Eyewitness identification for multiple perpetrator crimes
: examining underlying issues in memory and decision-making

  • Nina Tupper

Student thesis: Doctoral Thesis


The over-arching aim of the research conducted for this thesis was to examine
underlying issues in memory and decision-making that impact eyewitness
identification procedures in the context of multiple perpetrator crimes. In one survey and five experiments, we (i) explored key concerns in multiple perpetrator identifications in police practice in three EU countries (Police Survey), (ii) tested the independence of multiple identification decisions made successively (Experiments 1, 2 and 3) and (iii) examined the purported utility of using other faces as contextual cues for recognizing the faces of multiple perpetrators (Experiments 4 and 5). In the survey we asked police officers (from Sweden, Belgium, and the Netherlands) to describe how agencies in various countries conduct and regulate identification procedures with multiple perpetrators. Results demonstrated sizeable differences in police practice between countries and highlighted the importance of determining whether there are consequences of testing memory on multiple lineups presented in succession. In Experiments 1 and 2, participants watched a mock-crime film involving three perpetrators and later made three showup identification decisions, one showup for each perpetrator. Experiments 1 and 2 used similar procedures, with the exception of varied patterns of target-presence. Across both experiments, evidence for sequential dependencies for choosing behavior was inconsistent. In Experiment 1, responses on the second, target-present showup assimilated towards previous choosing. However, in Experiment 2, responses on the second showup contrasted previous choosing regardless of target-presence. Experiment 3 examined whether methodological differences between the recognition and eyewitness paradigms used in previous research on sequential dependencies might account for the inconsistent findings in Experiments 1 and 2. Participants studied pairs of words, landscapes, or faces, and were later tested for recognition. Sequential dependencies were detected in recognition decisions over many trials, including recognition for faces: the probability of a yes response on the current trial increased if the previous response was also yes (vs. no). However, choosing behavior on previous trials did not predict individual recognition decisions on the current trial. In Experiments 4 and 5, we sought replicate facilitative effects in cued face recognition, to (i) investigate the mechanisms underlying those effects, and (ii) determine whether such effects would extend to more than two faces. Participants encoded sets of individual, paired, or groups of four faces and were tested with no cues, correct cues (a face previously studied with the target test face), or incorrect cues (a never-before-seen face). Hit rates were not affected by either cue type or face encoding condition, but cuing of any kind (correct or incorrect) appeared to provide a protective buffer to reduce false-alarm rates in the two- and four-face conditions through increased sensitivity, but mostly reduced response bias. The present research on sequential dependencies for identification decisions suggests that the integrity of identification and recognition decisions is not likely to be impacted by making multiple decisions in a row. However, our findings suggest that cued face recognition may be a useful technique to use for reducing false recognition rates in contexts with multiple faces. Throughout the thesis, we argue for the systematic examination of influential factors that are both unique and inherent to practice, memory, and decision-making for multiple perpetrator identification and recognition.
Date of AwardSept 2017
Original languageEnglish
Awarding Institution
  • University of Portsmouth
SupervisorLorraine Hope (Supervisor), James Sauer (Supervisor) & Aldert Vrij (Supervisor)

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