The U.S. Court of Appeals for the Federal Circuit recently affirmed a decision of the United States Patent and Trademark Office Board of Patent Appeals and Interferences (the Board) that the introduction of claims that omit a critical element required by the specification was invalid for lack of written description. Mukherjee v. Chu, Case No. 06-1450 (Fed. Cir., Feb. 15, 2007) (Michel, C.J.).

A patent interference proceeding is a procedure conducted before the USPTO to determine which of two or more competing inventions is entitled to priority. In this case, Mukherjee, an inventor, filed an amendment to an application which provoked an interference with U.S. Patent No. 6,030,720, invented by Chu et al. Chu moved for a judgment that Mukherjee’s involved claims were unpatentable for failure to comply with the written description requirement of 35 U.S.C. § 112, ¶1, arguing that because the involved claims do not recite Electroactive Transition Metal Chalcogenide (ETMC) as part of the cathode component of a battery cell, the claims are broader than the specification on which they are based.

The Board agreed with Chu after it examined Mukherjee’s application and found that the inclusion of ETMC in the cathodes of an electrochemical cell was a distinguishing feature of the invention. However, Mukherjee’s claims did not include a requirement that the cathodes contain an ETMC. Mukherjee's application criticized non-ETMC cathodes in the prior art and specifically distinguished his invention over the prior art by disclosing that his ETMC cathodes overcame the drawbacks associated with the prior art. The Board cited one section of Mukherjee’s application that specifically stated that ETMC was a critical element in all cases. Chu presented an expert who testified that one of ordinary skill in the art would understand that Mukherjee’s invention was limited to ETMC cathodes, while Mukherjee presented an expert who testified that ETMC was optional since the battery cells would still work without the ETMC component. The Board credited the testimony of Chu’s expert since it was consistent with the written description.

On appeal Mukherjee argued that the Board did not consider all of his expert’s testimony and failed to consider one part of his application which allegedly disclosed a method of making a non-ETMC cathode. However, the Federal Circuit deferred to the Board’s discretion regarding the expert testimony. With regard to the alleged written description, the Court found that, contrary to Mukherjee’s assertion, the section in question disclosed only ETMC cathodes because the described protocol uses a slurry that contains ETMC. The Court also noted that Mukherjee’s application repeatedly stated that composite cathodes necessarily contain ETMC. The Court concluded that there was substantial evidence to support the Board’s determination that the Mukherjee application did not comply with the written description requirement.