The influencing behaviours of suspects during investigative interviews

In 2015, the UK enhanced protection for victims of domestic abuse by criminalising controlling and coercive (C&C) behaviour. However, there have been few prosecutions. One UK constabulary asked us to analyse a subset of their C&C interviews to help them understand what suspects are doing within investigative interviews that may lead their investigators to prematurely cease investigations. The constabulary provided interview transcripts from 25 C&C suspects. Based on the extant literature about persuasion and qualitative analysis of these interviews, we developed a taxonomy of 18 influencing behaviours suspects use to change the beliefs of their interviewers. These 18 behaviours varied across two dimensions of use: A) An instrumental – relational axis, where instrumental behaviours were those that related directly to evidence, and relational behaviours related less directly to evidence but rather aimed to change interview perceptions of investigation relevant people (the suspect, or victim), and B) A high – low power axis where some behaviours were used to apply pressure onto the interviewer, and others are used when the suspect is placed under pressure. We also noted that the 18 behaviours are not used equally, and suspects used four principal forms of influence: (1) rational arguments to convince of their innocence; (2); justifications in terms of denigrating the victims character or suggesting their behaviour provoked the suspects actions; (3) justifications to minimise perception of harm; and (4) presenting the suspect as an individual in need of help rather than punishment. Our initial taxonomy helped us to better understand the differing motives of suspects within interviews beyond a simple tell the truth versus lie dichotomy, and the taxonomy helps us to prepare interviewers for the kinds of arguments they may face. We also report preliminary evidence on the effectiveness of some of the influence behaviours from laboratory studies.