Patent Drafting and Claim Construction

Alpesh Pathak

To determine whether the patentee has right to exclude for a particular claimed invention, it is essential to know what is claimed and this process is called determining  the scope of the invention or claims construction. This exercise is called Markman Hearing when it is done by the court of law in the patent infringement litigation.

Markman Hearing is not only one of the most significant exercise in determining infringement but also equally important in formulating the strategies to design around patent. Federal circuit has taken several different stands for claims construction.

The issue of correct construction of  claims particularly, the definition of claim term is age old but it all started attracting patent professional with a landmark judgment in Texas Digital Systems Inc. v. Telegenix Inc (2002) three years ago wherein federal circuit went much further its previous guidelines rejecting the view that dictionaries should be characterized as mere extrinsic evidence, indicated a presumption in favor of using a dictionary to discern the ordinary meaning of claim terms. Surprisingly, this case federal circuit stated referring the intrinsic evidence before consulting dictionary “invites a violation of our precedent counseling against importing limitation into the claims”. Therefore subsequent to this decision there was a greater emphasis on use of dictionaries by litigants and courts.  However, this does not last long as to clarify the scattered interpretation and prevailing dilemma on given importance to the extrinsic evidence prior to intrinsic evidence, a year later another federal circuit panel, including two of the same three judges, sought to clarify Texas Digital judgment by noting the consulting “abstract dictionary definitions” alone is not sufficient. The court in Brokhill-Wilk 1, LLC v. Intuitive surgical Inc. (2003) ruled the consulting a dictionary is “simply a first step in the claim construction analysis” and “resort must always be made to the surrounding text of the claims in question, the other claims, the written description, and the prosecution history.”

Even after this clarification in Brookhill, the dilemma was still persisted in balancing the use of intrinsic and extrinsic evidence.

Consulting dictionary is practiced since times immemorial; however the practice of defining the term solely or primarily based on dictionary has attracted lot of debate in the recent past.

Ever since the en banc decision in Markman v. Westview Instruments Inc. (1995). Declaring that dictionaries are form of extrinsic evidence that may be used to aid “the court’s understanding of the patent,” there has been paradigm shift in the Federal Circuit’s position on  role of dictionaries in defining the claim term.

Novartis Pharmaceuticals Corp. v. Eon Labs Manufacturing Inc.
, Federal circuit held that when consultation of dictionary results in several possible definitions, intrinsic evidence should be relied on to determine the appropriate definition intended by the patentee. However, in another judgment Nystrom v. Trex Co., it was held by the panel that when there are more than one dictionaries definitions exists, Texas Digital  requires the selection of the broadest definition that is not inconsistent with the intrinsic evidence.

There exists another school of thought adopted by the Federal Circuit, under which, extrinsic evidence, which includes "expert testimony, inventor testimony, dictionaries, and technical treatises and articles," as well as prior art, is to be considered only where the claim meaning remains unclear after consideration of the intrinsic evidence.

For example, in order to act as lexicographer, patentee must define claim tem with sufficient clarity to put one skilled in the art on notice that the inventor intended to redefine the term. In Merck & Co. v. Teva Pharma (2005) the out come of the case turned on whether Merck, the patentee, had acted as its own lexicographer and had redefined the word “about”. The issue caused a split on the panel and demonstrates how far one must go to overcome a presumption of ordinary meaning for a term. Even though the district court credited Merck with acting as its own lexicographer in changing the meaning of “about” from its ordinary meaning of “approximately”, the Federal circuit reversed the  judgment and asserted that Merck had failed to redefine “about” to mean “exactly” in clear enough terms to justify such a counterintuitive definition. The federal circuit interpreted the term “about” to its ordinary meaning i.e. “approximately”.

In another most talked about judgment by Federal Circuit in Pfizer Inc. v. Teva Pharmaceuticals, (2005) the Federal circuit upheld the grant of a preliminary injunction in favor of Pfizer for the pharmaceutical composition of Quinapril. In doing so, the court addressed several claim construction issues raised by Ranbaxy who had filed an Abbreviated New Drug Application (ANDA). Here, the controversial claim term was “saccharide” and “saccharides” which was earlier construed by the district court as broadly including mono-, di, tri-, and polysaccharides but on appeal, Federal Circuit has affirmed the construction.  In Ranbaxy’s view “sugars” would include polysaccharides with up to ten monosaccharide units but would not include polysaccharides, such as microcrystalline cellulose, with more than ten monosaccharide units. However, Federal Circuit was not willing to base a narrow construction on a single isolated passage in the specification.

Lastly, the long awaited en banc opinion which was recently announced by the Federal Circuit in Phillips v AWH Corp. (2005) has laid down certain methodology to be used in claim construction. The opinion concluded that although dictionaries are recognized as one of many tools in claim construction analysis, a court’s primary focus should be on the language of the claims, the specification, and the prosecution history of the patent.  In this particular case Federal Circuit reapplied the methodology of the rule of Vitronics and held that the claims themselves, the specification, and to a lesser extent, the prosecution history form the primary tools of claims construction. Here the debated claim term was “baffles” constructed narrowly by district court which was eventually reversed by the en banc. Applying the revisited and much discussed methodology the court read the claims in the context of each other and the entire specification and found that nothing limited the claim term “baffles” structurally, to those oriented at angles other than 90°, or functionally, as able to deflect projectiles. The Court thus reversed the district court’s decision of no infringement and remanded. In summary, the primary focus of this case in determining the ordinary and customary meaning of a claim limitation is to consider the intrinsic evidence of the record viz. the patent itself, including the claims, the specification and if in evidence, the prosecution history, from the perspective of one of ordinary skill in the art.


For the forgoing discussion, it is apparent that Federal Circuit has in fact adopted different methodology at different stages depicted in the judgments over the last few years. In fact in the Paroxetine judgment the court particularly stated that “claims construction is not a policy driven enquiry but it is a contextual interpretation of language”. The second paragraph of 35 USC 112 also imposes a requirement for precision, or “definiteness,” in the drafting of claim language. However, when it comes to the court of law, the interpretation becomes deciding factor for invalidity and infringement issues.  Therefore, it is important to understand what is appropriate in a particular context rather than merely adopting the methodology set by different judgments because that methodology may be appropriate in those contexts only.      


  1. 35 U.S.C. 112
  2. Texal Digital Sys. Inc. v. Telegenix Inc. (Feb. Cir. 2002)
  3. Brokhill-Wilk 1, LLC v. Intuitive surgical Inc. (Fed. Cir. 2003)
  4. Vitronics Corp. v. Conceptronic, Inc. (Fed. Cir.  1996)
  5. Nystrom v TREX Co. (Fed. Cir. 2004)
  6. Merck & Co. v. Teva Pharma (Fed. Cir. 2005)
  7. Phillips v AWH Corp. (Fed. Cir. 2005)( en banc)