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May 16, 2006

Means-Plus-Function Claims

Applied Medical Resources sued United States Surgical for infringing 5,385,553, a surgery facilitating device, the latest suit in a long line of litigation. In its ruling, the CAFC enunciated a precise process for determining infringement of a means-plus-function claim.

Applied Medical Resources v. United States Surgical (CAFC 05-1314)

The process for interpreting a means-plus-function claim:

1. Determine the claimed function.
2. Identify the corresponding structure in the written description of the patent that performs that function.
3. Identify the relevant structure in the accused device. Literal infringement of a means-plus-function claim limitation requires that the relevant structure in the accused device perform the identical function recited in the claim and be identical or equivalent to the corresponding structure in the specification.
4. The plaintiff then has the burden to show that the accused device performs the identical claimed function in substantially the same way, with substantially the same result.

The CAFC identified two errors of importing an unclaimed function into a means-plus-function claim -

1. During claim construction, defining a claimed function to require more than is actually claimed.
2. During infringement analysis, improperly determining the way in which a disclosed structure performs the previously-defined function. In this step, the inquiry should be restricted to the way in which the structure performs the properly-defined function and should not be influenced by the manner in which the structure performs other, extraneous functions.

'553 claims a particular trocar, which "provides a channel through the abdominal cavity through which instruments can be inserted during laparoscopic surgery." The particulars of the technology do not impinge on the readability of the case law that the CAFC rolled out.

Claim construction of a means-plus-function limitation includes two steps. First, the court must determine the claimed function. JVW Enters. v. Interact Accessories, Inc., 424 F.3d 1324, 1330 (Fed. Cir. 2005). Second, the court must identify the corresponding structure in the written description of the patent that performs that function. Id.

Claim construction of a means-plus-function term next requires us to identify the disclosed structures in the patent specification for performing these claimed functions. JVW Enters., 424 F.3d at 1330.

Using the claim construction adopted by the district court for purposes of summary judgment, we next turn to an analysis of infringement. Literal infringement of a means-plus-function claim limitation requires that the relevant structure in the accused device perform the identical function recited in the claim and be identical or equivalent to the corresponding structure in the specification. Lockheed Martin Corp. v. Space Sys./Loral, Inc., 324 F.3d 1308, 1320 (Fed. Cir. 2003). Once the relevant structure in the accused device has been identified, a party may prove it is equivalent to the disclosed structure by showing that the two perform the identical function in substantially the same way, with substantially the same result. Kemco Sales, Inc. v. Control Papers Co., 208 F.3d 1352, 1364 (Fed. Cir. 2000). As the party asserting infringement, Applied ultimately bears the burden of proof.

Therefore, the only issue before us is whether, under the district court's adopted claim construction, there exists a genuine issue of material fact that the two perform the claimed functions in substantially the same way.

Applied argues that it presented evidence demonstrating a genuine issue of fact that the two perform the claimed functions in substantially the same way. For the reasons given below, we agree.

To prove structural equivalence under the function-way-result test, the court must first determine that the accused and disclosed structures perform the identical functions. The district court assumed that the two structures here do perform the identical function, under Applied's descriptions of those functions. The court was then required to determine the way in which these functions were performed by the two structures.

A court errs when it improperly imports unclaimed functions into a means-plus-function claim limitation. First, this can occur during claim construction by defining a claimed function to require more than is actually claimed. See JVW Enters., 424 F.3d at 1331. Second, the error can occur during infringement analysis if the court improperly determines the way in which the disclosed structure performs the previously-defined function. In this step, the inquiry should be restricted to the way in which the structure performs the properly-defined function and should not be influenced by the manner in which the structure performs other, extraneous functions.

Here, the district court committed the second type of error... [T]he district court improperly imported unclaimed functions when analyzing the way in which the disclosed embodiment performed the claimed function.

Because the district court burdened claim limitations with more functions than deserved, Applied's expert witness testimony, disregarded by the district court, becomes relevant, and the CAFC found, given the different construction, expert witness testimony during district court proceedings had raised "a genuine issue of material fact."

Remanded.

Posted by Patent Hawk at May 16, 2006 10:03 PM | Claim Construction