On May 12, 2015, the United States Court of Appeals for the Federal Circuit (CAFC) issued a decision in ArcelorMittal v. AK Steel (Fed. Cir. 2015), finding that its previous claim construction of an independent claim was impermissibly broadened by a dependent claim added in a reissue application filed more than two years after the original patent was issued.

In this ongoing litigation, the CAFC had previously affirmed the district court claim construction of the language “a very high mechanical resistance” in the independent claim 1 as meaning steel with a tensile strength greater than 1500 MPa.  The case was remanded to the district court on other grounds.

In the meantime the patentee, ArcelorMittal, successfully prosecuted a reissue application to issuance which included an added dependent claim that recites “[t]he coated steel sheet of claim 1, wherein said mechanical resistance is in excess of 1000 MPa.”

In this latest appeal, ArcelorMittal argued that the independent claim 1 is not broadened because the successful prosecution of the reissue shows that the USPTO considered the phrase “very high mechanical resistance” to be broader than construed by the CAFC.  However, the CAFC held that the district court was prohibited from revisiting the construction of the phrase “very high mechanical resistance” because of the “law-of-the-case doctrine” and thus the claims were impermissibly broadened in the reissue patent in violation of 35 U.S.C. § 251.  As noted by the CAFC, “[t]he law-of-the-case doctrine “posits that when a court decides upon a rule of law, that decision should continue to govern the same issues in subsequent stages in the same case.” Banks v. U.S., 741 F.3d 1268, 1276 (Fed. Cir. 2014) (quoting Christianson v. Colt Indus. Operating Corp., 486 U.S. 800, 815–16 (1988)) (internal quotation marks omitted).”