An Excess of Discretion? 'Thayer's Triumph' and the Uncodified Exclusion of Speculative Evidence

9 Pages Posted: 7 Jul 2016 Last revised: 17 Apr 2017

See all articles by David S. Schwartz

David S. Schwartz

University of Wisconsin Law School

Date Written: July 6, 2016


Modern evidence law is based on codes that expressly deny courts discretion to create common law rules categorically excluding evidence. And yet a commonly applied and important exclusion rule in evidence law appears to be uncodified: the law of evidence includes a broad rule against speculation. Yet the concept of speculation is not adequately explained or theorized. This essay offers a preliminary effort at gaining a more thorough understanding of what speculation is, how it tracks with the rules of evidence, and when it should and should not result in exclusions of evidence. The essay argues that speculation is best understood as the thought process of substituting dubious generalizations or factual hypotheses for facts that are missing or unsupported by evidence. Claims that evidence is speculative should be analyzed as a foundation problem under one or more of the codified foundation rules. Moreover, it should be recognized that not all speculation by the trier of fact is impermissible.

Keywords: Evidence, Federal Rules of Evidence, FRE, 701, 901, 104, 602, exclusion, relevance, speculative, speculation, conjecture, guessing, foundation, opinion, state of mind, relevance, conditional relevance

JEL Classification: K41: Litigation Process

Suggested Citation

Schwartz, David S., An Excess of Discretion? 'Thayer's Triumph' and the Uncodified Exclusion of Speculative Evidence (July 6, 2016). 105 California Law Review 591 (2017); Univ. of Wisconsin Legal Studies Research Paper No. 1386. Available at SSRN:

David S. Schwartz (Contact Author)

University of Wisconsin Law School ( email )

975 Bascom Mall
Madison, WI 53706
United States

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