Chinta & Fratangelo LLP

All claims in EON’s patent were found to be invalid because means-plus-function claims describing complex computer functionality are indefinite without algorithms to provide structure to the claims. Eon Corp. IP Holding LLC v. AT&T Mobility LLC, No. 2014-1392 (Fed. Cir. 5/6/2015).

EON owns US patent 5663757, issued 9/2/1997, directed to software in a “local subscriber data processing station,” that pertains to interactive TV features, like audience participation, voting, and purchasing of goods. In 2010, EON asserted this patent against smartphone manufacturers and cellular telephone providers, alleging they were infringing.

At the Delaware District Court, following the claim construction hearing, the court granted summary judgment that all the claims were invalid as indefinite. Eight terms were held to be indefinite. For example, the first one listed is: “means under control of said replaceable software means for indicating acknowledging shipment of an order from a remote station.”

On appeal, the Federal Circuit panel (Prost, Newman, and Bryson, opinion by Prost) upheld the District Court, relying largely on WMS Gaming Inc. v. Int’l Game Tech., 184 F.3d 1339-1348-49 (Fed. Cir. 1999) which set out a rule that the corresponding structure for a function performed by a software algorithm is the algorithm itself. EON’s problem is that there were no algorithms in the specification or claims.

EON argued that the “Katz Exception” applied (In re Katz, 639 F.3d 1303 (Fed. Cir. 2011)), which held that a standard microprocessor can serve as sufficient structure for “functions [that] can be achieved by any general purpose computer without special programming,” like “processing,” “receiving,” etc. But this panel describes Katz as a narrow exception to the WMS Gaming rule. The opinion cites several cases held indefinite under the WMS Gaming rule for failure to disclose a sufficient algorithm. Under Katz, a microprocessor or general purpose computer lends sufficient structure only to basic functions of a microprocessor. All other computer-implemented functions require disclosure of an algorithm.

The panel concludes that the disclosure of a general purpose computer or a microprocessor as corresponding structure for a software function does nothing to limit the scope of the claim and “avoid pure functional claiming.” So, “when a patentee invokes means-plus-function claiming to recite a software function, it accedes to the reciprocal obligation of disclosing a sufficient algorithm as corresponding structure.”

The panel affirms the district court finding that each of the eight claim terms at issue recited complicated, customized computer software. So there is no clear error in the district court’s factual findings, or ultimate conclusion of indefiniteness. All claims of the ‘757 patent are invalid.


The takeaway here for patent drafters is to be careful with means-plus-function claiming, and with software patents generally, to ensure that sufficient structure is provided in the specification to enable a person skilled in the art to practice the invention. The court finds that the patentee did not do that here, resulting in “pure functional claiming,” i.e., impermissibly attempting to claim mere ideas. So with patents that recite computer controlled functions, some minimal discussion of how the result will be obtained should be provided. Although this case uses the term algorithm, other representations of computer programming, like a flow chart, a set of if-then statements, or computer code (even if just snippets), would probably suffice.

While this case is limited to means-plus-function claiming, the same principle probably applies to any software claiming. Good drafters will use an algorithm or other representation of computer instructions in the claims or disclosure to provide sufficient structure and support to the claims.

For challengers of software patents, with or without means-plus-function claiming, look for some type of algorithm or computer instructions that support and give structure to a claimed function. The absence of sufficient disclosure can be an opening for a challenge based on written description or indefiniteness.

With patents (like the patent in this case) filed before the development of modern technologies, for example high speed wireless networking or smartphones, visionaries may have conceived of good ideas, but had no idea how such ideas would be implemented. For such inventors, means-plus-function claiming was an attractive tool to describe the concepts in the belief that the details would be worked out in the future by a hypothetical person of ordinary skill. These patents may be vulnerable to the kind of challenge raised in this case.

Case citation:

Eon Corp. IP Holding LLC v. AT&T Mobility LLC, No. 2014-1392 (Fed. Cir. 5/6/2015)

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