The nature of juridical proof
| Published date | 01 January 2017 |
| Date | 01 January 2017 |
| DOI | 10.1177/1365712716674794 |
| Subject Matter | Articles |
Article
The nature of juridical proof:
Probability as a tool in
plausible reasoning
Ronald J. Allen
Northwestern University Pritzker School of Law, Chicago, IL, United States;
Board of Foreign Advisors, Evidence Law and Forensic Sciences Institute, Beijng, People’s Republic of China;
Procedural Law Research Center, ZhengFa University, Beijing, People’s Republic of China
Abstract
The different contexts of forensic science and juridical decision making are explored to identify
the nature of juridical proof, the role of formalized probability theory in it, and how factual
inquiry proceeds in the differing domains.
Keywords
proof, probability, plausibility, Bayes theorem
This article may be disquieting to the forensic scientists in the room. I am going to explain why one of
their most cherished tools—probability theory (and its pragmatic offspring known as Bayes’ Theo-
rem)—is of very little significance in understanding the nature of juridical proof, and even less signifi-
cant as a guide to decision making.
Needless to say, probability theory and statistical derivatives such as hypothesis testing and
Bayesian analysis have been critically important components in the spectacular success story of
modern scientific achievements that has transformed the human condition. They are not the only
cognitive tools that have led to this success, however. Observation, the compiling of clinical
knowledge, and painstaking taxonomic efforts are just a few of the additional tools in the scientific
toolbox. Probability is also a mainstay of modern life outside the scientific realm. ‘Probability talk’
is so ubiquitous that giving examples seems almost silly—you and I are constantly talking about
whether we will ‘probably’ do this or whether that ‘probably’ happened, ranging o ver speculation
abouttheweathertothestateoftheeconomytowhowillwinthenextelectiontotherelationship
between human activity and global warming to the chance of extraterrestrial life to the existence
of god.
Legal systems participate in this discourse as well, and actually were among the first of the disciplines
to employ the language of probability. Formal probability theory arose in part to explain proof at trial,
and interestingly to decide how to fairly calibrate the winnings in gambling games; I leave it to you to
Corresponding author:
Ronald J. Allen, Northwestern University Pritzker School of Law, Chicago, IL, United States.
E-mail: rjallen@northwestern.edu
The International Journalof
Evidence & Proof
2017, Vol. 21(1-2) 133–142
ªThe Author(s) 2016
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DOI: 10.1177/1365712716674794
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