This research examined the impact of eyewitness identification decisions on student-investigators. Undergraduates played the role of police investigators and interviewed student-witnesses who in Studies 1 and 2 had been shown either a good or poor view of the perpetrator or in Study 3 viewed either a Caucasian or an Asian criminal, in a video-taped crime. Based on information obtained from the witness, student-investigators then chose a suspect from a database containing information about potential suspects and rated the probability that their suspect was the culprit. Investigators then administered a photo lineup to witnesses, and re-rated the probability that their suspect was guilty. Student-investigators were highly influenced by eyewitness identification decisions, typically overestimating the information gained from the identification decision (except under conditions that led witnesses to be very accurate), and generally did not differentiate between accurate and inaccurate witnesses.

Eyewitness identification evidence is often essential in criminal investigations, yet little is known about how police investigators evaluate identification evidence. This research simulated a police investigation by having participant-investigators obtain information about a crime, examine a database of potential suspects with the goal of choosing a likely suspect for the crime, and evaluate an eyewitness's lineup identification decision. Experiments 1 and 2 examined the effect of order of presentation of the eyewitness decision. When the eyewitness identified the investigator's suspect, ratings of the suspect's guilt were similar regardless of when the eyewitness decision occurred. However, when the witness reported that the culprit was not present in the lineup, a recency effect occurred (the information that was presented last had a larger impact). Experiment 3 continued to examine order effects while also examining how investigators evaluated alibi information and eyewitness testimony when they had already identified a suspect in the case. The investigators evaluated alibi evidence that was either strong or weak (in regards to exonerating the suspect) and eyewitness evidence involving a witness who either identified the investigator's suspect or rejected the suspect (by not making an identification). The order of presentation of the alibi information and eyewitness testimony was manipulated such that half of the participants received the alibi information before the eyewitness testimony while the other half received the alibi information after the eyewitness testimony. Both the eyewitness decision and alibi evidence affected ratings of guilt. A recency effect was present only in the ID Suspect/Strong alibi conditions, such that when investigators saw the witness identify the suspect and then received the strong alibi, they rated the likelihood that their suspect had committed the crime as lower than when they received the strong alibi first and then saw the witness identification. Otherwise, the two forms of evidence had an additive effect. Together, these studies provide a valuable examination of the influence of presentation order and the importance of different forms of evidence on role-playing police investigators.

This dissertation presents two individual-difference measures that could be used to assess the validity of eyewitness identification decisions. We designed a non-forced two-alternative face recognition task (consisting of mini-lineup test pairs, half of which included a studied face and half of which did not). In three studies involving a total of 583 subjects, proclivity to choose on pairs with two unstudied faces weakly predicted mistaken identifications on culprit-absent lineups, with varying correlation coefficients that failed to reach the value r = 0.4 found in Baldassari, Kantner, and Lindsay (under review). The likelihood of choosing correctly on pairs that included a studied face was only weakly predictive of correct identifications in culprit-present lineups (mean r of .2). We discuss ways of improving standardized measures of both proclivity to choose and likelihood to be correct when choosing. The second measure is based on the Guilty Knowledge Test (GKT), a lie detection method that utilizes an oddball paradigm to evoke the P300 component when a witness sees the culprit. This GKT-based lineup was intended to postdict identification accuracy regardless of witnesses’ overt responses, thus faces are used as stimuli. Half of participants were instructed to respond as if they knew the culprit and wanted to falsely exonerate him. P300 amplitudes evoked by the culprit were indistinguishable from those evoked by a different learned face but were larger than P3s evoked by unfamiliar faces in both the described lying condition and the group of participants who intentionally told the truth. / Graduate / 2018-12-05

Eyewitness identification is being researched for many years prior. However, research on eyewitness identifiaction was mostly conducted with crimes that involved only one perpetrator. For this reason, the present thesis focuses on eyewitness identification for a multiple perpetrator crime. The literature review summarises current knowledge regarding each aspect of recognition and tries to bring insight into the problem of recognition for multiple perpetrator crimes. For the empirical part of this thesis, an experiment was conducted, which aimed to compare simultaneous and sequential line-up identification accuracy. The experiment was changed from live to on-line enviroment due to the pandemic situation. The experiment was conducted on 151 young adult participants. Participants viewed a mock crime video recording involving a perpetrator and his accomplice. Participants were then randomly assigned two simultaneous or sequential line-ups and a target-present or target-absent condition. A week after viewing the video recording, each participant tried to identify the perpetrator and the accomplice in the assigned condition. Results indicated no statistically significant difference between simultaneous and sequential line-up identification. Discussion tries to explain possible influence of changing the...

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This study investigates the use of personal description as an investigation technique to identify suspects. The study entails qualitative data obtained from interviews with investigators, literature, as well as case studies. The study found that personal description can be used as an investigation technique to identify suspects. There are eight techniques that the investigator should apply in order to identify suspects or perpetrators of a criminal act. To conduct effective investigation, it is important for the criminal investigators to be familiar with the techniques of identification and the application thereof. The description of offenders plays an important role as far as arresting offenders is concerned. The methods used - or to be used - by investigators to describe a person were also discussed. It is important that the investigators should work with other government departments, private investigators and security officials, to implement this technique in order to identify and arrest offenders. / Police Practice / (M. Tech (Forensic Investigation))

This study investigates the use of personal description as an investigation technique to identify suspects. The study entails qualitative data obtained from interviews with investigators, literature, as well as case studies. The study found that personal description can be used as an investigation technique to identify suspects. There are eight techniques that the investigator should apply in order to identify suspects or perpetrators of a criminal act. To conduct effective investigation, it is important for the criminal investigators to be familiar with the techniques of identification and the application thereof. The description of offenders plays an important role as far as arresting offenders is concerned. The methods used - or to be used - by investigators to describe a person were also discussed. It is important that the investigators should work with other government departments, private investigators and security officials, to implement this technique in order to identify and arrest offenders. / Police Practice / (M. Tech (Forensic Investigation))

The research attempts to review the significance of personal description in the investigation of armed robbery cases in the Paarl policing cluster and to explore the value of identifying armed robbery suspects. The purposes of conducting this research were to evaluate the existing procedures that investigators use regarding personal description of armed robbery suspects with the intention of determining its strengths and weaknesses as well as by looking at how this procedure can be improved. Also, this research explored how investigators utilised the personal description as a technique in identifying the armed robbery suspects internationally, thereby establishing the best practices. Moreover, to recommend new procedures in obtaining a personal description of armed robbery suspects. Furthermore, to empower the South African investigators and other investigators in terms of how personal description can be recorded accurately in the case dockets and be effectively used in tracing the suspects of armed robbery cases. / Criminology and Security Science / M.A. (Criminal Justice)