The Discrediting Effect in Eyewitness Testimony1

Loftus (1974) had subjects read summaries of criminal trials that contained the testimony of either credible or discredited prosecution eyewitnesses, and found no effect of discrediting an eyewitness. Instead, almost as many subjects voted guilty with a discredited eyewitness as with a credible eyewitness; this led Loftus to the conclusion that jurors tend to overbelieve eyewitness testimony. Loftus's conclusion was subsequently challenged by others who reported a strong discrediting effect. A series of three experiments using college students was conducted to explore the characteristics of trial summaries that might account for the discrepancy in results, such as inclusion of judicial instructions concerning proof beyond a reasonable doubt, or an eyewitness's reaffirmation of his testimony following discrediting. In all cases, a strong discrediting effect was found. Apparently the discrediting effect appears regardless of wide variation in content of trial summaries. The present data do not support the overbelief claim.