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    History

    • The concept of modern scanning electron microscopy (SEM) is based on a design that was constructed in Germany in 1938. Manfred von Ardenne took a transmission electron microscope and added scan coils to it. The design has been enhanced several times since then.

    Significance

    • Forensic science involves analyzing and comparing known and unknown materials. Making conclusive determinations about materials and their origin can be crucial to the evidence in a case. Frequently the minute size of available samples of evidence creates a problem. Scanning electron microscopes help by using electron beams to capture an image of the specimen's surface. Forensic cases often contain the results from SEM analysis as part of their evidence.

    Types

    • SEM plays a crucial role in many forensic applications, including gunshot residue, shooting distance, identifying tool marks and trace evidence. Extremely small particles and microorganisms can be magnified, examined and projected in 3D. This includes such substances as paint particles and natural as well as artificial fibers. Forensic cases have relied heavily on SEM technology when identifying fingerprints, dead bodies, stolen property, forged documents and bite marks.

    Considerations

    • SEM operates differently from a conventional microscope, which works by utilizing light and multiple lenses. Instead, SEM uses electron beams. The beams focus on the evidence sample when it is placed into a vacuum chamber. Samples that do not naturally conduct electricity are treated before being placed in the chamber. This enables them to conduct electricity, thus allowing the electrons that are emitted from the sample to react to the electron beam. Scientists can therefore do further analysis.

    Warning

    • Although there are advantages of using scanning electron microscopy in forensic cases, there are also some issues that could affect whether the results can be viewed as credible. One issue is the fact that it is imperative to preserve the integrity and evidentiary value of the sample. Ordinarily, enough of the sample must be maintained to conduct a secondary, unbiased and objective test, if required. Another issue is the need to ensure that the findings are valid. This means that the results stem from equipment that is in good working condition and properly calibrated according to industry standards.

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