How Bayesian Are Judges?

28 Pages Posted: 10 Nov 2015

See all articles by Jack Knight

Jack Knight

Duke University School of Law

G. Mitu Gulati

Duke University School of Law

David F. Levi

Duke University - School of Law

Date Written: November 8, 2015

Abstract

Richard Posner famously modeled judges as Bayesians in his book, "How Judges Think?". A key element of being Bayesian is that one constantly updates with new information. This model of the judge who is constantly learning and updating, particularly about local conditions, also is one of the reasons why the factual determinations of trial judges are given deference on appeal. But do judges in fact act like Bayesian updaters? Judicial evaluations of search warrant requests for probable cause provides an ideal setting to examine this question because the judges in this context have access to information on how well they did on their probabilistic calculations (the officers who conduct the search have to file, in every case, a "return" detailing what was found in their search). Based on detailed interviews with thirty judges our answer to the "How Bayesian are Judges?" question is: Not at all. The puzzle we are left with, given that acting in a Bayesian fashion is normal behavior for the rest of us, is why we get these puzzling results for judges in the search warrant context?

Keywords: judicial behavior, probable cause, warrants, judges as Bayesians

JEL Classification: K00, K41

Suggested Citation

Knight, Jack and Gulati, Gaurang Mitu and Levi, David F., How Bayesian Are Judges? (November 8, 2015). Duke Law School Public Law & Legal Theory Series No. 2016-2. Available at SSRN: https://ssrn.com/abstract=2687813 or http://dx.doi.org/10.2139/ssrn.2687813

Jack Knight

Duke University School of Law ( email )

210 Science Drive
Box 90362
Durham, NC 27708
United States

Gaurang Mitu Gulati (Contact Author)

Duke University School of Law ( email )

210 Science Drive
Box 90362
Durham, NC 27708
United States

David F. Levi

Duke University - School of Law ( email )

210 Science Drive
Box 90362
Durham, NC 27708
United States
919-613-7001 (Phone)

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