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Chapter 14 Notes Part 3

Chapter 14 Notes Part 3. Fingerprints. Preservation of Developed Prints. Once a latent print has been developed, it must be permanently preserved for future comparison and possible use in court as evidence. Preservation of Developed Prints.

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Chapter 14 Notes Part 3

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  1. Chapter 14 Notes Part 3 Fingerprints

  2. Preservation of Developed Prints • Once a latent print has been developed, it must be permanently preserved for future comparison and possible use in court as evidence.

  3. Preservation of Developed Prints • A photograph must be taken before any further attempts at preservation.

  4. Preservation of Developed Prints • Any camera with a close up lens may be used for photographing fingerprints.

  5. Preservation of Developed Prints • Additional photographs must be taken to provide an overall view of the print’s location with respect to other evidential items at the crime scene.

  6. Preservation of Developed Prints • Once photographs have been secured, one of two procedures is to be followed.

  7. Preservation of Developed Prints • If the object is small enough to be transported, it should be preserved in its entirety.

  8. Preservation of Developed Prints • The fingerprints on the object should be covered in cellophane so it will be protected from damage.

  9. Preservation of Developed Prints • Prints on large immovable objects that have been developed with powder can best be preserved by “lifting.”

  10. Preservation of Developed Prints • The most popular type of lifter is broad, clear, adhesive tape.

  11. Preservation of Developed Prints • When the tape is applied to the powdered print and then pulled up, the powder is transferred to the tape. • The tape is then placed on a card that provides a good background contrast with the powder.

  12. Digital Imaging for Fingerprint Enhancement • When fingerprints are lifted from a crime scene, they are not usually in perfect condition, making the analysis much more difficult.

  13. Digital Imaging for Fingerprint Enhancement • Digital imaging software can be used to enhance fingerprints for the most accurate and comprehensive analysis.

  14. Digital Imaging for Fingerprint Enhancement • Digital imaging is the process by which a picture is converted into a digital file.

  15. Digital Imaging for Fingerprint Enhancement • The image produced in a digital file is composed of numerous square electronic dots called pixels.

  16. Digital Imaging for Fingerprint Enhancement • Resolution reveals the degree of detail that can be seen in an image, and is measured in pixels. • The more pixels, the more detail that can be seen in an image.

  17. Digital Imaging for Fingerprint Enhancement • The input of pictures into a digital imaging system is usually done through the use of scanners, digital cameras, and video cameras.

  18. Digital Imaging for Fingerprint Enhancement • After a picture has been converted into a digital image made of pixels, several methods can be employed to enhance it. • The brightness can be adjusted.

  19. Digital Imaging for Fingerprint Enhancement • The contrast between the image and the background can be adjusted.

  20. Digital Imaging for Fingerprint Enhancement • Color can also be adjusted to improve the image of a fingerprint.

  21. Digital Imaging for Fingerprint Enhancement • An important and useful tool, especially for fingerprint identification, is the compare function. • This feature places two images side by side.

  22. Chapter 14 Review • Fingerprints are a reproduction of skin ridges found on the palm side of the fingertips.

  23. Chapter 14 Review • Basic principles of fingerprinting are: • 1. A fingerprint is an individual characteristic. • 2. A fingerprint remains unchanged during an individual’s lifetime. • 3. Fingerprints have general ridge patterns that permit them to be systematically classified.

  24. Chapter 14 Review • All fingerprints are divided into 3 classes: loops, whorls, and arches.

  25. Chapter 14 Review • The individuality of a fingerprint is not determined by its general shape or pattern, but by a careful study of its ridge characteristics.

  26. Chapter 14 Review • AFIS aids the process of fingerprint comparison by converting the image of a fingerprint into digital minutiae.

  27. Chapter 14 Review • Prints deposited by sweat and oil that are invisible are called latent fingerprints.

  28. Chapter 14 Review • Visible prints are made when fingers touch a surface after being in contact with a material such as blood, paint, grease, etc.

  29. Chapter 14 Review • Plastic prints are impressions of fingerprints left in a soft material such as wax, soap, or dust.

  30. Chapter 14 Review • Latent prints developed on hard and nonabsorbent surfaces are preferably developed by application of fingerprint powder.

  31. Chapter 14 Review • Prints on porous surfaces generally require treatment with a chemical.

  32. Review Questions • 1. True or False: Once a latent fingerprint has been developed, it must be permanently preserved for future comparison and use in the courtoom.

  33. Review Questions • 2. True or False: Any camera that has a close up lens can be used to photograph a visualized fingerprint.

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