Tuesday, 6 January 2009

Are the police any better than us at judging the accuracy of eye-witness statements?

Plenty of research has been conducted into the ability of people, including police officers, to judge whether people are lying: most of us are useless, while new research suggests the police may be better. However, little research has been conducted into whether, deliberate deception aside, people can judge the accuracy of eye-witness statements. This is an important issue given how unreliable eye-witnesses can be, even when they think they're telling the truth.

Now Torun Lindholm has made a start at plugging this gap in the literature, by presenting lay people, detectives and judges with eye-witness statements about a kidnapping they were shown on video. The participants' task was to say which statements were true and which were false.

The results showed the judges and lay people performed little or no better than if they'd simply guessed at the accuracy of the statements. However, the police detectives performed better, showing a moderate to good ability to distinguish true from false eye-witness statements. All the participants showed a bias towards saying the statements were accurate and all reported using the same cues to make their judgements: the difficulty of the questions put to witnesses, the plausibility of the witnesses' answers and the witnesses' apparent confidence in their answers. It's possible the police officers' superior performance came from their use of cues that they didn't realise they were using.

Another finding was that the participants ability to judge the accuracy of eye-witness statements was better when statements were presented by written transcript rather than by video, perhaps because people focus on unreliable cues when viewing a video. Lindholm said this result, if backed up by further research, could have real-life implications for how witness statements are presented.

"The fact that current evidence suggests that testimony transcripts provide a better basis for accuracy judgements than does live or taped testimony raises concerns regarding the orality principle to which most legal systems adhere - that only testimony given orally at court should be considered in legal procedures," Lindholm wrote.
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ResearchBlogging.orgTorun Lindholm (2008). Who can judge the accuracy of eyewitness statements? A comparison of professionals and lay-persons Applied Cognitive Psychology, 22 (9), 1301-1314 DOI: 10.1002/acp.1439

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

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