Background
Hammond Development International owns a family of related patents covering a communication system that allows a device to remotely execute applications — broadly, a system for what might today be called cloud computing or thin-client technology. Google previously filed inter partes review (IPR) petitions challenging Hammond’s U.S. Patent No. 8,490,483 and obtained a final written decision from the Patent Trial and Appeal Board finding certain claims of that patent unpatentable.
Google then filed a second IPR against a related Hammond patent, U.S. Patent No. 9,015,816, which shares the same specification as the ’483 patent but uses somewhat different claim language to describe similar subject matter. The PTAB had to decide whether the invalidity findings from the first IPR bound it in the second one under collateral estoppel — also known as issue preclusion — even though the claims in the two patents were not worded identically.
The Court’s Holding
The Federal Circuit affirmed in relevant part, holding that collateral estoppel can apply across IPR proceedings even when the patent claims at issue use different language, as long as the differences do not materially alter the question of patentability. The dispositive inquiry is not whether the claims are identical, but whether the issues of patentability are the same.
In this case, claim 18 of the ’483 patent required certain computing activities to occur on “one or more application servers.” Claim 18 of the ’816 patent split those activities between two separately described application servers. The PTAB found, and the Federal Circuit agreed, that this difference did not materially change the patentability analysis: the prior art reference (Gilmore) already disclosed the underlying concept of distributing application functions across servers, and a person of ordinary skill in the art would readily have found it obvious to run the applications on separate servers. Because the core patentability question remained the same, collateral estoppel from the first IPR applied to invalidate the corresponding claim in the second IPR.
Key Takeaways
- Collateral estoppel in IPR proceedings applies when the issues of patentability are identical between two proceedings — not when the patent claims themselves are word-for-word the same.
- Patent owners who own families of related patents with overlapping subject matter face risk that an adverse IPR ruling on one patent will be preclusive against claims in related patents, even if those claims are worded differently.
- Minor linguistic variations in claim language — such as splitting a single server requirement into two separate server requirements — will not defeat collateral estoppel if the underlying patentability question remains the same.
- Petitioners pursuing serial IPRs against related patents in the same family should consider arguing for collateral estoppel as an additional invalidity ground when prior IPR decisions are available.
Why It Matters
This decision has important implications for patent portfolio strategy. Companies that own patent families — groups of related patents covering the same underlying technology but using different claim language — must now account for the risk that a successful IPR challenge to one patent in the family can be used to knock out claims in sibling patents, even if those claims are not identical. The ruling incentivizes patent owners to draft claims across a family with more substantive variation, not just linguistic variation, if they want to avoid preclusion.
For defendants and IPR petitioners, the ruling is an invitation to proactively raise collateral estoppel arguments when a prior IPR has already resolved the relevant patentability question. Rather than relitigating the same prior art and arguments before the Board, petitioners can invoke issue preclusion to streamline the proceeding and avoid inconsistent outcomes across related patents covering the same inventive concept.