Eyewitness identification of multiple perpetrators

• Main Author: Hobson, Zoe J.
• Published: London South Bank University 2013
• Subjects: 347.066
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.593649

Eyewitness identification is crucial in the apprehension and prosecution of criminals and it is thought to be one of the major determining factors in jury decision making. Making accurate identifications is therefore imperative, yet research has demonstrated that a number of variables can influence an eyewitness’ identification performance. One such factor is the number of perpetrators seen in the crime event. Recently, both within England and Wales and around the world, there has been a dramatic increase in crimes which involve multiple perpetrators. In contrast, only a few isolated studies have examined eyewitness performance of identifying multiple perpetrators of one crime, all of which have suggested that accuracy is poor, but few studies have made direct comparisons to single perpetrator identifications. This research aimed to explore multiple perpetrator identification performance, and extend previous literature to examine theoretical explanations behind eyewitnesses’ performance. The first study explored the extent of multiple perpetrator identifications within England and Wales and reports the results from a survey distributed to all police identification units within each force. Four further experimental studies were then conducted. Study 2 used an eyewitness paradigm to systematically explore the effects of single and multiple perpetrators at both the encoding (crime event) and retrieval (identification) stage, with results indicating that there was a multiple perpetrator disadvantage, highlighting that multiple perpetrators cause the greatest interference at the encoding stage of the process. Study 3 considered divided attention as a theoretical explanation for the poor identification performance of multiple perpetrators by integrating a change blindness paradigm and eyewitness paradigm, again comparing between single and multiple perpetrator crimes. As those who viewed a multiple perpetrator event were less likely to notice the change in perpetrator, and identification performance was poor, Study 4 questioned whether cueing a witness using intentional instructions could focus their attention to one particular perpetrator and subsequently improve identification performance, with positive results. Since the previous experiments had found an effect of divided attention, Study 5 examined whether the similarity of the perpetrators also caused interference at encoding, with results suggesting that they do. As multiple perpetrators in one crime event appear to cause interference in the perceptual process at the encoding, or crime, stage, future research needs to identify further methods of aiding witnesses to accurately encode the information and subsequently retrieve it, whether this is through elaborate instructions, or identification procedures.