British Columbia

Police interrogation tactics can plant false memories, UBC study finds

Many of the interrogation tactics used by police forces in Canada can make suspects falsely believe they committed the crimes they are accused of, suggests new research from the University of B.C. Okanagan.

Study participants remembered elaborate details of crimes they hadn't committed

The interviewers in the study used common police interrogation techniques to convince many participating undergraduate students that they had committed a crime when they were younger. (Science Photo Library RM/Getty Images)

Many of the interrogation tactics used by police forces in Canada can make suspects falsely believe they committed the crimes they are accused of, suggests new research from the University of B.C. Okanagan.

The research study involved 60 undergraduate students who were asked to recall two different memories — a true memory that was provided by their parents, and a false memory of a criminal or violent activity they had done when they were younger.

The interviewers asked the participants about the memories, using the same persuasive tactics used in Canadian police interrogations, and by the end of three separate hour-long interview sessions more than 70 per cent of the participants thought the fake memory they had been asked to recall had actually happened.

Stephen Porter, a UBC Okanagan professor who teaches forensic psychology, says police forces have begun to use less manipulative interview tactics. (UBC)

"[They] came to believe and endorse that they had engaged in this kind of criminal behaviour, which ranged from assaults to assault with a weapon to serious thefts," said Stephen Porter, a psychology professor who co-authored the study published in the Psychological Science journal.

The participants were so convinced that they'd actually committed these crimes that they even gave "extremely rich accounts" of what they believed had happened.

"They were reporting extensive detail about getting arrested, what had happened, going to jail, their parents picking them up eventually, and to the point that they experienced significant guilt for these wrongdoings that they in fact hadn't committed," he said.

Common police tactics

The study conducted in October 2013 only included participants whose caregivers said they hadn't committed crimes or had a criminal record.

Some participants were asked to recall a false memory that was of a non-criminal but traumatic event — and almost 80 per cent believed it.

"We used tactics that are very very common in the Canadian interrogation room, for example, offering, what police call incontrovertible evidence … in this case we said, 'Your parents had informed us that you did this crime and you were arrested.' In real life police would say, 'You failed a polygraph' or 'We have this kind of evidence or that kind of evidence.'"

Porter said some of the other methods used were to tell participants it was normal they didn't remember the traumatic event they were being told to believe, and to ask leading questions.

"We suspect that if we added more interviews, we kept going, we may have gotten close to 100 per cent," he said.

Porter said there is a shift already happening in police forces across the country to move toward "less deceptive, less manipulative interview tactics."


To hear the full interview listen to the audio labelled: New UBC research shows that police interrogation methods can result in false memories of committing crimes

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