Picture the scene: a bare interview room with a nasty cheap table and a few chairs, a flickering strip light illuminating a cocky villain, two cops firing questions. Time to cough!
Despite the movies it seems this may not be the best way to get a confession. Recent research has shown that a supportive (smiling, nodding, cup of tea, biscuit?) interrogator has a positive effect on interviewing. Interestingly truth tellers provide more detail than liars, but only with a supportive interviewer. It seems that by creating a calm and reassuring environment the second interviewer helps the honest interviewee to tell their (true) story in greater detail; but that this makes the lack of genuine detail available to the villain stand out more…
Original article: Samantha Mann, Aldert Vrij, Dominic J. Shaw, Sharon Leal, Sarah Ewens, Jackie Hillman, Par Anders Granhag, Ronald P. Fisher (2013). Two heads are better than one? How to effectively use two interviewers to elicit cues to deception. Legal and Criminological Psychology DOI: 10.1111/j.2044-8333.2012.02055.x
BPS blog on same research: http://bps-research-digest.blogspot.com/2013/09/forget-good-cop-bad-cop-real-psychology.html