Collective interviewing of suspects

When people are interviewed about possible wrongdoing that has been committed in groups, they typically are interviewed separately. Yet, in several settings it would be more intuitive and convenient to interview suspects together. Importantly, such collective interviews could yield verbal cues to deception. This is the first deception experiment to investigate collective interviewing. Twenty-one pairs of truth tellers and 22 pairs of liars were interviewed pair-wise about having had lunch together in a restaurant. Given that truth tellers adopt a “tell it all” strategy in the interviews while, in contrast, liars prefer to keep their stories simple, we predicted that pairs of truth tellers would (i) interrupt and (ii) correct each other more, and would (iii) add more information to each other's answers than pairs of liars. The results supported these hypotheses. Theory-driven interventions to elicit more cues to deception through simultaneous interviewing are discussed.

► Collective interviewing means interviewing pairs of suspects together.
► Truth tellers interrupted and corrected each other more than liars and also added more information to each other's stories.
► The verbal differences reflect truth tellers ‘tell it all’ and liars’ ‘keep it simple’ approaches.
► Collective interviews may be useful for stop and search duties and border patrols.