Forensic Chemistry and Toxicology - Petrography in Crime Detection PDF 2024

Forensic Chemistry and Toxicology Study Guide 8 – Petrography as applied to Crime Detection ____________________________________________________________________________________________________ LEARNING 2. Geological Material Examination: Geologi...

Forensic Chemistry and Toxicology Study Guide 8 – Petrography as applied to Crime Detection ____________________________________________________________________________________________________ LEARNING 2. Geological Material Examination: Geological materials such as rocks, minerals, and OBJECTIVES sediments can also provide valuable clues in After studying this module, you as a future crime investigations. Petrography allows Criminologist should be able to: forensic experts to determine the source of these materials, potentially tying a suspect to a) Discover the significance of petrography in the location where evidence was collected. crime detection. 3. Toolmark and Microscopic Analysis: b) Provide the different component of soil Petrography enables the examination of leading to crime detection. toolmarks and microscopic features on c) Apply soil analysis to scientific crime objects or surfaces. This can be instrumental detection. in determining whether a particular tool or weapon was used in a crime, potentially connecting it to a suspect or a specific TOPIC location. OUTLINE 4. Construction Materials Analysis: In cases involving property crimes or accidents, 1. Definition of Petrography and its application petrography can be used to identify the in Crime Detection composition of construction materials like 2. Soil Analysis concrete, asphalt, or ceramics. This 3. Dust and Dirt knowledge can help in identifying the source 4. Proper Sampling, Handling and Preserving of of these materials, assisting in the Soil, Dust and Dirt Evidences investigation. 5. Methods And Techniques in Examining Soil, 5. Geological Profiling: Just as criminal Dirt and Dust profilers create profiles of suspects, DEFINITION OF petrographers can create geological profiles PETROGRAPHY AND ITS of crime scenes. By analyzing the APPLICATION IN CRIME mineralogical and geological characteristics DETECTION of a location, investigators can gain insights into where a suspect may have been or where a crime might have occurred. Petrography is a branch of geology that plays a 6. Expert Testimony: Forensic petrographers crucial role in forensic science especially in the field often serve as expert witnesses in court, of crime detection. In order to understand the origins, providing their analysis and interpretations to composition, and characteristics of this evidence, it assist judges and juries in understanding the focuses on the detailed examination of rocks, significance of geological evidence in a case. minerals, and their microscopic features. For crime detection, petrography provides valuable insights into Petrography in crime detection is a specialized and the analysis of trace evidence, including soil, powerful tool that allows forensic scientists to minerals, and geological materials found at crime analyze and interpret geological and mineralogical scenes or on suspects. By understanding the evidence. By understanding the origins and principles and applications of petrography, forensic characteristics of trace materials, investigators can investigators can link physical evidence to specific establish links between suspects, crime scenes, and locations, objects, or suspects, thereby aiding in the physical evidence. This introduction sets the stage resolution of criminal cases. for a comprehensive module on petrography in crime detection, which will delve deeper into the principles, Petrography in Crime Detection: methodologies, and real-world applications of this fascinating field, ultimately aiding in the pursuit of 1. Soil Analysis: Soil is one of the most common justice. types of trace evidence found at crime scenes. By employing petrographic SOIL ANALYSIS techniques, forensic scientists can identify the mineralogical composition, texture, and geographic origin of soil samples. This Forensic Soil Analysis is the use of soil science and information can be used to link a suspect's other disciplines (e.g., geochemistry and geology) to shoes or clothing to a particular crime scene, aid in criminal investigations. Since each soil helping establish a potential connection. possesses unique properties that serve as identification markers, soils can be traced and matched to each other. For example, clay embedded different shaped peds or clumps (e.g., blocky in the sneaker of a criminal can be traced back to a or platy) that occur within the soil. specific clay type found along a lake where a murder a. Blocky peds are small multi-grain victim was discovered. conglomerates (i.e. clumps of grains) Each soil type has unique characteristics that provide b. Prismatic or columnar peds are important clues about its history, formation, and vertical columns. location of origin, such as color, texture, and c. Platy peds are flat, sheet-like structure. For example, the color of a soil indicates its conglomerates. history as well as the compounds present in the soil. d. Granular soil is crumbly. White or gray soil may contain lime or have been e. Single-grained soil lacks peds. leeched, while black or gray soil indicates that the soil contains organic materials and/or moisture. Red, brown, or yellow soil usually indicates the presence of iron compounds. Sometimes horizons can form in soils, which are layers of soil that are distinguished from each other by their unique physical and chemical properties. The creation of such a “layer cake” is often referred to as a soil profile, which is a record of soil formation over time. Classification of Color, Texture, and Structure of Soil 1. Soil color is classified according to the Munsell Color Chart which specifies colors based on three color dimensions: hue, value (lightness), and chroma (color purity). The Munsell color scheme is the official color system for soil research in the United States. 2. Soil texture is determined by the relative proportion of sand, silt and clay found in each soil: Figure 1: Soil Structure a. Sand is gritty to the touch and the individual grains can be seen with It is essential to acknowledge the limitations of soil the naked eye. Sandy soils are analysis in petrography. While it can link a suspect or coarse in texture and are the largest evidence to a particular location, it cannot definitively of the three size classes. prove guilt. Other factors, such as the suspect's alibi b. Silt is smooth and slippery to the or the presence of additional evidence, must also be touch, like flour or baby powder. The considered. individual grains are much smaller than those of sand. These individual DUST AND DIRT particles can only be seen with a microscope. c. Clay is sticky when wet. It can easily be rolled into balls between the Dust refers to fine, dry particles of matter that are forefinger and thumb. The individual suspended in the air. These particles can be particles are extremely small and composed of a wide range of materials, including soil, can only be seen with an electron pollen, skin cells, minerals, and organic matter. Dust microscope. Clay soils are the finest can originate from natural sources like soil erosion, in texture and the smallest of the volcanic activity, or plant debris, as well as from three size classes. human activities such as industrial processes, 3. Soil Structure is another unique soil property. construction, and vehicle emissions. Some soils are composed of single grain Dirt, on the other hand, generally refers to loose, dry particles, while other soils may include soil or earth that has settled on surfaces. It's a cementing agents, such as calcium broader term that encompasses various types of carbonate (CaCO3), iron (Fe), or organics, particulate matter, including minerals, organic which hold the soil particles together. These material, and possibly contaminants. Dirt typically particles adhere to each other to form results from soil being moved or disturbed, for example, by natural processes like wind or water Study Guide 8 – Forensic Chemistry and Toxicology | Page 2 of 4 erosion, or human activities such as digging, walking, 4. Source Differentiation: Different types of dust or vehicle movement. and dirt have unique characteristics, allowing forensic scientists to distinguish between Difference between Dust and Dirt: samples from different locations. 5. Cross-Contamination Prevention: While dust and dirt are related, they differ primarily in Understanding the nature of dust and dirt is their location and form. Dust is typically airborne and essential for preventing cross-contamination consists of fine, particulate matter suspended in the during evidence collection, storage, and air. Dirt, on the other hand, is settled on surfaces and analysis. comprises loose soil or earth. 6. Environmental Forensics: Dust and dirt Classification of Dust and Dirt: analysis can be applied in environmental investigations to trace pollution sources, 1. Mineral Dust: This category includes assess contamination levels, and monitor particles primarily composed of minerals like changes in environmental quality. quartz, feldspar, clay minerals, and other crystalline materials. Mineral dust can be a PROPER SAMPLING, HANDLING significant component of both natural AND PRESERVING OF SOIL, DUST AND DIRT EVIDENCES geological processes (e.g., volcanic eruptions) and anthropogenic activities (e.g., construction). Sampling: 2. Organic Dust: This category includes particles of biological origin, such as pollen, 1. Use Clean Tools: Ensure that all tools and spores, and plant fragments. Organic dust containers used for sampling are clean and can be allergenic and is often encountered in uncontaminated. Metal or glass containers are natural environments with vegetation. preferred because they are less likely to introduce 3. Combustion Residues: These are fine contamination. particles resulting from the incomplete 2. Avoid Cross-Contamination: Prevent cross- combustion of organic material. They can contamination by using separate tools and include soot, ash, and other carbonaceous containers for each sample location. Clean tools materials. Combustion residues are common and containers between collections. in environments with high levels of burning, 3. Collect a Representative Sample: Gather samples such as urban areas or industrial sites. from various points within the area of interest. 4. Industrial Dust: This category encompasses Take samples from different depths if possible. particles generated from industrial Mix the collected material to create a composite processes, such as metal grinding, cement sample that represents the entire area. production, and chemical manufacturing. 4. Document the Sampling Process: Keep detailed These particles can contain a wide range of records of the sampling process, including the materials, including metals, minerals, and date, time, location, and specific sampling chemicals. methods used. Photograph the collection process to document the condition of the area. Relevance to Forensic Science: 5. Label and Document Each Sample: Label each container with a unique identifier that 1. Trace Evidence Analysis: Dust and dirt can corresponds to the sampling location. Include serve as crucial trace evidence in forensic detailed notes on each sample's physical investigations. They can link individuals, characteristics and source. objects, or vehicles to specific locations. 6. Protect Samples from Environmental Conditions: 2. Scene Reconstruction: By analyzing the Store samples in a manner that prevents changes composition and distribution of dust and dirt, in their condition due to temperature, moisture, or forensic experts can reconstruct events, other environmental factors. such as the movement of individuals or vehicles, and provide insights into the Handling: timeline of a crime. 3. Geographical Profiling: The mineral 1. Wear Appropriate Personal Protective Equipment composition of soil and dust can provide (PPE): Use gloves, masks, and other protective clues about the geographical origin of gear to minimize the risk of contaminating or samples. This information can be vital in altering the evidence. missing persons cases or when identifying 2. Minimize Handling: Minimize contact with the the source of evidence. evidence to avoid transferring contaminants Study Guide 8 – Forensic Chemistry and Toxicology | Page 3 of 4  from your hands or clothing. Use clean tools for 3. X-Ray Diffraction (XRD): XRD is used to identify handling. the crystalline structure of minerals in soil and dust samples. It can be helpful in determining the 3. Secure and Seal Containers: Ensure that mineral composition of a sample. containers are securely sealed to prevent the loss 4. X-Ray Fluorescence (XRF): XRF is employed to of material during transport and storage. determine the elemental composition of soil and dust. It's particularly useful for identifying trace Preserving: elements and heavy metals. 5. Inductively Coupled Plasma Mass Spectrometry 1. Air-Dry When Appropriate: For some types of soil (ICP-MS): ICP-MS is used to quantify trace or dirt evidence, air-drying may be necessary to elements in soil and dust samples, providing prevent mold growth. Spread samples on clean, highly sensitive and accurate results. dry surfaces and allow them to air-dry naturally. 6. Chemical Analysis: Chemical tests can reveal 2. Seal in Airtight Containers: After air-drying (if information about the composition of soil and applicable), seal the evidence in airtight, non- dust, including the presence of organic matter, contaminating containers to prevent changes in pH levels, and the concentration of specific moisture content or contamination. chemicals or pollutants. 3. Avoid Contamination: Continue to handle the 7. Stratigraphy Analysis: Stratigraphy involves evidence with care to prevent contamination, and examining the layering and deposition history of avoid opening containers unnecessarily. soil samples. It can help establish the 4. Store in Secure Locations: Store evidence in a chronological sequence of events at a crime secure and controlled environment, such as an scene. evidence room or a laboratory, to prevent 8. Geographic Information Systems (GIS): GIS can tampering or degradation. be used to map and analyze the distribution of METHODS AND TECHNIQUES IN soil types and compositions across a crime EXAMINING SOIL, DIRT AND scene or geographic area, aiding in source DUST identification. 9. Thin-Layer Chromatography (TLC): TLC can be used to separate and identify organic Forensic analysis of soil, dirt, and dust involves a compounds, such as plant extracts or range of methods and techniques to examine these contaminants, in soil or dirt samples. materials and gather valuable information for criminal investigations. Here are some of the Prepared by: methods and techniques commonly used in forensic JUSTIN MIGUEL F. SEBIAL soil, dirt, and dust analysis: Faculty, College of Arts and Sciences 1. Visual Examination: Preliminary examination involves visually inspecting soil, dirt, or dust samples. This includes noting color, texture, and the presence of any macroscopic features like plant fragments, minerals, or other contaminants. 2. Microscopy: Microscopy techniques are essential for examining fine details of soil and dust samples. a. Light Microscopy: This is used to examine the physical characteristics of soil, including particle size, shape, and mineral composition. b. Scanning Electron Microscopy (SEM): SEM can provide high-resolution images of particles, aiding in the identification of minerals and morphological features. c. Transmission Electron Microscopy (TEM): TEM offers even higher magnification and is useful for studying the internal structure of micro-sized particles. Study Guide 8 – Forensic Chemistry and Toxicology | Page 4 of 4