Presumptions in Legal Argumentationraju_514 271..300

Abstract. In this paper a theoretical definition that helps to explain how the logical structure of legal presumptions is constructed by applying the Carneades model of argumentation developed in artificial intelligence. Using this model, it is shown how presumptions work as devices used in evidentiary reasoning in law in the event of a lack of evidence to assist a chain of reasoning to move forward to prove or disprove a claim. It is shown how presumptions work as practical devices that may be useful in cases in which there is insufficient evidence to prove the claim to an appropriate standard of proof. Recent work in the interdisciplinary area between artificial intelligence and law has advanced logical models of presumption and the burden of proof using an argumentation approach (Gordon and Walton 2009; Prakken and Sartor 2009). However, presumption and its companion notion of burden of proof have been said to be two of the slipperiest concepts in law (Strong 1992, 449). After surveying the various notions of presumption in the law of evidence, and showing how disparate they are, Allen (1981, 865