1 Giving reasons pro et contra as a debiasing technique in legal decision making FRANK ZENKER Department of Philosophy & Cognitive Science, Lund University, Sweden frank.zenker@fil.lu.se CHRISTIAN DAHLMAN Law Faculty, Lund University, Sweden christian.dahlman@jur.lu.se RASMUS BÅÅTH Department of Philosophy & Cognitive Science, Lund University, Sweden farhan.sarwar@psy.lu.se FARHAN SARWAR Department of Psychology, Lund University, Sweden rasmus.baath@lucs.lu.se We report on the results of deploying the debiasing technique “giving reasons pro et contra” among professional judges at Swedish municipal courts (n=239). Experimental participants assessed the relevance of an eyewitness’s previous conviction to his credibility in the present case. Results are compared to data from lay judges (n=372). The technique produced a small positive debiasing effect in the sample of Swedish judges, while the effect was negative among lay judges. KEYWORDS: debiasing technique, heuristics and biases, legal decision-making, prior conviction, witness scenario 1. INTRODUCTION How to improve decisions is a pertinent question whenever judgments are unavoidable. The decisions that judges and juries must reach virtually every day provide a case in point, a fortiori when these bear