An investigation of fingermark submission decision making
HC Earwaker · UCL Discovery (University College London) · 2017
This thesis investigates the submission of fingermark evidence from the fingerprint laboratory (where the enhancement of crime scene fingermarks occurs) to the fingerprint bureau (where examiners compare crime scene and suspect fingermarks) within UK forensic science. Initial research presented in this thesis identifies a discrepancy between laboratory practitioner mark submission decision making and the usability decisions made by fingerprint examiners, in the case of ambiguous fingermarks, leading to the potential for a loss of evidence that could be used to identify a suspect. Further empirical research explores the components of this decision process through consideration of decision success, cues, thresholds, and factors that influence the decision process. Qualitative research explores the rationale behind the mark submission decisions of practitioners, identifying a common reliance on a numerical value of characteristics present as a threshold for submission. The reliability of the use of a minutiae count as a method for increasing the objectivity of the submission is further investigated and variation between the minutiae cue detection of practitioners and examiners is identified. A contrast effect is found to occur in relation to practitioners making submission decisions concerning fingermarks in situ on exhibits that contain background marks, and this effect is discussed in relation to the differences in practitioner and examiner quality determination procedure. The findings of these empirical studies are presented and explained in terms of psychological theories of judgement and decision making, as well as in terms of their procedural and practical implications for fingerprint evidence recovery, and their wider implication within the holistic forensic process and criminal justice system.