lifetime.34 Uniqueness and persistence are necessary conditions for friction ridge identification to be feasible, but those conditions do not imply that anyone can reliably discern whether or not two friction ridge impressions were made by the same person. Uniqueness does not guarantee that prints from two different people are always sufficiently different that they cannot be confused, or that two impressions made by the same finger will also be sufficiently similar to be discerned as coming from the same source. The impression left by a given finger will differ every time, because of inevitable variations in pressure, which change the degree of contact between each part of the ridge structure and the impression medium. None of these variabilities—of features across a population of fingers or of repeated impressions left by the same finger—has been characterized, quantified, or compared.35

To properly underpin the process of friction ridge identification, additional research is also needed into ridge flow and crease pattern distributions on the hands and feet. This information could be used to limit the possible donor population of a particular print in a statistical approach and could provide examiners with a more robust understanding of the prevalence of different ridge flows and crease patterns. Additionally, more research is needed regarding the discriminating value of the various ridge formations and clusters of ridge formations.36 This would provide examiners with a solid basis for the intuitive knowledge they have gained through experience and provide an excellent training tool. It also would lead to a good framework for future statistical models and provide the courts with additional information to consider when evaluating the reliability of the science. Recently, research has begun to build some of this basis.37


F. Galton. 1892. Fingerprints. New York: MacMillan; H. Cummins and C. Midlo. 1943. Finger Prints, Palms and Soles: An Introduction of Dermatoglyphics. Philadelphia: The Blakiston Company; A. Hale. 1952. Morphogenesis of volar skin in the human fetus. The American Journal of Anatomy 91:147-173; S. Holt and L.S. Penrose. 1968. The Genetics of Dermal Ridges. Springfield, IL: Charles C Thomas Publishing; W. Montagna and P. Parakkal. 1974. The Structure and Function of Skin. New York: Academic Press; J. Raser and E. O’Shea. 2005. Noise in gene expression: Origins, consequences, and control. Science 39:2010-2013.


Some in the friction ridge community point to an unpublished 1999 study by the Lockheed-Martin Corporation, the “50K vs. 50K Fingerprint Comparison Test,” as evidence of the scientific validity of fingerprint “matchup.” But that study has several major design and analysis flaws, as pointed out in D.H. Kaye. 2003. Questioning a courtroom proof of the uniqueness of fingerprints. International Statistical Review 71(3):524. Moreover, even if it were valid, the study provides only a highly optimistic estimate of the reliability of friction ridge analyses, biased toward highly favorable conditions.


Haber and Haber also provide a sensible research agenda for enhancing the validity of fingerprint comparisons.


E.g., C. Neumann, C. Champod, R. Puch-Solis, N. Egli, A. Anthonioz, and A. Bromage-Griffiths. 2007. Computation of likelihood ratios in fingerprint identification for configurations of any number of minutiae. Journal of Forensic Sciences 52(1):54-64; N.M. Egli,

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