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    Forensic trace evidence

    Forensic trace evidence analysis involves identifying and evaluating trace materials that can be as small as a hair strand or a fabric thread. Completion of this procedure requires special tools and expertise. Please note that certain steps of the analysis are only able to be performed by certified laboratory personnel due to the potentially sensitive and legal nature of these activities.

    Equipment, Software and Other Items Needed:

    1. Sterilized tweezers, swabs and containers for the collection of evidence
    2. Microscope (preferably, a comparison microscope for side-to-side comparisons)
    3. Personal protective equipment (PPE) – gloves, lab coat, and safety goggles
    4. Specialized light sources – UV light, ALS (alternate light source)
    5. Evidence Labels and Bags
    6. Vacuum or tape lifters
    7. Digital Camera
    8. Fume hood
    9. Software for digital image analysis (e.g., Adobe Photoshop, ImageJ)
    10. Relevant chemical reagents dependent on specific trace evidence (e.g., Luminol for blood, Ninhydrin for fingerprints)
    11. Analytical Instruments – SEM (Scanning Electron Microscope), FTIR (Fourier Transform Infrared Spectroscopy), GC-MS (Gas Chromatography-Mass Spectrometry), depending on what is required to examine the evidence.

    Primary and Foundational Concepts

    1. Locard’s Exchange Principle – Every contact leaves a trace. Which means when a perpetrator comes in contact with the environment, there is likely an exchange of materials that can serve as evidence.
    2. Transfer Evidence – The type of evidence based on Locard’s principle. These could be fibers, soils, hairs that unknowingly attached to the perpetrator.
    3. Individual and Class Characteristics – Individual characteristics are unique to a particular item where class characteristics are common to a group of items.

    Step-by-Step Guide:

    Step 1: Collection of Trace Evidence

    1.1. Wear appropriate personal protective equipment (PPE) to prevent contamination of the scene.

    1.2. Use sterilized tweezers, swabs, and containers to collect small samples. Evidence such as fibers and hair might have to be collected using tape or vacuum lifts.

    1.3. Use specialized light sources, like UV light or ALS, to find evidence that might not be visible in normal light. For example, bodily fluids.

    1.4. Take photographs of evidence in its original setting before collecting it.

    1.5. Place collected evidence in appropriate containers ensuring to avoid cross-contamination, and properly label each item collected.

    Step 2: Transport and Storage of Trace Evidence

    2.1. Secure collected evidence in sealed evidence bags and maintain the chain of custody.

    2.2. Store collected evidence in a secure and appropriate environment so as to maintain its integrity.

    **Step 3: Preliminary Examination and Classification **

    3.1. Categorize and classify evidence according to their types (hair, fiber, glass etc.).

    3.2. Perform a preliminary visual analysis under a microscope, comparing evidence with known control samples when possible.

    Step 4: Analytic Tests

    4.1. Depending on the type of evidence and test requirements, prepare the sample accordingly. This might involve dissolving, coating, or crushing the sample.

    4.2. Use relevant analytical techniques such as SEM, FTIR, GC-MS etc., to analyze the composition and characteristics of the sample. For example, SEM can show the morphology and elemental composition of the sample, while FTIR can help determine the chemical bonds and functional groups in an organic compound.

    Step 5: Data Interpretation and Reporting

    5.1. Interpret the data from the analytical tests and draw conclusions about the origin, identity, and significance of the trace evidence.

    5.2. Compile a detailed report including the methods used, findings, and interpretations.

    Step 6: Testifying

    6.1. Prepare to present and defend findings in court, if necessary, as an expert witness.