Working Paper No. 09-22:
Fixing Patent Boundaries

Author(s):

Tun-Jen Chiang

Date Posted: March 2009

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Abstract:

The claims of a patent are its boundaries, defining the scope of exclusion. This boundary function of claims is undermined by the fact that claims can be changed throughout the life of the patent, thereby moving the patent boundary. A boundary that can be moved-at-will is one that the public cannot rely upon.

This Article explores the problems of malleable patent boundaries. If claim amendment is made to permit a patentee to capture something he did not foresee when filing the patent application, the amendment confers an unexpected windfall that did not contribute to incentives to invent before filing. If claim amendment is done to permit a patentee to capture something he did foresee but mistakenly failed to claim initially, the amendment allows the patentee to shift the loss of his own mistake to third-parties. Either way, the amendment is inefficient.

I propose that patent boundaries should be fixed upon patent issuance, and post-issuance claim amendment disallowed. Because claims before issuance do not create public reliance, pre-issuance amendment should be retained. Nonetheless, the possibility of inefficient windfalls requires that pre-issuance amendment not be given retroactive priority to limit the ability to capture later developments.