In a reminder to draft a strong specification, the Federal Circuit on Wednesday found the claims in Diebold Nixdorf, Inc. v. ITC invalid as indefinite for insufficient structure in support of means-plus-function language. This decision reversed an International Trade Commission (ITC) finding of validity and infringement.

When claims recite an element only functionally, and when the specification does not teach adequate corresponding structure to accomplish the claims’ functions, the claims may be invalid as indefinite.

The patent in this case is for an ATM-type apparatus. In case a user inserts a cheque but then later decides not to deposit it, the apparatus has a “cheque standby unit ... configured to hold” a cheque for a moment. The specification further discusses the cheque-holding functions with little or no specific structure. One of the figures contains about two dozen elements, including a double line as an element number 120, which is a “cheque temporary standby unit.” At the ITC, the Administrative Law Judge heard the testimony of the patentee’s expert witness and found that the term “cheque standby unit” on its own itself indicated adequate structure.

Writing for a unanimous panel at the Federal Circuit, Judge O’Malley found that “cheque standby unit” in this context is a “means-plus-function” element, even though the claim does not use the word “means.” The Federal Circuit found that the evidence failed to establish an understanding of “cheque standby unit” as any type of structural term, dismissing the expert testimony as “unsupported, and largely unhelpful” because it did not identify structural aspects which could be understood from the term itself. The court further observed that the dependent claims and specification are silent as to any structure for the cheque standby unit, and that the drawing does not really show the structure of a cheque temporary standby unit.

Functional language can be a useful tool in patent claims, but under U.S. patent law, structureless, functionally-recited elements are limited to the specification’s structures and whatever might be found as an equivalent. If the specification lacks adequate structure, potential infringers may not have enough information to determine whether they fall within such broad functionally-recited limitations. U.S. patent law deals with this problem by declaring such patent claims invalid as indefinite.