US Federal Circuit Construes “Consisting Of” in Markush Group as Being Limited to Recited Elements Only

On August 4, 2016, in Multilayer Stretch Cling Film Holdings v Berry Plastics Corporation, 2015-1420, the United States Court of Appeals for the Federal Circuit (the Court), Taranto J dissenting in part, construed the Markush claim language, “being selected from the group consisting of”, as being limited to only the recited elements in the claim.

The Court focused on the transitional phrase, “consisting of”, stating that the phrase is a term of art in patent law, with a distinct and well established meaning.  The Court stated that the use of this term “to set off a patent claim element creates a very strong presumption that that claim element is ‘closed’ and therefore ‘exclude[s] any elements, steps, or ingredients not specified in the claim.”  The Court held that to overcome this “exceptionally strong presumption”, “the specification and prosecution history must unmistakably manifest an alternative meaning”.   The majority agreed with the dissent that the specification, including the dependent claims, suggested that the broader invention included other elements not listed in the Markush group contained in the independent claims; nevertheless, this was insufficient to overcome the very strong presumption created by the patentee’s use of “consisting of”.

The Court also considered whether the transitional phrase, “consisting of”, could include blends of the recited elements, and concluded that the patent specification (intrinsic evidence) was unequivocal, and that this phrase was open to the blends.

Summary By: Junyi Chen