An eyewitness testimony is the evidence given in court or a police investigation by someone who has witnessed a crime or accident. For many years psychologists have investigated the factors that can affect the accuracy of eyewitness reports, in order to ensure that the evidence provided during investigations is reliable and accurate. Psychologists have identified several factors that can have a detrimental effect on the accuracy of eyewitness reports, including misleading information, through leading questions or postevent discussion, and anxiety.

Misleading Information – Post‐Event Discussion

One source of misleading information comes from leading questions, as detailed above. However, misleading information in the real world can come from other sources, for example other witnesses (cowitnesses), when they discuss the details of a crime or accident, following an incident. This is known as post‐event discussion.

Gabbert et al. (2003) 

Aim: To investigate the effect of post‐event discussion on the accuracy of eyewitness testimony. 

Method: The sample comprised 60 students from the University of Aberdeen and 60 older adults recruited from a local community.

Participants watched a video of a girl stealing money from a wallet. The participants were either tested individually (control group) or in pairs (co‐witness group). The participants in the co‐witness group were told that they had watched the same video; however, they had in fact seen different perspectives of the same crime and only one person had actually witnessed the girl stealing. Participants in the co‐witness group discussed the crime together. All of the participants then completed a questionnaire, testing their memory of the event.

Results: 71% of the witnesses in the co‐witness group recalled information they had not actually seen and 60% said that the girl was guilty, despite the fact that they had not seen her commit a crime. 

Conclusion: These results highlight the issue of post‐event discussion and the powerful effect this can have on the accuracy of eyewitness testimony. 

Evaluating Gabbert et al. (2003)

The results of Gabbert et al. also have questionable ecological validity. The participants in the cowitness condition witnessed different perspectives of the same crime, as would typically be the case in real‐life crimes. However, as in Loftus and Palmer’s research, these witnesses knew they were taking part in an experiment and were more likely to have paid close attention to the details of the video clip. Therefore, these results do not reflect everyday examples of crime, where witnesses may be exposed to less information.

Gabbert et al. tested two different populations, university students and older adults, and found little difference between these two conditions. Therefore, her results provide good population validity and allow us to conclude that post‐event discussion affects younger and older adults in a similar way.  

Although Gabbert et al.’s results provide an insight into the effect of post‐event discussion on the accuracy of eyewitness testimony, we are unable to conclude why the distortion occurs. The distortion could be the result of poor memory, where people assimilate new information into their own accounts of the event and are unable to distinguish between what they have seen and what they have heard. On the other hand, it could be that the distortion occurs due to conformity and the social pressure from the co‐witness. Further research is required to answer this question.

Anxiety

Loftus (1979) [not to be confused with Loftus & Palmer (1974)] reported the findings of Johnson & Scott (1976) who conducted an experiment to see if anxiety affects the accuracy of eyewitness testimony and facial recognition.

Loftus (1979) / Johnson & Scott (1976)

Aim: To investigate whether anxiety affects the accuracy of eyewitness testimony.

Method: Participants were invited to a laboratory where they were told to wait in the reception area. A receptionist who was seated nearby excused herself to run an errand, leaving the participant alone. The experiment used an independent groups design, as participants were then exposed to one of two conditions: 1) In the ‘no‐weapon’ condition, participants overheard a conversation in the laboratory about equipment failure. Thereafter, an individual (the target) left the laboratory and walked past the participant holding a pen, with his hands covered in grease. 2) In the ‘weapon’ condition, participants overheard a heated exchange and the sound of breaking glass and crashing chairs. This was followed by an individual (the target) running into the reception area, holding a bloodied letter‐opening knife. 

Both groups were then shown 50 photographs and ask to identify the person who had left the laboratory. The participants were informed that the suspect may, or may not, be present in the photographs.

Results: Those who had witnessed the man holding a pen correctly identified the target 49% of the time, compared to those who had witnessed the man holding a knife, who correctly identified the target 33% of the time. 

Conclusion: Loftus claimed that the participants who were exposed to the knife had higher levels of anxiety and were more likely to focus their attention on the weapon and not the face of the target, a phenomenon known as the weapon focus effect. Therefore, the anxiety associated with seeing a knife reduces the accuracy of eyewitness testimony.

Evaluation of Anxiety as a Factor Affecting EWT

A real‐life case study by Yuille & Cutshall (1986) contradicts the results of Loftus (1979) and the weapon focus effect. Yuille & Cutshall investigated the effect of anxiety in a real‐life shooting, in which one person was killed and another person seriously wounded. 21 witnesses were originally interviewed by investigating police and 13 witnesses, aged between 15 and 32, agreed to take part in Yuille and Cutshall’s follow‐up research interview, 4–5 months later. Yuille and Cutshall found that the 13 witnesses who took part in the follow‐up interview were accurate in their eyewitness accounts five months later, and little change was found in their testimonies. All of the major details of their reports remained the same and only minor details, including estimates of age, height and weight, changed. Furthermore, the witnesses avoided responding in a biased way to leading questions and the anxiety experienced at the time of the event had little or no effect on their subsequent memory for the event. These results refute the weapon focus effect and the results of Loftus (1979), and show that in real‐life cases of extreme anxiety, the accuracy of eyewitness testimony is not affected. 

Loftus’ (Johnson & Scott’s) research has been criticised for lacking ecological validity. Although the participants were waiting in the reception area outside the laboratory, they may have anticipated that something was going to happen, which could have affected the accuracy of their judgements. Furthermore, the results from real‐life case studies (see above) refute the findings of Loftus and suggest that her results do not represent real‐life cases of extreme anxiety.  

A final criticism of Loftus (Johnson & Scott) is that numerous ethical guidelines were broken. The participants were deceived about the nature of the experiment and not protected from harm. Loftus (Johnson & Scott) exposed some of the participants to a man holding a bloodied knife, which could have caused extreme feelings of anxiety. This is an issue, as these participants may have left the experiment feeling exceptionally stressed and anxious, especially if they, or someone they knew, had been involved in a knife crime.