Our Bizarre System for Proving Copyright Infringement

Stanford Public Law Working Paper No. 1661434

57 Journal of the Copyright Society 719 (2010)

32 Pages Posted: 21 Aug 2010 Last revised: 28 Apr 2020

Date Written: August 18, 2010


At the heart of copyright infringement cases is “substantial similarity” between the plaintiff’s and the defendant’s works. But while every circuit agrees on the centrality of substantial similarity, that basic agreement conceals surprising differences in what exactly we mean by substantial similarity and how it is to be proven in court. And the majority approach, defined by the Second Circuit in Arnstein v. Porter and the Ninth Circuit in Sid and Marty Krofft, has the analysis of proof exactly backwards – permitting analytic dissection of the works and expert testimony where the question is one that should be handed to the members of the jury, and falling back on the “ordinary observer” test on the very questions that require careful dissection by the court. I argue that the Arnstein and Krofft tests make no sense. A better model draws from software copyright cases, which give filtration and dissection of unprotectable elements a more central role.

Suggested Citation

Lemley, Mark A., Our Bizarre System for Proving Copyright Infringement (August 18, 2010). 57 Journal of the Copyright Society 719 (2010). Available at SSRN: https://ssrn.com/abstract=1661434 or http://dx.doi.org/10.2139/ssrn.1661434

Mark A. Lemley (Contact Author)

Stanford Law School ( email )

559 Nathan Abbott Way
Stanford, CA 94305-8610
United States

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