Amendments during reissue may be deemed broadening and thereby render a patent unenforceable if they broaden a previous and controlling claim construction from prior litigation even if the PTO’s broadest reasonable interpretation may perceive them as narrowing. Here, for example, an amendment during reissue clarifying the meaning of “very high mechanical resistance” as “wherein said mechanical resistance is in excess of 1000 MPa” when this phrase was construed during prior litigation to mean in excess of 1500 MPa was found to be an impermissible broadening because the prior construction was controlling. It may therefore be best to avoid amendments during reissue that broaden (outside of the permissible broadening window) a claim construction from prior litigation even if the PTO allows the amendments.
Background / Facts: The patent being asserted here is directed to a specific type of steel sheet that has “a very high mechanical resistance” after thermal treatment. Following an unfavorable claim construction in prior litigation construing the claimed phrase “very high mechanical resistance” as limited to steel with a tensile strength greater than 1500 MPa, the patentee filed for a reissue (outside of the permissible broadening window) that attempted to clarify the meaning of “very high mechanical resistance” as “wherein said mechanical resistance is [only] in excess of 1000 MPa.”
Issue(s): Whether this additional limitation is in fact an impermissible broadening amendment in view of the court’s earlier claim construction.
Holding(s): Yes. “Because the law-of-the-case doctrine prohibited the district court from revisiting the construction of ‘very high mechanical resistance’ in the [original] patent, we agree that claims 1 through 23 were impermissibly broadened in violation of § 251.” Although “[u]nder the mandate rule and the broader law-of-the-case doctrine, a court may only deviate from a decision in a prior appeal if ‘extraordinary circumstances’ exist,” “[t]he successful prosecution of the [reissue] patent is not ‘new evidence’ sufficient to trigger the extraordinary circumstances exception to the mandate rule and the law-of- the-case doctrine. Permitting a reissue patent to disturb a previous claim construction of the original claims would turn the validity analysis under 35 U.S.C. § 251 on its head.”