Purpose. Much crime is witnessed by more than one eyewitness, and witnesses may learn information about other witness's decisions throughout the identification and trial process. The objective of this paper was to investigate whether hearing about a co-witness's type of lineup decision and subsequent confidence level affects another witness's type of lineup choice.
Methods. A total of 304 undergraduate students watched a crime video with a confederate co-witness. After the video, the witnesses completed an identification task. Prior to completing the task, the participant learned that the confederate co-witness either chose from or rejected the lineup and was subsequently confident or not confident in that decision (or heard no co-witness information). Participants completed the identification task using either a target present (TP) or target absent (TA) lineup.
Results. Overall, those who heard the co-witness chose from the lineup were more likely to choose from the lineup than those who heard no co-witness information or who heard the co-witness rejected the lineup. In addition, witnesses who chose from the lineup and heard the co-witness chose from or rejected the lineup expressed more confidence in that choice if the co-witness was more confident versus if the co-witness was less confident.
Conclusions. In cases of multiple witnesses, identification decisions may not be independent pieces of evidence. Therefore, it is important that police separate co-witnesses throughout the identification process.