University of Twente Student Theses


Guilt Presumptions in Police Suspect Interviews: The Effect of Confirmation Bias on Guilt Judgement and Deception Detection

Zeppelzauer, Lisa (2023) Guilt Presumptions in Police Suspect Interviews: The Effect of Confirmation Bias on Guilt Judgement and Deception Detection.

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Abstract:Despite modern forensic technology for the identification of perpetrators, confirmation bias in the form of police officers' guilt assumptions can cause an innocent suspect to be wrongfully convicted for a crime. This study investigates whether confirmation bias continues to have an effect on police’s guilt judgement when questioning is standardised by using an interview script, with neutrally formulated, open questions. Also, we hypothesised that confirmation bias will affect how police officers decide if a suspect is lying or telling the truth (deception judgement) and what behavioural cues they attend to, to make that judgement. Participants received a fictional case description and evidence against a suspect about investigating the suspect's involvement in a case of drug dealing, while the guilt primed group received a guilt manipulation, with the purpose of priming the participants to think that the suspect is guilty. The innocent primed group received identical information about the case, while instead received a manipulation that the suspect is likely to be innocent. Participants reported their guilt judgement ratings, before and right after conducting the role played interview. The suspect in the role play was actually innocent and explained the found evidence against them during the interview. The guilt manipulation was just about not effective, while the guilt group condition did show higher guilt judgement scores than the innocent group condition prior to the interview, suggesting that there was possible confirmation bias at hand. However, there was no effect found between the groups on post - interview guilt judgement, therefore we rejected our hypothesis that guilt assumptions affect ultimate guilt judgement. Importantly, both groups, primed with innocence and with guilt, tended to judge the innocent suspect as guilty, before and after conducting the interview. Also, we did not find any significant difference between the conditions, in how participants made their deception judgement, and what behavioural cue they attended to.
Item Type:Essay (Bachelor)
Faculty:BMS: Behavioural, Management and Social Sciences
Subject:77 psychology
Programme:Psychology BSc (56604)
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