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Strengthening Forensic Science in the United States: A Path Forward
sources.25 From this base of experience, the fingerprint community asserts that the latent print examiner learns to judge whether there is sufficient detail (which varies with image quality) to make a source determination during the evaluation phase of ACE-V.
The latent print community in the United States has eschewed numerical scores and corresponding thresholds, because those developed to date26 have been based only on minutia, not on the unique features of the friction ridge skin (e.g., lengths of ridges, shapes of ridges, crease lengths and shapes, scar lengths and shapes). Additionally, thresholds based on counting the number of features that correspond, lauded by some as being more “objective,” are still based on primarily subjective criteria—an examiner must have the visual expertise to discern the features (most important in low-clarity prints) and must determine that they are indeed in agreement. A simple point count is insufficient for characterizing the detail present in a latent print; more nuanced criteria are needed, and, in fact, likely can be determined.
Reporting of Results
SWGFAST has promulgated three acceptable conclusions resulting from latent print comparison: individualization (or identification), exclusion, or inconclusive.27 Although adherence to this standard is common, some latent print examiners report either “identification” or “negative” results. “Negative” (or sometimes “not identified”) is an ambiguous conclusion, and it could mean excluded, inconclusive, or unable to locate after exhaustive search. It is problematic that the meaning of “negative” may be specific to a particular agency, examiner, or case.
Latent print examiners report an individualization when they are confident that two different sources could not have produced impressions with the same degree of agreement among details. This is a subjective assessment. There has been discussion regarding the use of statistics to assign match probabilities based on population distributions of certain friction ridge features. Current published statistical models, however, have not matured past counts of corresponding minutia and have not taken clarity into consideration. (This area is ripe for additional research.) As a result, the friction ridge community actively discourages its members from testifying in terms of the probability of a match; when a latent print examiner testifies that two
T. Busey and J. Vanderkolk. 2005. Behavioral and electrophysiological evidence for configural processing in fingerprint experts. Vision Research 45:431-448.
See, e.g., I.W. Evett and R.A. Williams. 1996. A review of the sixteen points fingerprint standard in England and Wales. Journal of Forensic Identification 46(1):49-73.