Abstract
Latent print examiners use their expertise to determine whether the information present in a comparison of two fingerprints (or palmprints) is sufficient to conclude that the prints were from the same source (individualization). When fingerprint evidence is presented in court, it is the examiner's determination—not an objective metric—that is presented. This study was designed to ascertain the factors that explain examiners' determinations of sufficiency for individualization. Volunteer latent print examiners (n = 170) were each assigned 22 pairs of latent and exemplar prints for examination, and annotated features, correspondence of features, and clarity. The 320 image pairs were selected specifically to control clarity and quantity of features. The predominant factor differentiating annotations associated with individualization and inconclusive determinations is the count of corresponding minutiae; other factors such as clarity provided minimal additional discriminative value. Examiners' counts of corresponding minutiae were strongly associated with their own determinations; however, due to substantial variation of both annotations and determinations among examiners, one examiner's annotation and determination on a given comparison is a relatively weak predictor of whether another examiner would individualize. The extensive variability in annotations also means that we must treat any individual examiner's minutia counts as interpretations of the (unknowable) information content of the prints: saying “the prints had N corresponding minutiae marked” is not the same as “the prints had N corresponding minutiae.” More consistency in annotations, which could be achieved through standardization and training, should lead to process improvements and provide greater transparency in casework.
Highlights
Latent print examiners compare latents to exemplars, to determine whether the two prints originated from the same source. (See Glossary, Appendix S1.) Testimony on fingerprint evidence presented in court is based on the examiner’s expert opinion, not an objective metric: ‘‘The criteria for absolute identification in fingerprint work are subjective and ill-defined
Sixteen individualization determinations (1% of all individualizations) had fewer than seven corresponding minutiae marked; most of these can be explained as having additional corresponding features or as invalid annotation
High minutia counts are not limited to value for individualization (VID) and individualizations: there are high-count value for exclusion only (VEO) determinations and high-count inconclusive determinations; the majority of these determinations are on prints with discontinuous areas or low-clarity minutiae
Summary
Latent print examiners compare latents (friction ridge impressions from the fingers, palms, or feet of an unknown subject) to exemplars (prints deliberately collected from known subjects), to determine whether the two prints originated from the same source. (See Glossary, Appendix S1.) Testimony on fingerprint evidence presented in court is based on the examiner’s expert opinion, not an objective metric: ‘‘The criteria for absolute identification in fingerprint work are subjective and ill-defined. (See Glossary, Appendix S1.) Testimony on fingerprint evidence presented in court is based on the examiner’s expert opinion, not an objective metric: ‘‘The criteria for absolute identification in fingerprint work are subjective and ill-defined. They are the product of probabilistic intuitions widely shared among fingerprint examiners, not of scientific research.’’ [1] Because of the societal implications of fingerprint testimony, it is important to understand what examiners consider sufficient information for individualization determinations. An examiner’s determination of individualization is that examiner’s assessment that the information in the two prints is in sufficient agreement to conclude that they came from the same source. In 1973, the International Association for Identification resolved that there was no basis for requiring a ‘‘pre-determined minimum number of friction ridge characteristics’’ for individualization [12]
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