Written by
Caitlin Correia, PhD student, Center for Applied Psychological Science
PhD supervisors: Dr Shiri Portnoy, Professor Paul van Schaik, Dr Kim Collins
In October 2022, I began my PhD in Psychology focusing on the effects of an interviewer’s presumption of guilt on suspect verbal behaviour and jury decision making.
Over the course of several decades the use of guilt-presumptive behaviour has been a topic of interest for researchers. Researchers, like myself, have been interested in the way an interviewer can affect a suspect’s ability to provide accurate and informative alibis (verbal behaviour). After all it has been recognised that the way an investigator approaches an interview can shape the whole investigation.
Nowadays it is imperative that when conducting an interview, the interviewer follows the PEACE (Planning & Preparation, Engage & Explain, Account, Closure and Evaluation) model of investigative interviewing. This ensures that suspects are given a fair and equal opportunity to provide their statement while the interviewer remains free from any preconceived bias (Smalarz et al., 2016). However, researchers have discovered that despite extensive training, police interviewers can struggle to avoid biases and often regress to using substandard techniques. These interview techniques can include coercion and the use of closed and leading questions, as a result of existing beliefs and bias (Ask & Granhag, 2005).
Portnoy et al. (2019) previously explored the effect of guilt presumptive behaviour on the verbal behaviour of a suspect. In their study, they employed a single suspect interview with a guilt presumptive interviewer. The researchers hypothesised that participants interviewed under the guilt belief would provide higher number of correct details (i.e. quantity of details that were remembered) and have higher accuracy rates (i.e. number of correct details remembered out of the total number of details provided) compared to the innocent belief. Despite having a null result, this research opened the potential for future research to examine how factors, such as time delays and repeating interviewing, can also affect suspects’ verbal behaviour alongside guilt presumptive interviewers.
The existing academic literature suggests that an individual’s memory deteriorates over time which may result in suspects inadvertently omitting details from their statements providing incorrect details in their alibis (Crozier et al., 2017). In turn, eyewitnesses are at an increased risk of the interviewer asking them a higher rate of guilt presumptive questions if it is believed the eyewitness is hiding something. This begs the question that if these results were found in eyewitness studies, what is to say that a suspect’s verbal behaviour will not also be affected? However, Portnoy et al.’s (2019) research suggests that suspects are inclined to be as informative and accurate as possible, despite potential gaps in memory. This would be especially so for an innocent suspect attempting to prove their innocence. A similar concept is found with repeated interviewing. As new evidence emerges, potential suspects are interviewed several times. During which, interviewers may allow bias to change their approach towards the suspect and interview them in a guilt presumptive manner (Tuckey & Brewer, 2003). As such, the suspect may attempt to be more informative and accurate in their alibi to prove their innocence towards the interviewer.
My PhD will expand on Portnoy et al. (2019) by conducting a mixed-methods exploration of factors that influence suspects’ verbal behaviour. This research can inform the practices used by the police and improve the quality of future interviews that are conducted. Furthermore, to take the research to the next level my PhD will explore how interviewers use of guilt presumptive behaviour influences the verdict given by members of the jury. Jurors are members of the public and are not required to undergo any training to partake in jury duty. As a result, jurors are unable to identify the use of accusatory questioning and situational risk factors influencing the verbal behaviour presented by the suspects. Furthermore, jurors are inclined to believe that suspects who provide more precise and informative alibis are trying to prove their innocence as they have something to hide, contradicting Portnoy et al’s. (2019) findings. When or if a suspect ends up being convicted and the case goes to court, suspect alibis are entered into evidence and evaluated by the selected jurors. Accordingly, further research is needed to reduce the number of miscarriages of justice by providing jurors with basic training on what is ethical interviewing. As a result, findings from this additional study can create an essential tool that will be implemented to the members of the public before they sit jury duty.
References
Ask, K., & Granhag, P. A. (2005). Motivational sources of confirmation bias in criminal investigations: the need for cognitive closure. Journal of Investigative Psychology and Offender Profiling, 2(1), 43-63. https://doi.org/10.1002/jip.19
Crozier, W. E., Strange, D., & Loftus, E. F. (2017). Memory errors in alibi generation: How an alibi can turn against us. Behavioural sciences & the law, 35(1), 6-17. https://doi.org/10.1002/bsl.2273
Portnoy, S., Hope, L., Vrij, A., Granhag, P. A., Ask, K., Eddy, C., & Landstrom, S. (2019). “I think you did it!”: Examining the effect of presuming guilt on the verbal output of innocent suspects during brief interviews. Journal of Investigative Psychology and Offender Profiling, 16(3), 236-250. https://doi.org/10.1002/jip.1534
Smalarz, L., Madon, S., Yang, Y., Guyll, M., & Buck, S. (2016). The perfect Match: DO criminal stereotypes bias forensic evidence analysis? Law and Human Behaviour, 40(4), 420-429. https://doi.org/10.1037/lhb0000190
Tuckey, M. R., & Brewer, N. (2003). How Schemas affect eyewitness memory over repeated retrieval attempts. Applied Cognitive Psychology, 17(2) 785-800. https://doi.org/10.1002/acp.906