Volume 50, Issue 5 (September 2005)

    A Large-Scale Statistical Analysis of Barefoot Impressions

    (Received 31 July 2004; accepted 23 April 2005)

    Published Online: August


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    In an earlier paper, outlines of footprints of persons walking normally were studied to determine whether different people make verifiably distinct footprints. Our basic null hypothesis is: given a footprint outline trace made by Subject A (Alice), then Subject B (Bob), a distinct person, cannot produce a footprint outline trace indistinguishable from that of Alice. We showed in the previous work that the probability of a chance match is less than 10−8. In this paper we report two new advances in our research. First, we establish a rigorous mathematical framework for calculating worstcase and average chance-match probabilities. Second, we repeat the previous experiment to substantiate the earlier results, but with an expanded population sample size and a more representative and significantly bigger repeated sample. These improvements and a new automated tracing procedure for extracting all numerical measures lead to a sharpened accuracy with average chance match probabilities of 7.88 × 10−10 for a general population. In other words, the odds of a chance match are one in 1.27 billion.

    Author Information:

    Yamashita, AB
    Royal Canadian Mounted Police, Ottawa, Ontario

    Pressman, AE
    Carnegie Mellon Univ., Pittsburgh, PA

    Pressman, IS
    Carleton University, Ottawa, Ontario

    Kennedy, RB
    Royal Canadian Mounted Police, Ottawa, Ontario

    Chen, S
    Statistics Canada, Ottawa, Ontario

    Stock #: JFS2004277

    ISSN: 0022-1198

    DOI: 10.1520/JFS2004277

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    Title A Large-Scale Statistical Analysis of Barefoot Impressions
    Symposium , 0000-00-00
    Committee E30