How Jurors Evaluate Fingerprint Evidence: The Relative Importance of Match Language, Method Information, and Error Acknowledgment

Fingerprint examiners use a variety of terms and phrases to describe a finding of a match between a defendant\u27s fingerprints and fingerprint impressions collected from a crime scene. Despite the importance and ubiquity of fingerprint evidence in criminal cases, no prior studies examine how jurors evaluate such evidence. We present two studies examining the impact of different match phrases, method descriptions, and statements about possible examiner error on the weight given to fingerprint identification evidence by laypersons. In both studies, the particular phrase chosen to describe the finding of a match-whether simple and imprecise or detailed and claiming near certainty-had little effect on participants\u27 judgments about the guilt of a suspect. In contrast, the examiner admitting the possibility of error reduced the weight given to the fingerprint evidence-regardless of whether the admission was made during direct or cross-examination. In addition, the examiner providing information about the method used to make fingerprint comparisons reduced the impact of admitting the possibility of error. We found few individual differences in reactions to the fingerprint evidence across a wide range of participant variables, and we found widespread agreement regarding the uniqueness of fingerprints and the reliability of fingerprint identifications. Our results suggest that information about the reliability of fingerprint identifications will have a greater impact on lay interpretations of fingerprint evidence than the specific qualitative or quantitative terms chosen to describe a fingerprint match

How Jurors Evaluate Fingerprint Evidence: The Relative Importance of Match Language, Method Information, and Error Acknowledgment

Fingerprint examiners use a variety of terms and phrases to describe a finding of a match between a defendant\u27s fingerprints and fingerprint impressions collected from a crime scene. Despite the importance and ubiquity of fingerprint evidence in criminal cases, no prior studies examine how jurors evaluate such evidence. We present two studies examining the impact of different match phrases, method descriptions, and statements about possible examiner error on the weight given to fingerprint identification evidence by laypersons. In both studies, the particular phrase chosen to describe the finding of a match-whether simple and imprecise or detailed and claiming near certainty-had little effect on participants\u27 judgments about the guilt of a suspect. In contrast, the examiner admitting the possibility of error reduced the weight given to the fingerprint evidence-regardless of whether the admission was made during direct or cross-examination. In addition, the examiner providing information about the method used to make fingerprint comparisons reduced the impact of admitting the possibility of error. We found few individual differences in reactions to the fingerprint evidence across a wide range of participant variables, and we found widespread agreement regarding the uniqueness of fingerprints and the reliability of fingerprint identifications. Our results suggest that information about the reliability of fingerprint identifications will have a greater impact on lay interpretations of fingerprint evidence than the specific qualitative or quantitative terms chosen to describe a fingerprint match

Hierarchical mixture models for assessing fingerprint individuality

The study of fingerprint individuality aims to determine to what extent a fingerprint uniquely identifies an individual. Recent court cases have highlighted the need for measures of fingerprint individuality when a person is identified based on fingerprint evidence. The main challenge in studies of fingerprint individuality is to adequately capture the variability of fingerprint features in a population. In this paper hierarchical mixture models are introduced to infer the extent of individualization. Hierarchical mixtures utilize complementary aspects of mixtures at different levels of the hierarchy. At the first (top) level, a mixture is used to represent homogeneous groups of fingerprints in the population, whereas at the second level, nested mixtures are used as flexible representations of distributions of features from each fingerprint. Inference for hierarchical mixtures is more challenging since the number of unknown mixture components arise in both the first and second levels of the hierarchy. A Bayesian approach based on reversible jump Markov chain Monte Carlo methodology is developed for the inference of all unknown parameters of hierarchical mixtures. The methodology is illustrated on fingerprint images from the NIST database and is used to make inference on fingerprint individuality estimates from this population.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS266 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org