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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 A photograph must be taken before any further attempts at preservation. Preservation of Developed Prints Any camera with a close up lens may be used for photographing fingerprints. 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. Preservation of Developed Prints Once photographs have been secured, one of two procedures is to be followed. Preservation of Developed Prints If the object is small enough to be transported, it should be preserved in its entirety. Preservation of Developed Prints The fingerprints on the object should be covered in cellophane so it will be protected from damage. Preservation of Developed Prints Prints on large immovable objects that have been developed with powder can best be preserved by “lifting.” Preservation of Developed Prints The most popular type of lifter is broad, clear, adhesive tape. 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. 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. Digital Imaging for Fingerprint Enhancement Digital imaging software can be used to enhance fingerprints for the most accurate and comprehensive analysis. Digital Imaging for Fingerprint Enhancement Digital imaging is the process by which a picture is converted into a digital file. Digital Imaging for Fingerprint Enhancement The image produced in a digital file is composed of numerous square electronic dots called pixels. 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. 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. 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. Digital Imaging for Fingerprint Enhancement The contrast between the image and the background can be adjusted. Digital Imaging for Fingerprint Enhancement Color can also be adjusted to improve the image of a fingerprint. 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. Chapter 14 Review Fingerprints are a reproduction of skin ridges found on the palm side of the fingertips. 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. Chapter 14 Review All fingerprints are divided into 3 classes: loops, whorls, and arches. 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. Chapter 14 Review AFIS aids the process of fingerprint comparison by converting the image of a fingerprint into digital minutiae. Chapter 14 Review Prints deposited by sweat and oil that are invisible are called latent fingerprints. 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. Chapter 14 Review Plastic prints are impressions of fingerprints left in a soft material such as wax, soap, or dust. Chapter 14 Review Latent prints developed on hard and nonabsorbent surfaces are preferably developed by application of fingerprint powder. Chapter 14 Review Prints on porous surfaces generally require treatment with a chemical. 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. Review Questions 2. True or False: Any camera that has a close up lens can be used to photograph a visualized fingerprint.