The Psychological Foundations of Evidence Law

320 pages

January, 2016

ISBN: 9780814783870



Also available in



Part of the Psychology and the Law series


Michael J. Saks is Regents Professor at the Arizona State University where he is on the faculties of the Sandra Day O’Connor College of Law and the Department of Psychology. He is the past co-editor of Modern Scientific Evidence: The Law and Science of Expert Testimony.

All books by Michael J. Saks

Barbara A. Spellman is Professor of Law (and former Professor of Psychology) at the University of Virginia. She is the former editor of Perspectives on Psychological Science.

All books by Barbara A. Spellman

Evidence law is meant to facilitate trials that are fair, accurate, and efficient, and that encourage and protect important societal values and relationships. In pursuit of these often-conflicting goals, common law judges and modern drafting committees have had to perform as amateur applied psychologists. Their task has required them to employ what they think they know about the ability and motivations of witnesses to perceive, store, and retrieve information; about the effects of the litigation process on testimony and other evidence; and about our capacity to comprehend and evaluate evidence.  These are the same phenomena that cognitive and social psychologists systematically study.
The rules of evidence have evolved to restrain lawyers from using the most robust weapons of influence, and to direct judges to exclude certain categories of information, limit it, or instruct juries on how to think about it. Evidence law regulates the form of questions lawyers may ask, filters expert testimony, requires witnesses to take oaths, and aims to give lawyers and factfinders the tools they need to assess witnesses’ reliability. But without a thorough grounding in psychology, is the “common sense” of the rulemakers as they create these rules always, or even usually, correct? And when it is not, how can the rules be fixed?
Addressed to those in both law and psychology, The Psychological Foundations of Evidence Law draws on the best current psychological research-based knowledge to identify and evaluate the choices implicit in the rules of evidence, and to suggest alternatives that psychology reveals as better for accomplishing the law’s goals.  


  • “Michael J. Saks and Barbara A. Spellman have succeeded brilliantly in doing what too few have attempted and many fewer still have accomplished. This book casts a bright light onto the dusty suppositions of evidence doctrine and employs contemporary psychological science to take the measure of the modern rules. Elegantly written and comprehensive in scope, Saks and Spellman’s work establishes a new standard for interdisciplinary scholarship.”

    —David L. Faigman, John F. Digardi Distinguished Professor of Law, University of California, Hastings

  • "In this book, two of the world’s most knowledgeable experts on psychology and law show that the legal rules of evidence are based largely on conjectures about how people think about evidence. Saks and Spellman persuasively demonstrate that some of those conjectures are well-founded, some not, and some are completely at odds with the scientific literature. Who knew?"

    —Jonathan J. Koehler, Beatrice Kuhn Professor of Law, Northwestern University School of Law

  • “Anyone seeking a treasure trove of new ideas will come away motivated, as the authors admirably achieve their noble goal of bringing attention to the need for more psychological research related to the Rules.”