Dateline: October, 2007, Issue 1
Does testimony of trivial details hurt or help a witness' credibility?
Witnesses can offer more or fewer details in their testimony, and these details can be trivial or central. Research suggests that when witnesses offer testimony that is more detailed, even when the details are trivial, they are perceived to be more credible.
Bell and Loftus (1988) had mock jurors read a summary of a court case involving a man accused of murdering a store clerk during a robbery. A prosecution eyewitness was positive the defendant had shot the clerk, while a defense eyewitness was positive that the defendant had not. Each eyewitness described the store items that the defendant requested as either a few store items (low detail) or Kleenex, Tylenol, and a 6-pack of Diet Pepsi (high detail). When the prosecution eyewitness offered the detailed list of items, jurors were more likely to find the defendant guilty than when the prosecution eyewitness simply said the defendant requested a few store items.
Bell and Loftus reported in 1989 that detailed testimony influenced judgments of guilt, even when the detail was unrelated to the culprit (e.g., another person in the store purchased Milk Duds and a can of Diet Pepsi). Detailed testimony was especially powerful when an opposing witness testified not being able to remember the trivial details. When eyewitnesses provided more trivial details, they were judged to be more credible, to have a better memory for the culprit's face, and to have paid more attention to the culprit.
While jurors believe that a good memory for trivial details makes a witness more credible, research shows that just the opposite is actually the case. Wells and Leippe (1981) exposed people to a staged theft and later asked them to make an identification of the culprit. People not able to remember peripheral details (e.g., pictures on the wall) were more likely to make an accurate identification. Nonetheless, jurors evaluated witnesses to the theft as more credible if they remembered peripheral details.
Persuasive impact exists to "trivial persuasion," and the minor details that a witness reports can be as influential as information that has genuine significant value.
Source Bell, B. E., & Loftus, E. F. (1988). Degree of detail of eyewitness testimony and mock juror judgments. Journal of Applied Social Psychology, 18, pp. 1171-1192.
Source Bell, B. W., & Loftus, E. F. (1989). Trivial persuasion in the courtroom: The power of (a few) minor details. Journal of Personality and Social Psychology, 56, pp. 669-679.
Source Wells, G. L., & Leippe, M. R. (1981). How do triers of fact infer the accuracy of eyewitness identifications? Using memory for peripheral detail can be misleading. Journal of Applied Psychology, 64, 440-448.