Before the publication of the Devlin Report (1976), eye witness testimonies were assumed to be accurate and reliable and therefore were often used as sole evidence in prosecution. However, the report highlighted the lack of reliability of eye witness testimonies due to various factors.
Leading questions are a main factor influencing the accuracy of eye witness testimonies. A main study investigating this factor was by Loftus and Palmer (1974). They split 45 participants into 5 different groups and had them watching 7 films of different traffic accidents. To reduce order effects, each group was shown the films in a different order. After the film, the participants were asked a series of questions, including ‘How fast were the cars going when they hit each other?’ Each group had a different verb in place of ‘hit’; smashed, collided, bumped or contacted. It was found that those who were asked the verb ‘smashed’ thought the car was going faster than those who were asked the verb ‘contacted’. This shows that the form of the question can have a significant effect on witnesses’ answers; therefore leading questions can affect the accuracy of recall.
However, this study was criticised for having low ecological validity. It was completed in a lab experiment and so was not real life; did the participants take the experiment seriously? Foster, Libkuman, Schooler and Loftus (1994) found that when participants thought they were watching a real life robbery, their identification of the robber was more accurate.
The study also had low emotional arousal, which may affect accuracy. After interviewing 110 real witnesses to bank robberies, those witnesses who had been threatened were more accurate in their recall than onlookers. This continued to be true 15 months after the event (Christianson & Hubinette, 1993).
Support for the study comes from Loftus and Zanni (1975), who had participants watching a film of a car accident and then asked half of them ‘Did you see a broken headlight?’ The other participants were asked if they saw ‘the broken headlight’. There was no broken headlight, but those who were asked about ‘the headlight’, were more likely to say they did. In contrast, however, Yuille and Cutshall (1986) interviewed witnesses 4 months after an armed robbery in Canada and included 2 leading questions. Despite the leading questions, the witnesses provided accurate recall which matched their original statement. This shows that post event information may not affect recall and that eye witness testimonies can be reliable.
Because of these factors, plus other things, eye witness testimonies can no longer be used as sole evidence in court, and are usually not the most important piece of evidence.
References:
Christianson, S., & Hubinette, B. (1993). Hands up! A study of witnesses’ emotional reactions and memories associated with bank robberies. Applied Cognitive Psychology, 7(5), 365-379. doi: 10.1002/acp.2350070502
Devlin, Lord Patrick (1976). Report to the Secretary of State for the Home Department of the Departmental Committee on evidence of identification in criminal cases. London: HMSO.
Foster, R. A., Libkuman, T. M., Schooler, J. W., & Loftus, E. F. (1994). Consequentiality and eyewitness person identification. Applied Cognitive Psychology, 8(2), 107-121. doi: 10.1002/acp.2350080203
Loftus, E. F., & Palmer, J. C. (1974). Reconstruction of automobile destruction: An example of the interaction between language and memory. Journal of Verbal Learning and Verbal Behavior, 13(5), 585-589.
Loftus, E. F., & Zanni, G. (1975). Eyewitness testimony: The influence of the wording of a question. Bulletin of the Psychonomic Society, 5(1), 86-88.
Yuille, J. C., & Cutshall, J. L. (1986). A case study of eyewitness memory of a crime. Journal of Applied Psychology, 71(2), 291-301. doi: 10.1037/0021-9010.71.2.291
Fallon Dennis 