“The name of the game is the claim,” coined Federal Circuit Justice Giles Rich. The claim determines the “metes and bounds” of the patent. And, only by properly construing the claim language can the scope of the patent be determined.

Properly construing the claim language to define the scope of the patent benefits both the patentee and the public. The patentee, in return for disseminating new information (the invention), benefits from exclusive territory as defined by the claims. The public, aware of the exclusive territory, benefits by utilizing the creative fodder remaining outside the patent: New ideas flourish and science and the useful arts progress.

Properly construing a claim, however, requires overcoming inevitable ambiguities in the claim language. Ambiguities can occur when patent drafters attempt to fully describe novel concepts with words and two-dimensional black-and-white drawings. Through the use of exemplary embodiments of the invention, the true inventive spirit and creative concept takes form and substance. This claim-drafting process, however, is an art – words are paint on canvas, subject to the artist’s perspective; replete with human imperfections and incomplete understanding.

Accepting that words may imprecisely define novel inventions, the judicially created Doctrine of Equivalents (DOE) attempts to provide fair and just protection of the patentee’s rights as established in the claims. This doctrine recognizes that a change that performs substantially the same function as the literal claim element, in substantially the same way, to achieve substantially the same result, may infringe, if not literally, then under the Doctrine of Equivalents.

The Doctrine of Equivalents obscures the clearly delineated scope of the patent grant and frustrates the public’s benefit. Instead of a fence-line creating an obvious boundary between the exclusive territory reserved to the patentee and the creative fodder remaining available to the public, it creates a murky swamp of no-man’s land mired between what clearly lies within the patent and what clearly lies outside.

Minimizing the obscuring affect of the Doctrine of Equivalents, the judicially created doctrine of Prosecution History Estoppel restricts claims to narrower meaning based on the patentee’s activities during prosecution. Prosecution History Estoppel arises when a claim is amended for any reason pertaining to patentability – any reason that relates to statutory requirements to obtain a patent. A narrowing amendment, the addition of a claim limitation during prosecution, creates a presumptive surrender of equivalents. It does not create a complete bar to all equivalents to the entire amended claim: Instead, the patentee presumptively forfeits all equivalents to the amended claim element.

Proper claim construction embraces these two opposing doctrines and applies a set of guidelines taught through the opinions of the CAFC and, occasionally, the Supreme Court. These guidelines, however, do not make claim construction a science: It remains an art. The guidelines instruct full use of the entire intrinsic record – both the patent itself and the prosecution file history. One guideline requires claims to be construed in light of the patent specification and prosecution history on an element-by-element basis. Another guideline instructs preservation of the validity of claims.

Preserving validity of the claims requires consistently construing claims according to their ordinary and customary meaning, as defined by those of skill in the art and in light of the intrinsic record, including the language of the claims themselves. The patentee, however, may act as lexicographer and define a term contrary to or inconsistent with the ordinary meaning.

These two, possibly opposing constructs - the patentee as lexicographer and the ordinary and customary meaning – introduce ambiguity in the claims. The anticipated en banc decision in Phillips may address how to resolve certain aspects of this ambiguity including when it is appropriate to use extrinsic evidence, such as technical dictionaries and technical experts, to determine the ordinary and customary meaning.

Well-established guidelines assist the construction of ambiguous claim language. Yet, despite continual refinements to the guidelines, claim construction remains an art and uncertainty in the scope of the patent arises, much to the detriment of the patentee and the public. The awaited opinion in Phillips likely will not offer a panacea, but rather, provide a little more science to the art of claim construction. Hopefully, the awaited decision will not prove the opposite: “Striving to better, oft we mar what’s well.”