In LifeNet Health v. LifeCell Corporation, one of the many issues the Federal Circuit decided was that functional claim language did not create a divided infringement situation, even though an independent actor could impact whether the functional limitation was met. Under the court’s decision, since the limitation was a negative one, an independent actor could negate infringement, but his or her action is not required to establish infringement.

The Functional Claim Language At Issue

The patent at issue was LifeNet’s U.S. Patent No. 6,569,200, directed to plasticized soft tissue grafts. Claim 1 includes the functional claim language at issue:

1. A plasticized soft tissue graft suitable for transplantation into a human, comprising:
a cleaned soft tissue graft having an internal matrix; and
one or more plasticizers contained in said internal matrix;
said one or more plasticizers are not removed from said internal matrix of said plasticized soft tissue graft prior to transplantation into a human.

The Federal Circuit decision notes that “the non-removal limitation was added to the claims during prosecution” to overcome a prior art rejection.

A jury found that the claims were infringed and not shown to be invalid, and the district court denied LifeCell’s post-trial motions. Thus, LifeCell appealed to the Federal Circuit.

The Federal Circuit Decision

The Federal Circuit decision was authored by Chief Judge Prost and joined by Judges Reyna and Chen.

As summarized by the Federal Circuit, LifeCell’s functional claim language/divided infringement argument was based on the theory that “the non-removal limitation cannot be met until an independent third party, such as a surgeon, actually prepares and uses the accused products, and it is unknown at the time that LifeCell sells a graft if and how that graft will be used for transplantation.” On the other, LifeNet “counter[ed] that ‘the final product that leaves LifeCell’s hands is complete and . . . infringes in that condition’ without affirmative action by a third party.”

The Federal Circuit resolved this issue–and avoided having to reverse the district court’s finding that the claims were not indefinite–by treating the functional claim language as a limitation that describes the claimed product rather than specifying a method step:

Functional limitations recited in the negative may describe a capability or structural element. See Amgen Inc. v. Hoechst Marion Roussel, Inc., 314 F.3d 1313, 1329 (Fed. Cir. 2003) (holding that “non-naturally occurring” and “not isolated” were structural elements defining the source of the claimed material, rather than steps for obtaining it). ….

Here, … the non-removal limitation clarifies that the recited plasticizer has not been removed and, because the plasticizer is biocompatible, can remain in the internal matrix of the tissue graft during transplantation, i.e., it need not ever be removed. This limitation is met without action by a third party. It is satisfied by the graft from the moment it is manufactured unless and until the plasticizer is removed from the internal matrix before transplantation.

Therefore, the non-removal limitation does not relieve LifeCell of direct infringement.

Directly addressing the alleged indefiniteness of the functional claim language, the court stated:

[T]he non-removal limitation defines a property of the recited plasticizer in that the plasticizer is biocompatible and does not need to be removed from the internal matrix before transplantation in the context of apparatus claims 1-4, so no later action by a user of the tissue graft is necessary. Those claims therefore do not mix an apparatus with a method of using that apparatus, and the district court did not err in denying JMOL as to indefiniteness.

Do Two Wrongs Make A Right?

Practitioners may avoid including what could look like a method step in product claims in view of decisions like IPXL Holdings, LLC v., Inc., 430 F.3d 1377 (Fed. Cir. 2005), where the Federal Circuit invalidated a claim that combined “two separate statutory classes of invention,” i.e., product and process. Practitioners also may avoid including “negative” claim limitations, since many prefer to define the claimed subject matter by what the invention is, rather than what it is not. Here, however, LifeNet successfully enforced claims that defined its product with negative functional claim language that reads like a method step.

Would the court have reached the same conclusions on divided infringement and non-indefiniteness if the functional claim language were recited more positively?

… said plasticized soft tissue graft is transplanted into a human
without prior removal of said one or more plasticizers.

The key here seems to be crafting functional claim language that will be interpreted as defining a property of the claimed product rather than a method of using the claimed product.