On February 24, 2014, in Elcommerce.com, Inc. v. SAP AG, the US Court of Appeals for the Federal Circuit vacated the US District Court for the Eastern District of Pennsylvania's judgment of invalidity of Elcommerce.com's system claims and held that SAP was required to present expert testimony to meet its burden of proof on indefiniteness (No. 2011-1369, (Fed. Cir. Feb. 24, 2014)).

The district court found the means-plus-function system claims invalid for failure to comply with 35 U.S.C. § 112 based on SAP's argument that the patent specification did not disclose any corresponding structure. SAP did not present any expert testimony or other evidence of the existing knowledge in the field and argued that Federal Circuit precedent did not require such evidence where there is no structure disclosed in the specification.

On appeal, the Federal Circuit held that the district court erred in accepting only attorney argument in support of its invalidity decision. The court explained that a means-plus-function claim is indefinite only if a person of ordinary skill in the art would be unable to recognize a structure in the specification and associate it with the corresponding function in the claim. The court held that the burden was on SAP to prove its indefiniteness case and that in the absence of any expert testimony, there was a failure of proof.

Although the court held that SAP could not meet its burden without presenting expert testimony, the court did not expressly hold that expert testimony would be required in all cases. The court did not elaborate on the circumstances under which expert testimony might be required. In a dissenting opinion, Judge Wallach criticized the majority's holding on the system claims as contrary to prior cases where the court has held that expert testimony is not required to prove indefiniteness of a means-plus-function claim when the specification does not disclose a corresponding structure.

The court's decision serves as a reminder to patent applicants to include structural support in the specification for any means-plus-function claims. Patent litigants, however, may not be able to rely solely on the patent's disclosure and should be prepared to present expert testimony in support of an indefiniteness claim.