January 1, 2002


Enforcing a patent against others in patent litigation is a formidable task. One can expect no shortage of issues to litigate given the adversarial nature of patent litigation, the potential of high damages, and the financial resources of partisan parties with polarized interests. Eliminating and minimizing obstacles to proving patent infringement begins long before a court case is filed. Indeed, past actions undertaken to obtain a patent are often critical to winning a patent infringement award.

While there are many areas of action taken or foregone during the patent application process which bear greatly upon the outcome of patent litigation, no instance is more fundamental than defining the scope of the invention by its patent claims. The crucible of modern patent litigation examines, in excruciating detail, the "intrinsic record" of the patent so as to reveal how the patent claims were obtained, why they were obtained, and the extent of proprietary right obtained by them.

This paper will focus on the integral relationship between the patent applicant's submittal and prosecution of patent claims during patent examination and the future finding of an infringement thereof. Patent claims define the applicant's invention and its attendant scope of proprietary exclusivity that may be enforced against others. Patent claims are the focus of the infringement determination phase of U.S. patent litigation that centers upon "claim construction" and "claim coverage over the accused matter" to find either literal patent infringement or patent infringement under the doctrine of equivalents. The patent claims, however, are established in the past prior to the infringement question and its resolution. Fortunately, by understanding the procedural and substantive aspects of how a patent infringement determination is made, one schooled thereby can take steps during patent claim prosecution to avoid or minimize many impediments to a patent infringement award. By exploring lessons one can put into practice now, one can reap victory in future patent litigation from the seeds of foresight.

Understanding Our Goals for a Patent Before We Journey

Let us first be clear on what our goals are in obtaining a patent before we run the gauntlet of enforcing the patent against others in litigation.

A patent grants its owner a territorial right to exclude others from making, selling, and using the subject matter of the patent as defined in its patent claims for a limited term, usually twenty years from application filing date. The market exclusivity for the patented invention is a powerful economic advantage offering many avenues of exploitation. The owner may keep the patent to himself so as to effectively be the sole legal source of the patented invention in the patent territory during the patent term, or may license the invention to others for royalties during the patent term, or may sell and transfer the patent as an intellectual property asset. When the invention is in high demand and the patent owner has the ability to sufficiently supply the invention in response thereto, being the sole legal source of supply captures and dominates the market while developing long-term customer relationships. Even without the ability to fully supply the demand for an invention, the patent owner still enjoys the ability to license others to practice the invention in return for royalties. In any case, a patent can be sold or transferred, either alone or as a valuable component of a sale, merger, acquisition or other business transaction of assets. However, there is a significant limit to the advantages of a patent: the exclusivity and market power only extend to the scope of the patent claims.

Further, when the invention, as defined in its patent claims, enjoys market success others are naturally attracted to the technological trade and might seek to enter the market as a licensee of the patent owner, as a competitor which fairly competes by virtue of "designing around" the patent claims defining the invention, or as an outright infringer. In all of these scenarios, the patent and its "file history" detailing how the patent claims were obtained will be closely scrutinized. A potential licensee can surely be expected to undertake a careful examination of the patent claims in its due diligence to determine the necessity of having to obtain a license to gain the market entry. A would be design around competitor will likewise study the patent claims focusing upon how to legally compete by staying outside of the scope of the patent claims. Even an infringer will have to be proved to be an infringer by engaging in prohibited activity falling within the scope of patent claims.

Before one is concerned with patent litigation let us not lose sight of the forest for the trees: the domain of exclusivity and the ability to exploit the same, keeping competitors away and preventing design around competition, and stopping infringers, all depend on past actions undertaken by the patent owner defining the scope of the patent claims.

The Nature of Patent Claims and Why Patent Applications Must Tread Carefully

A patent may have as many patent claims as is justified by novelty, utility, non-obviousness, and specific description over the "prior art2." Each patent claim defines the scope and boundaries of the patented invention for licensing, design around, and infringement purposes analogous to the way the legal description of a plot of land determines a trespass thereon. Each patent claim serves as a legal notice of the scope of the patent owner's right and what others must refrain from.

The purpose of a patent claims is not to explain the technology or how it works, but to state the legal boundaries of the patent grant. Claims claim, while the "specification" of a patent teaches. The patent specification must teach one of ordinary skill in the art how to make and use the invention, and the patent claims must particularly point out and distinctly claim the subject matter that the Applicant regards as his invention.3 The latter "distinctly claiming" requirement means that the claims must have a clear and definite meaning when construed in the light of the complete patent document.4 The degree of linguistic precision necessary for adequate claims is a function of the nature of the invention subject matter.

A patent claim program must distill the necessary and the essential over the prior art while foreseeing the future. Certainly the "elements" and "limitations" of a patent claim must define over that which has gone before and that which would be obvious to one of ordinary skill in the art. An unrelenting focus upon those select "elements" and "limitations" which are truly necessary to accomplish the foregoing and which achieve a benefit, advantage, or superiority gained by the invention lays the groundwork for future success in patent litigation and in the ancillary areas of licensing, exploitation, and preventing design around competition. Such a focus allows for patent claims to be carefully drafted and prosecuted while being mindful of what is necessary or essential in each claim, what is arbitrary or optional to each claim, what is covered by each claim, what and who is foreclosed by each claim, and what would others do to avoid each claim. Such a focus also addresses several audiences keenly interest in the claims, including the patent examiner, the person of ordinary skill in the art, opposing patent counsel, judges, licensees, design around competitors, intellectual property asset managers, investors, and others with present or future need to examine the patent and the scope of its proprietary right established by the defined claims.

The Law of U.S. Patent Infringement

One wins a patent infringement award based on the past actions of patent claim prosecution.

Patent infringement analysis requires two separate inquiries.5 The first is "claim construction," a determination, as a matter of law, of the scope of the properly interpreted patent claim without reference to the accused product or method. The second inquiry is "claim coverage over the accused matter," the factual findings of whether the properly construed claim encompasses the accused matter made, sold, or used without authority.

(A) Claim Construction Is Based on a Public Record

The first step in a patent infringement analysis is to properly interpret the asserted claims. "The construction of claims is simply a way of elaborating the normally terse claim language in order to understand and explain, but not to change, the scope of the claims."6 Courts must not alter what the patentee has chosen to claim as his invention because "...courts do not rework claims. They only interpret them."7 The job here is to properly construe the asserted patent claims, not to "enlarge, diminish, or vary" the limitations in the claims.

The United States Court of Appeals for the Federal Circuit explained the overall claim interpretation process as follows:8

"It is well settled that, in interpreting an asserted claim, the court should look first to the intrinsic evidence of record, i.e., the patent itself, including the claims, the specification and, if in evidence, the prosecution history. Such intrinsic evidence is the most significant source of the legally operative meaning of disputed claim language. "All intrinsic evidence is not equal however. ... First, we look to the claim language. ...Then we look to the rest of the intrinsic evidence, beginning with the specification and concluding with the prosecution history, if in evidence.....

If the claim language is clear on its face, then our consideration of the rest of the intrinsic evidence is restricted to determining if a deviation from the clear language of the claims is specified. A deviation may be necessary if "a patentee [has chosen] to be his own lexicographer and uses terms in a manner other than their ordinary meaning."... A deviation may also be necessary if a patentee has "relinquished [a] potential claim construction in an amendment to the claim or in an argument to overcome or distinguish a reference.".... If however the claim language is not clear on its face, then our consideration of the rest of the intrinsic evidence is directed to resolving, if possible, the lack of clarity. ..."Resort to the specification is particularly important where the claim limitations in dispute include technical terms that are defined in the specification. However, in looking to the specification to construe claim terms, care must be taken to avoid reading "limitations appearing in the specification ... into [the] claims."... "We recognize that there is sometimes a fine line between reading a claim in light of the specification, and reading a limitation into the claim from the specification."... In locating this "fine line" it is useful to remember that we look "to the specification to ascertain the meaning of the claim term as it is used by the inventor in the context of the entirety of his invention," and not merely to limit a claim term....

"If the meaning of the claim limitations is apparent from the totality of the intrinsic evidence, then the claim has been construed. If however a claim limitation is still not clear, a court may look to extrinsic evidence to help resolve the lack of clarity. Relying on extrinsic evidence to construe a claim is "proper only when the claim language remains genuinely ambiguous after consideration of the intrinsic evidence."... "Such instances will rarely, if ever, occur."...

"Extrinsic evidence may always be consulted, however, to assist in understanding the underlying technology. ... But extrinsic evidence may never be used "for the purpose of varying or contradicting the terms in the claims."...

"Throughout the construction process, it is important to bear in mind that the viewing glass through which the claims are construed is that of a person skilled in the art."

Interpreting the asserted claims to determine their scope thus begins with a review of the public record "intrinsic evidence," which consists of the claim language, the specification written description, and the prosecution history.9 The language of the patent claims, the patent document specification, and the prosecution history of how the patent was obtained are "the most significant source[s] of the legally operative meaning of disputed claim language."10

This "intrinsic" "public record" evidence is the "most significant source" of evidence to be used when interpreting patent claims and when the public record "unambiguously describes the scope of the patented invention" resort to "extrinsic" evidence outside the public record, such as expert or inventor testimony, is improper.11 Although "extrinsic evidence" outside of the public record of how the patent was obtained may be accepted by the court to enhance its understanding of the technology,12 extrinsic evidence cannot be used to contradict the established meaning of the claim language.13 Extrinsic evidence may be necessary to educate the court about the language in which the patent is written. But this evidence is not for the purpose of clarifying ambiguity in claim terminology. It is not ambiguity in the document that creates the need for extrinsic evidence but rather the unfamiliarity of the court with the terminology of the art to which the patent is addressed.14

The lesson here is clear. The actions that the patent applicant takes during the course of prosecuting his patent claims establishes the "intrinsic" "public record" such that "the die is cast" well before patent litigation. Claim interpretation is based upon a public record serving as a public notice as to the scope of the patent claims involved.

Let us look closer at what the Federal Circuit requires when it says: "To ascertain the meaning of claims, we consider three sources: the claims, the specification, and the prosecution history."15

Regarding the first source of meaning, the claims, one must first turn "to the words of the claim which define the metes and bounds of the invention."16 Terms in a claim mean what they say and give full effect to their ordinary and accustomed meaning to one skilled in the art unless it appears from the patent and its file history that the inventor used them differently.17

Claims, however, do not have meaning removed from the context from which they arose, because "the claims are directed to the invention that is described in the specification."18 The second source of meaning, the specification, must be considered. The descriptive part of the specification aids in ascertaining the scope and meaning of the claims inasmuch as the words of the claims must be based upon the description. For claim construction purposes, the specification description may act as a sort of dictionary, which explains the invention and may define terms used in the claims.19

Although the specification may be of aid in interpreting the meaning of a claim, the particular embodiments and examples appearing in the specification will not generally be read into the claims.20 Thus, it is entirely proper to use this specification to interpret what the patentee meant by a word or phrase in the claim, but this is not to be confused with adding an extraneous limitation appearing in the specification, which is improper. An "extraneous" limitation is one read into a claim from the specification wholly apart from any need to interpret what the patentee meant by particular words or phrases in the claim.21

Finally, the prosecution history is a third source to be used to determine the scope and meaning of the claims. The prosecution history limits the interpretation of the claims so as to exclude any interpretation that may have been disclaimed or disavowed during the prosecution in order to obtain claim allowance. This exclusion arises because of "prosecution history estoppel." A patentee may not offer an interpretation of a claimed term for purposes of litigation that would alter the indisputable public record consisting of the claims, the patent specification, and prosecution history, and treat the claims as a "nose of wax"22 to be shaped one way for purposes of obtaining the patent and another for purposes of alleging infringement.

Claim interpretation, as a question of pure law, is amenable to summary judgment. The mere disagreement over the meaning of a term within a claim does not necessarily create a genuine issue of material fact.23 Any other rule would be unfair to competitors who must be able to rely on the patent documents themselves in ascertaining the scope of a patentee's right to exclude.24

(B) Claim Coverage over the Accused Matter

Once an interpretation of a claim has been made as a matter of law, that same interpretation must be employed in determining literal infringement and infringement under the doctrine of equivalents.25 The patent owner must prove by a preponderance of the evidence that the alleged infringer has "made, used, or sold" a product or employed the method/process coming within the scope of the patent claims in suit.26 Thus, the second step in the two-step process of determining infringement is whether any patent claim, as properly interpreted, covers or "reads on" the accused product or employed method/process.

1. Literal Infringement

Infringement can be literal or found under the doctrine of equivalents. Literal infringement requires that every element and limitation set forth in the claim must be found in the accused product or method/process, exactly.27 The entire claim language literally "reads upon" the accused matter. All, "100" percent, of the elements and limitations of the patent claim "read upon" the accused matter, not just "95" percent of them.

2. Infringement under the Doctrine of Equivalents

Even if one or more of the elements of a patent claim are not literally present in an accused product or method/process, the accused matter may still infringe under the judicially created doctrine of equivalents if, on an element-by-element basis assessed according to an objective standard, the accused product or method/process contains elements identical or equivalent to each claim element of the patent claim.28 However, each individual element of a claim and every limitation must still be met exactly or by a substantial equivalent in the accused matter for infringement to occur under the doctrine of equivalents.29 The doctrine of equivalents thus prevents the risk of injustice that may result from a limited focus on words alone.30

The U. S. Supreme Court has stated:

"[C]ourts have recognized that to permit imitation of a patented invention which does not copy every literal detail would be to convert the protection of the patent grant into a hollow and useless thing. Such a limitation would leave room for—indeed encourage—the unscrupulous copyist to make unimportant and insubstantial changes and substitutions in the patent which, though adding nothing, would be enough to take the copied matter outside the claim, and hence outside the reach of law."31

"Infringement under the doctrine of equivalents requires an intensely factual inquiry."32

In some cases, the change in the accused device is so facially "unimportant and insubstantial" that little additional guidance is needed for a fact finder to determine whether an accused device includes an equivalent of a claim limitation. For example, if an accused infringer has simply separated into two components what the patentee has claimed as one component, a fact finder might indeed find such a change "insubstantial."33

In appropriate cases the function way result test offers additional guidance on the question of equivalence. Under this test, the fact finder determines whether the element in the accused device "does substantially the same thing in substantially the same way to get substantially the same result" as the claim limitation.34

The essential predicate of the doctrine of equivalents is the notion of identity between the patented invention and its equivalent. The particular linguistic framework used in applying the doctrine of equivalents is less important than the requirement that the test be probative of the essential inquiry, which is whether the accused matter contains elements identical or equivalent to each element of the patent claim.35 Thus, to infringe a claim under the doctrine of equivalents, the accused matter must include an equivalent for each literally absent claim limitation.36

The doctrine of equivalents is not limited to equivalents that are disclosed within the patent itself, or to equivalents that were known at the time the patent was issued, because the proper time for evaluating equivalency, and therefore the knowledge of interchangeability between accused and claimed elements within the possession of those skilled in the art, is at the time of infringement not at the time the patent was issued.37

The doctrine of equivalents, however, is not a tool for expanding the protection of a patent after examination has been completed.38 Application of the doctrine of equivalents does not enlarge the scope of a claim. Instead, the doctrine of equivalents provides the same protection to the substance of the claim's scope because, if there are no substantial differences between the claimed and accused products on an element-by-element basis, "they are the same in the eyes of the patent law."39 The courts have no right to enlarge a patent beyond the scope of its claims as allowed by the U.S. Patent Office. The "scope" is not enlarged if courts do not go beyond the substitution of equivalent elements when the doctrine of equivalents is applied to individual elements of the patent claim, not the invention as a whole. The doctrine of equivalents is not allowed such broad play as to effectually eliminate an individual element in its entirety.

Other limitations apply to the doctrine of equivalents. The prior art restricts the range of equivalents. A patentee cannot obtain under the doctrine of equivalents, coverage he could not lawfully have obtained from the USPTO by literal claims or to exclude others so broadly as to ensnare subject matter within the public domain.40

The doctrine of equivalents is also limited by "prosecution history estoppel." An "estoppel" arises when one is concluded and forbidden by law to speak against one's own act or deed so that inconsistent positions of conduct may not be taken to the loss or injury of another. Thus, a patentee should not be able to obtain, through litigation, coverage of subject matter relinquished during patent prosecution. A patent owner cannot obtain a claim construction through the application of the doctrine of equivalents that would resurrect subject matter surrendered during prosecution of a patent claim.41 The legal standard for determining what subject matter was relinquished is an objective one, measured from the vantage point of what a competitor was reasonably entitled to conclude, from the prosecution history, that the applicant gave up to procure issuance of the patent.42

Prosecution history estoppel as applied to the doctrine of equivalents is at the heart of the blockbuster Festo43 case presently pending before the U.S. Supreme Court. Before this case, prosecution history estoppel normally arose when a change of claim scope was made in order to overcome an examiner's rejection based on prior art. Prior to Festo, it was usually necessary to look at the specific change in claim scope and the reason for it, in ascertaining whether an estoppel had arisen by virtue of the change.44 A concession made or position taken to establish patentability in view of prior art on which the examiner had relied, was a substantive position on the technology for which a patent is sought, and would generally generate an estoppel.45 In such situations, a court is not later free to review "the correctness of" the examiner's prior art objection in deciding whether to apply prosecution history estoppel, but, consistent with the notion that claims serve both a definitional and a public notice function, will presume a substantial reason related to patentability for including the limiting element added by amendment.46 Although this presumption is subject to rebuttal if an appropriate reason for a required amendment is established, that burden is upon the patentee.47

3. The Festo Caveat of Prosecution History Estoppel under the Doctrine of Equivalents

The U.S. Supreme Court will soon deliver its opinion in Festo.

Regardless of the final decision in Festo, patent infringement under the doctrine of equivalents still requires that the accused product contain each element of the claim, literally or by its substantial equivalent. Each claim element is still material to defining the scope of the patented invention, and a doctrine of equivalents analysis must be applied to individual claim elements, not to the invention as a whole. An element in the accused matter is still equivalent to a claim element if the differences between the two are "insubstantial" to one of ordinary skill in the art.

However, according to the Federal Circuit's holding in Festo, when a patent claim has been amended for any reason relating to the statutory requirements for patentability so as to narrow the scope of the claim, no range of equivalents is available for that amended claim element. A prosecution history estoppel arises for the amended claim element such that its scope of protection is now defined by its literal/exact terms. The effective scope of patents with amended narrowing limitations therefore cannot extend beyond the literal wording of such amended elements.48

This holding is very controversial and may well not be the law when the U.S. Supreme Court speaks on the matter. Under the Federal Circuit's decision in Festo, every narrowing amendment to a patent claim made for a reason relating to patentability, not just to avoid prior art, gives rise to "prosecution history estoppel" with respect to that amended element which completely bars the application of the doctrine of equivalents. No infringement can occur unless such an amendment's exact, literal terms are satisfied. This "complete bar" was adopted by the majority of the Federal Circuit's en banc decision to give certainty to the process of determining the scope of protection afforded by a patent. With a complete or absolute inflexible bar, both the public and the patentee know that once an element of a claim is narrowed by amendment for a reason related to patentability, that element's scope of coverage will not extend beyond its literal terms. There is no speculation or uncertainty as to the exact range of equivalents that might be available. The patentee and the public can look to the prosecution history, a public record, to determine if any prosecution history estoppel arises as to any claim element. If so, that element's scope of protection is clearly defined by its literal terms serving both the notice and definitional function of patent claims.

The minority/dissent opinions of the controversial Federal Circuit Festo "complete bar" holding decry that this new rule is a radical departure from prior precedent and prior sufficient safeguards upon the doctrine of equivalents resulting in patents now having truly hollow protection. The doctrine of equivalents was created to prevent "fraud on a patent," such as near-literal copying of the claimed invention with the addition of merely insubstantial changes in order to avoid liability for literal infringement. For the minority/dissent opinions, the prior safeguards of the "all elements rule" and "prosecution history estoppel," applied per a "flexible bar," were sufficient to balance the competing needs of granting meaningful protection to patentees and of notifying the public of the effective scope of a patentee's claims. When a patent claim is narrowed by a change of language during prosecution of the patent, for example by adding a claim element or by adding a limitation to an existing claim element, the substance of that change is reflected in the public record or "file history" of the application. This communication between the applicant and the patent examiner as established in the public record notifies the public as to potential additional limits on the enforceable scope of the changed patent claim. A "flexible bar" determines this "limiting effect within a spectrum ranging from great to small to zero" depending on the nature and purpose of the amendment and considering factors such as the breadth and reason of the examiner's rejection, the manner in which the patent applicant changed his claims to overcome rejection, and the nature of the technology at issue.49 As most patents contain claims that were amended during prosecution, the majority's "complete bar" rule is feared to effectively strip patentees of their rights to assert infringement under the doctrine of equivalents.

Judge Michel powerfully dissented from the majority's "complete bar" rule in Festo that there is no range of equivalents available for an amended claim element. The judge even offered a recipe of how one can copy another's patent if the majority's new rule remains intact after the U.S. Supreme Court review:

"Today's ruling will allow copyists to readily avoid liability despite practicing a substantial equivalent of the claimed invention. Anyone seeking to lawfully copy a patented technology will only have to adopt the following method: (1) read the prosecution history to identify amendment made for patentability reasons; (2) copy every other limitation exactly, but substitute any known interchangeable structure, matter, or step for any limitation that has been amended. Any change, no matter how unimportant and insubstantial, to even one amended claim limitation will be sufficient to avoid liability under the majority's rule."...

"The copyist's first step in exploiting today's ruling to avoid liability, then, would be to identify a claim limitation that was amended for patentability reasons. ...The second step, then, would be to determine the most convenient substitute for this limitation." 50

Lessons to Apply Now to Foster a Later Determination of Patent Infringement

With the judges of the Federal Circuit, the day-to-day citadel of U.S. patent law, polarized in their en banc Festo decision as to the ultimate scope of patent claims for infringement purposes, what guidance should we now adopt to maximize a future finding of patent infringement?

It is perhaps best we return to fundamental hallmarks of the art of writing patent claims, because the actions taken when at that stage are prominently scrutinized in determining patent infringement regardless of how the law of patent infringement evolves. Itemized below are several points of consideration when drafting patent claims that are likely to have a great bearing upon whether a finding of infringement occurs:

1. Command of language is a must; all words of a patent claim must be measured for scope both singularly and collectively.

Do we not all wish we had Dante's command of language? There is no pity for us of lesser ability as the task of writing patent claims relentlessly demands a comprehensive vocabulary extremely sensitive to scope, shade, and accurate recognition of meaning. A curse upon prior art searching and its application to pending patent claims, is the fact that different people describe things differently while their meanings or teaching may still have a bearing upon the patent claims. Nevertheless, a careful consideration of how others state their patent claims in similar technical art areas will assist in establishing an initial concordance of potential terminology to use in describing one's own invention. Even so, room for creative description will always remain. Differing employments of nouns will give patent elements differing breadth of meanings, and selection of differing adjectives will provide differing limitations upon those elements. Words of structure, function, relation, location, content, shape, properties, range, degree, et cetera, all must be measured for their connotations and implications both as individual words and in their combined claim context. As if this task is not complicated enough, consider further that the patent claims are written to differing audiences, at different points in time, such as initially to the patent examiner but later to patent litigants and their judge and/or jury.

2. Focus upon the essential, necessary, vital elements and limitations of the patent claim that achieve benefit, advantage, or superiority; then distinguish prior art with precision and clarity at a point from which you can still maintain the largest claim breadth for such critical elements and limitations.

Patent claims must define over the prior art in a novel, non-obvious way, hence it is a good starting point to focus upon any claim element or limitation that is truly necessary to achieve the same, especially when it involves a point of newness or difference giving rise to benefit, advantage, or superiority, a likely source of non-obviousness. These critical elements demand more attention, particularly with respect to two boundaries. The first boundary is the demarcation of what is the prior art and where the applicant's invention begins. The second boundary is the outer limit extent of the invention as defined by the patent claim. Such lines of demarcation cannot be haphazardly drawn. Wording of sufficiently broad scope must be used in an independent patent claim so that it is, at least, commensurate with the essential elements of applicant's invention that are new and different departing from the previous and giving rise to the benefit, advantage, or superiority. Preferably, such wording will also encompass foreseeable or potential design developments or modifications to such critical elements that seek to capture the benefits, advantage, or superiority they yield.

3. Draft multiple "clean" independent patent claims of varying scope and dwell upon them before they are submitted.

Only necessary inventive subject matter is included in the independent patent claim. Elements of a patent claim that are optional, desirable, alternative, or environmental can be added as dependent patent claims. Importantly, independent claims can be drafted in varying scope, such as broad, intermediate, and narrow, as an effective strategy to deal with the Festo "complete bar" rule.

The Festo decision rewards patent claims that issue without narrowing amendment. Certainly before Festo, it was easier to submit one independent claim of broad scope followed by several dependent claims whittling away at that scope by adding an additional claim element or an additional limitation on a previously advanced claim element. When a prior art rejection was made upon examination, often subject matter of one of the dependent claims capable of distinguishing the cited and applied art would then become fodder for insertion by amendment into the independent claim. With Festo however, that new matter added by amendment becomes an exact, literal limitation upon the amended independent claim for infringement purposes that cannot be satisfied by an accused equivalent element under the doctrine of equivalents. With such a state of affairs, why not submit several independent claims of varying scope, first broad, then intermediate, and even narrow restricted to accurately defining a particular commercial embodiment or permutation of the invention? This approach can yield independent claims issuing without narrowing amendment to preserve doctrine of equivalents infringement. The approach is also well adopted for "multiple embodiment" disclosures of the invention. Instead of relying merely upon a generic umbrella claim with dependent itemizing claims, draft several independent claims. Until the U.S. Supreme Court brings finality to the Festo "complete bar" rule, such an approach is a safer course to preserve doctrine of equivalents infringement.

Next, "cleanup" the proposed original claims. Messy patent claims violate basic rules of patent claim draftsmanship. Claim errors, such as no antecedent basis, indefiniteness, a lack of specification or claim support, inferential claiming, double inclusion, alternate expression, and improper functionality, among other matters, need to be corrected by proofreading. Under Festo, a rejection of claims under 35 USC 112, second paragraph, for failure to particularly point out and distinctly claim the subject matter of the invention, while technically not a prior art rejection, involves a statutory prerequisite for the patent triggering the "complete bar" rule for narrowing amendments made for "a substantial reason related to patentability."51 A cleanup must be especially undertaken for the claims of translation-based filings, such as the English language U.S. filing of a corresponding foreign priority application.

Having done the foregoing, take a short break before taking up the claims again. Is every word truly necessary? Will another word be better? Can the scope and content be improved? Draft and review, draft and review, draft and review until you start to settle upon a patent claim program. Then, dwell upon the claims once again with an eye towards what a competitor would do to design around the patent claims or otherwise take advantage of them. Also look at the claims to judge their sufficiency to catch additional types of infringers, or compel additional licensees. Will the claims cover infringement by manufacturers, sellers, users, those that actively induce infringement, and those that contribute to infringement? For example, multiple claim formats may be used to obtain independent claim coverage to a component of an product, a portion of the assembly of the product, the entire product, the product as part of a greater assembly, a system employing the product, a method of making the product, a method of use, ... the idea being to view the inventive subject matter from different perspectives and consider them in drafting a comprehensive claim program.

Once this is done, write the patent specification consistent to support such claims and teach those of ordinary skill in the art the best mode to make and use the invention covered by the claims. Afterward, the claims must be reviewed yet again for modification in view of the detailed technical writing and drawings supporting them, especially if there are multiple embodiments of the invention.

4. The public record established then speaks now; be careful how you form it and avoid prosecution history estoppel.

The interplay between the applicant and patent examiner is established in a public record showing how the patent claims were allowed. This process starts with the applicant's submittal of the original claims which the applicant hopes are allowable, such claims are examined by the examiner in light of the prior art, and, if the claims are not allowable, the examiner states certain tentative conclusions and reason therefore which the applicant may respond to. The applicant often responds by changing the claim language, either to overcome prior art or to more distinctly advance the claims, with the amended claims being reconsidered by the examiner. This common practice of "patent prosecution" is memorialized in the file history and becomes the later focal point of patent litigants during the infringement determination issues of claim construction, claim coverage, and prosecution history estoppel. That focal point, especially if Festo remains intact after U.S. Supreme Court review, will be aimed at any narrowing amendment to an asserted claim.

The patent applicant must be guarded in any response to the examiner to prevent a "prosecution history estoppel" being established on the public record. Claim amendment practice requires an applicant to avoid prosecution history estoppel by taking heed of several general rules:

a. Choose amended claim language carefully with as much care as submitting the original claim;

b. Avoid inserting needless limits upon the effective scope of an amended claim;

c. Review the difference between the originally submitted claim and the amended claim to determine what has been surrendered in that difference and whether it is truly necessary to do so to overcome the prior art or otherwise respond to the examiner;

d. Distinguish first the most pertinent of the cited and applied prior art references avoiding too much argument in doing so, then address the secondary art references as failing behind the most pertinent reference, or as being not properly combinable with the primary reference;

e. Distinguish a cited and applied prior art reference on the basis of the characteristics of and language statements in the art reference itself, minimizing any comment upon applicant's patent claims.

f.  When there are multiple features of the invention to use to distinguish over the cited and applied art, distinguish on the basis of a selected feature that preserves, and allows silence upon, applicant's vital claim elements giving rise to benefit, advantage, or superiority;

g. Avoid distinguishing prior art with undue argument and shotgun approaches stating numerous grounds, especially if the same requires applicant to comment upon his own claims;

h. Do not comment on what is not necessary to be commented upon; and

i.  Brevity of response is to be appreciated as lengthy comment and argument is a breeding ground for prosecution history estoppel.

5. Make literal infringement a patent claim's first goal, sufficient to cover the embodiments of commercial reality and their potential design around.

The Festo controversy concerns infringement under the doctrine of equivalents. Courts have never had difficulty finding infringement of a valid claim when the accused infringement was within the literal wording of the claim. Do not depend upon the doctrine of equivalents, but rather define the invention with patent claims sufficient to literally "read upon" foreseeable infringing activity. Have patent claims that literally cover what is necessary to commercial embodiments and their design around. For example, in pharmaceutical cases, claim language must literally cover that which has received regulatory approval. Let the doctrine of equivalents cast its pale upon those attempting exploitation with the hindsight benefit of the patent's disclosure as a secondary offensive measure. First, ensnare an infringer by the literal language of the patent claims.


Catching patent infringers is perhaps analogous to catching fish by a net. Like a patent claim, the net must be valid, having not only integrity but also a breadth of coverage sufficient for casting and to ensnare that within it. A big net, like a broad patent claim, is far more useful. A net with large loopholes will miss many fish just as an unduly restrictive patent claim gains no extensive dominion over others. An effective net is a good tool that can withstand turbulent waters with strength to bear its catch, similar to an effective patent claim holding firm in the test of litigation. The path of the net and the patent claim each may one day met with the unexpected and be tried thereby. For both, today's catch is dependent upon the care of yesterday.


1 Copyright 2002, Much Shelist
2 35 U.S.C. 101, 102, 103, 112.
3 35 U.S C. Section 112, Para. 2
4 Standard Oil Co. v. American Cyanamid Co., 774 F.2d 448, 452, 227 USPQ 293, 296 (Fed. Cir. 1985).
5 Mannesmann Demag Corp. v. Engineered Metal Products Co., 793 F.2d 1279, 1280, 230 USPQ 45 (Fed. Cir. 1986); Read Corp. v. Portec, Inc., 970 F.2d 816, 821, 23 USPQ2d 1426 (Fed. Cir. 1992).
6 Embrex, Inc. v. Serv. Eng'g Corp., 216 F.3d 1343, 1347, 55 USPQ2d 1161,1161 (Fed. Cir. 2000).
7 Autogiro Co. of America v. United States, 384 F.2d 391, 395-96, 155 USPQ 697, 701 (Ct. Cl. 1967).
8 Interactive Gift Express, Inc. v. Compuserve Inc., 231 F.3d 859, 865, 56 USPQ2d 1647, 1652-53 (2000), {citations omitted}.
9 Embrex, Inc. v. Serv. Eng'g Corp., 216 F.3d 1343, 1347, 55 USPQ2d 1161, 1163 (Fed. Cir. 2000).
10 Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582, 39 USPQ2d 1573, 1576 (Fed. Cir. 1996).
11 Id., at 1577.
12 EMI Group N. Am., Inc. v. Intel Corp., 157 F.3d 887, 892, 48 USPQ2d 1181, 1184 (Fed. Cir. 1998)
13 Mantech Envtl. Corp. v. Hudson Envtl. Servs., Inc., 152 F.3d 1368, 1373, 47 USPQ2d 1732, 1736 (Fed. Cir. 1998).
14 Advanced Cardiovascular Sys., Inc. v. Scimed Life Sys., Inc., 887 F.2d 1070, 1076, 12 USPQ2d 1539, 1544 (Fed. Cir. 1989) {"The purpose of expert testimony is to provide assistance to the court in understanding, when the claims are technologically complex or linguistically obscure, how a technician in the field, reading the patent, would understand the claims.}
15 Markman v. Westview Instruments, Inc., 52 F.3d 967, 979, 34 USPQ2d 1321, 1329 (Fed. Cir. 1995) {en banc}, affirmed 517 U.S. 370, 116 S.Ct. 1384, 38 USPO2d 1461(1996).
16 Envirotech Corp. v. Al George Inc., 730 F.2d 753, 759, 221 USPQ 473, 477 (Fed. Cir. 1984).
17 ZMI Corp. v. Cardiac Resuscitator Corp., 844 F.2d 1566, 1571, 6 USPQ2d 1557 (Fed. Cir. 1988).
18 Netword, LLC v. Centraal Corp., 242 F.3d 1347, 1352, 58 USPQ2d 1076, 1079 (Fed. Cir. 2001)
19 See, In re Vogel, 422 F.2d 438, 441, 164 USPQ 619, 622 (CCPA 1970) {"Occasionally the disclosure will serve as a dictionary for terms appearing in the claims, and in such instances the disclosure may be used in interpreting the coverage of the claim.")
20 Constant v. Advanced Micro-Devices, Inc., 848 F.2d 1560, 1571, 7 USPQ2d 1057 (Fed. Cir.), cert. denied 488 U.S. 892 (1988).
21 E.I. DuPont v. Philips Petroleum Company, 849 F.2d 1430, 1432-34, 7 USPQ2d 1129 (Fed. Cir.), cert. denied 488 U.S. 986 (1988).
22 Senmed, Inc. v. Richard-Allan Med. Indus., Inc., 888 F.2d 815, 819 n.8, 12 USPQ2d 1508, 1512 n.8 (Fed. Cir. 1989).
23 Intellicall, Inc. v. Phonometrics, Inc., 952 F.2d 1384, 1387, 21 USPQ2d 1383, 1386 (Fed. Cir. 1992).
24 Southwall Technologies, Inc. v. Cardinal IG. Co., 54 F.3d 1570, 34 USPQ 2d 1673, 1678-1679 (Fed. Cir.), cert. denied 116 S.Ct. 515 (1995)
25 Id.
26 SRI Int'l. v. Matsushita Elec. Corp., 775 F.2d 1107, 1123, 227 USPQ 577 (Fed. Cir. 1985) {en banc}; 35 U.S.C. Section 271(a).
27 Becton Dickinson & Co. v. C.R. Bard, Inc., 922 F.2d 792, 796 (Fed. Cir. 1990); Johnston v. IVAC Corp., 885 F.2d 1574, 1580 (Fed.Cir.1989) {"Where a claim does not read on an accused product exactly, there can be no literal infringement."}; Perkin-Elmer Corp. v. Westinghouse Elec. Corp., 822 F.2d 1528, 1533 (Fed. Cir. 1987).
28 Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 117 S.Ct. 1040, 41 USPQ 2d 1865, 1875-76 (1997); Pennwalt Corp. v. Durand-Wayland, Inc., 833 F.2d 931, 935-36, 4 USPQ2d 1737 (Fed. Cir. 1987) (en banc), cert. denied, 485 U.S. 961 (1988).
29 Read Corp, supra at 822.
30 Laitram Corp. v. Cambridge Wire Cloth Co., 863 F.2d 855, 856 57, 9 USPQ2d 1289, 1291 (Fed. Cir. 1988), cert. denied, 490 U.S. 1068 (1989).
31 Graver Tank & Mfg. Co. v. Linde Air Prods. Co., 339 U.S. 605, 607, 85 USPQ 328, 330 (1950).
32 Vehicular Tech. Corp. v. Titan Wheel Int'l, Inc., 212 F.3d 1377, 1381, 54 USPQ2d 1841, 1844 (Fed. Cir. 2000).
33 Dolly, Inc. v. Spalding & Evenflo Cos., 16 F.3d 394, 398, 29 USPQ2d 1767, 1770 (Fed. Cir. 1994) {"An accused device may infringe under the doctrine of equivalents even though a combination of its components performs a function performed by a single element in the patented invention." (citing Intel Corp. v. Int'l Trade Comm'n, 946 F.2d 821, 832, 20 USPQ2d 1161, 1171 (Fed. Cir. 1991)}; see also Richardson v. Suzuki Motor Co., Ltd., 868 F.2d 1226, 1239 1240, 9 USPQ2d 1913, 1923 (Fed. Cir. 1989).
34 Corning Glass Works v. Sumitomo Elec. U.S.A., Inc., 868 F.2d 1251, 1260, 9 USPQ2d 1962, 1969 (Fed. Cir. 1989); Graver Tank, supra.
35 Warner-Jenkinson Co., supra at 1875.
36 Dawn Equip. Co. v. Kentucky Farms, 140 F.3d 1009, 1015, 46 USPQ2d 1109, 1113 (Fed. Cir. 1998).
37 Warner-Jenkinson Co., supra at 1874.
38 Hormone Research Foundation, Inc. v. Genetech, Inc., 904 F 2d 1558, 1564, 15 USPQ2d 1039, 1044 (Fed. Cir. 1990).
39 Graver Tank & Mfg. Co., supra at 608; Hilton Davis Chemical Co. v. Warner-Jenkinson Co., 35 USPQ 2d 1641, 1653 (Fed. Cir. 1995).
40 Wilson Sporting Goods Co. v. David Geoffrey & Assoc, 904 F.2d 677, 14 USPQ2d 1942, 1948 (Fed. Cir. 1990) "Thus, since prior art always limits what the inventor could have claimed, it limits the range of permissible equivalents of a claim" See also, Insta-Foam Products, Inc. v. Universal Foam Systems, Inc., 906 F. 2d 698, 15 USPQ2d 1295 (Fed. Cir. 1990).
41 Haynes International Inc. v. Jessop Steel Co., 8 F.3d 1573, 1579, 28 USPQ2d 1652, 1655-56 (Fed. Cir. 1993); Loctite Corp. v. Ultraseal Ltd., 781 F.2d 861, 870, 228 USPQ 90, 96 (Fed. Cir. 1985).
42 Prodyne Enterprises, Inc. v. Julie Pomerante, Inc., 743 F.2d 1581, 1583, 223 USPQ 477, 478 (Fed. Cir. 1984); Hoganas AB v. Dresser Indus., Inc., 9 F.3d 948, 28 USPQ2d 1936 (Fed. Cir. 1993).
43 Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 234 F.3d 558, 56 USPQ2d 1865 (Fed Cir. 2000) {en banc}, cert. granted, 121 S. Ct. 2519 (2001).
44 Bayer Aktiengesellschaft v. Duphas Int'l Research B.V., 738 F.2d 1237, 1243, 222 USPQ 473, 481 (Fed. Cir. 1984); Hughes Aircraft Co. v. United States, 717 F.2d 1351, 1363, 219 USPQ 473, 481) (Fed. Cir. 1983).
45 Pall Corp. v. Micron Separations, Inc., 66 F.3d 1211, 36 USPQ2d 1225, 1231 (Fed. Cir. 1995).
46 See, Warner-Jenkinson Co., supra at 1872-73, footnote 7.
47 Id. at 1876.
48 Festo Corp., supra at 1872, 1878.
49 Hughes Aircraft Co., supra at 1363.
50 Festo Corp., at 1911.
51 Id., at 1871.

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