When defending a patent infringement claim, an accused infringer often possesses dozens of prior art references that could render the patent claims obvious.   Often the local patent rules are vague as to whether an accused infringer must disclose every precise combination of prior art references rendering the claims invalid or whether the accused infringer can generally identify the types of combinations of prior art that could render the claims invalid.  

In Rambus v. Nvidia Corporation (.pdf), Case No. C-08-3343 (N.D.Cal. Nov. 29, 2011), the plaintiff Rambus moved to strike Nvidia’s invalidity contentions on the basis that Nvidia did not identify each and every precise combination of prior art that could render the patent claims obvious.  Nvidia defended its contentions explaining that “Nvidia provided charts for each primary reference that included all of the secondary references [in a group] that, when combined with the primary reference…render the asserted claims obvious.”  In his finding that the contentions were acceptable, Special Master Infante cited to Keithley v. The Homestore.com, Inc., 553 F.Supp.2d 1148, 1149-51 (N.D.Cal. 2008) and Avago Technologies General IP PTE Ltd. v. Elan Microelectronics Corp., 2007 WL 951818 (N.D. Cal. Mar. 8, 2007) which held that it was acceptable for a defendant to organize its prior art references into groups and then claim that its theory of obviouosness was true for every possible combination between the groups.  Although the Avago court recognized that this method could result in billions of possible obviousness contentions, the disclosure still satisfied the local patent rule because it “reasonably specifies the combination of prior art references that allegedly render Avago’s patents obvious.”  Accordingly, Rambus’s motion to strike the invalidity contentions was denied.

Key Takeaway:  Should a litigant have a large number of prior art references that when combined in many different ways could render the patent claims obvious, the litigant should consider asserting invalidity combinations in group format if permitted by the local patent rules and corresponing case law.

For a different perspective, see Eastern District of Texas Local Patent Rule 3-3(b) requiring the following for invalidity contentions, “If a combination of items of prior art makes a claim obvious, each such combination, and the motivation to combine such items, must be identified;…”  (emphasis added)