Police hand gestures can influence witness testimony

Hand gestures of police interviewers can make eyewitnesses believe they saw something they didn't.

This is the finding of research by Dr Daniel Gurney from the University of Hertfordshire - given as a poster presentation at the British Psychological Society Annual Conference in Glasgow.

72 participants were shown mock-up CCTV footage of a theft by Dr Gurney. An on-screen 'police officer' then asked questions about the theft. All participants were asked the same questions, but the questioner varied the hand gestures he performed as he spoke. For example, when asking, 'Did you notice any jewellery?' he performed a gesture that could 'implant' information (e.g. a 'ring' gesture to the finger or 'watch' gesture on the wrist).

A significant number of people reported information that was consistent with the hand gesture they saw. "We were investigating whether interviewers can influence witnesses through nonverbal means," said Dr Gurney. "By subtle manipulation of simple hand gestures we showed it was possible to make people believe they had seen something that wasn't there."

The study 'Can misleading hand gestures influence eyewitness testimony?' is the first to examine whether hand gestures can influence witness reports and it adds to the wealth of research on susceptibility of eyewitnesses to misleading verbal questions.

Dr Gurney said: "It has long been known that the wording of questions can be misleading, but this is the first study to show that gestures, which are often hardly noticed, can also mislead."

"We are aware of the power of nonverbal behaviour in all kinds of human interactions, and this one is no exception," Professor Pine added. "These findings have considerable implications for interview techniques of witnesses in criminal justice settings and beyond."