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Defining the Difficulty of Fingerprint Comparisons

NCJ Number
Date Published
National Institute of Justice
This report summarizes the methodology and findings of a research project that developed a metric to determine the difficulty of matching latent and known fingerprints, linking that difficulty to error rates.
The research determined that fingerprint examiners used in the study recognized when they were likely to make an error on a fingerprint comparison; and in aggregate, they were able to recognize when other examiners were likely to err as well. Based on these findings, the researchers concluded that their research demonstrates error rates are a function of comparison difficulty, which varies among matching analyses. This research lays a foundation for finding objective print characteristics that can be used to quantify the difficulty of each fingerprint comparison. Researchers report that their work indicates the “feasibility of an automated system that could grade the difficulty of print comparisons and predict likely error rates” for each match analysis. The research created a database from 103 fingers. Each print was first taken using ink (a standard practice by police agencies), so as to make the print as clear as possible. The person who contributed a print was then asked to use the same finger to touch a number of surfaces in a variety of ways in creating a range of latent prints typical of those found at a crime scene. The latent prints were lifted using powder and then scanned with an imaging system. Researchers used 200 latent and known print pairs for the study, half of which were a match and half of which were a close non-match. Using these pairs in various combinations, 56 fingerprint experts each made match/non-match judgments for each print, providing confidence and difficulty ratings. The overall accuracy across all of the trials was 91 percent.
Date Created: March 21, 2018