Research in Japan suggests that a ‘relationship-based’ police interviewing style gets the best results

In 1995 members of a religious cult called Aum Shinirikyo carried out a Sarin gas attack on the Tokyo subway that killed two station staff and injured several hundred people. One of those questioned by the police as a member of the cult was Dr Hayashi Ikuo. During interviews, Ikuo made a voluntary decision to confess his involvement in the attack.  He was later sentenced to indefinite imprisonment.

In an autobiography written in prison, Ikuo described his feelings about his interrogation by police before standing trial: “At that time, I felt reassured by the fact that I had someone who would understand my true intentions without prejudice. I thought I could trust Mr I and Mr F [police interrogators]. I made up my mind to tell them everything I knew.”

Prize-winning research undertaken in Japan by Dr Taeko Wachi, while a PhD candidate in the Department of Psychology at the University of Cambridge, suggests that a ‘relationship-based’ interviewing style in which interrogators listen closely and attempt to form good relationships with suspects is more likely to elicit true confessions than other styles.

Dr Wachi’s research comprised three studies of attitudes to, and experiences of, police interviewing in Japan. The first study explored information on interrogation techniques gathered from almost 280 police officers. The analysis of questionnaires led to the identification of four interview styles: evidence-focused, confrontational, undifferentiated and relationship-focused.

The second study was a ‘crime experiment’ in which more than 230 members of the public took part. It was designed to reveal which of the interviewing techniques identified in the first study were most likely to elicit true confessions and prevent false confessions. Overall, 74 out of 114 ‘guilty’ participants confessed to their notional ‘crime’ but none of the ‘innocent’ participants made false confessions. Relationship-focused interviewing was most likely to elicit a confession.

The third study examined questionnaires from more than 290 offenders in 36 prisons. All of them had been convicted of serious crimes including murder, rape and kidnapping. This third study – which was administered by means of a questionnaire – was the first of its kind in Japan and thus broke new ground in terms of identifying which interviewing styles led offenders to confess.  

Again, relationship-focused interviewing was particularly effective in eliciting confessions from suspects who had not decided, before interrogation, whether or not to confess their crimes or had decided to deny the allegations against them.

The research suggested that the relationship-based interviewing style has a positive effect on both police officers’ and suspects’ feelings after interrogation. Those offenders who confessed to crimes during a relationship-based interview did so as the result of internal pressures, such as “I confessed because I felt guilty about the crime”, rather than external pressures, such as “I confessed because of police pressure during the interview”.

In view of the lack of in-depth research into investigative interviewing techniques in Japan, Dr Wachi’s work makes a significant contribution to understanding the wide number of factors that affect this complex process. It should be noted, however, that most participants in the study were male.

As Dr Wachi points out, there are significant differences, as well as similarities, between the structure of criminal processes in Japan and those in Western Europe and the USA. In Japan the law allows for suspects to be held for 23 days before initiating prosecution: this maximum detention period contrasts with 24 hours (generally) in the UK, 48 hours in Hong Kong and just four hours in Australia.

It has thus been argued that interrogations play a much more important role in Japanese criminal investigations than in other countries. In recent years, several high-profile false confessions have drawn attention to the possible impact of interviewing techniques on suspects’ feelings and decisions about confessions and denials. Training of police officers in interviewing is being stepped up.

Interestingly, the Japanese public (in addition to crime victims and their families) exhibits a strong desire for offenders to talk about their criminal motives and explain their criminal acts. Interrogation meets this public interest by helping offenders to give accounts of their cases in detail.

Last month it was announced that Dr Wachi had won first place in the 2013 American Psychology-Law Society Dissertation Awards.  As part of her prize she is invited to attend, and present a poster at, the AP-LS Conference in New Orleans, Louisiana in March, 2014.  The AP-LS committee reviewers described her dissertation as “highly original… because of the breadth of interrogation factors it addresses”.

An impressive aspect of the research was Dr Wachi’s design and implementation of a crime experiment which was tested on a range of people recruited from the general public, widely varying in age and from a diversity of backgrounds.  In contrast, previous crime experiments have used university students who tend to be from a narrow age range and educational level.

At Cambridge, Dr Wachi’s research was supervised by Professor Michael Lamb of the Department of Psychology.  He said: “I was delighted to hear that Taeko had won this award.  Her persuasive study was comprehensive and very significant, especially because we are increasingly aware of the risks that false confessions may lead to the conviction and incarceration of innocent people.  Taeko’s findings add to the growing body of evidence that more humane rather than coercive interviewing practices are likely to elicit confessions from guilty individuals, a pattern evident in Western countries, too.”

Dr Wachi has been working for the National Research Institute of Police Science (attached to the National Police Agency, Japan) since 2005. She was able to study for a PhD at Cambridge thanks to a scholarship from the Japanese Government Long-Term Overseas Fellowship Program.

Her background gave her the advantage of an in-depth understanding of, and close working relationship with, the National Police Agency, Supreme Public Prosecutors’ Office and Ministry of Justice, which enabled her to conduct the studies of police officers and prisoners.

Dr Wachi is currently conducting research into interrogations of those with learning disabilities as well as on public opinions about interviewing techniques. She intends to continue her research into criminal investigation on behalf of the National Police Agency by providing scientific findings about interrogations of various types of suspects.

For more information about this story contact Alexandra Buxton, Office of Communications, University of Cambridge, amb206@admin.cam.ac.uk, 01223 761673