Encouraging eyewitnesses to falsely corroborate allegations: effects of rapport-building and incriminating evidence

Building rapport involves developing a harmonious relationship with another person and conveying understanding and acceptance towards that person. Law enforcement officers use rapport-building to help gather information from witnesses. But could rapport-building, in some situations, work to contaminate eyewitness testimony? Research shows that compelling incriminating evidence can lead people to corroborate false accusations made against another person. We investigated whether rapport-building – when combined with either Verbal or Verbal+Visual false evidence – might boost these corroboration rates. Subjects took part in a pseudo-gambling task, in which their counterpart was falsely accused of cheating. Using a 2 (Rapport: Rapport vs. No-rapport) × 2 (Incriminating Evidence: Verbal vs. Verbal+Visual) between-subjects design, we persuaded subjects to corroborate the accusation. We found that both rapport and verbal+visual incriminating evidence increased the compliance rate. Even when the incriminating evidence was only presented verbally, rapport-building subjects were almost three times as likely to corroborate a false accusation compared to subjects who did not undergo rapport-building. Our results suggest that although there is widespread and strong support for using rapport-building in interviews, doing so also has the potential to aggravate the contaminating power of suggestive interview techniques.