title: A large-scale statistical analysis of barefoot impressions.
abstract: 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 x 10-(10) for a general population. In other words, the odds of a chance match are one in 1.27 billion.
authors.affiliation: Forensic Identification Research Services, Royal Canadian Mounted Police, Ottawa, Ontario K1A 0R2, Canada.
authors.forename: Robert B
authors.initials: RB
authors.lastname: Kennedy
authors.forename: Sanping
authors.initials: S
authors.lastname: Chen
authors.forename: Irwin S
authors.initials: IS
authors.lastname: Pressman
authors.forename: A Brian
authors.initials: AB
authors.lastname: Yamashita
authors.forename: Ari E
authors.initials: AE
authors.lastname: Pressman
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D005260:Female; D005528:Foot / Q000033:anatomy & histology*; D005554:Forensic Medicine / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008954:Models, Biological; D025341:Principal Component Analysis; D011336:Probability