Definition for "Limitation" in the Context of Prosecution History Estoppel and the All Elements Rule: A Proposed Solution to the Troubling Dictum in Kustom Signals V. Applied Concepts

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United States Patent Law is one of the most rapidly evolving areas of law,1 and the past few years have been particularly eventful. One of the focuses of recent debate has been the doctrine of equivalents, a long-standing legal doctrine designed to protect patent holders from fraud.2 The Court of Appeals for the Federal Circuit (CAFC)-a court created two decades ago for the purpose of harmonizing and clarifying patent law3-has been heavily involved in this debate, along with the United States Supreme Court. In the wake of two monumental cases decided by these two courts,4 the CAFC recently decided the case of Kustom Signals v. Applied Concepts.5 In a troubling dictum, the Kustom Signals court announced that "[t]he word 'or' is not itself an 'element' of an apparatus or a step of a method, and its presence to signify alternative elements does not convert 'or' into an element."6 This IMAGE FORMULA3

statement reveals inconsistency and definitional problems in the law. This Note will discuss those problems and propose a solution.

The underlying problem revealed by this dictum is that "element" has not been satisfactorily defined by the courts. The fundamental policies of patent law require that such central terms be defined.7 Patentees must have notice of what their patent is worth.8 The public must know where the patentee's rights end.9 A stable economy requires law that is predictable and clear, and this is especially important in patent law. The first part of the solution is to eliminate the use of the word "element" and to instead use the word "limitation." Second, "limitation" must be defined functionally, so that the practical effect of even a single word can be recognized by the law. Part II will present the legal background and cases that frame the debate. Part III will provide details of the Kustom Signals case itself, and Part IV will propose and analyze a two-step solution to the current confusion in this area of law: (1) replacement of the word "element" with the word "limitation" in prosecution history estoppel and the All Elements Rule, and (2) clear definition of the word "limitation" tailored to bring consistency and accomplish the policies underlying these legal doctrines.


Article I, section eight of the U.S. Constitution gives Congress the power to "promote the Progress of Science ... by securing for limited Times to ... Inventors the exclusive Right to their... Discoveries."10 Congress has used this power to establish various patent statutes,11 and the modern components of patent law have roots in patent statutes and cases more than a century old.12 The current patent statute requires that all new patents issued by the IMAGE FORMULA6

Patent and Trademark Office (PTO) be useful,13 novel,14 and not obvious.15 These basic requirements can be stated simply, but federal courts have long been elaborating and interpreting what these three requirements actually mean-attempting to find specific meaning in these general terms.

Patents give limited legal monopoly rights to inventors or their assigns, but the scope of those rights depends on the quality and wording of the patent itself. There are two critical times for determining whether a patent passes muster under the statutory standard: when the application is submitted to the scrutiny of an examiner at the PTO to determine whether it should issue as a patent and when litigation arises concerning the already-issued patent. Despite the fact that an issued patent enjoys a presumption of validity,16 litigation often presents the more rigorous test for a patent because an accused infringer will often, as a defense to infringement, attack the validity of the patent being asserted. Litigation also differs from examination in that the patent claims are compared, not only to the prior art,17 but also to the accused device or process. …