Prosecution Disclaimer And Its Relationship To Prosecution History Estoppel

Introduction

A few other attorneys and I were discussing how statements in a patent’s file history affect claim construction.  During this discussion, as in almost every discussion about a patent’s file history, the question of “prosecution history estoppel” came up.  Why, I thought, were we discussing prosecution history estoppel in the context of claim construction?  One of the other attorneys attempted to explain that prosecution history estoppel prevents a patentee from amending his claims and later attempting to assert those claims in a way that is inconsistent with the amendment.  His answer, while a technically correct statement of fact, didn’t actually answer the question.  Prosecution history estoppel does prevent asserting a claim in a manner inconsistent with earlier amendments, but only to the extent of limiting the scope of equivalent elements available under the doctrine of equivalents.

A few months later, a related question brought the proper role of prosecution history estoppel issue to the forefront again.  I was asked, “If prosecution history estoppel does not prevent a patentee from surrendering subject matter and later asserting that his claims cover the surrendered subject matter, what does?”  This question, like the attempted explanation discussed above, slightly misses the point. Prosecution history estoppel does prevent a patentee from asserting previously surrendered subject matter - but only in the context of the doctrine of equivalents.  Thus, the idea for this article was conceived.

Perhaps you have heard others referring to prosecution history estoppel in the context of claim construction, or have even done so yourself.  You not alone.  Even federal judges have mistakenly referred to prosecution history estoppel when discussing claim construction issues.  See Ballard Med. Prods. v. Allegiance Healthcare Corp., 268 F.3d 1352, 1358-59 (Fed.Cir.2001)(disregarding district court’s “unconventional” use of term prosecution history estoppel in context of claim construction).

Of course, even though the Federal Circuit may have disregarded the district court’s “unconventional” use of the term prosecution history estoppel in Ballard, it would be unwise to assume that every court will be as forgiving of the same mistake – especially when made by one of the parties to a lawsuit.  And I suspect that a well informed opposing counsel would not overlook such a mistake.  

In the situations described above, prosecution disclaimer was the relevant doctrine, not prosecution history estoppel.  While both prosecution history estoppel and prosecution disclaimer work to prevent a patentee from recapturing previously surrendered subject matter, it is prosecution disclaimer that affects how a claim is construed.  This article will address both prosecution history estoppel and prosecution disclaimer, hopefully illuminating their similarities and differences.

Prosecution History Estoppel

“A patent protects its holder against efforts of copyists to evade liability for infringement by making only insubstantial changes to a patented invention.”  Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd., 535 U.S. 722, 726 (2002).  This concept is embodied in the doctrine of equivalents, which “allows the patentee to claim those insubstantial alterations that were not captured in drafting the original patent claim but which could be created through trivial changes.”  Id.at 733.  But the doctrine of equivalents can create uncertainty about exactly what a patent protects.  Id. at 726.  And inventors might try to improperly use the doctrine of equivalents to “recapture in an infringement action the very subject matter surrendered as a condition of receiving the patent.” Id. at 735.

The doctrine of prosecution history estoppel addresses these problems by preventing a patentee from arguing infringement under the doctrine of equivalents based on subject matter surrendered during prosecution of his patent.  See id. at 733 (“Prosecution history estoppel ensures that the doctrine of equivalents remains tied to its underlying purpose.”). There are two varieties of prosecution history estoppel, according to the Federal Circuit:  1) estoppel by amendment; and 2) argument-based estoppel.  Salazar v. Procter & Gamble Co., 414 F.3d 1342, 1344 (Fed.Cir.2005).

Estoppel by amendment is the most commonly referred-to version of prosecution history estoppel.  The doctrine of prosecution history estoppel (by amendment) states that a narrowing amendment, made for purposes of patentability, gives rise to a rebuttable presumption that the patentee is estopped from asserting infringement based on subject matter equivalent to the subject matter surrendered by the amendment.  Festo 535 U.S. at 727, 741.  Argument-based prosecution history estoppel, on the other hand, limits the scope of equivalents based on statements made by the patentee during prosecution.  Litton Sys., Inc. v. Honeywell, Inc., 140 F.3d 1449, 1458 (Fed.Cir.1998) (abrogated on other grounds) (“This court has acknowledged that even arguments made during prosecution without amendments to claim language – if sufficient to evince a clear and unmistakable surrender of subject matter – may estop an applicant from recapturing that surrendered matter under the doctrine of equivalents.”).  

It is important to note that prosecution history estoppel, whether arising from arguments or amendments, is relevant only to limiting the doctrine of equivalents; it is not relevant to determining the literal scope of a claim.  See Festo 535 U.S. at 741 (“When the patentee has chosen to narrow a claim, courts may presume the amended text was composed with awareness of this rule and that the territory surrendered is not an equivalent of the territory claimed.”); see also Biodex Corp. v. Loredan Biomedical, Inc., 946 F.2d 850, 862 (Fed.Cir.1991) (“Therefore, Biodex is technically correct in asserting that the doctrine of prosecution history estoppel is “irrelevant” to determination of literal claim scope.”).  It is this constraint, i.e. that prosecution history estoppel does not to limit the literal scope of a claim, which seems to be its most commonly overlooked aspect.  See Spectrum Intern., Inc. v. Sterilite Corp., 164 F.3d 1372, 1378 n.2 (Fed.Cir.1998) (“Our recourse to language emphasizing the relinquishing of subject matter during prosecution should not be construed to undermine the clear distinction between following the statements in the prosecution history in defining a claim term, and the doctrine of prosecution history estoppel, which limits expansion of the protection under the doctrine of equivalents when a claim has been distinguished over relevant prior art.”) (internal quotations and citations omitted). 

Prosecution Disclaimer¹

Like prosecution history estoppel, prosecution disclaimer prevents a patentee from reclaiming subject matter surrendered through statements or claim amendments during prosection.  Omega Eng'g., Inc. v. Raytek Corp., 334 F.3d 1314, 1324 (Fed.Cir.2003) (stating patentees precluded from recapturing through claim interpretation specific meanings disclaimed during prosecution); Sentry Protection Prods., Inc. v. Eagle Mfg. Co., 400 F.3d 910, 915 (Fed.Cir.2005) (finding district court's application of prosecution disclaimer based on claim amendment sound).  Unlike prosecution history estoppel, however, prosecution disclaimer, limits the literal scope of a claim based on a patentee’s unequivocal disavowal a particular meaning of a claim.  Cordis Corp. v. Medtronic Ave, Inc. 511 F.3d 1157, 1177 (Fed.Cir.2008); Sentry 400 F.3d at 915 (stating that expressly disclaiming subject matter during prosecution modifies scope of claim); see Omega 334 F.3d at 1325-26 (explaining that prosecution disclaimer requires alleged disavowing actions or statements to be clear and unmistakable).

The Federal Circuit has adopted the doctrine of prosecution disclaimer as a “fundamental precept” of its claim construction jurisprudence.  Id. at 1324.  In explaining its reasons for doing so, the Federal Circuit relied on Supreme Court precedent, as well as its own case law.  Some of the cases particularly relevant to understanding prosecution disclaimer are discussed briefly below.

Supreme Court Precedent

The Supreme Court has not explicitly recognized prosecution disclaimer, but after analyzing Supreme Court decisions, the Federal Circuit concluded, “The doctrine of prosecution disclaimer is well established in Supreme Court precedent, precluding patentees from recapturing through claim interpretation specific meanings disclaimed during prosecution.” Id. at 1324 citing  Schriber-Schroth Co. v. Cleveland Trust Co., 311 U.S. 211, 220-21 (1940) ("It is a rule of patent construction consistently observed that a claim in a patent as allowed must be read and interpreted with reference to claims that have been cancelled or rejected, and the claims allowed cannot by construction be read to cover what was thus eliminated from the patent.").

The Federal Circuit’s conclusion that prosecution disclaimer is well established in Supreme Court precedent, however, may be slightly overstated.  The cases cited in the Federal Circuit’s analysis are directly on point only to the extent prosecution disclaimer applies to amendments.  Consider, for example, the case of Schriber, in which the Supreme Court held a patent invalid, because during prosecution of the patent, the patentee had withdrawn claims that included reference to flexible web-like structures. Id. at 220.  The Court held that a claim cannot be construed to include a feature that has been surrendered by amendment. Id. at 222-23.  Even though cited as supporting prosecution disclaimer, generally, Shriber seems to directly support only prosecution disclaimer by amendement.

Another Supreme Court case the Federal Circuit cited in support of prosecution disclaimer is Crawford v. Heysinger, 123 U.S. 589, 602-04 (1887).  In Crawford, the Supreme Court limited the literal scope of a claim directed to a stapling device based on subject matter surrendered by the patentee’s amendments.  See Id. at 607 ( “Those elements, in those forms, in claims 1 and 2, were made necessary by the requirements of the Patent Office, before it would grant the reissue, and the applicant, having voluntarily made the limitations, is bound by them.”).  Crawford, like Schriber, appears to have been decided on the basis of subject matter disclaimed by amendments.

Another case cited by the Federal Circuit in support of its statement that prosecution disclaimer is well established in Supreme Court precedent, Goodyear Dental Vulcanite Co. v. Davis,102 U.S. 222, 227 (1880), is perhaps more on-point than either Shriber or Crawford, because Goodyear involved both statements and amendments.  See Goodyear, 102 U.S. at 227-28 (discussing patentee’s understanding based on letter to Commissioner and corresponding claim amendments).  In Goodyear, the Supreme Court, apparently taking into account both statements and amendments made during prosecution, limited the literal scope of a patent based on the “avowed understanding of the patentee, expressed by him, or on his half, when his application for the original patent was pending.”  Goodyear, 102 U.S.at 227- 28 (“In view of this there can be no doubt of what Cummings understood he had patented…”).  Although the Supreme Court’s decision in Goodyear supports prosecution disclaimer based on both limiting statements and claim amendments, it is not completely clear that it supports the doctrine of prosecution disclaimer based on statements alone.

Federal Circuit Precedent

While there may be some question as to what degree prosecution disclaimer is established by Supreme Court precedent, there can be little doubt that the doctrine of prosecution disclaimer is well established in Federal Circuit precedent.  In Southwall Techs. Inc. v. Cardinal IG Co., 54 F.3d 1570 (Fed.Cir.1995) the Federal Circuit stated, “The prosecution history limits the interpretation of claim terms so as to exclude any interpretation that was disclaimed during prosecution.”  Id. at 1576.  And as early as 1998, the Federal Circuit explicitly recognized that statements made by a patentee could be used to limit the literal scope of a claim.  Spectrum, 164 F.3d at 1378 (“Unambiguous intrinsic evidence in turn provides sufficient input to the rules of claim construction, in particular in this case, the rule that explicit statements made by a patent applicant during prosecution to distinguish a claimed invention over prior art may serve to narrow the scope of a claim.”).  In 2003, the Federal Circuit announced the doctrine of prosecution disclaimer, describing it as a “fundamental precept of claim construction.”  Omega, 334 F.3d at 1323.

In other cases, the Federal Circuit has relied on the underlying principles of prosecution disclaimer in finding that literal scope of a claim was limited by the patentee during prosecution: Ballard, 268 F.3d at 1358 (upholding finding of disclaimer based on statements distinguishing prior art ventilating/aspirating apparatus); Bell Atlantic Network Servs., Inc. v. Covad Commc’ns Group, Inc., 262 F.3d 1258, 1273-74 (Fed.Cir.2001) (limiting a claimed transceiver to three modes stated in the specification based, in part, on statements made by patentee to distinguish prior art); Sentry 400 F.3d 910 at 915 (excluding multi-component assembly from claim scope based on disclaimer by amendment).

Conclusion

Statements and amendments made during prosecution can limit a claim’s scope in two different contexts.  The way a claim is construed, that is the literal scope of a claim, may be limited by prosecution disclaimer.  The equivalents of claim elements available under the doctrine of equivalents may be limited by the doctrine of prosecution history estoppel.   By remaining focused on these two different uses of the prosecution history, you can be assured of properly applying the doctrines of prosecution disclaimer and prosecution history estoppel.

Endnotes