Prior convictions, conduct and disposition: A scientific perspective

The use of prior conduct and convictions in criminal proceedings has been a controversial issue for over a hundred years. Rarely does a year go by without another call from lawmakers or prominent citizens for prior convictions and ‘history’ to be made available to tribunals to resolve issues of guilt. Yet the debate seems to have reached an impasse, with the proponents of either side facing off at 20 paces, armed only with the familiar arguments that have failed to prevail in the past. The lack of resolution in the debate suggests that it needs to be reframed. The present article proposes a perspective based on broader scientific methodology, analysing factual decisions in a criminal trial as a form of probabilistic argument. The psychology of probabilistic reasoning is examined with a focus on the effect of attributional information on judgments of probability. The logical structures of factual reasoning about disposition, tendency, similar facts and coincidence are then put under the microscope to expose some new arguments, some weaknesses in old arguments, and some quantitative relations that affect probability judgments in this area.