Researchers have found that when you have more than one witness being interviewed at the same time, there is a high chance they will help to correct any errors the other may report. Two recent studies were published by legal psychologists Annelies Vredeveldt and Peter van Koppen at Vrije University Amsterdam show that witnesses make far less errors in their reporting when they are interviewed in groups than when they are interviewed on their own. This stands in sharp contrast with current police guidelines to always interview witnesses separately.

The research collaboration involved VU Amsterdam and the Toneelschuur theatre in Haarlem. In their first study the researchers asked attendees of an emotional play to testify about a rape and murder scene they saw a week prior. Witnesses were interviewed either in pairs or by themselves. Two witnesses who were interviewed at the same time reported the same information but made substantially fewer errors than two witnesses that were interviewed separate from one another. In the second study, researchers interviewed a much larger number of people. Of those 80, they found the same results.

These findings are surprising, as previous legal psychological research showed that witnesses are able to contaminate one another’s reports and their memory of the event they are discussing. The difference lies in the fact that in those studies artificial ways were used in order to increase errors, such as letting the witness talk to actors who were pretending to be witnesses of the same crime who would introduce errors into their discussions. In contrast, the research by VU Amsterdam investigated naturalistic discussions between witnesses.

The research showed that couples with an effective communication style were also able to remember far more information as a team than couples who communicated on a less effective level. The research found that the best way of collaborating is to repeat or rephrase the statements made by your partner and then elaborate by adding more information.

According to the team, the research findings show that collaboration between witnesses can also have benefits. Until this point, most people assumed that discussion between witnesses has only disadvantages. Vredeveldt and Van Koppen believe this research is going to lead to widespread interest from both academics and police practitioners. The team plans to continue their research and see if they can’t stumble across some new interview styles that may be able to benefit police during their interviews. Larger studies are expected to take place later this year, with researchers looking forward to what they may uncover.

The research has been published in two international academic journals so far: the first in Memory journal and the second study can be found in Legal and Criminological Psychology journal. The studies form part of the research conducted by the Amsterdam Laboratory of Legal Psychology (or ALLP).