane. In radial fractures, the rib marks indicate the direction of the force. The force acts on the same side as the tangential parts of the rib marks Help to determine the origin of the force applied to the glass. **Heckle marks.** Heckle marks are found between rib marks on the broken surface of glass. **Angle of firing.** Can help locate the position of the shooter. 1. Bullet was perpendicular to the windowpane: entry hole will be round. 2. Shooter fires from the left: glass pieces go right, exit hole will be an oval shape pointing right. 3. Shooter fires from the right: glass pieces go left, exit hole will be an oval shape pointing left. [Techniques used for elemental analysis:] - Scanning Electron Microscopy-energy Dispersive Spectrometry. - X-ray Fluorescence. - Neutron Activation Analysis. - Flameless Atomic Absorption Spectrometry. - Spark-source Mass Spectrometry. - Inductively Coupled Plasma- Optical Emission Spectrometry. - Inductively Coupled Plasma- Mass Spectrometry. - Laser Ablation-inductively Coupled Plasma-mass Spectrometry. **SOIL.** Soil is any disintegrated surface material, natural or artificial that lies on or near the earth's surface. - Natural = rocks, minerals, vegetation, animal matter - Manufactured = glass, paint, asphalt, brick fragments. **Soil as evidence:** Traces of soil found on victim's or suspect's body, or articles may give the prediction about the place where it may have come from. - In sexual assault cases, soil on victim's clothes may confirm the actual place that assault conducted. - In hit & run cases, mud on tire treads may confirm the place of accident. **Forensic importance of soil:** - Soils are like fingerprints. Because every type of soil has own unique properties. This means that origin of the soil sample can be identified. - Soil is highly individualistic. - Soil materials are easily described & characterized by color & using various analytical methods. - Soil materials are easily located & collected. **[The unique properties of soil:]** 1. Sediment. Sediment specifically refers to smaller particles that have been weathered and transported from a larger source. - Small particles that have broken off from a larger rock due to natural processes and can be carried away to different places by wind, water, or other forces. - Sediment determines the soil's texture, structure etc.... - The size & type of sediment particles (like sand, clay) directly influence the texture of the soil. Sandy soil -- feels gritty because of larger sediments. 2. Color. Soil color is unique property because it provides insights into the soil's organic matter content, mineral composition, drainage conditions, weathering processes and environmental history. - By looking at color, we can get so much information about the soil. - Depending on different locations, we will also find different colors of soil. - Grey soil mean that organic material or moisture is present. - Black soil suggests the same. - Red, brown, or yellow soil generally suggests that there is iron present. 3. Structure. Structure indicates whether a soil is composed of a single grain particle or not. Soil structure tells us whether the soil particles are just loose & separate or if they are grouped together into clumps called peds. - Granular structure. Usually less than 0.5cm in diameter. Commonly found surface horizons. - Blocky structure. Irregular blocks that are 1.5 -- 5.0cm in diameter. - Prismatic structure. Vertical columns of soil. Usually found in lower horizons. - Columnar structure. Vertical columns of soil that have a salt "cap" at the top. - Platy structure. Thin, flat plates of soil that lie horizontally. Found in compacted soil. - Single grained. Soil is broken into individual particles that do not stick together. Sandy soil. **[Types of soil:]** 1. Sandy soil. - Consists of small particles of weathered rock. - Has very low nutrients - Has poor water holding capacity. - Poorest type for growing plants. - Good for the drainage system. 2. Silt soil. - Smaller particles. - Made up of rock & other mineral particles. - Smooth & fine quality of the soil (holds water better than sand) - Found near the river, lake & other water bodies. 3. Clay soil. - Smallest particles. - Tightly packed together with each other with very little or no airspace. - Very good water storage qualities. - Densest & heaviest type of soil. 4. Loamy soil. - Combination of sand, silt and clay. - Has the ability to retain moisture & nutrients. - Agricultural soil. - Has higher calcium & pH levels because of its inorganic origins. \+ Peaty soil. - Dark brown or black in color - Easily compressed due to its high-water content - Rich in organic matter. - Peat contains acidic water. - Shallow, stony & free draining - Plants in chalky soil may show poor growth and yellow leaves (chlorosis) because their roots can\'t absorb enough iron and manganese. **Soil horizon.** The soil is arranged in different layers. Each of these layers are called soil horizon. 1. O horizon -- Organic layer. (Humus) - Uppermost layer. - Rich in organic matter such as the remains of plants & dead animals. - Black brown or dark brown in color. - Thin in some soil, thick in some other, or absent in the rest. 2. A horizon -- Topsoil. (Minerals with humus) - Found below the O horizon. - Contains the maximum organic matter of the soil. - Also called "humus" layer. - Region of intense biological activity. - Has the most nutrients. - Held together by plant root. 3. E horizon -- Eluviation layer. (Leached minerals & organic matter) - Consists of nutrients leached from O & A horizons. - Made up mostly of sand & silt, quartz & other resistant materials due to leaching of clay, minerals, and organic matter. - Absent in most soils, common in forested areas. 4. B horizon -- Subsoil. (Deposited minerals & metal salts) - Lighter in color. Because of lower humus content. - Region of deposition of certain minerals & salts of certain metals (iron oxides, aluminum oxides, calcium carbonate in large proportions) 5. C horizon -- Parent rock. (Partly weathered rock) - Also known as regolith or saprolite. - All the upper layers developed from this layer. - Devoid of any organic matter. - Plant roots do not penetrate this layer. 6. R horizon -- Bedrock. (Unweathered parent rock) - Consists of unweathered igneous, sedimentary & metamorphic rocks. - Highly compact. - Made up of granite, basalt, quartzite, sandstone & limestone. **FORENSIC EXAMINATION OF SOIL.** **[Collection of standard/reference soil sample: ]** - Standard/reference soils are to be collected at various intervals within a 100-yard radius of the crime scene for comparison to the questioned soil. a. Standard/reference soil: collected from locations that are known & documented, which could include nearby areas, similar environments or known sources for comparison. b. Questioned soil: collected from the crime scene or related items for comparison. - For standard/reference samples: only a tablespoon or two of the top layers of soil is collected and placed in individual plastic containers & labeled according to location. - Soil must be collected at all alibi locations that the suspect claims. **[Collection of soil sample:]** - Before any soil can be tested or analyzed, it must be collected and properly contained. - Swabbing technique is used to collect soil samples. - The sample should be dried and placed in a properly sized, sealable container. - Tools used for collection: spatula, palette knife, spoon, tweezer, plastering trowel, soil core. - These tools must be made of stainless steel. Because it is resistant to corrosion, scratching. - **For wet soil samples**, do not dry the samples before transporting to the lab to prevent crumbling and damage. If sample have to be dried, remove the container lids and place them in sealed paper bags to air dry gradually. Avoid using accelerated drying methods, like ovens. **[Preservation of soil samples:]** - Soil sample should be taken to forensic lab, unopened, immediately after collection. - If this is not possible for any reason, sample need to place into a dark, refrigerated space at 2°C. - Do not freeze the samples. Freezing can destroy organic evidence that found in the soil. **[Packaging of soil samples:]** 1. Plastic containers: - Use rigid, airtight & watertight plastic containers for storing soil samples. - Avoid using paper / polythene bags as they are prone to punctures. 2. Metal containers: - Avoid using metal containers because they may introduce contaminants into the samples. 3. Glass jars: - Use glass jars if the soil may react with plastic but be cautious as glass can break. - Ensure that the lids are lined with non-reactive materials to avoid any interaction with sample. 4. Labeling: - All samples should be properly labeled in the field using pre-determined code. **[Removal of blood from blood-stained soil:]** 1. Preparation of saline solution: dissolve 85mg of **sodium chloride (NaCl)** in 100ml of distilled water to create a 0.85% saline solution. 2. Pour the blood-stained soil sample in saline solution and stir for separation of blood. 3. After few hours, decant the water & wash with distilled water. 4. Dry the sample in a hot oven / hot plate at 105°C. 5. Keep it in a desiccator. **EXAMINATION:** - Microscopy Observations: (stereomicroscope) 1. Take some soil sample on a clean microscopic slide/glass plate and make its thin layer. 2. Place the slide/plate with the soil sample on the viewing stage of stereomicroscope. 3. Observe soil samples using different magnifications. 4. Observe the color of soil particles after drying at 105°C. 5. Observe the nature & shape of the particles, such as - Geometrical shapes - Black particles (coal dust, black minerals) - Red particles (brick dust, red ash, iron oxide, metal oxide) - Colorless particles (quartz grains or other colorless mineral fragments) - Green particles (potentially indicating green minerals) - Vegetation particles (grass, leaf fragments, seeds, evidence of microorganisms) 6. Find out the traces of foreign materials. - Dung / cloth fibers - Glass fragments - Hair / wooden particles. - Microscopical observation with Chemical Reagents: 1. Take small portion of the soil sample and moisten it with water. 2. Add small drop of **concentrated hydrochloric acid (HCl)** to the moistened soil sample. 3. Observe the reaction under a microscope, particularly looking for: - Bubbles arising from solid particles indicate insoluble carbonates (chalk, limestone) - Yellowing color indicates the presence of soluble iron. To confirm, add a few drops of potassium ferrocyanide solution to the sample. The appearance of green color confirms the presence of soluble iron. - Particle size distribution: 1. Take an accurately weighed quantity (50gm) of soil sample. 2. Arrange all the set of sieves in numerical order and shake the soil. 3. After shaking, collect the soil retained on each sieve separately and weigh it accurately. 4. Calculate its percentage. - Ignition test: Purpose: to test water holding capacity of soil or moisture content. 1. Take exactly 1gm of soil sample (W0) from sieve which have been dried at 105°C. 2. Heat at 110-150°C for 1 hour, then cool it to room temperature. 3. Reweigh accurately & record the loss in weight & change in color. (W1) 4. Calculate percentage of loss on ignition to the nearest 0,1 & compare it with control sample. - pH measurement: Purpose: observe the acid-alkali behavior of the soil, pH value of soil sample. 1. Dissolve weighed quantity (1gm of soil sample in 100ml distilled water & stir thoroughly) 2. Filter it. Take the filtrate & measure the pH value. 3. Add 10 ml, 20ml, 30ml, 40ml and so on successively on solution, measure the pH values after each dilution & observe their variations. 4. Perform the same pH measurement process for a control soil sample under same conditions. 5. Compare the pH values of suspect soil sample with the control soil sample. - Density distribution of soil particles: Principle used; soil particles will sink in a liquid that is less dense than the particles. And float in a liquid that is more dense than the particles. - 2 different liquids of different density are mixed together, they will diffuse into one another, and its density will as: