Abstract
Eyewitnesses play a vital role in advancing criminal investigations—often providing details that are crucial to apprehending perpetrators or justifying charges. To better align with the evidence base on enhancing episodic recall, in 2007 the New Zealand Police conducted a major overhaul of the way in which police officers conduct investigative interviews with witnesses. Despite considerable improvements in training structures, however, there is ongoing concern that current practices do not account for the unique challenges faced by police who interview witnesses of serious crime—especially those who make allegations of sexual assault. In this thesis, we began to address these concerns in three ways: 1) by examining how well New Zealand police officers undergoing specialist interview training are able to maintain their new skills in the field (Study 1), 2) by examining how interviewers currently elicit legislatively important details from complainants of sexual assault (Study 2), and 3) by examining the efficacy of an increasingly-used—yet unvalidated—interviewing technique at enhancing detailed recall from witnesses (Study 3).
In Study 1, we examined how well New Zealand specialist interviewers utilise best-practice interviewing guidelines 18 months following training. Based on past research suggesting that prior interviewing performance, expert feedback, and self-evaluation of interviewing ability might be associated with the maintenance of sound interviewing practices, we also examined whether each of these factors, measured 12 months earlier, could predict performance. We found that the majority of interviewers were able to maintain best-practice interviewing over the 12-month period, but their prior performance scores did not predict their subsequent level of performance. Furthermore, the amount of written feedback and self-evaluation at 6 months was not related to interviewer performance a year later. After controlling for prior interview ability, however, we found that the amount of critical feedback comments interviewers received 6 months post-training was associated with poorer interviewing ability 18 months after training had ceased.
In Study 2, we examined how interviewers elicit legislatively important details from complainants of sexual assault. Overall, we found that interviewers were largely adhering to best-practice interviewing techniques, and asked few of the types of questions that are considered to be inappropriate. We found evidence, however, that the interviews were not well focused; interviewers asked numerous questions unrelated to the alleged offence, and asked significantly more questions that did not elicit legislatively important details than questions that did.
In Study 3, we empirically tested the utility of an increasingly-used interviewing technique aimed to enhance the amount of detail witnesses provide. Participants watched a video of a simulated bank robbery and were then interviewed about what they saw. We gave two-thirds of the participants an example of the level of detail we wanted them to provide, by describing to them either an action (getting out of a chair) or a non-action (a pen). We found using an object—but not an action—to demonstrate the desired level of detail increased the number of details that participants reported during free recall, but that this effect ‘washed out’ after two follow-up open-ended questions. There was also some suggestion that additional detail could come at the expense of accuracy.
We raise several possibilities for how police interviewing practices might be modified in line with these findings. We also argue that adapting current interviewing procedures to meet the specific needs of interviewers and complainants in sexual assault cases should be at the forefront of investigative interviewing research.