Page 104 - Automated Fingerprint Identification Systems (AFIS)
P. 104

CHAPTER 5


                 FROM PRINT TO IDENTIFICA TION














          This chapter provides further details on both tenprint and latent print pro-
          cessing. In addition, images of equipment used in the capture and search
          processes, as well as flow diagrams of AFIS processing, are supplied. The images,
          generously provided by Sagem Morpho, are representative of the generic
          design and features provided by all AFIS vendors. The chapter concludes with
          a discussion of the value of accurate and reliable reports, which can be obtained
          with AFIS systems.



          5.1 AFIS COMPONENTS
          The goal of the identification process is to make as many identifications as pos-
          sible with the given resources. In the world of tenprint applications, this process
          is quantity driven, with the need to respond to a request with a complete crim-
          inal history or rap sheet within a limited time period (perhaps 3 hours). For
          latent print applications, the goal is to make as many identifications as possible
          by searching millions of records and producing a candidate list that is likely to
          contain a match to the latent print image.
             Tenprint systems usually rely on the minutiae from two index fingers, two
          thumbs, or a combination of fingers and thumbs. While the system compares
          the minutiae, the examiner compares the side-by-side finger images on a
          monitor. Increasingly, AFIS administrators are adopting a “lights out” approach
          on some or all of the tenprint searches as the systems improve in accuracy. For
          example, it is now possible to search by using the patterns of all ten finger
          images, combined with the images of two index fingers and two thumbs, get a
          candidate with a high matching score, compare that with the results of a name
          search, and confirm the identification, all without human intervention or
          review.
             In contrast, latent prints found at a crime scene are generally less complete
          than the nail-to-nail image found in the AFIS database. Criminals usually do
          not choose to leave all ten finger images (let alone nail-to-nail rolls!) at a crime
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