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Experiment 4 Stereomicroscopes and Firing Pin Impressions (Tool Marks)

The stereomicroscope (SM) is a crucial piece of equipment in the forensic laboratory. It is used by forensic scientists for the examination of all types of physical evidence. Forensic biologists use the SM to examine potential blood and seminal stains; forensic trace evidence examiners use the SM to examine glass fragments, paint chips, hairs, fibers, textiles, ropes, broken objects, and soil, to mention just a few; forensic anthropologists use the SM to examine skeletal remains; odontologists use the SM to examine bite marks; and forensic archeologists use the SM to examine all manner of artifacts. Therefore, it is not surprising that firearms and tool mark examiners frequently make use of the SM in their preliminary examinations of firearms, bullets, projectiles, cartridges, shell casings, ballistics, and obliterated numbers. This type of microscope is also very useful in the preparation of samples for further analysis with other techniques such as x-ray diffraction, microspectrophotometry, and scanning electron microscopy. The primary reason the SM is used for so many applications in forensic science laboratories is that it produces a moderately magnified, three-dimensional, macroscopic image, thereby allowing for the close-up examination of most forms and types of physical evidence.