Official PTO statistics indicate that approximately two-thirds of patents that emerge from reexamination result in some change to their claims.  Ten percent of claims are canceled outright.  Some critics assert that there is insufficient granularity in these PTO statistics to reflect situations where some but not all asserted claims are either found to be invalid or are substantially amended.  Where claims are substantively amended, the accused infringers may not be liable for past damages under intervening rights law.  This can be crucial where the patent term is short or the accused infringers have clear and inexpensive design-around options.

More specifically, substantive amendments made during reexamination may defeat damages for past infringement under the statutory doctrine of intervening rights [35 U.S.C. §§ 252, 307(b), 316(b)].  A patent owner cannot seek damages for claims that are not substantially identical to the original claims [Bloom Eng’g Co. v. N. Am. Mfg. Co., 129 F.3d 1247, 1250 (Fed. Cir. 1997)].  There is no per se rule for determining whether a claim is not “substantially identical” [Laitram Corp. v. NEC Corp., 952 F.2d 1357, 1358 (Fed. Cir. 1991)]. The analysis includes examining “the claims of the original and the reexamined patents in light of the particular facts, including prior art, the prosecution history, other claims, and any other pertinent information” [Id. at 1362-63].  The determination is a legal one, and a claim is changed if its scope is changed [Tennant Co. v. Hako Minuteman, Inc., 878 F.2d 1413, 1417 (Fed. Cir. 1989)].

If a claim is not substantially identical, then a patentee may not seek damages for product sales prior to issuance of the reexamination certificate.  If damages have already been awarded, a defendant may seek to have damages vacated since the claims were void ab initio.  Again, because of the potential impact on damages, reexamination requests should be filed on all patents-in-suit, if possible, and on all the asserted claims.

Concepts

• Substantially Amended Claims
• Doctrine of Intervening Rights
• Vacating as Void Ab Initio

Cases

• Bloom Eng’g Co. v. N. Am. Mfg. Co. (Fed. Cir. 1997)
• Laitram Corp. v. NEC Corp. (Fed. Cir. 1991)
• Tennant Co. v. Hako Minuteman, Inc. (Fed. Cir. 1989)