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A fingerprint is an impression of the friction ridges of all or any part of the finger. Peer Reviewed Glossary of the Scientific Working Group on Friction Ridge Analysis, Study and Technology (SWGFAST) A friction ridge is a raised portion of the Epidermis on the palmar (palm and fingers) or plantar (sole and toes) skin, consisting of one or more connected ridge units of friction ridge skin. These ridges are sometimes known as "dermal ridges" or "dermal Papilla e". Fingerprints may be deposited in natural secretions from the eccrine glands present in friction ridge skin (secretions consisting primarily of water) or they may be made by ink or other contaminants transferred from the peaks of friction skin ridges to a relatively smooth surface such as a fingerprint card.Olsen, Robert D., Sr. (1972) “The Chemical Composition of Palmar Sweat” ''Fingerprint and Identification Magazine'' Vol 53(10) The term fingerprint normally refers to impressions transferred from the pad on the last joint of fingers and thumbs, though fingerprint cards also typically record portions of lower joint areas of the fingers (which are also used to make identifications). IDENTIFICATION Fingerprint identification (sometimes referred to as ''dactyloscopy'' Ashbaugh, David R. (1991) "Ridgeology". ''Journal of Forensic Identification'' Vol 41 (1) ISSN: 0895-l 73X ) is the process of comparing questioned and known friction skin ridge impressions (see Minutiae ) from fingers, palms, and toes to determine if the impressions are from the same finger (or palm, toe, etc.). The flexibility of friction ridge skin means that no two finger or palm prints are ever exactly alike (never identical in every detail), even two impressions recorded immediately after each other. Fingerprint identification (also referred to as individualization) occurs when an expert (or an expert computer system operating under threshold scoring rules) determines that two friction ridge impressions originated from the same finger or palm (or toe, sole) to the exclusion of all others. PRINT TYPES Latent prints Although the word latent means hidden or invisible, in modern usage for Forensic Science the term latent prints means any chance or accidental impression left by friction ridge skin on a surface, regardless of whether it is visible or invisible at the time of deposition. Electronic, chemical and physical processing techniques permit visualization of invisible latent print residue whether they are from natural secretions of the eccrine glands present on friction ridge skin (which produce palmar Sweat , Sebum , and various kinds of Lipid s), or whether the impression is in a contaminant such as motor oil, blood, paint, ink, etc. Latent prints may exhibit only a small portion of the surface of the finger and may be smudged, distorted, or both, depending on how they were deposited. For these reasons, latent prints are an “inevitable source of error in making comparisons,” as they generally “contain less clarity, less content, and less undistorted information than a fingerprint taken under controlled conditions, and much, much less detail compared to the actual patterns of ridges and grooves of a finger.” Zabell, Sandy "Fingerprint Evidence" Journal of Law and Policy {Link without Title} Patent prints These are friction ridge impressions of unknown origin which are obvious to the human eye and are caused by a transfer of foreign material on the finger, onto a surface. Because they are already visible they need no enhancement, and are generally photographed instead of being lifted in the same manner as latent prints. Plastic prints A plastic print is a friction ridge impression from a finger or palm (or toe/foot) deposited in a material that retains the shape of the ridge detail.Johnson, P. Lee (1973) "Life of Latents" ''Identification News'' Vol 23(1) Commonly encountered examples are melted candle wax, putty removed from the perimeter of window panes and thick grease deposits on car parts. Such prints are already visible and need no enhancement, but investigators must not overlook the potential that invisible latent prints deposited by accomplices may also be on such surfaces. After photographically recording such prints, attempts should be made to develop other non-plastic impressions deposited in natural finger/palm secretions (eccrine gland secretions) or contaminates. CLASSIFYING FINGERPRINTS Before computerization replaced manual filing systems in large fingerprint operations, manual fingerprint classification systems were used to categorize fingerprints based on general ridge formations (such as the presence or absence of circular patterns in various fingers), thus permitting filing and retrieval of paper records in large collections based on friction ridge patterns independent of name, birth date and other biographic data that persons may misrepresent. The most popular ten print classification systems include the Roscher system, the Vucetich system, and the Henry system. Of these systems, the Roscher system was developed in Germany and implemented in both Germany and Japan , the Vucetich system was developed in Argentina and implemented throughout South America, and the Henry system was developed in India and implemented in most English-speaking countries.Engert, Gerald J. (1964) "International Corner" ''Identification News'' Vol 14(1). In the Henry system of classification, there are three basic fingerprint patterns: Arch, Loop and Whorl. Henry, Edward R., Sir (1900) ''Classification and Uses of Finger Prints'' London: George Rutledge & Sons, Ltd. There are also more complex classification systems that further break down patterns to plain arches or tented arches. Loops may be Radial or Ulna r, depending on the side of the Hand the tail points towards. Whorls also have sub-group classifications including plain whorls, accidental whorls, double loop whorls, and central pocket loop whorls. |
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