Interviews are a crucial part of criminal investigations and legal proceedings. However, getting suspects to provide accurate and detailed statements is often challenging, and a lack of information can contribute to a stalemate in the investigation. Therefore, more effective interview techniques are needed. To address this, one potential avenue is to focus on the strategies that guilty suspects use to appear innocent during interrogations.
An interviewing technique that motivates suspects to share more
In her doctoral research, Lina Nyström, PhD student at the Department of Psychology, has further developed and tested The Shift-of-Strategy (SoS) Approach. The starting point for this interview technique is that the verbal strategies suspects use in investigative interviews can be influenced by their perception of what evidence the interviewer holds.
“The purpose of The Shift-of-Strategy Approach is to strategically present evidence in a way that motivates suspects who voluntarily participate in interviews to change their strategy and provide more useful information to the investigation,” says Lina Nyström.
The approach makes suspects perceive that maintaining a withholding strategy is counterproductive to appearing innocent, and therefore, they tend to become more forthcoming. The information that emerges stands the chance of advancing investigations.
The reevaluation of the SoS approach showed that it works well in several contexts. Guilty suspects tended to change their strategy and share more useful information with the interviewers. Furthermore, those who were interviewed with the SoS approach felt more successful in appearing innocent when they disclosed more information, supporting the psychological mechanisms underpinning the approach.
The SoS approach was compared with a method where the interviewer questioned the participants without disclosing what evidence they already possessed.
“A prerequisite for the SoS approach to work well is that there is sufficient evidence to present and structure the questioning around during the interview,” explains Lina Nyström.
One of the studies included both guilty and innocent participants, to examine whether the SoS approach might negatively affect the statements of innocent individuals. The results showed that innocent participants shared just as much information regardless of whether evidence was presented during the interview or not. This means that the SoS method is unlikely to be problematic to use with innocent suspects.
Randomized controlled experiments with 800 interviews
The thesis consists of three sub-studies with five experiments. All studies were randomized controlled trials (RCTs) with an experimental design, aimed at evaluating an interview technique. In total, more than 800 interviews were conducted within the three sub-studies.
Participants were recruited both online and on site at the Department of Psychology. They performed several simulated crimes, which they were later interviewed about. Their statements were analyzed in terms of how much accurate and new information they revealed during the interviews.
Participants also completed a questionnaire about how they experienced the interview, their perceived success in appearing innocent, what strategies they used, and whether they changed strategies during the process.
The justice system needs more evidence-based interviewing techniques
“This evaluation of The Shift-of-Strategy Approach is valuable because it is important to develop effective interviewing techniques that can be used within the justice system. The methods must also be ethically sound, that is, interviewers should never lie about evidence and avoid accusatory tactics altogether,” says Lina Nyström.
Text: Katarina Englund
