Algorithm Written in Prose Provides Sufficient Structure for a Means-Plus-Function Claim Term

In a patent infringement case involving two touchscreen device patents brought against nine manufacturers and/or sellers of laptop computers, tablet computers and handheld devices, the U.S. Court of Appeals for the Federal Circuit reversed the district court’s judgment of invalidity with respect to three claims, but affirmed the judgment of non-infringement as to all defendants.   Typhoon Touch Techs., Inc. v. Dell, Inc., et al., Case No. 09-1589 (Fed. Cir., Nov. 4, 2011) (Newman, J.). 

The district court’s judgment of invalidity was based on its conclusion that the claim term “means for cross-referencing,” a term written in the statutory form authorized by 35 U.S.C. § 112 ¶ 6, was indefinite.   Typhoon conceded that the structure to support the term is not explicitly disclosed in the specifications of the two patents.   The district court referred to this “concession” in its opinion and further relied on Federal Circuit precedent for the premise that a means-plus-function term is indefinite (under 35 U.S.C. § 112, ¶ 2) when the specification “simply describes the function to be performed, not the algorithm by which it is performed.”  Typhoon appealed. 

The Federal Circuit took issue with the district court’s apparent narrow definition of the term “algorithm,” explaining that the term should be understood more broadly to mean “[a] fixed step-by-step procedure for accomplishing a given result; usually a simplified procedure for solving a complex problem, also a full statement of a finite number of steps.”   The Court further indicated that a patentee need not include computer code in the specification for a computer-implemented procedure in order to comply with the requirements of § 112, ¶ 2.   Instead, a procedural algorithm may be expressed “in any understandable terms including as a mathematical formula, in prose, or as a flow chart, or in any other manner that provides sufficient structure.”

Applying these criteria, the Federal Circuit concluded that the term “means for cross-referencing” was supported by sufficient structure in the specifications and thus not indefinite.   Specifically, the Court concluded that the specifications of the two patents recite in prose a four-step algorithm for computer-implemented cross-referencing.   The Court further found that defendants presented no evidence that a programmer of ordinary skill in the field would not understand how to implement the recited function.

Although it reversed the judgment on invalidity, the Federal Circuit affirmed the district court’s holding that the defendants were not liable for infringement.   Typhoon stipulated to judgment of non-infringement based on the district court’s constructions of three claim terms as requiring a device to actually perform, or be configured or programmed to perform, each of the functions stated in the claims.   On appeal, Typhoon argued that the district court injected a “use” requirement into the apparatus claims and that it was sufficient if a device was merely capable of being configured or programmed to perform the functions stated in the claims.  The Federal Circuit rejected Typhoon’s arguments and confirmed the district court’s constructions.      

Practice Note:   A claim limitation related to a computer-implemented procedure written in statutory means-plus-function form can avoid invalidity for indefiniteness so long as the specification recites clearly in prose or otherwise the steps to be implemented by persons skilled in computer programming.