The standard of proof in criminal trials should require that the evidence presented by the prosecution is robust. This requirement of robustness says that it must be unlikely that additional information would change the probability that the defendant is guilty. Robustness is difficult for a judge to estimate, as it requires the judge to assess the possible effect of information that the he or she does not have. This article is concerned with expert witnesses and proposes a method for reviewing (...) the robustness of expert testimony. According to the proposed method, the robustness of expert testimony is estimated with regard to competence, motivation, external strength, internal strength and relevance. The danger of trusting non-robust expert testimony is illustrated with an analysis of the Thomas Quick Case, a Swedish legal scandal where a patient at a mental institution was wrongfully convicted for eight murders. (shrink)

An argument that makes use of a generalization activates the prototype for the category used in the generalization. We conducted two experiments that investigated how the activation of the prototype affects the persuasiveness of the argument. The results of the experiments suggest that the features of the prototype overshadow and partly overwrite the actual facts of the case. The case is, to some extent, judged as if it had the features of the prototype instead of the features it actually has. (...) This prototype effect increases the persuasiveness of the argument in situations where the audience finds the judgment more warranted for the prototype than for the actual case, but decreases persuasiveness in situations where the audience finds the judgment less warranted for the prototype than for the actual case. (shrink)

We investigate argumentation where an expression is substituted with a less precise expression. We propose that the effect that this deprecization has on the audience be called deprecization effect. When the audience agrees more with the less precise version of the argument, there is a positive deprecization effect. We conducted an experiment where the participants were presented with a court room scenario. The results of the experiment confirm the following hypothesis: If the participants find it hard to agree with the (...) precise version of the argument and accept the use of the imprecise term, they will agree more with the imprecise version of the argument. Furthermore, we show that a person who reacts in this way to deprecization commits the fallacy of equivocation. (shrink)