The Decision-Making of Judges: On the Suitability of Appeal as a Means of Judicial Error Correction Against the Background of Statistical and Psychological Findings

• Applicant: Dr. Cara Warmuth
• Subject Area: Private Law
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 549331651

The thesis examines the decision-making process of judges, in particular when deciding on an appeal - intended as a means of correcting errors - in civil proceedings in accordance with §§ 511 et seq. German rules of civil procedure (Zivilprozessordnung, ZPO). In doing so, statistical methods and psychological findings are used to derive legal implications for the appeal process. The focus is on cognitive biases that influence the decision-making process of (appeal) judges and thus possibly also their judgement on the case. The results suggest that appellate judges may tend to irrationally affirm the first-instance decision. This appeal-specific affirmation bias could have an impact on the outcome of appeal proceedings. The likelihood of an erroneous first-instance judgement actually being recognized as erroneous and corrected accordingly by the appeals court would then be lower than might be expected under "ideal" conditions. The thesis discusses the legal implications of the results of this and other psychological findings, proposing, among other things, the integration of a preliminary blind procedure at the courts of appeal as a countermeasure against the affirmation bias. Although the effectiveness of this type of procedure could not yet be determined with statistical certainty within the scope of the work due to an insufficient number of participants, the results suggest that it could help to prevent the affirmation bias from arising. The main purpose of the thesis was to examine the effectiveness of error correction by a second-instance court in civil proceedings. By combining law with statistics and psychology, it was intended to create a new, empirically based perspective on the justification for the existence and design of an error correction instance in legal proceedings. In addition to providing an overview of the latest research on psychological influences on a judge’s decision-making, the thesis successfully demonstrated the existence of an affirmation bias in German civil proceedings (most importantly, with "real" judges), after it had previously only been tested and demonstrated with students and with sole regard to the US court system. The purpose of the thesis was achieved, for based on its empirical findings on cognitive biases in the decision-making of judges and on the basis of its own statistical model on the "ideal" success rate of appeals, the thesis draws the conclusion that it is reasonable and justified to set up a means of error correction for judicial decisions - but that there is still room for improvement. Furthermore, as the results of the thesis are in part based on the analysis of unpublished data from official statistics, the additional objective of providing new statistical material and making it accessible was equally achieved.

• DFG Programme: Publication Grants