Claim Construction in Patent Litigation
Posted Sunday, January 22, 2012.
When interpreting the meaning of patent claim terms, the words are generally given the ordinary and customary meaning that they would have to a person of ordinary skill in the art in question at the time of the invention. The process of ascertaining that meaning is called claim construction.
Court decisions have provided a framework for claim construction in a patent litigation. The first principle is that intrinsic evidence is the first place to look for the meaning of claim terms. Markman v. Westview Instruments, Inc., 517 U.S. 370 (1996) divided evidence for construing claim terms into an intrinsic evidence category and an extrinsic evidence category. Intrinsic evidence is the patent itself, including the claims and specification, along with the prosecution history. It includes affidavits made by inventors, and any content submitted on an Information Disclosure Statement. Extrinsic evidence is anything that is not intrinsic evidence, for example, an inventor’s in-court testimony as to his understanding of the claim terms.
Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576 (Fed. Cir. 1996) furthered the principle, by stating that when the intrinsic evidence unambiguously settles the meaning of a claim term, extrinsic evidence should not be relied upon at all (“is entitled to no weight”) in claim construction. Vitronics also prioritized the various pieces of intrinsic evidence. The specification should always be consulted to ensure the drafter has not defined a term differently than the common meaning of that term. The prosecution history is also to be consulted, although it is given less weight, recognizing that the prosecution history represents a negotiation between the applicant and the USPTO, such that any given document in the file history may not represent the final meaning ascribed to a term.
Phillips v. AWH Corp., 415 F.3d 1303 (Fed. Cir. 2005), affirmed that the intrinsic evidence is most important in claim construction. Particularly, the Federal Circuit held that over-reliance on dictionary definitions was to be avoided. A dictionary may still be consulted when a claim term is left ambiguous by the specification, provided the definition is still used within the context of the specification.
When drafting a patent claim, leaving a claim term undefined in the specification can be perilous. The USPTO, in applying the broadest reasonable interpretation principle, can find a dictionary meaning broader than what is intended by the applicant, resulting in a rejected claim or invalidated patent. For example, in a re-examination case appealed from the BPAI where a patent claim for a financial instrument to receive an inflation adjustment “directly” after a change in a market indicator, “directly” was not defined in the specification or prosecution history, but the applicant’s intent ostensibly was that the instrument be tied to the indicator (“a continuous, one-to-one correlation with the inflation rate”). But the Federal Circuit found a dictionary definition where “directly” meant “in a little while.” This broader view of the claim was sufficient to support rejection of the claim. In re Trans Tex. Holdings Corp., 498 F.3d 1290 (Fed. Cir. 2007). Here, locking down the meaning of the term “directly” in the specification could have distinguished the subject matter from the prior art.