Police investigators can bias witnesses? memory of criminals

Eyewitnesses are highly susceptible to the power of suggestion, finds research by Iowa State University psychologist Gary Wells, PhD, and his graduate student, Amy Bradfield. When crime investigators comment on the choice a witness makes when selecting from a police lineup?which, legally, they can do?they sway witnesses? testimony at trial, Wells says.

'If you tell the witness they?ve got the right suspect, they tend to drop any reluctance they might have had about their choice,' says Wells. 'It can change their entire testimony about the event. They?ll say they got a clear view of the suspect and picked him right out of the lineup.'

Such misleading testimony can lead juries to convict the wrong person of the crime, a strong possibility considering how easily eyewitness testimony sways juries, says Wells.

The findings, published in the June issue of APA?s Journal of Applied Psychology (Vol. 83, No. 3, p. 360?376), come from two studies involving 353 undergraduate students. Experimenters briefly showed students a grainy video image of a gunman caught on tape before robbing a Target store and shooting its security guard. They asked students to choose the assailant?s image from five photographs (none of which was of the assailant).

Students were most confident in their choice and claimed the most vivid recollection of the assailant when experimenters told them they?d chosen the 'actual suspect in the case.' By comparison, students given no feedback, or told their choice was wrong, were uncertain of the right choice.

Students were most likely to double-check their choice when experimenters immediately asked them if they were sure they?d picked the right person.

?B. Murray