Generally, a claim examined by the U.S.P.T.O is given its broadest reasonable interpretation in light of and consistent with the specification of the application or patent in which it appears (hereinafter “broad reasonable standard”).  The rationale for applying the broad reasonable standard is that claims of applications and patents examined by the U.S.P.T.O can be amended. (MPEP § 2111)  There are, however, two important and little known exceptions when the broad reasonable standard is not applied by the U.S.P.T.O. One exception arises in interferences where an applicant “copies” the claim of a targeted patent or application to provoke the interference.  In this case, if a party challenges the patentability of the “copied” claim pursuant to 35 U.S.C. §112, first paragraph, the “copied” claim is interpreted in light of the specification of the targeted patent or applicationSee Agilent v. Affymetrix, 567 F.3d 1366, 91 USPQ2d 1161 (Fed. Cir. 2009). A second exception arises when an expired patent is in ex parte or inter partes reexamination.  In patent reexamination proceedings, reexamination of an expired patent is proper since the patent remains enforceable for six years after expiration (to collect past damages) and its claims cannot be amended once the patent expires.  MPEP § 2258(I)(G) provides the following guidance on claim interpretation during reexamination: claims are given the broadest reasonable interpretation consistent with the specification and limitations in the specification are not read into the claims (In re Yamamoto, 740 F.2d 1569, 222 USPQ 934 (Fed. Cir. 1984)). In a reexamination proceeding involving claims of an expired patent, claim construction pursuant to the principle set forth by the court in Phillips v. AWH Corp., 415 F.3d 1303, 1316, 75 USPQ2d 1321, 1329 (Fed. Cir. 2005) (words of a claim “are generally given their ordinary and customary meaning” as understood by a person of ordinary skill in the art in question at the time of the invention) should be applied since the expired claim are not subject to amendment. The statutory presumption of validity, 35 U.S.C. 282, has no application in reexamination (In re Etter, 756 F.2d 852, 225 USPQ 1 (Fed. Cir. 1985)). That a claim term can have two different meanings in reexamination dependent on whether the patent is expired can be of utmost importance.  Application of a Phillips type claim construction can be useful in avoiding clarifying amendments.  Such amendments, if deemed substantive in a subsequent litigation, would surrender at least past damages based upon intervening rights. Will the Central Reexamination Unit (“CRU”) apply the Phillips standard when interpreting claims of an expired patent? Two unpublished and non-precedential decisions by different panels of the Board of Patent Appeals and Interference (“Board”) shed some light on that question.  In Ex parte Personalized Media Communications, Inc., Appeals 2007-4044 and 2008-0334, Reexamination Control Nos. 90/006,697, 90/006,841, and 90/006,800 (BPAI, 2008), a panel of the Board concluded that claim language of an expired patent can be construed more narrowly than its ordinary and customary meaning only to the extent needed to resolve an ambiguity.  If the claim term is clear, the panel concluded that the broad reasonable standard generally applied by the U.S.P.T.O should be used.  See also Ex parte Peng Tan, Appeal 2006-3235, Reexamination Control No. 90/006,696 (BPAI, 2008)(affirmed by the Fed. Cir.). What should be the burden of proof standard in such circumstances?  Since claims of an expired patent in reexamination cannot be amended and thus enjoy a district court (i.e., Phillips) type of claim construction, should the CRU be required to make a clear and convincing rather than preponderance of the evidence showing when rejecting a claim of an expired patent in reexamination?  Cf. In re Etter, 756 F.2d 852, 225 USPQ 1 (Fed. Cir. 1985) where the  Federal Circuit concluded that the statutory presumption of validity, 35 U.S.C. § 282, has no application in reexamination. Curiously, however, the court in Etter relies upon the ability of patentees to amend claims in reexamination as justification to disregard the statutory presumption of validity provided by 35 U.S.C. § 282.   Is Etter controlling law regarding the proper treatment accorded expired patents for claim interpretation purposes in reexamination? Consider Etter (225 USPQ at 8) in this respect: In litigation, where a patentee cannot amend his claims, or add new claims, the presumption, and the rule of claim construction (claims shall be construed to save them if possible), have important roles to play. In reexamination, where claims can be amended and new claims added, and where no litigating adversary is present, those roles and their rationale simply vanish. As Etter clearly predated inter partes reexamination, and did not consider expired patents, this is an issue worth watching.  Practitioners should be well advised to consider these important distinctions when representing the patent owner in reexamination proceedings involving expired patents.