United Streaming: The Value of Evidence Name Alexander Torres Complete this worksheet as you watch the video. 1. The job of the Forensic Science Unit is to collect physical evidence. 2. To document a tire track, it is first photographed and then casts are made using dental cement that is poured into a metal form. 3. Investigators use a high-powered light to trace the path to the victim. The light shines at wavelengths that cause materials to fluoresce and orange goggles help make evidence stand out sharply. 4. Evidence that is collected at a crime scene is sent to the Department of Law Enforcement and is analyzed by a chemest, who goes through the debris that is collected at a crime scene. 5. carpet fibers are valuable clues because they can link suspects to a specific location. 6. The tire track expert studies the photographs taken at the crime scene to examine the tread pattern to determine what kind of vehicle uses that kind of a tire. 7. Tire treads are made up of geometric shapes called pitches. The key to tire identification is to match differences in pitches. They also examine tiny cuts on the surface called sites that were molded into the tire by small metal teeth. 8. The final pieces of evidence needed for an airtight case was obtained by investigators offering a dog bathing service. During the bath, investigators gathered some dog hair and also got carpet fibers from the living room, which matched those found at the crime scenes. 9. Forensic science has become one of the justice system's most powerful Tools but can do great harm if they are misused. In one case, hairs from a crime scene lead to the conviction of an innocent man. 10. Hairs are not distinct enough to be linked to an Individual. They most investigators could ever say are that "hairs could have come from the same source" but can never say that hairs come from a given individual. Word Bank Carpet Casts Chemist Conviction Evidence Fibers Hair Individual Light Orange Pattern Photographed Physical Pitches Sites Source Tools Wavelengths Word Bank Authentic Broken Carbon Dating Color Cuticle DNA Holes Innocence Linseed Medium Medulla Microscope Paint Patterns Rungs Scholars Tissues Walnut
11. To compare hair samples, investigators examine the hair's Colors to see pigment distribution. Investigators also examine the outer sheath, called the cuticle , which grows in overlapping scales. Some hairs have a visible inner shaft, called a medula . In other hairs, the medulla appears cracked or broken or they have no medulla. 12. Each cell in the body contains dna , which is shaped like a twisted ladder with rungs. The sequence of the rungs is unique for each individual. Scientists can remove DNA from body tissues and fluids and make it key segments of it visible on x-ray film. The patterns produced in the films can positively link a suspect to DNA from a crime scene or exclude a suspect. DNA evidence was able to exclude an ex-boyfriend as well as the suspect, which proved his innocence . 13. Forensic scientists and scholars can study a painting to determine if it is Authentic or a forgery. A forensic scientist can try to determine the painting's age by taking samples of the paint and placing them on a microscope slide. Each color is made from a different mineral or vegetable base and gives it a unique appearance under a polarizing light microscope . 14. Investigators can also analyze the medium , which is a substance that suspends the pigment and allows painters to use it on a canvas. The most common medium is linseed oil, but Leonardo da Vinci also used walnut oil. 15. Samples of the canvas can be removed for carbon dating to reveal the age of the canvas itself. 16. The test results could not rule out the possibility that the painting was created by Leonardo da Vinci, so the painting's owner turned to scholars to help him. The scholars noticed the hole in Christ's wrist, which DaVinci did in his paintings.
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