'You need to work down the memory but avoid threatening things'

Forensic psychologist Ray Bull has been praised for helping police interview a traumatised rape victim

Ray Bull received a rare commendation from the Metropolitan Police Force this week for his help with a rape case. Eighteen months ago, the forensic psychologist at Leicester University helped an officer interview a victim who had little recollection of a violent rape. His suggestions helped the victim recall memories that ultimately led to a conviction and a 14-year prison sentence for the rapist.

Professor Bull's research on "cognitive interviewing", which uses established principles of human memory to aid recall, is used in police training already. "It involves reinstating context to try to help people get back to the past and remember," he said.

He briefed the interrogating officer, watched the interview live by video link and gave advice during breaks. "If a person has gone through traumatising rape, the mind tries to defend itself against the most traumatic part of the memory. The details are like the top of an iceberg - you need to work your way down the iceberg while keeping away from things that are psychologically threatening," he said.

"When the interviewee appears to be stressed, go back and ask about something they talked about earlier that's non-stressful, even if it's no longer of interest. Police officers find this difficult because they want to get to the heart of the matter quickly, but they have to take their time," said Professor Bull, who has written expert reports in nearly 100 cases and testified in numerous trials.