United States - Claim Construction

It is well established that the purpose of claim construction is to determine what a claim means to the person skilled in the art. When construing the meaning of a claim, all features of the claim must be considered and each limitation given its proper weight.

Traditionally, the primary tools for this have been the claim language itself, the specification in the light of which the claims are to be read (including reference to what the applicant distinguishes as being part of the prior art), the prosecution history, and the prior art. After 2002, a line of cases started to place more emphasis on the use of dictionaries than had hitherto been common, mainly because these seemed to be a more objective basis for determining meaning. This led to some confusion and the Federal Circuit decided to address the issue en banc in Phillips v. AWH Corp.

In this decision, the court reaffirmed that the claims had to be read through the eyes of one skilled in the art and interpreted as of the effective filing date of the patent. That being the case, the place to start was with the patent specification and the prosecution history. Although specifically stating that courts need not carry out their analysis in any particular order, the Federal Circuit noted that this analysis should include the language of the claims themselves to see whether the terminology used elsewhere in the claims sheds light on what is meant by a particular term. The court must also consider the specification to see how the term in question is used there. The court noted that the specification is supposed to describe the invention. Consequently, one should be able to determine what a claim to that invention means by reading the specification. The prosecution history should also be consulted, although the court noted that because this represents an ongoing negotiation, it may be less clear than the specification. Nevertheless, it can be a guide as to how the inventor used a particular term at the relevant date. Extrinsic evidence, including dictionaries and expert testimony, can also be useful. However, expert testimony that is "clearly at odds with the claim construction mandated by the claims themselves, the written description and the prosecution history" should be discounted and extrinsic evidence should generally be considered less reliable than the intrinsic evidence, but the district court should consider it keeping in mind "the flaws inherent in each type of evidence and assess that evidence accordingly." This having been said, the court recognized the validity of the reasoning that underlay the reliance on dictionary definitions, namely to avoid the risk that features of the specification might incorrectly be read into the claims. However, this could be avoided by simply using the specification to see how one skilled in the art would understand a claim term and not assuming that the teaching of a single embodiment limits the scope of the invention as such.

Prior to hearing the case, the court requested briefing on several questions, many of which it left unanswered by its decision. (The decision is generally felt to have done little to clarify the way in which claims should be construed beyond making it clear that dictionaries should not normally be the paramount source of information as to the meaning of a claim term.) A dissent by judges Meyer and Newman criticized the majority opinion for not taking the opportunity of calling for more deference to be given to the trial judge's claim interpretation.

One example of a change following the Phillips case is Nystrom v. TREX Co. where, following the decision in Phillips, the Federal Circuit withdrew a prior opinion in which it had held that the term "board", as used in a claim, had a broad meaning independent of the material from which it was made (this having been based on a dictionary definition), and replaced this with a narrow meaning that the item in question had to have been made of wood because this was what was disclosed in the specification. The specification had discussed flooring in the context of wooden boards used for a deck, but contained nothing explicitly saying that the boards had to be made of wood. The essential feature of the invention seems to have been the shape of the top surface of the board, which was designed to aid water run-off and to have had little to do with the material from which the board was made. Nevertheless, the specification contained a comment that, by improving water run off, one could avoid standing water on the deck and so avoid problems of deterioration caused by such standing water. The court concluded from this that the applicant must have intended that the board was made from wood. The court also looked at some statements in the prosecution history that had a "wooden" connotation, but which do not seem ever to have stated explicitly that the items in question had to be made of wood.