Based on conflicting Federal Circuit case law, many academics have written, and many practitioners likely believe, that claim meanings or their applications may expand over time for purposes of literal infringement. But this common wisdom is wrong. Under existing Federal Circuit rules, the first precedent controls in the event of a conflict over doctrine, unless and until reversed en banc. The first precedent on the issue, the 2000 Schering Corp. v. Amgen, Inc. case, held that claim scope does not reach after-arising technologies for literal infringement and suggested that if it did, then such claims would lack written description support. Under existing validity precedents, temporally expanding claim scope would violate both § 112(a)’s enablement and written description requirements, as explicitly held in the 1977 In re Hogan decision and as implied by the more recent 2010 Ariad Pharmaceuticals v. Eli Lilly & Co. en banc decision. Further, were claims able to expand over time for literal infringement, they would violate the axiomatic equivalency of claim scope for validity and infringement. Once it is recognized that claim scope for literal infringement does not protect against after-arising technologies, further resort will be made to seek such protection under the doctrine of equivalents. This not only highlights the importance of the Ariad Pharmaceuticals decision but also will cause a big change to current practices and will lead to increased uncertainty regarding the scope of patent protection.

This Article explains why academics and practitioners may be confused regarding the U.S. law of literal infringement’s temporal scope. It describes the conflicting cases that have led to that confusion. And it explains why § 112(f)’s rule of construction for functional claiming language may be understood to limit all claim scope to temporally fixed, known-to-be equivalent technologies. This Article concludes by noting potential conflict with the pioneering invention doctrine and concerns should the law be changed to permit claiming the future