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Abstract

Jury members are confronted with highly complex, ill-defined problems. Coherence based reasoning (Pennington & Hastie, 1992; Simon, 2004), which partially relies on intuitive-automatic processing (Glöckner & Betsch, 2008), empowers them to nonetheless make meaningful decisions. These processes, however, have a downside. We tested possible negative effects in a set of studies. Particularly, we investigated whether standards of proof are muted by stronger coherence shifts, and whether the probative value of the evidence is not properly taken into account. We found that U.S. model jury instructions for preponderance of the evidence and beyond a reasonable doubt influence conviction rates in the intended direction and are not undermined by coherence shifts, although probabilistic estimations of these standards are inappropriate. However even massive changes in explicitly stated probabilities, while holding the overall constellation of facts constant, did not influence conviction rates and the estimated probability for conviction. We argue that improvements for legal procedure should focus on measures to circumvent the negative side-effects of coherence based reasoning in general and to specifically make probabilistic information better evaluable for decision makers in law.