105 California Law Review __ (forthcoming April 2017)
Abstract
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.
