It is true, not even police officers know who is telling the truth. And anyone who tells you different is — yes — a liar. The Evidence in the News blog has a comment. Note, the comment on the research is consistent with the research. There is ample valid research to show that police officers are no better than the citizen in telling if someone is lying. The critical distinction is not that the police office can tell a person is lying but the ability to identify signs of lying. This leads to a hunch or gut instinct so the police officer uses various questioning techniques to eventually get the person to confess. Later of course the police officer says she knew the person was lying — the perfect example of my Rule of Reasoning by Hindsight.
Fingering Liars: Ask Witnesses to Tell the Story Backwards
A substantial body of research demonstrates that people are poor lie detectors. Even professionals, like police officers, perform poorly in controlled tests; they often err in separating liars from truth tellers. How can attorneys tell if their clients are lying? How can they identify lies during witness interviews? And is there any way to reveal a witness's lies to the jury?
A recent article by Aldert Vrij and colleagues highlights an intriguing new approach. When forced to recount an event in reverse chronological order, liars demonstrated more noticeable cues of deceit. They mentioned fewer details, made more speech hesitations, spoke more slowly, and shuffled their legs and feet more often than truth tellers. Responding in part to these cues, police officers in a controlled experiment were able to detect liars and truth tellers more accurately when witnesses related their stories in reverse chronological order.
Similar techniques might work for lawyers. To check a client's or witness's truthfulness, ask the individual to tell the story backwards. To expose more visible cues of deceit on the witness stand, ask an opposing witness to relate details in reverse chronological order.
The research appears in Aldert Vrij et al., Increasing Cognitive Load to Facilitate Lie Detection: The Benefit of Recalling an Event in Reverse Order, 32 Law & Human Behavior 253 (2008).
As always, I recommend you follow Deception Blog.