This article develops an original rhetorical framework for analyzing the logic of legal arguments and then applies it to unpack a post-conviction DNA testing controversy currently before the Supreme Court. My framework extends Aristotle's concept of logos by specifying different logical types of proof in legal argument. The Osborne case now before the Court concerns how DNA proof intersects with legal process and the procedural barriers to prisoners' accessing DNA evidence after conviction. After parsing the persuasive dynamics in the federal litigation preceding Osborne, I make a prediction on what argument logic will prevail in the Court.
Drawing on the work of Aristotle, neo-Aristotelian argument scholars, and contemporary jurisprudence, I first construct an original taxonomy of logos that distinguishes between modes of proof in legal argument. This taxonomy characterizes prototypical differences in formal, empirical, narrative, and categorical arguments by reference to the logical and rhetorical roles of their constituent premises, inferences, and conclusions.
I then use my new vocabulary to frame an in-depth case study of federal-court litigation over post-conviction access to DNA evidence under 42 U.S.C. Section 1983. I describe the history of this discourse, and engage in close readings of two arguments – the concurring opinions of Judge Michael Luttig and Chief Judge Harvie Wilkinson in the Harvey II case – that represent the competing rhetorical poles of the debate. I classify Luttig's argument logos as formal, and Wilkinson's as narrative. After examining all published decisions that have considered the Section 1983 issue since Harvey II, I argue that Luttig's formal logos has successfully persuaded federal courts. I therefore predict that Luttig's logic on the procedural dispute in Osborne will prevail at the Supreme Court. By closely dissecting this argument over DNA, I bring fresh perspective on the rhetorical DNA of a legal argument.
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