Divided Infringement, Economics, and the Common Law

This essay responds to and builds on "Economic Theory, Divided Infringement, and Enforcing Interactive Patents," an article published by Professor Keith Robinson. In his article, Professor Robinson analyzed liability under various tests courts have developed to address the so-called "divided infringement" problem, which arises when multiple entities perform the steps of a method patent claim, under the three leading economic theories of patent law — reward theory, prospect theory, and rent-dissipation theory. In particular, Professor Robinson concluded that imposition of liability for divided infringement of method claims under joint enterprise principles is consistent with all three of these theories. This essay surveys recent developments in the law of divided infringement and shows how they have complicated the liability landscape that Professor Robinson described in his article. Furthermore, the essay applies Professor Robinson's approach to imposition of liability for divided infringement under the principles of causal responsibility, which I described in an earlier article, "Causal Responsibility and Patent Infringement." The essay concludes that liability based on causal responsibility — which, like joint enterprise, has deep roots in the common law — is also consistent with reward theory, prospect theory, and rent-dissipation theory. In addition, the essay considers broader implications of relying on common-law attribution principles in patent cases.