Patent Must Clearly Disclose Structure Corresponding to the "Means," or the Doctor Can’t Cure the Indefiniteness Disease

The U.S. Court of Appeals for the Federal Circuit has recently held that if a patent specification fails to disclose structure clearly corresponding to the function of a means-plus-function clause, the claim is invalid for indefiniteness. Cardiac Pacemakers, Inc. v. St. Jude Medical, Inc., Case No. 01-1198 (Fed. Cir. July 11, 2002).

The one independent claim, directed to a defibrillator, listed numerous "means" elements, including detecting means, charging means and three monitoring means. The Court interpreted the functional language regarding the "third monitoring means" as requiring one structure to perform two functions, monitoring an ECG signal from the detecting means and activating a charging means in the presence of an abnormal cardiac rhythm needing correction. As disclosed, a doctor could perform both functions, but the specification did not disclose structure that was part of the defibrillator which performed both the monitoring and activating functions in the manner claimed. The Court noted that the doctor is not an element of the claimed defibrillator.

The Court explained that construction of a means-plus-function limitation involves two steps, identifying the claimed function and determining the corresponding disclosed subject matter. Ordinary principles of claim construction govern interpretation of the claim language describing the function. After identifying the claimed function, the claim interpreter must determine what structure disclosed in the specification, if any, corresponds to the claimed function. In order to qualify as corresponding structure, a structure must not only perform the stated function, but the specification must clearly associate the structure with the performance of the stated function. This inquiry is undertaken from the perspective of a person of ordinary skill in the art. Alternative embodiments may disclose different corresponding structure(s). However, at least one embodiment must disclose corresponding structure for the claim to be valid. If no disclosed embodiment discloses corresponding structure, the claim is invalid for failure to satisfy the definiteness requirement of § 112, ¶ 2.

The Court noted that as a general proposition, multiple structures can perform a single claimed function, but only where the claim language permits and only where the specification clearly identifies the multiple structures as the corresponding structure (citing In re Knowlton). However, on the facts in the Cardiac Pacemakers case, the Federal Circuit held that the claim language did not permit separate, i.e., multiple structures, to perform the dual functions recited in the particular "monitoring means" clause and that the claim therefore was invalid.

Practice Note: When drafting an application having a means-plus-function claim elements, the drafter should make sure that the specification clearly describes one or more elements of the apparatus/system as performing each stated function in each mean-plus-function claim element. When amending means-plus-function claim language, be sure that the amended functional language has clear support in the specification, i.e., that the specification clearly associates the disclosed structure with the stated claim function.