Markush Group Closed to Unlisted Elements, but Open to Blends of Listed Elements

In Multilayer Stretch Cling Film Holdings, Inc., v. Berry Plastics Corp., [2015-1420, 2015-1477] (August 4, 2016) the Federal Circuit reversed the claim construction, and thus vacated summary judgment of non-infringement that was predicated on that claim construction.

At issue was U.S. Patent No. 6,265,055, related to multi-layer stretch
cling films having at least seven individual layers, which claimed:

each layer being selected from the group consisting of linear low density polyethylene, very low density polyethylene, ultra low density polyethylene, and metallocene-catalyzed linear low density polyethylene resins;

The district court construed this language as requiring each layer must contain only one class of the listed resins, and no other resins, thereby excluding blends of more than one type of listed resin and all unlisted resins.

The parties agreed that the claim language was an Markush group.  The Federal Circuit agreed with the district court that the group is closed to resins other than those listed in the group.  The Federal Circuit said that what was critical the transitional phrase “consisting of,” a term of art in patent law with a distinct and well-established meaning that creates a very strong presumption that that claim element is “closed.”

The Federal Circuit rejected the patent owners argument that dependent claims expanded the scope of the Markush group, noting that while other claims can be valuable sources of enlightenment as to the meaning of a claim term, the language of a dependent claim cannot change the scope of an independent claim whose meaning is clear on its face, observing:

The dependent claim tail cannot wag the independent claim dog.

However the Federal Circuit disagreed with the district court over whether the claims permitted mixtures of the four plastics set forth in the Markush group.  The Federal Circuit noted that under Abbott, the Markush group is therefore presumed closed to blends. The question is whether that presumption is overcome by a combination of other claim language and the specification itself.  The Federal Circuit found that the intrinsic evidence of the patent is unequivocal that the inner layers described in claims 1 and 28 are open, not closed, to blends of the recited resins.  The Federal Circuit noted that the resins listed do not constitute four entirely different species but instead overlap to some
extent.  Moreover, claim 24 recites that at least one layer comprises a blend of at least two of said resins.  Finally, the Federal Circuit observed that the specification similarly supports construing the element as open to blends, as it repeatedly and consistently references blends in describing any and all resins, including the four resins of the claim.

In the light of this strong intrinsic evidence, the Federal Circuit held that the Markush group must be read as open to blends of the four listed resins.