Strategies for Using the Written Description Requirement to Invalidate Broad Patent Claims

In an earlier blog post ( we addressed the question of whether and to what extent U.S. law limits the breadth of patent claims that are otherwise novel and non-obvious. As we explained, both the Written Description and Enablement requirements of U.S. patent law may limit claim scope even if the prior art does not. On October 29 the Court of Appeals for the Federal Circuit issued an opinion in Synthes USA, LLC, et al. v. Spinal Kinetics, Inc. holding that the Synthes’ spinal implant claims were invalid under the Written Description requirement because they recited a “third plate including a plurality of openings” while the originally-filed application described only “circumferential grooves.” In other words, the specification described only a specific type of opening (“grooves”) and a specific location on the claimed third plate (“the circumference”). The Federal Circuit affirmed a jury verdict of invalidity under the written description requirement because the claims covered all types of openings and locations for placing them on the claimed third plates while the specification was far narrower.

“Black letter” patent law includes many competing principles that are in tension with one another, as this case illustrates. Under the rules applicable to interpreting claim language, claims are not to be limited to a preferred embodiment, even if it is the only embodiment in the specification. However, in order to satisfy the written description requirement (and be valid) a patent must convey to those skilled in the art that the inventor had possession of the claimed invention, not merely the disclosed embodiments. This tension begs the question of how you determine whether claims that are broader than the specification embodiments are nevertheless valid under the written description requirement.

Addressing this tension is a place where good, creative lawyering is key. The Synthes decision provides a nice example of this. The first thing the decision reveals is that characterizing and framing the issue is critical. In this case, the accused infringer argued that the claims covered any type of opening located anywhere on the third plate. Based on this characterization, the accused infringer developed expert and factual testimony showing the various challenges that would arise using different types of openings located at different places on the “third plate.” In particular, the accused infringer relied on evidence of how it arrived at its opening style and placement location to show how these features affected the intended use of the product and to show how much work it took to arrive at the final design. The Federal Circuit held that this evidence was sufficient to show that one skilled in the art would not have understood that the inventors were in possession of an implant that included any type of opening located anywhere on the third plate simply by disclosing a single embodiment with grooves located around the circumference.

The Synthes case reveals a few key strategy points for using the written description requirement to attack broad claims that are supported by a narrow disclosure:

1. Characterize the nature of the breadth relative to the disclosed embodiments.

2.  Consult with experts and technical personnel to identify a set of alternative, undisclosed embodiments that would be embraced by the broad claim language.

3.  Determine the impact of the various alternative embodiments on the intended use of the claimed invention and the nature of any work or modifications that might be required to make them work.

4.  Take appropriate discovery of the patent holder to further develop 1-3.

5.  Based on 1-4, develop the argument as to why one skilled in the art would not have been presumed to have been in possession of the broad claim asserted by the patent holder based on the patent’s narrower embodiments.

Many of the patent cases filed in the U.S. involve claims that are significantly broader than the disclosed embodiments. In some cases, it may not be possible to find prior art to invalidate the patent claims based on a lack of novelty or obviousness. Thus, the written description requirement and/or the enablement requirement can provide a critical avenue for attacking the validity of such patents.