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Confirmation Bias in Criminal Cases
Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Law, Department of Law.ORCID iD: 0000-0002-3811-7517
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Description
Abstract [en]

Confirmation bias is a tendency to selectively search for and emphasize information that is consistent with a preferred hypothesis, whereas opposing information is ignored or downgraded. This thesis examines the role of confirmation bias in criminal cases, primarily focusing on the Swedish legal setting. It also examines possible debiasing techniques.

Experimental studies with Swedish police officers, prosecutors and judges (Study I-III) and an archive study of appeals and petitions for new trials (Study IV) were conducted. The results suggest that confirmation bias is at play to varying degrees at different stages of the criminal procedure. Also, the explanations and possible ways to prevent the bias seem to vary for these different stages. In Study I police officers’ more guilt presumptive questions to apprehended than non-apprehended suspects indicate a confirmation bias. This seems primarily driven by cognitive factors and reducing cognitive load is therefore a possible debiasing technique. In Study II prosecutors did not display confirmation bias before but only after the decision to press charges, as they then were less likely to consider additional investigation necessary and suggested more guilt confirming investigation. The driving forces need further examination. Study III suggests that pretrial detentions influence judges’ perception of the evidence strength, making them more likely to convict, in cases where they themselves detained. This is indicative of a confirmation bias with social explanations, which, possibly, can be mitigated by changing decision maker between detention and main hearing. The confirmatory reasoning in Study I-III can be considered rational or irrational, following different types of rationality, like probabilistic or judicial rationality. In Study IV, statistical estimates based on empirical data from the Apellate Courts and the Supreme Court indicate that far from all wrongfully convicted who appeal or petition for a new trial are acquitted. A robustness analysis confirmed that these overall conclusions hold over a wide variety of assumptions regarding unknown parameters.                         

Also, the usage of empirical methods to study law and legal phenomena is discussed. The concept of Evidence-Based Law (EBL) is used to exemplify how empirical legal research may benefit both legal scholarship and law in a wider sense.

Place, publisher, year, edition, pages
Uppsala: Department of Law, Uppsala University , 2018. , p. 284
Keywords [en]
legal decision making, bias, confirmation bias, criminal cases, criminal procedure, police, prosecutor, judge, legal system, empirical legal research, evidence based law, debiasing technique
National Category
Law and Society Applied Psychology
Research subject
Jurisprudence
Identifiers
URN: urn:nbn:se:uu:diva-351709ISBN: 978-91-506-2720-6 (print)OAI: oai:DiVA.org:uu-351709DiVA, id: diva2:1237959
Public defence
2018-09-28, Sal IV, Universitetshuset, Biskopsgatan 3, 753 10 Uppsala, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2018-09-05 Created: 2018-08-10 Last updated: 2018-09-05
List of papers
1. The Presumption of Guilt in Suspect Interrogations: Apprehension as a Trigger of Confirmation Bias and Debiasing Techniques
Open this publication in new window or tab >>The Presumption of Guilt in Suspect Interrogations: Apprehension as a Trigger of Confirmation Bias and Debiasing Techniques
2018 (English)In: Law and human behavior, ISSN 0147-7307, E-ISSN 1573-661X, Vol. 42, no 4, p. 336-354Article in journal (Refereed) Published
Abstract [en]

This research tests whether a police officer’s decision to apprehend a suspect triggers confirmation bias during an interrogation. The study also tests two strategies to reduce confirmation bias: (1) decoupling decision to apprehend from interrogation and (2) reducing cognitive load for the interrogating police officer. In Experiment 1, Swedish police officers (N = 60) were faced with 12 scenarios in which they either had to decide for themselves whether to apprehend a suspect or were informed about the corresponding decision by another police officer or a prosecutor. Participants then prepared questions for a suspect interrogation and evaluated the trustworthiness of the suspect’s denial or confession. The same method was used in Experiment 2 but with law and psychology students (N = 60) as participants. In Experiment 3, psychology students (N = 60) prepared interrogation questions either by freely producing their own or by choosing questions from a preset list. Overall, apprehended suspects were interrogated in a more guilt presumptive way and rated as less trustworthy than non apprehended suspects. However, the tested debiasing techniques, primarily reducing cognitive load for the interrogating police officer, hold some potential in mitigating this bias.

Place, publisher, year, edition, pages
American Psychological Association (APA), 2018
Keywords
confirmation bias, cognitive bias, debias, police, interrogation, apprehension, investigation
National Category
Law and Society Psychology
Research subject
Jurisprudence
Identifiers
urn:nbn:se:uu:diva-351671 (URN)10.1037/lhb0000287 (DOI)000439922500004 ()29963877 (PubMedID)
Available from: 2018-08-09 Created: 2018-08-09 Last updated: 2018-10-18Bibliographically approved
2. From devil's advocate to crime fighter: confirmation bias and debiasing techniques in prosecutorial decision-making
Open this publication in new window or tab >>From devil's advocate to crime fighter: confirmation bias and debiasing techniques in prosecutorial decision-making
2019 (English)In: Psychology, Crime and Law, ISSN 1068-316X, E-ISSN 1477-2744, Vol. 25, no 5, p. 494-526Article in journal (Refereed) Published
Abstract [en]

This research examines the role of confirmation bias in prosecutorial decisions before, during and after the prosecution. It also evaluates whether confirmation bias is reduced by changing the decision maker between arrest and prosecution. In Experiment 1, Swedish prosecutors (N = 40) assessed 8 scenarios where they either decided themselves or were informed about a colleague's decision to arrest or not arrest a suspect. Participants then rated how trustworthy the suspect's statement was as well as the strength of new ambiguous evidence and the total evidence. They also decided whether to prosecute and what additional investigative measures to undertake. In Experiment 2 the same method was used with Law and Psychology students (N = 60). Overall, prosecutors' assessments before the prosecution indicated that they were able to act as their own devil's advocate. Also, their assessments while deciding about whether to prosecute were reasonably balanced. However, after pressing charges, they displayed a more guilt-confirming mindset, suggesting they then took on the role as crime fighters. This differed from the student sample in which higher levels of guilt confirmation was displayed in relation to arrested suspects consistently before, during and after a prosecution decision. The role of prosecutors' working experience is discussed.

Place, publisher, year, edition, pages
Taylor & Francis Group, 2019
Keywords
confirmation bias, cognitive bias, criminal procedure, arrest, prosecute, debiasing
National Category
Law and Society
Research subject
Jurisprudence
Identifiers
urn:nbn:se:uu:diva-351673 (URN)10.1080/1068316X.2018.1538417 (DOI)000466385700005 ()
Available from: 2018-08-09 Created: 2018-08-09 Last updated: 2019-05-22Bibliographically approved
3. "Guilty, No Doubt": Detention Provoking Confirmation Bias in Judges' Guilt Assessments and Debiasing Techniques
Open this publication in new window or tab >>"Guilty, No Doubt": Detention Provoking Confirmation Bias in Judges' Guilt Assessments and Debiasing Techniques
2019 (English)In: Psychology, Crime and Law, ISSN 1068-316X, E-ISSN 1477-2744, Vol. 25, no 3, p. 219-247Article in journal (Refereed) Published
Abstract [en]

This research examines whether judges’ pretrial detention decisions trigger confirmation bias in their guilt assessments. It also tests two strategies to mitigate confirmation bias: (1) to have different judges decide about detention and guilt and (2) to reduce cognitive load by structuring the evaluation of evidence. In Experiment 1, Swedish judges (N = 64) read 8 scenarios in which they either decided themselves about detention or were informed about a colleague’s decision. Then, participants rated the defendant’s trustworthiness, the strength of each piece of evidence, the total evidence and decided about guilt. In Experiment 2, Law students (N = 80) either first rated each piece of evidence separately and then the total evidence (structured evaluation) or only the total evidence (unstructured evaluation), and then decided about guilt. Overall, detained defendants were considered less trustworthy and when participants themselves detained, they rated the guilt consistent and total evidence as stronger and were more likely convict, compared to when a colleague had detained. The total evidence was considered stronger after unstructured than structured evaluations of the evidence but the evaluation mode did not influence guilt decisions. This suggests that changing decision maker holds greater debiasing potential than structuring evidence evaluation. 

Keywords
cognitive bias, confirmation bias, detention, judge, guilt, debiasing
National Category
Law and Society Psychology
Research subject
Jurisprudence
Identifiers
urn:nbn:se:uu:diva-351675 (URN)10.1080/1068316X.2018.1511790 (DOI)000459692500001 ()
Available from: 2018-08-09 Created: 2018-08-09 Last updated: 2019-03-21Bibliographically approved
4. Self-correction of wrongful convictions: is there a ‘System-level’ confirmation bias in the Swedish legal system’s appeal procedure for criminal cases?—Part I
Open this publication in new window or tab >>Self-correction of wrongful convictions: is there a ‘System-level’ confirmation bias in the Swedish legal system’s appeal procedure for criminal cases?—Part I
2018 (English)In: Law, Probability and Risk, ISSN 1470-8396, E-ISSN 1470-840X, Vol. 17, no 4, p. 311-336Article in journal (Refereed) Published
Abstract [en]

In this study, we propose that confirmation bias may not only be present in the behaviors of individual agents in the judicial system but can also be recognized at a system-level as an inability to self-correct, that is, an inability to acquit wrongfully convicted who appeal or petition for a new trial. To assess the self-correctional ability a very low error rate of wrongful convictions in the District Courts in 2010-2014 was tentatively assumed. An empirical review of appeals (Part I) and petitions for new trials (Part II) in the Courts of Appeal and Supreme Court between 2010 and 2014 was carried out to evaluate to what extent these legal remedies can be expected to change wrongful convictions into acquittals. Realistic assumptions and empirical estimates of real-world statistics suggest that at least 34.67 % of the wrongfully convicted remained convicted despite the possibility both to appeal and petition for a new trial. A robustness analysis was performed to ascertain that the conclusions hold under a wide variety of assumptions about the unknown statistics. According to additional analyses the odds of an acquittal were low even for appeals referring to new innocence supportive evidence and for private individuals claiming to be innocent of e.g. assault or murder the odds of being granted new criminal trials were particularly low.

Keywords
confirmation bias, wrongful conviction, appeal, new trial, legal system, organization
National Category
Law and Society Psychology
Research subject
Jurisprudence
Identifiers
urn:nbn:se:uu:diva-351677 (URN)10.1093/lpr/mgy018 (DOI)000456537600003 ()
Available from: 2018-08-09 Created: 2018-08-09 Last updated: 2019-02-18Bibliographically approved
5. Self-correction of wrongful convictions: is there a “System-level” confirmation bias in the Swedish legal system’s appeal procedure for criminal cases?—Part II
Open this publication in new window or tab >>Self-correction of wrongful convictions: is there a “System-level” confirmation bias in the Swedish legal system’s appeal procedure for criminal cases?—Part II
2018 (English)In: Law, Probability and Risk, ISSN 1470-8396, E-ISSN 1470-840X, Vol. 17, no 4, p. 337-356Article in journal (Refereed) Published
Abstract [en]

In this study, we propose that confirmation bias may not only be present in the behaviors of individual agents in the judicial system but can also be recognized at a “system-level” as an inability to self-correct, that is, an inability to acquit wrongfully convicted who appeal or petition for a new trial. To assess the self-correctional ability a very low error rate of wrongful convictions in the District Courts in 2010-2014 was tentatively assumed. An empirical review of appeals (Part I) and petitions for new trials (Part II) in the Courts of Appeal and Supreme Court between 2010 and 2014 was carried out to evaluate to what extent these legal remedies can be expected to change wrongful convictions into acquittals. Realistic assumptions and empirical estimates of real-world statistics suggest that at least 34.67 % of the wrongfully convicted remained convicted despite the possibility both to appeal and petition for a new trial. A robustness analysis was performed to ascertain that the conclusions hold under a wide variety of assumptions about the unknown statistics. According to additional analyses the odds of an acquittal were low even for appeals referring to new innocence supportive evidence and for private individuals claiming to be innocent of e.g. assault or murder the odds of being granted new criminal trials were particularly low.

Keywords
legal system, confirmation bias, wrongful conviction, appeal, new trial, organization
National Category
Law and Society Psychology
Research subject
Jurisprudence
Identifiers
urn:nbn:se:uu:diva-356848 (URN)10.1093/lpr/mgy019 (DOI)000456537600004 ()
Available from: 2018-08-09 Created: 2018-08-09 Last updated: 2019-02-18Bibliographically approved

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