An improved factor based approach to precedential constraint

Abstract

In this article I argue for rule-based, non-monotonic theories of common law judicial reasoning and improve upon one such theory offered by Horty and Bench-Capon. The improvements reveal some of the interconnections between formal theories of judicial reasoning and traditional issues within jurisprudence regarding the notions of the ratio decidendi and obiter dicta. Though I do not purport to resolve the long-standing jurisprudential issues here, it is beneficial for theorists both of legal philosophy and formalizing legal reasoning to see where the two projects interact.

HYPO’S legacy: introduction to the virtual special issue

“…We have seen that there are precedents indicating preferences, precedents providing a framework of issues as in Rigoni (2015), and tentatively identified precedents which introduced additional factors. Are there others?…”

“…As can be seen from the papers in this special issue and the many other papers referred to in this introduction, HYPO and it descendants-especially CATO-have had an enormous influence, setting the agenda for a variety of investigations carried out by different groups over three decades. As a result, the role of legal cases in moving from legal facts through intermediate concepts to issues and a final verdict is relatively well understood and has been formalised in Horty and Bench-Capon (2012) and Rigoni (2015). Also it has given rise to implementations which have performed well in empirical evaluations, capable of predicting case outcomes in more than 90% of cases, as shown in Ashley and Brüninghaus (2009) and Chorley and Bench-Capon (2005b).…”

“…Horty is the starting point for Rigoni (2015), who likes the rule based representation of cases, especially because it is able to maintain the venerable distinction between ratio deciendi and obiter dicta. Rigoni associates Horty's broadened rules with ratio deciendi.…”

Before and after Dung: Argumentation in AI and Law

“…In this way a body of case law can be represented as a knowledge base of rules or a logical theory. This representation has proved fruitful in developing a logic of precedential reasoning in [67] and [100].…”

“…This work uses argumentation methods making extensive use of argument schemes and argument graphs, which it says are similar to those of Carneades, to model the value judgements involved in deciding cases. The formal accounts of precedential constraint in [67] and [100] depend crucially on the relation of case and rule based reasoning advanced in [98].…”