Digging into the Foundations of Evidence Law
22 Pages Posted: 24 Jan 2017 Last revised: 15 Apr 2017
Date Written: January 22, 2017
This essay reviews “The Psychological Foundations of Evidence Law” by Michael Saks and Barbara Spellman. Part I describes the book and its many insights. Part II focuses on the psychological (or logical) model that the book presents for understanding relevance and probative value. Saks and Spellman assume that the arithmetic difference between posterior and prior probabilities is a suitable measure of probative value. The essay questions this formulation. Using simple examples and a minimum of mathematics, it explains both likelihood ratios and Bayes’s factors and indicates the role they play in different theories of statistical inference and learning. It shows how these quantities (or variants on them) help explicate the meaning of evidentiary weight for individual items or collective bodies of evidence.
Keywords: evidence, jury psychology, Bayes factor, likelihood ratio, probative value, relevance, weight of evidence
JEL Classification: C00, C11, C19
Suggested Citation: Suggested Citation