Why Priest-Klein Cannot Apply to Individual Issues in Patent Cases

8 Pages Posted: 21 Aug 2012 Last revised: 25 Mar 2013

See all articles by Jason Rantanen

Jason Rantanen

University of Iowa - College of Law

Date Written: August 15, 2012


The Priest-Klein hypothesis is commonly used to support the expectation of a fifty-percent success rate for patent holders on issues such as obviousness or inequitable conduct. As this essay explains, such a use of Priest-Klein is mathematically flawed. At best, the Priest-Klein hypothesis only applies to the selection of disputes, not the selection of individual issues. Due to the presence of multiple issues in patent cases, there is axiomatically no basis for inferring that a patentee would expect a fifty-percent chance of winning on each one. This essay supports its argument with theory and examples, demonstrating why application of the Priest-Klein hypothesis to individual issues - particularly in explaining or analyzing the results of empirical studies of doctrinal issue outcomes in patent law - is incorrect. This is not to say that such studies cannot yield useful and insightful results, but that conclusions about their meaning should not be based on deviations from a fifty-percent success rate.

Keywords: patent, Priest-Klein, empirical

Suggested Citation

Rantanen, Jason, Why Priest-Klein Cannot Apply to Individual Issues in Patent Cases (August 15, 2012). U Iowa Legal Studies Research Paper No. 12-15, Available at SSRN: https://ssrn.com/abstract=2132810 or http://dx.doi.org/10.2139/ssrn.2132810

Jason Rantanen (Contact Author)

University of Iowa - College of Law ( email )

Melrose and Byington
Iowa City, IA 52242
United States

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