Myths About Avoiding Prosecution History Estoppel

In the recent Federal Circuit case Honeywell, Int'l. Inc. v. Hamilton Sundstrand Corp., 370 F.3d 1131 (Fed. Cir. 2004) (en banc), the court held that a presumption of prosecution history estoppel arises when a patent applicant cancels an independent claim and rewrites its first dependent claim in independent form. Since then, patent attorneys and industry watchdogs have repeatedly misinterpreted the cause of this estoppel. Worse, many have advocated the dangerous strategy of initially writing dependent claims in independent form as a means of avoiding the estoppel. Such a strategy is useless in avoiding estoppel and highly counterproductive. Patent prosecutors should leave dependent claims in dependent form and, instead, avoid estoppel by using the strategies suggested below.

The patentee in Honeywell was asserting infringement under the doctrine of equivalents. Under the doctrine, a device that does not fall within the literal boundaries of a patent's claims may nevertheless infringe if it performs substantially the same function in substantially the same way to obtain substantially the same result as the claimed device. The doctrine is of great value to patentees because it lets them expand the scope of their patent to cover devices that are only insubstantially different from the literal scope of their claims.

The doctrine of equivalents is tempered by prosecution history estoppel. Estoppel prohibits the patentee from using the doctrine of equivalents to recapture territory that was surrendered to obtain the patent. In the landmark case Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co. Ltd., 535 U.S. 722 (2002), the Supreme Court held that a presumption of estoppel arises when an amendment narrows the patent's scope and is made for any reason related to patentability.

During the prosecution of the Honeywell patent, the examiner rejected various independent claims as obvious but indicated that the claims that directly depended from those claims would be allowable if rewritten in independent form. The applicant cancelled the rejected claims and rewrote the appropriate dependent claims in independent form. These now-independent claims issued as part of the patent, but when Honeywell tried to expand the scope of those rewritten claims using equivalents, the court imposed a presumption of estoppel.

There are several widespread misconceptions surrounding the court's holding. Many think the rewriting alone triggered the estoppel, perhaps because the only change to the asserted claim was its being rewritten. Others seem to think that both events ' the canceling of the antecedent claim and the rewriting of the dependent claim ' are necessary to invoke estoppel and therefore avoiding one of the events will avoid estoppel. These two misconceptions lead many to advocate favoring independent claims over dependent claims so that rewriting dependent claims during prosecution can be avoided.

For example, a recent article in Nevada Lawyer stated the court's holding as “restating a dependent claim in independent form during prosecution gives rise to presumptive estoppel.” and suggested that patent applicants “need to consider drafting many more independent claims.” Sam Niece & Adrienne Yeung, Another Nail in the Doctrine of Equivalents' Coffin, Nev. Law., Sept. 2004, at 22.

Avoiding dependent claims, however, is a useless, dangerous practice. Doing so will not avoid estoppel and will have several negative side effects. Application costs will increase because independent claims have higher fees than dependent claims. Redundancy of claim language will create more opportunities for mistakes and, in turn, more fodder for litigation. Prosecution and examination will take longer because the organization and simplification offered by dependent claims has been lost.

Favoring independent claims will not avoid estoppel because rewriting a dependent claim in independent form, whether coupled with the canceling of its antecedent claim or not, plays no part in triggering estoppel. The Festo court held that an amendment must narrow the patent's scope before it invokes presumptive estoppel. Changing the form of a dependent claim, however, leaves the patent's scope unchanged. A dependent claim incorporates all the limitations of its antecedent claims; its scope is the same regardless of whether it's written in independent or dependent form.

Although it's true that canceling a claim and rewriting one of its dependent claims in independent form invokes estoppel, the estoppel is triggered purely by the cancellation. The rewriting does nothing to trigger estoppel because it does not narrow the patent's scope. Accordingly, canceling a claim invokes estoppel by itself. Indeed, this was the Federal Circuit's holding in Mycogen Plant Science, Inc. v. Monsanto, Co., 252 F.3d 1306 (Fed. Cir. 2001). Therefore, the court would have imposed estoppel in Honeywell even if the asserted claim had originally been written in independent form and never rewritten.

The misconceptions surrounding Honeywell seem to stem from several areas in the majority and dissenting opinions that are ambiguous, misleading, or imprecise. For example, the majority opinion repeatedly says it's addressing whether rewriting coupled with cancellation of the antecedent claim triggers estoppel. The unwary reader might think this means both prosecution events are necessary to invoke estoppel. But a simpler explanation is that the court repeatedly mentions both events for narrative integrity. It mentions two events because the history of the claims at issue includes two events, not because both events are required to invoke estoppel.

The most misleading problem area and an undoubted cause of the bad advice above is Judge Pauline Newman's dissenting opinion. She implies that favoring independent claims will avoid the estoppel in Honeywell by outlining the negative consequences that will result from the use of such a strategy. Her foreshadowing, however, is misleading because it's based on a misunderstanding of the majority opinion. She says the majority holds that the rewriting of a dependent claim into independent form is a narrowing amendment. In fact, the majority repeatedly says it's considering the rewriting event coupled with the canceling event and, as explained above, the cancellation is the event that makes the amendment narrowing and invokes estoppel.

Judge Newman seems to have fallen victim to the problem areas in the majority opinion that have trapped other unwary readers. Although examination of those areas is outside the scope of this article, careful analysis will reveal their best interpretation does not support the above misconceptions either.

Despite the attention given to Honeywell, the decision hardly ventures into new legal territory. The heart of the decision is the basic rule from Festo applied to a particular set of prosecution events. When the extraneous event ' rewriting a dependent claim ' is stripped away, the simple narrowing event of canceling a claim is all that remains. Since the claims were canceled to obtain the patent, the patentee is presumptively estopped from later reclaiming that surrendered territory using the doctrine of equivalents.

This does not mean, however, that estoppel should be taken lightly. Since it will be difficult for Honeywell to rebut the presumption of estoppel, estoppel will likely cost Honeywell at least $46 million, the amount the jury had awarded it at trial. Given such severe consequences, patent applicants and prosecutors must take vigilant action to preserve the scope of their patent claims by avoiding estoppel.

The first step to avoiding estoppel is ignoring the harmful myths that surround it and avoiding the bad habits that cause it:

• Do not write dependent claims in independent form. Doing so will not avoid estoppel, and it will only make the application process expensive, inefficient, and error prone.
• Do not think estoppel is applied on a claim-by-claim basis. Even if a particular claim's scope is never changed, one may still be estopped from expanding that claim's scope using the doctrine of equivalents because of the amendment or cancellation of other claims.
• Do not file an initial application with excessively broad claims only to whittle away the patent's scope during negotiations with the Patent and Trademark Office until reaching a patentable set of claims. Every time the patent's scope is narrowed, the applicant is laying the foundation for prosecution history estoppel.

Next, use the following strategies to minimize the impact of estoppel or avoid it altogether:

• Increase the amount of effort put into drafting the claims for the initial application. For example, understand the extent of the prior art as much as possible. To this end, perform the best patentability search possible given the client's financial and time constraints.
• Increase the use of means plus function claims. Although prosecution history estoppel may cause these claims to lose equivalents under the doctrine of equivalents, they may still be entitled to equivalents under 35 U.S.C. 112, sixth paragraph.
• Avoid narrowing claims for reasons of patentability as much as possible. For example, state a reason for amending a claim that is unrelated to patentability and appeal improper claim rejections.
• If narrowing activity is unavoidable, ensure that new claims and amendments to existing claims cover as many equivalents as possible. Identify which claims will be subject to estoppel and make their language as broad as possible while still being patentable.

Finally, remain informed about the inevitable changes in these areas of law and fully understand the rationale behind any patent prosecution advice before adopting it.

In the recent Federal Circuit case Honeywell, Int'l. Inc. v. Hamilton Sundstrand Corp., 370 F.3d 1131 (Fed. Cir. 2004) (en banc), the court held that a presumption of prosecution history estoppel arises when a patent applicant cancels an independent claim and rewrites its first dependent claim in independent form. Since then, patent attorneys and industry watchdogs have repeatedly misinterpreted the cause of this estoppel. Worse, many have advocated the dangerous strategy of initially writing dependent claims in independent form as a means of avoiding the estoppel. Such a strategy is useless in avoiding estoppel and highly counterproductive. Patent prosecutors should leave dependent claims in dependent form and, instead, avoid estoppel by using the strategies suggested below.

The patentee in Honeywell was asserting infringement under the doctrine of equivalents. Under the doctrine, a device that does not fall within the literal boundaries of a patent's claims may nevertheless infringe if it performs substantially the same function in substantially the same way to obtain substantially the same result as the claimed device. The doctrine is of great value to patentees because it lets them expand the scope of their patent to cover devices that are only insubstantially different from the literal scope of their claims.

The doctrine of equivalents is tempered by prosecution history estoppel. Estoppel prohibits the patentee from using the doctrine of equivalents to recapture territory that was surrendered to obtain the patent. In the landmark case Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co. Ltd., 535 U.S. 722 (2002), the Supreme Court held that a presumption of estoppel arises when an amendment narrows the patent's scope and is made for any reason related to patentability.

During the prosecution of the Honeywell patent, the examiner rejected various independent claims as obvious but indicated that the claims that directly depended from those claims would be allowable if rewritten in independent form. The applicant cancelled the rejected claims and rewrote the appropriate dependent claims in independent form. These now-independent claims issued as part of the patent, but when Honeywell tried to expand the scope of those rewritten claims using equivalents, the court imposed a presumption of estoppel.

There are several widespread misconceptions surrounding the court's holding. Many think the rewriting alone triggered the estoppel, perhaps because the only change to the asserted claim was its being rewritten. Others seem to think that both events ' the canceling of the antecedent claim and the rewriting of the dependent claim ' are necessary to invoke estoppel and therefore avoiding one of the events will avoid estoppel. These two misconceptions lead many to advocate favoring independent claims over dependent claims so that rewriting dependent claims during prosecution can be avoided.

For example, a recent article in Nevada Lawyer stated the court's holding as “restating a dependent claim in independent form during prosecution gives rise to presumptive estoppel.” and suggested that patent applicants “need to consider drafting many more independent claims.” Sam Niece & Adrienne Yeung, Another Nail in the Doctrine of Equivalents' Coffin, Nev. Law., Sept. 2004, at 22.

Avoiding dependent claims, however, is a useless, dangerous practice. Doing so will not avoid estoppel and will have several negative side effects. Application costs will increase because independent claims have higher fees than dependent claims. Redundancy of claim language will create more opportunities for mistakes and, in turn, more fodder for litigation. Prosecution and examination will take longer because the organization and simplification offered by dependent claims has been lost.

Favoring independent claims will not avoid estoppel because rewriting a dependent claim in independent form, whether coupled with the canceling of its antecedent claim or not, plays no part in triggering estoppel. The Festo court held that an amendment must narrow the patent's scope before it invokes presumptive estoppel. Changing the form of a dependent claim, however, leaves the patent's scope unchanged. A dependent claim incorporates all the limitations of its antecedent claims; its scope is the same regardless of whether it's written in independent or dependent form.

Although it's true that canceling a claim and rewriting one of its dependent claims in independent form invokes estoppel, the estoppel is triggered purely by the cancellation. The rewriting does nothing to trigger estoppel because it does not narrow the patent's scope. Accordingly, canceling a claim invokes estoppel by itself. Indeed, this was the Federal Circuit's holding in Mycogen Plant Science, Inc. v. Monsanto, Co., 252 F.3d 1306 (Fed. Cir. 2001). Therefore, the court would have imposed estoppel in Honeywell even if the asserted claim had originally been written in independent form and never rewritten.

The misconceptions surrounding Honeywell seem to stem from several areas in the majority and dissenting opinions that are ambiguous, misleading, or imprecise. For example, the majority opinion repeatedly says it's addressing whether rewriting coupled with cancellation of the antecedent claim triggers estoppel. The unwary reader might think this means both prosecution events are necessary to invoke estoppel. But a simpler explanation is that the court repeatedly mentions both events for narrative integrity. It mentions two events because the history of the claims at issue includes two events, not because both events are required to invoke estoppel.

The most misleading problem area and an undoubted cause of the bad advice above is Judge Pauline Newman's dissenting opinion. She implies that favoring independent claims will avoid the estoppel in Honeywell by outlining the negative consequences that will result from the use of such a strategy. Her foreshadowing, however, is misleading because it's based on a misunderstanding of the majority opinion. She says the majority holds that the rewriting of a dependent claim into independent form is a narrowing amendment. In fact, the majority repeatedly says it's considering the rewriting event coupled with the canceling event and, as explained above, the cancellation is the event that makes the amendment narrowing and invokes estoppel.

Judge Newman seems to have fallen victim to the problem areas in the majority opinion that have trapped other unwary readers. Although examination of those areas is outside the scope of this article, careful analysis will reveal their best interpretation does not support the above misconceptions either.

Despite the attention given to Honeywell, the decision hardly ventures into new legal territory. The heart of the decision is the basic rule from Festo applied to a particular set of prosecution events. When the extraneous event ' rewriting a dependent claim ' is stripped away, the simple narrowing event of canceling a claim is all that remains. Since the claims were canceled to obtain the patent, the patentee is presumptively estopped from later reclaiming that surrendered territory using the doctrine of equivalents.

This does not mean, however, that estoppel should be taken lightly. Since it will be difficult for Honeywell to rebut the presumption of estoppel, estoppel will likely cost Honeywell at least $46 million, the amount the jury had awarded it at trial. Given such severe consequences, patent applicants and prosecutors must take vigilant action to preserve the scope of their patent claims by avoiding estoppel.

The first step to avoiding estoppel is ignoring the harmful myths that surround it and avoiding the bad habits that cause it:

• Do not write dependent claims in independent form. Doing so will not avoid estoppel, and it will only make the application process expensive, inefficient, and error prone.
• Do not think estoppel is applied on a claim-by-claim basis. Even if a particular claim's scope is never changed, one may still be estopped from expanding that claim's scope using the doctrine of equivalents because of the amendment or cancellation of other claims.
• Do not file an initial application with excessively broad claims only to whittle away the patent's scope during negotiations with the Patent and Trademark Office until reaching a patentable set of claims. Every time the patent's scope is narrowed, the applicant is laying the foundation for prosecution history estoppel.

Next, use the following strategies to minimize the impact of estoppel or avoid it altogether:

• Increase the amount of effort put into drafting the claims for the initial application. For example, understand the extent of the prior art as much as possible. To this end, perform the best patentability search possible given the client's financial and time constraints.
• Increase the use of means plus function claims. Although prosecution history estoppel may cause these claims to lose equivalents under the doctrine of equivalents, they may still be entitled to equivalents under 35 U.S.C. 112, sixth paragraph.
• Avoid narrowing claims for reasons of patentability as much as possible. For example, state a reason for amending a claim that is unrelated to patentability and appeal improper claim rejections.
• If narrowing activity is unavoidable, ensure that new claims and amendments to existing claims cover as many equivalents as possible. Identify which claims will be subject to estoppel and make their language as broad as possible while still being patentable.

Finally, remain informed about the inevitable changes in these areas of law and fully understand the rationale behind any patent prosecution advice before adopting it.