Establishing evidence through undercover and collective intelligence interviewing

We examined the potential of undercover interviewing and collective interviewing in eliciting cues to deceit in intelligence interviews. Twenty-four pairs of truth tellers and 23 pairs of liars undertook a mission in which they were interviewed covertly in a park by an undercover interviewer, and then had a later formal, forensic-style interview with a second interviewer. Truth tellers and liars went to the park for different reasons and carried out somewhat different activities. Liars were instructed that if they were asked about their activities to conceal their true reason for visiting the park and to pretend to be there for the same reason as truth tellers. Based on theoretical principles about short-term gains, lack of cognitive flexibility, tendency to avoid reporting potential incriminating information, memory deficits, lack of imagination, and transaction information search, we expected liars to be less forthcoming about their meeting with the undercover interviewer and to show less overlap in their answers in the undercover and formal interviews. We also expected them to report fewer unexpected events, and to consult each other less during the formal interview. The hypotheses were supported and the implications for intelligence interviewing are discussed.