What an Eyewitness Can Give Us

Courts have long treated a confident witness as a strong one, and the research of the past forty years has been read as showing that the confidence is worthless. That reading goes too far. In carefully run identifications, where the witness is told the suspect may be absent, where the people in the line-up resemble the description rather than each other, and where no feedback is given, confidence recorded at the moment of the first identification predicts accuracy quite well.

[A] What destroys the relationship is what happens afterwards. A witness who is told that the person they picked is the one the police suspected becomes markedly more confident without becoming more accurate, and the same witness will later remember having been sure at the time. [B] Confidence, in other words, is not a fixed property of a memory but a quantity that keeps being edited, and by the time it reaches a courtroom it has usually passed through several hands. [C] The practical conclusion is not that juries should ignore confidence but that they should ignore all of it except the first expression of it, which is the only version formed before the witness learned anything new. [D] That is a demanding requirement, since it means the value of the evidence is fixed within seconds and cannot be recovered later by careful questioning.