Fingerprint Comparison Expertise

Forensic fingerprint examiners are awarded 'expert' status within courts of law and are presumed to have specialist knowledge and ability that would not be found within the general population, yet questions arise as to whether expertise in forensic fingerprint comparison is a scientifically valid and reliable process. To explore this assumption, a novel online fingerprint aptitude test was created (Chapter 2) to measure the abilities of untrained controls ('Novices'), fingerprint examiners-in-training ('Trainees'), and qualified fingerprint examiners ('Experts') in a variety of fingerprint tasks (Chapter 3). Analyses focussed on group and individual differences in performance. Accuracy in latent print comparison differentiated the abilities of these three groups, and Experts demonstrated a level of performance that scarcely any Novices were able to match. This thesis therefore proposes a cognitive theory of fingerprint comparison expertise that reflects superior performance by fingerprint examiners in the most challenging aspects of fingerprint comparison. In addition, this theory suggests that there should be a clear separation in the performance of fingerprint examiners and untrained observers, with any overlap in abilities not a marker of expertise. This theory of expertise was further expanded by the application of a battery of perceptual tasks, designed to reflect the varied cognitive components of fingerprint comparison (Chapter 4). This test battery data demonstrates that fingerprint expertise is underpinned by an ability in feature matching, and mental rotation with non-fingerprint stimuli, and a role for global processing during latent print comparison. Conversely, perceptual processes such as visual short-term memory and visual search did not demonstrate the same relationship with fingerprint identification. This thesis concludes with suggestions for future research and recommendations for incorporating these findings into police selection processes for fingerprint examiner recruitment.