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This article focuses on the question of how decision makers with no relevant scientific background can (if at all) legitimately evaluate conflicting scientific expert testimonies and determine their relative reliability. Sceptics argue that non-experts can never reach justifiable conclusions regarding the merits of conflicting expert testimonies because they lack the fundamental epistemic capacity to make such judgement calls. In this article, I draw on works on epistemology, philosophy of practical reasoning, philosophy of science, science and technology studies, and legal theory in order to scrutinize recent proposals to solve the problem of conflicting scientific expert testimonies. Addressing this question is of ultimate importance due to the idea that immanent in the idea of rule-of-law there is an intellectual due process norm, which articulates that epistemically arbitrary legal decisions are also not legally justified. This article is divided into two Sections. In Section 2, I describe the basic philosophical inquiries underlying the debate about expert testimony. In particular, I first elaborate on the philosophy of testimony and its epistemic justifications, then move to the idea of epistemic deference, and finish with philosophical accounts of expertise. Section 3 presents the problem of conflicting scientific expert testimonies and analyses recent attempts to solve it as formulated by Ward Jones, Alvin Goldman and Scott Brewer. I argue that there is no single criterion (or set of criteria) upon which the non-expert could rely in order to make a rationally justified decision in each and every case in which he faces conflicting scientific expert testimonies. The alternative view here defended is to stop looking for an epistemic panacea and accept the idea that testimonial reliability operates differently within different kinds of testimony-and differently within the same kind of testimony at different times.

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