I. INTRODUCTION
Recently, significant change has taken place to the U.S. case law relating to patent infringement.
Decisions of the U.S. Supreme Court ("the Court") and the Court of Appeals for the Federal Circuit (the "Federal Circuit") in two patent infringement suits have radically altered the landscape on how a U.S. court must now determine infringement of a U.S. patent claim. These law suits, Hilton Davis2 and Markman3, as well as others discussed in this article, have their most immediate impact on patent litigators in the enforcement of U.S. patent rights. Nevertheless, patent drafters and patent prosecutors will be wise to review their practices and make changes where necessary to accommodate these recent rulings. Otherwise, a patent drafter or patent prosecutor may inadvertently and unnecessarily restrict the scope of patent claims during preparation and prosecution of a patent application.
An infringement of a U.S. patent claim under U.S. case law may be established in one of two ways, either by literal infringement or by infringement under the doctrine of equivalents. This article focuses on some strategies for a practitioner to follow while drafting and prosecuting a U.S. patent application in order to obtain the maximum scope of patent protection afforded by the issuing U.S. patent under a doctrine of equivalents infringement analysis. Nevertheless, many of the strategies suggested in this article are also expected to be useful for obtaining broader protection under a literal infringement analysis.
II. PRINCIPLES OF INFRINGEMENT LAW AFTER HILTON DAVIS AND MARKMAN
A. BRIEF SUMMARY OF BASIC PRINCIPLES OF INFRINGEMENT
As stated above, the infringement of a U.S. patnt claim under U.S. case law may be established in one of two ways, either by literal infringement or by infringement under the doctrine of equivalents. Literal infringement exists where the accused product or process contains each element and limitation specified in at least one claim of the patent in suit. Infringement under the doctrine of equivalents generally exists where the accused product or process contains each element and limitation, or its equivalent, specified in at least one claim of the patent in suit.
The "function-way-result" test has been the traditional test applied for determining equivalence between an element of a claim and the accused product or process. This test asks the question whether the alleged equivalent element of the accused product or process performs "substantially the same function in substantially the same way to obtain substantially the same result" as the claimed element.
B. THE HILTON DAVIS DECISION
1. DOCTRINE OF EQUIVALENTS IS VALID
In Hilton Davis, the Supreme Court affirmed the validity of the doctrine of equivalents as a means for determining infringement. The Court rejected arguments that the doctrine of equivalents should be abolished, and it rejected arguments that special equitable bases must be present before a patent holder is entitled to ask for infringement relief under the doctrine of equivalents. Hence a patent owner is entitled to seek relief for infringement under the doctrine of equivalents as a matter of right in all U.S. patent infringement cases, not simply those bearing some equitable basis.
2. EQUIVALENCY IS BASED UPON INSUBSTANTIAL DIFFERENCES The Court maintained the general principle that an accused product or process infringes under the doctrine of equivalents where it contains elements identical or equivalent to each claimed element in a patented invention. The Court stated that there is no single correct test for determining equivalency and that the test may differ depending upon the case. Generally, the essential guideline set forth by the Court is that the application of the doctrine of equivalents rests on the substantiality of the differences between the claimed and accused product or process. Where there are insubstantial differences between an element of a claimed and accused product or process, equivalence should generally be found. After Hilton Davis, it is clear that the traditional function-way-result test is still an accepted test for determining equivalency, but it is not the only test.
3. EQUIVALENCY DETERMINED ON ELEMENT-BY-ELEMENT BASIS
The Court clearly held that equivalence between a patent claim and an accused product must be analyzed on an element-by-element basis. In doing so, the Court did away with a judicial doctrine occasionally relied upon by U.S. courts for determining equivalence using an "overall equivalency" or "invention as a whole" analysis. In particular, the Court stated:
4. PROSECUTION HISTORY ESTOPPEL IS CLARIFIED
The Court's statements with respect to the doctrine of prosecution history estoppel are expected to have their greatest impact on the patent prosecutor. The doctrine of prosecution history estoppel is intended to prevent a patent holder from recapturing under the doctrine of equivalents the subject matter of a claim that was surrendered during prosecution to obtain an allowance of the patent claim. The Court in Hilton Davis upheld the doctrine of prosecution history estoppel as a legal limitation on the doctrine of equivalents. However the Court essentially limited the types of claim amendments which create an estoppel to those amendments made to overcome the prior art. Hence, claim amendments made for "reasons unrelated to patentability" should not give rise to prosecution history estoppel.
Under Hilton Davis, the burden is placed on the patent holder to establish that the reason for an amendment made during prosecution was unrelated to patentability. If the patent holder demonstrates such a reason, a court must consider the purpose of the amendment and decide whether an estoppel is precluded. Where the patent holder does not establish such a purpose, the court must now presume that the claim amendment was made for purposes of overcoming the prior art, such that an estoppel will apply.
C. THE MARKMAN DECISION
1. CLAIM INTERPRETATION IS A QUESTION OF LAW
In Markman, the Supreme Court affirmed the Federal Circuit's landmark ruling that it is the responsibility of the trial judge to construe the claim language as a question of law. Under the Markman decision, a trial judge must primarily look to "intrinsic evidence" to determine the meaning of the claim language. Intrinsic evidence includes the patent, its claims and the specification, and if in evidence, the patent prosecution file history.
Specifically, the trial judge must primarily look to the words of the claims themselves to define the scope of the invention. A claim term is interpreted in accordance with its ordinary and customary meaning, unless it is apparent from the patent and the prosecution history that the inventor used the term with a different meaning. In addition, it is always necessary for the trial judge to review the specification to determine whether the inventor has used any terms in a manner inconsistent with their ordinary meaning. The specification acts as a dictionary when it expressly defines terms used in the claims or when it defines words by implication. Thirdly, the trial judge may consider the prosecution history of the patent if in evidence. The prosecution history limits the interpretation of claim terms so as to exclude any interpretation that was disclaimed during prosecution.
Only if the claim language is still ambiguous may the trial judge turn to "extrinsic evidence", for example inventor or expert testimony, to determine the meaning of the claims.
2. DETERMINATION OF EQUIVALENCE IS QUESTION OF FACT
Upon determining the meaning of the claims, the trial judge makes a determination whether every element of the claim is literally present in the accused product or process. If not, the trial judge determines whether every element of the claim is literally or equivalently present in the accused product or process. If the evidence is such that a reasonable jury could determine that two elements are equivalents under the doctrine of equivalents, the jury is responsible for deciding this question of fact where the trial is by jury. On the other hand, where the evidence is such that no reasonable jury could determine the two elements to be equivalent, the trial judge may grant partial or complete summary judgement on the question of infringement under the doctrine of equivalents.
D. EFFECT ON PATENT DRAFTING AND PROSECUTION
As summarized above, the Hilton Davis and Markman decisions set forth new legal guidelines for establishing infringement by a patent holder. These new guidelines have important implications for the patent drafter and patent prosecutor. The three substantive areas of patent practice which warrant the patent practitioner's attention are (1) drafting the original patent claims, (2) drafting the patent specification, and (3) prosecuting the patent application. Each of these areas will be discussed below in turn.
III. DRAFTING THE PATENT CLAIMS
Under Markman, a patent claim is construed primarily in view of the words of the patent claims in light of the specification. To ensure the maximum protection for an invention, the patent practitioner should begin with a careful preparation of the patent specification and claims. Typically, many experienced patent practitioners begin this process by first drafting the patent claims, and then drafting the patent specification.
A. ORIGINAL CLAIMS SHOULD DEFINE OVER THE PRIOR ART
One practical step for obtaining a maximum scope of protection under the doctrine of equivalents is to avoid unnecessary amendments to the original claims during prosecution to overcome the prior art. Such amendments also unnecessarily limit the scope of equivalents to which the claims are entitled, in view the Hilton Davis decision.
The patent claims should be drafted in view of the closest prior art in an effort to present original claims that are not overbroad. The patent claims may still be drafted broadly, such as by using generic terminology, but they should be drafted at the point of novelty to patentably define over the prior art.
In some cases, a practitioner does not have available the closest prior art when drafting the claims. In these cases, a patent search is recommended to aid in drafting the original claims in order to avoid potential prosecution history estoppel.
Some practitioners prefer to draft overbroad original claims, to ensure that the scope of the patent claims allowed by the Examiner, particularly in the case of a first Action allowance, is not narrower than that which the inventor is entitled. These practitioners would be wise to reconsider their approach to avoid an unnecessary limitation on the scope of the allowed claims under the doctrine of equivalents arising from an estoppel.
Where the original patent claims are drafted overbroadly, either in literally encompassing the prior art or encompassing obvious subject matter, an Examiner can be expected to reject the claims over the prior art. Subsequent amendments to the claims to define over the prior art will be necessary to overcome an anticipation rejection under 35 U.S.C. § 102 and may be necessary to overcome an obviousness rejection under 35 U.S.C. § 103. Such amendments related to patentability can be expected to give rise to prosecution history estoppel with respect to the element or limitation added to overcome the prior art. Thus, the element or limitation added to the claim by amendment to define over the prior art may be entitled to a limited range of equivalency under the doctrine of equivalents. To find infringement of the claim, it should be expected that the accused product must literally satisfy such claimed element or limitation which is amended during prosecution to define over the prior art.
On the other hand, prosecution history estoppel might be avoided where the originally presented claims were drafted to patentably define over the prior art. Where the claim issues with no amendments having been effected during prosecution for reasons related to patentability, each element and limitation of the claims enjoy a more liberal application of the doctrine of equivalents.
The benefit of this approach is apparent from the following illustration. Suppose two hypothetical patents issue having an identical claim. The claim of the first patent was overbroad when originally filed such that it necessitated an amendment during prosecution to define over the prior art. The claim of the second patent defined over the prior art when originally filed such that no amendment was necessitated during prosecution for reasons related to patentability. For purposes of literal infringement, the scope of the issued claims of these hypothetical patents are identical. However, under the doctrine of equivalents, the scope of protection afforded by the second patent's claim is greater than that provided by the first patent's claim. This is because the second patent's claim is generally entitled to the application of the doctrine of equivalents for all claim elements and limitations, whereas the first patent's claim is barred from application of the doctrine of equivalents with respect to the element or limitation added by amendment to define over the prior art. Note that the claim elements and limitations which are not amended during prosecution to define over the prior art are still entitled to application of the doctrine of equivalents.
A patent practitioner cannot assume that foreseeable limitations required by the Examiner to define over the prior art will result in a de minimus effect on the scope of the patent claims under the doctrine of equivalents. Indeed, such amendments, like all amendments made during prosecution of a patent application to define over the prior art, might provide a road map to potential infringers for avoiding infringement.
B. CLAIMS SHOULD AVOID UNNECESSARY ELEMENTS AND LIMITATIONS
Another practical step for obtaining the maximum degree of protection under the doctrine of equivalents is to concisely define the invention in the patent claims and avoid any unnecessary elements and limitations. This practice has traditionally been followed by experienced patent practitioners. Nevertheless, this practice takes on increased importance after the Hilton Davis decision upholding the "element-by-element" approach to infringement analysis and abolishing the "invention as a whole" analysis.
Initially, it is noted that there is some uncertainty as to how the courts will apply the "element-by-element" analysis method, particularly in chemical and process claims which do not contain the traditional concept of elements found in mechanical and electrical device claims. The Court in Hilton Davis appeared to equate the term "element" with "limitation". For example, in discussing the lower pH limit introduced into the process claims of the Hilton Davis patent during prosecution, the Court stated "[t]hus, while a lower limit of 6.0, by its mere inclusion, became a material element of the claim, that did not necessarily preclude the application of the doctrine of equivalents as to that element." Furthermore, it is noted that the Federal Circuit has shifted its analysis in recent decisions from discussing claimed "elements" to discussing claimed "limitations".4
A conservative approach suggested by the authors for now until this uncertainty is clarified is to treat the "element-by-element" analysis as equivalent to a "limitation-by-limitation" analysis. Thus in drafting a patent claim, a patent practitioner should envision that the claim will only be infringed if the accused device or process satisfies every limitation of the claim, either literally or by equivalents. Such approach might help the patent drafter to consider the necessity of each limitation in the claim, whether the limitation is structural, functional or another.
Recent Federal Circuit decisions make clear that the doctrine of equivalents analysis will not be applied in a manner to disregard any meaningful claim limitation. For example in Sage Products5, a case decided after Hilton Davis, the Federal Circuit refused to find infringement of a claim to a medical waste disposal container under the doctrine of equivalents, stating:
Accordingly, the burden is placed on the patent practitioner now more than ever before to foresee alternatives to the claimed invention and to seek claims with the fewest structural and functional encumbrances. In drafting the claims, a patent practitioner should therefore consider every claim term as a potential limitation, whether or not it is intended to be a limitation. The claim should be purged of any claim term which is not essential to define the invention under the requirements of U.S. law, that is 35 U.S.C. § 112, § 102 and § 103. Alternative embodiments of the invention should be envisioned, and the claim should be drafted with the fewest elements and limitations necessary to define the invention and such alternative embodiments. These steps will make it more difficult for infringers to avoid the claims, both under the doctrine of equivalents as well as under literal infringement.
At the same time, the skilled practitioner must balance the benefits of broad claiming against the negative consequences of being forced to limit the claims during prosecution, thereby limiting the range of equivalents due to estoppel.
C. DRAFT CLAIM LANGUAGE IN CLEAR UNAMBIGUOUS TERMS
Under Markman, the trial judge is ultimately responsible for determining the meaning of the patent claims during a patent infringement suit. The patent practitioner should keep in mind that many trial judges do not have technical backgrounds. It is therefore advisable to draft claims in a clear manner directed to a non-technical person. Use of appropriate grammar, simple sentence structure and helpful punctuation enhance the clarity and readability of the claims. Where a choice is available, use of non-technical terms over technical terms in the claim may be preferable.
Following the guidelines established in Markman, the trial judge must primarily look to the words of the claims themselves to define the scope of the invention. A claim term is interpreted in accordance with its ordinary and customary meaning, unless it is apparent from the patent and the prosecution history that the inventor used the term with a different meaning. Courts routinely look to standard and technical dictionaries to determine the "ordinary and customary meaning" of claim terms. The patent practitioner should thus ensure that the words used in the claim comply with their ordinary and customary meaning. If the inventor has used any terms which are potentially inconsistent with their ordinary meaning, consideration should be given to using a more accurate term. Alternatively, it is advisable for the specification to include a clear explanation of the meaning of the term intended by the inventor.
If a claim term is still deemed to be ambiguous following this inquiry, a trial judge is permitted to look to the prosecution history of the patent if it is in evidence to discern the meaning of the claim term. A patent practitioner who thus discovers an ambiguity in a claim term during prosecution could take the opportunity to state on the record the intended meaning of the term.
In drafting claims, a patent practitioner should not expect that a patentee will be permitted by a trial judge to present testimony by the inventor or an expert as to the intended meaning of an ambiguous claim term. The Markman decision provides that a trial judge may hear such "extrinsic evidence" if necessary. However the Federal Circuit has stated in a later decision, Vitronics6, that "[i]n most situations, an analysis of the intrinsic evidence alone will resolve any ambiguity in a disputed claim term. In such circumstance, it is improper to rely upon extrinsic evidence." In reversing the trial court's decision which relied upon expert testimony to construe the claim language, the Federal Circuit further stated that the need for a trial judge to consider such extrinsic evidence "will rarely, if ever, occur".
In view of the foregoing, the patent practitioner should strive to make claim terms as definite as possible. Relative terms such as "higher", "wider", etc. should generally be avoided. Such terms create ambiguity in the claim as to the intended scope. This can lead to rejection and avoidable amendment.
Ambiguity in a claim provides an infringer with a basis to dispute the meaning of the words of the claim and the claim scope. While the patent practitioner cannot foresee all claim terms which later are determined to be ambiguous, ambiguity is best avoided at the claim drafting stage when the patent practitioner has freedom to select the claim terms to define the invention.
Some patent practitioners might consider the scope of a claim to be potentially increased by ambiguity in the claim. Even if such outcomes have occasionally been true in the past, this practice is a risky course for obtaining a desired claim scope. Moreover, the Federal Circuit has recently held that ambiguous claim language will now be interpreted by the courts against the patentee in favor of a narrower interpretation. In Athletic Alternatives7, the Federal Circuit stated:
Efforts to ensure that the claim language is clear and unambiguous will increase the likelihood that a patent claim will be interpreted by the trial judge in accordance with the meaning and scope intended by the inventor and the patent practitioner.
D. BE WARY OF MEANS-PLUS-FUNCTION CLAIMS
If means-plus-function claims are desired, the patent drafter should include corresponding claims without means-plus-function language. According to the Federal Circuit's decision in In re Donaldson8, claims including means-plus-function elements invoke the provisions of 35 U.S.C. § 112, sixth paragraph, both for infringement as well as for patentability purposes. Under 35 U.S.C. § 112, sixth paragraph, an element expressed in means-plus-function language is construed to cover only "the corresponding structure, material or acts described in the specification and equivalents thereof". Claims that are determined to contain means-plus-function elements are often held to have a narrower interpretation of the claimed element than if a broader generic term were used instead.
The patent practitioner must exercise care in drafting a claim to avoid invocation of 35 U.S.C. § 112, sixth paragraph. Despite several recent Federal Circuit decisions9 attempting to clarify this point, there is still some confusion over the particular claim language which a patent practitioner should use to define a claim element which will not invoke 35 U.S.C. § 112, sixth paragraph. Generally, a claim element which is expressed with the following two points in mind will avoid invocation of 35 U.S.C. § 112, sixth paragraph. First, the claim element should not recite the term "means", since the term "means" creates a presumption in favor of 35 U.S.C. § 112, sixth paragraph. Second, the term selected to describe the claim element should not recite a function, if possible, and should clearly not be defined solely in terms of a stated function.
IV. DRAFTING THE PATENT SPECIFICATION
A. DRAFT FOR THE NON-TECHNICALLY TRAINED READER
As a result of Hilton Davis and Markman, the decision-making responsibility of the trial judge is increasing in U.S. infringement cases. Nevertheless, the jury still retains much responsibility in patent cases, such as in the determination of equivalency of claim elements in infringement actions, and in the determination of validity of a claim in declaratory actions and counterclaims. No requirements exist under U.S. law for trial judges or jury members deciding patent issues to possess any particular level of technical skills or training. Hence, the critical decisions reached in patent cases in the U.S. are often made by persons with non-technical backgrounds.
It is therefore advisable for the patent practitioner to draft the patent specification in a clear manner so that the invention may be well comprehended by a non-technically skilled person. Technical aspects of the invention should be explained clearly. Technical terms should be defined where feasible. The specification may also be drafted in a manner to highlight the advantages of the invention over the prior art. The likelihood of a favorable outcome in an infringement action should be increased where the claimed invention and its advantages over the prior art can be readily understood by the judge and jury from reading the specification.
B. DEFINE IMPORTANT CLAIM TERMS
Under Markman, the trial judge must interpret claims in accordance with their ordinary and customary meaning, unless the patent and prosecution history show that the inventor used the term with a different meaning. Where the specification contains an express definition of the claim term, the trial judge must interpret the claim term in accordance with the definition stated in the specification.
If the practitioner has any doubt that the intended meaning of a claim term is at odds with the ordinary and customary meaning of the term, the practitioner should clearly include an express definition of the claim term in the specification. Even if the meanings of the claim terms used by the inventor are believed to be in accordance with their ordinary and customary meanings, the practitioner might be well advised to include a definition of important claim terms in the specification.
This is because where there is no definition of an important claim term in the specification, the trial judge must interpret the meaning of the term, taking into consideration arguments of the accused infringer as to the meaning of the term. An accused infringer can be expected to go to extreme lengths to dispute the meaning of important claim terms, in an effort to convince the trial judge to construe the meaning of the claim in a manner which would result in a finding of non-infringement. In determining the meaning of claim terms, trial judges are often found to be in error by the Federal Circuit10. These cases include some in which the trial judge erroneously agreed to the meanings of claim terms argued by accused infringers. Accordingly, a practitioner can increase the likelihood that important claim terms will be correctly interpreted by a trial judge in accordance with the inventor's intended meaning by including an express definition of important claim terms in the specification.
Including an express definition of a claim term in a specification can also be used to provide an increased scope of protection for an invention. Since the patentee is "free to be his own lexicographer", a claim term may be defined in the specification to have a broader meaning than its ordinary and customary meaning. Such definition can then provide a patent claim with a broader scope of protection, both literally and under the doctrine of equivalents, than the claim might otherwise be entitled.
An illustration of this point can be seen in Novo Nordisk11. In this case, the claims of a Genentech patent were directed to a method for producing a recombinant human growth hormone. While naturally occurring human growth hormone ("hGH") is a 191 amino acid protein, the specification defined the term "human growth hormone" to include a 192 amino acid form "met-hGH" produced by recombinant means. Novo argued that the meaning of the term "human growth hormone" must be limited to naturally occurring hGH. But the Federal Circuit agreed with Genentech that the claim term included met-hGH in view of the definition of the term and other teachings in the specification. While this interpretation did not become a critical point determining the outcome of the case, the case shows that a patent drafter who defines a claim term more broadly than a term's ordinary and customary meaning may literally cover an accused product whereas in the absence of the specification definition the claims may only arguably cover the product under the doctrine of equivalents.
C. DESCRIBE INVENTION IN BROAD TERMS
The skilled practitioner will readily appreciate the need to describe the invention broadly in the specification. The description of the invention should correlate with the scope of the original claims which are to be filed. Thus, the description of the broadest invention should be no more limited than the invention to be claimed in the independent claims. Narrower embodiments should be described as optional and preferred, corresponding to the dependent claims. In this way, there is a correspondence in breadth of the invention described in the specification and the invention claimed in the claims. In addition, generic terminology should be used where appropriate to broadly define a claim element. A detailed description of species encompassed by the genus should also be included as is customary. Such genus and species descriptions will maximize the scope of the claims. Alternative embodiments should be envisioned and described, both structurally and functionally, to maximize the potential range of equivalents. If means-plus-function claims are present, a detailed description of exemplary structures should be included. In addition, a description of the functional requirements of the means element should be included, to maximize the possibility of an accused structure being considered to be an equivalent.
D. AVOID DEDICATION OF UNCLAIMED EMBODIMENTS TO THE PUBLIC
While striving for a broad nonlimiting disclosure, the practitioner must be careful not to describe embodiments in the specification which are not claimed. The claims should be reviewed to ensure that they literally cover all embodiments of the invention described in the specification for which patent protection is desired.
If an embodiment is described in the specification for which protection is not desired, the description of the embodiment should be cancelled from the specification. It is a well-established rule that subject matter disclosed but not claimed in a patent application is dedicated to the public. Moreover, it is clear according to a recent Federal Circuit decision that this rule applies to prevent a finding of infringement under the doctrine of equivalents. In Maxwell12, the Federal Circuit reversed a trial court's finding of infringement of claims to a shoe patented by Maxwell. Maxwell's original claims were limited to a particular fastening system. She disclosed in her specification, without ever claiming them, several alternative fastening systems. The Federal Circuit held that there was no infringement, either literally or under the doctrine of equivalents, since Maxwell, by not claiming the alternative embodiments, had dedicated these embodiments to the public. Thus, alternative embodiments described but not claimed in the specification will not be considered to be "equivalents" under a doctrine of equivalents analysis. Such alternative embodiments may be freely used by a potential infringer to avoid infringement of the patent claims.
E. BE CAREFUL DESCRIBING PRIOR ART
Statements made by a patentee in a patent specification to distinguish the invention over the prior art should be made carefully. Such statements have been used by the Federal Circuit in several recent cases to limit the scope of the patent claims to find non-infringement.
For example in Sofamor13, the claims were directed to a spinal implant including a "body attaching means". The court looked to the teachings of the specification to interpret the claim term. The specification taught that the invention overcame a disadvantage of the prior art implants having a body attaching means with a "plug and a separate locking screw". The accused device used a "plug and a separate locking screw" in its body attaching means, hence the court found that the specification expressly excluded this element of the accused device from the scope of the claim. Hence, care should be taken not to describe the prior art overbroadly in the specification.
V. PROSECUTING THE PATENT APPLICATION
The foregoing discussion focuses on steps which the patent drafter can take before filing in order to minimize the number of claim amendments that are needed during prosecution. Such steps thereby minimize the risk of the claim scope being limited by prosecution history estoppel. On the other hand, the following discussion focuses on steps which the patent prosecutor can take after filing to minimize prosecution history estoppel.
A. AMENDMENTS TO CLAIMS
Under Hilton Davis, a new rebuttable presumption was created that places the burden on the patent applicant to avoid prosecution history estoppel. Essentially, all claim amendments will be presumed to be made for reasons of overcoming the prior art. The burden will be on the patentee to establish that the amendment was made for a reason unrelated to patentability. If the patentee is unable to overcome this burden with convincing evidence, the claim element or limitation which is added is expected to be barred from application of the doctrine of equivalents.
The patentee will be given an opportunity during an infringement suit to establish that a claim amendment was made for a purpose unrelated to overcoming the prior art. The evidence may be testimony by the inventor or the patent prosecutor. However such evidence presented during litigation will be subject to attack by the accused infringer as being self-serving and might be given little weight by the trial judge.
A preferable way to avoid these potential problems is for the patent prosecutor to make a statement on the record about the purpose of the claim amendment when the amendment is presented. Such a statement is generally expected to be given more weight by the trial judge than those merely submitted during litigation. However such statement must still be credible to be convincing. A mere statement that claim amendments are presented to better define the invention under 35 U.S.C. § 112 generally can not be expected to be convincing if the claims are solely rejected under 35 U.S.C. § 102 or § 103.
It is unclear at this time how much evidence will be necessary to overcome the presumption. It is also unclear exactly what reasons for making amendments will be deemed "reasons unrelated to patentability". It is assumed that such reasons relate to matters under 35 U.S.C. § 112 and 35 U.S.C. § 101. Future decisions of the Federal Circuit will be important to clarify these questions.
Furthermore, it is uncertain at this time exactly what statements a practitioner should make on the record to place the patentee in the best position during litigation to avoid prosecution history estoppel. The practitioner might need to provide different degrees of statements depending upon the particular grounds of rejection, claim amendments and prior art at issue.
For example, if the grounds of rejection are solely under 35 U.S.C. § 112 and/or § 101, a brief statement by the practitioner would appear to be sufficient, stating that the amendments are presented to better define the invention to overcome the rejection under 35 U.S.C. § 112 and/or § 101. If a more cautious approach is desired, the practitioner could state how each amendment overcomes each particular issue raised in the Action. The record would then be clear that each claim amendment was submitted for purposes unrelated to patentability, and it seems unlikely that the court would find otherwise.
Where the claims are rejected both under 35 U.S.C. § 112 and 35 U.S.C. § 102 or § 103, it is expected to be important for the practitioner to provide a detailed statement pointing out the purpose of the amendments presented to overcome the issues raised under 35 U.S.C. § 112. If there is no such explanation, the patentee stands the risk that prosecution history estoppel will be unnecessarily applied to claim elements or limitations which are added for purposes unrelated to patentability.
Regarding prior art rejections, a question arises whether the reasons for amending a claim to avoid prior art should be stated. Ordinarily, the practitioner would wish to present arguments why the claim amendments define the claims over the prior art. This practice seems necessary to continue, in order to make the response fully responsive, and in order to better convince the Examiner as to the patentability of the invention over the prior art.
Nevertheless, in responding to such rejections, the practitioner should be cautious in making unnecessary arguments why the claims as amended distinguish over the prior art. Making weak alternative arguments might give rise to a broader estoppel under the doctrine of equivalents.
Further, the practitioner should be cautious in presenting claim amendments which are in fact presented for purposes unrelated to patentability. If the amendment is unavoidable, the practitioner should include a detailed explanation expressing how the amendment better defines the invention and is unrelated to defining over the prior art.
Furthermore, and perhaps most importantly, a practitioner should not necessarily assume or characterize an entire claim amendment as being presented to overcome the prior art. The prior art may not dictate the entire claim change that is made. When a rejection based on prior art does not dictate the claim change that was made, it is necessary for the court to look at the specific change and the reason it was made in order to ascertain whether an estoppel has risen by virtue of the change. The practitioner should thus try to distinguish claim amendments which are essential for defining over the art from claim amendments which are otherwise necessary to better define the invention. This distinction may be unclear or non-existent. At a minimum, a statement made on the record by the practitioner that the amendment is also presented to "better define the invention", i.e. under 35 U.S.C. § 112, might be helpful to preserve some scope of equivalents during litigation for that part of the claim amendment which is later found not essential to define over the art.
For example in Hilton Davis, the patentee inserted a claim limitation that the claimed process was conducted "at a pH from approximately 6.0 to 9.0". The parties agreed that the upper pH limit was added to distinguish over the prior art. Hence under Hilton Davis, the upper pH limit is barred from application of the doctrine of equivalents. On the other hand, the parties disputed the reason for adding the lower pH limit. The Court remanded the case back to the Federal Circuit for further proceedings to determine whether the patentee can establish that such amendment was effected for reasons unrelated to patentability. If the patentee can establish that the lower pH limit was added for reasons unrelated to patentability, such as to better define the invention under 35 U.S.C. § 112, the lower pH limit should be entitled to application of the doctrine of equivalents.
Another case on point is James River14, a district court decision decided after Hilton Davis. In this case, the court held that a claim amendment added to better define the invention over the prior art was still entitled to a scope of equivalents. The claim limitation at issue was "substantially integrated fibrous structures generally inseparable into their constituent layers". The court narrowly construed the amendment to conclude that only a part of the claim limitation was added to define over the prior art. The remainder of the amendment was held to be entitled to application of the doctrine of equivalents. While the case is ambiguous and it is uncertain how the Federal Circuit would view the holding, the case suggests that it might be possible to preserve some scope of equivalents for a claim amendment made responsive to a prior art rejection.
In summary, the practitioner should try to state specific reasons for making claim amendments, particularly if the amendment is made for reasons unrelated to patentability. If a prior art rejection is of record, the practitioner should refrain from generally stating that the amendment is submitted to overcome the prior art. If possible, the practitioner should try to distinguish claim amendments to define over the prior art from claim amendments to "better define" the invention.
B. AMENDMENTS FOR EARLY ALLOWANCE
The claims should not be amended to obtain an early allowance without careful consideration. Today, with the twenty-year term, it is tempting to accept allowance of claims to less than the claim scope to which the applicant is entitled. However, a rebuttable presumption is now created that the claims were amended to avoid prior art. This presumption may be difficult to overcome during litigation, especially if the Examiner's reasons for allowance state that the claims were amended to overcome a rejection based on prior art. Broader claims can of course be pursued in a continuing application. But for enforceability of the issuing patent, it would be helpful to minimize the potential scope of estoppel as much as possible.
Prosecution history estoppel in these cases might be limited by pointing out on the record any amendments which are for purposes unrelated to patentability. It is likely that such statements made by the Examiner on the record will be given more weight by the trial judge than those made by the patentee. Hence the practitioner might ask the Examiner during a negotiation of the claim amendments whether the Examiner is amenable to make the desired statements in an Examiner's Reasons for Allowance statement. Alternatively, the practitioner should submit the desired statements on the record.
C. EXAMINER INTERVIEW
An interview with the Examiner can be an ideal opportunity to expedite prosecution by identifying claim language which will obtain an allowance of the claims. The practitioner and the Examiner can explore numerous claim amendments of the record, reaching an agreement on allowable language or at least expediting the process. Often it is possible to avoid the customary series of written responses presenting different claim amendments and arguments before obtaining an allowance. Prosecution history estoppel can minimized where the claim amendments and arguments made of record are minimized. Nevertheless, to minimize the effect of prosecution history estoppel where the claims are amended, the practitioner might ask the Examiner to state on the record the amendments which were made for purposes unrelated to patentability. Alternatively, the practitioner should make such statements. Presently there is a proposal by the U.S. Patent Office to tape record interviews between the Examiner and patent applicant and prepare a transcript. The purpose of the transcript would be to provide a complete account of the interview to help the trial court interpret reasons why claim amendments are made.
D. OTHER STATEMENTS ON THE RECORD
The practitioner should exercise care in presenting arguments during prosecution, characterizing the invention and distinguishing the claimed invention over the prior art. All express statements made by the patentee during prosecution which could induce an Examiner to allow the claims may be held to limit the scope of the claims. This includes statements made in an Information Disclosure Statement distinguishing the claimed invention over the prior art.15
Hence, the practitioner should be careful not make overbroad statements regarding the invention and not generalize how the invention defines over the prior art. Such statements should be as specific as possible. When referring to specific prior art references, a conservative approach is to characterize the prior art narrowly staying close to the language of the reference.
VI. CONCLUSION
Public concern has increased in recent years over the uncertain scope of U.S. patent claims under the doctrine of equivalents. The Hilton Davis and Markman decisions appear to address those concerns, by creating new limitations and requirements for finding patent infringement, particularly under the doctrine of equivalents. Patent practitioners should heed these decisions or risk obtaining patent claims having a narrower scope than necessary.
The above discussion suggests some strategies for the patent practitioner to consider for obtaining the maximum protection which might be afforded by a patent claim. Patent practitioners will need to keep abreast of further court decisions clarifying the principle rules set forth in Hilton Davis and Markman.
