If a patent owner has disclosed, but not claimed some embodiments of the invention, resort to the doctrine of equivalence to protect such unclaimed embodiments may be lost through the doctrine of prosecution history estoppel. Let’s assume, for sake of argument, that the patent application that led to the patent contained no claims to the genus covering the species set forth as separate embodiments of the invention and the prosecution history of the patent contained no arguments applicable to the unclaimed embodiments. Consequently, if the patent is less than two years old, the patent owner may seek to correct this error in claiming less than she was entitled to claim through the filing of a broadened reissue application claiming the previously unclaimed embodiments of the invention. The doctrine of impermissible recapture in such circumstances would not apply. In accordance with MPEP § 1412.01: Claims presented in a reissue application are considered to satisfy the requirement of 35 U.S.C. 251 that the claims be "for the invention disclosed in the original patent" where: (A) the claims presented in the reissue application are described in the original patent specification and enabled by the original patent specification such that 35 U.S.C. 112 first paragraph is satisfied; and (B) nothing in the original patent specification indicates an intent not to claim the subject matter of the claims presented in the reissue application. The presence of some disclosure (description and enablement) in the original patent should evidence that applicant intended to claim or that applicant considered the material now claimed to be his or her invention. **** **>One should understand<, however, >that< the mere failure to claim a disclosed embodiment in the original patent (absent an explicit statement in the original patent specification of unsuitability of the embodiment) would not be grounds for prohibiting a claim to that embodiment in the reissue. Filing a reissue application to claim previously unclaimed embodiments of the invention must be filed within two years of the issuance of the original patent, if claims to the previously unclaimed embodiments would read on something which the original claims do not. This would presume that no claims to the genus covering all the embodiments of the invention existed in the original patent. The test for a broadening reissue is whether the reissue patent claims would be infringed without infringing the original patent claims. This gambit will avoid the loss of potentially valuable patent rights where the patent owner did not file a voluntary divisional application to seek protection for the previously unclaimed embodiments of the invention before issuance of the original patent.

Part 1 of this series focused on the importance of a good prior art search prior to filing a request for inter partes reexamination.  Part 2 examines the exceptions to the estoppel provisions of § 315(c).  Specifically, this blog entry identifies situations in which a party might still be able to contest in litigation the validity of a patent that was the target of an unsuccessful request for inter partes reexamination.

Estoppel does not apply to patent claims for which no request for reexamination was ordered.  Simply filing a request for inter partes reexamination, by itself, does not automatically trigger estoppel.  The language of § 315(c) does not trigger estoppel unless the “request for inter partes reexamination results in an order under section 313.”  For any request for which the Patent Office does not find a substantial new question of patentability, there is no estoppel.  Thus, estoppel still applies in situations where the Patent Office orders reexamination of a patent claim on the basis of some, but not all, of the prior art presented by the third-party requester as raising a substantial new question of patentability of that patent claim.

Estoppel only applies to the third-party requester.  The estoppel provision of § 315(c) applies not only to a “third-party requester” but also possibly those in privy with the third-party requester as a real party-in-interest.  The express language of § 315(c) is different from the estoppel provision of 35 U.S.C. § 317, which applies to third-party requesters and their privies with respect to subsequent requests for inter partes reexamination.  Thus, one might assume, that the § 315(c) estoppel applied to litigants is more limited than the § 317 estoppel applied to future requests for inter partes reexamination.  The problems with that assumption are exposed when one considers that a third-party requester acting for the benefit of a litigant is really placing the litigant in the position of the real party-in-interest.  Although § 315(c) literally applies only to the third-party requester, the provisions of § 315(c) could easily be subverted if the term “third-party requester” were limited to the particular attorney or entity making the request.  Thus, it is unlikely that a litigant can avoid estoppel if another entity makes a request for inter partes reexamination designed to benefit the litigant.  (See related blog post, discussing Troll Busters LLC.)  Practically speaking, courts should interpret “third-party requester” to include real parties-in-interest.

Another scenario that arises frequently is one in which there are multiple accused infringers in a litigation.  If some parties choose to participate in the filing of a request for inter partes reexamination while other parties opt out, do the parties opting out fall victim to the estoppel provision of § 315(c)?  In these situations, the parties should not be estopped from presenting any invalidity arguments in litigation merely because they made a strategic decision not to participate in inter partes reexamination.

Estoppel does not apply to invalidity grounds which the requester could not have raised in inter partes reexamination.  Because a request for inter partes reexamination can only be based on patents and printed publications, prior art that is neither a patent nor a printed publication is fair game in an invalidity defense in subsequent litigation proceedings.  This issue was analyzed in the case of ACCO Brands, Inc. v. PC Guardian Anti-Theft Products, Inc.  In that case, the court determined that “estoppel does not apply to grounds for invalidity based on prior art that was not and could not have been before the PTO.”  The plaintiff sought to prevent the defendant from using physical samples of computers as a basis for invalidity because the defendant had relied upon printed brochures for those computers as a basis for inter partes reexamination, which resulted in the confirmation of all claims of the plaintiff’s patent.  The court declined to invoke the estoppel provision of § 315(c) to prevent the defendant from relying on the physical computers as evidence of invalidity because the computers were not patents or printed publications – the only type of prior art that the Patent Office considers during reexamination – and they raised new issues with respect to the novelty of certain claim limitations.

Estoppel does not apply to prior art that was unavailable.  The language of § 315(c) prevents estoppel from operating with respect to “newly discovered prior art unavailable to the third-party requester and the Patent and Trademark Office at the time of the inter partes reexamination proceedings.”  This exception can be viewed as a specific statutory example of invalidity grounds that fall outside the “could have raised” language in § 315(c), but it is significant enough to warrant separate discussion.  Clearly, there is no estoppel under § 315(c) if a particular patent or printed publication did not exist at the time of the inter partes reexamination proceedings, and clearly there is estoppel if the third-party requester had actual knowledge of a particular patent or printed publication.  In between those extremes, there is little guidance from the case law as to what constitutes “unavailable” prior art.

The conference reports pertaining to § 315 appear to impose an actual knowledge requirement for prior art to be considered unavailable:  “Prior art was unavailable at the time of the inter partes reexamination if it was not known to the individuals who were involved in the reexamination proceeding on behalf of the third-party requester and the US Patent Office.”  H.R. Rep. No. 106-464 (November 9, 1999).  The Patent Office however, has taken a view that is less accommodating to third-party requesters. Under the Patent Office view, a court, depending on the particular facts and circumstances, can exclude prior art that could have been discovered through a diligent search for prior art. USPTO Report to Congress on Inter Partes Reexamination at 6; Official Gazette 1234:97 (May 23, 2000).

In practice, a court is more likely interpret the phrases “could have raised” and “unavailable” broadly to include prior art that could have been discovered through a diligent search.  Such a policy serves to conserve judicial resources by reducing the number of invalidity issues that can be raised in litigation and serves to provide a quid pro quo for an accused infringer seeking to stay litigation pending the results of inter partes reexamination.  If a third-party requester is permitted to deliberately remain ignorant of patents and printed publications that would otherwise be discovered through a diligent search, then there is less incentive for the court to grant a stay of litigation because inter partes reexamination could not eliminate from the litigation the patents and printed publications that the accused infringer uncovers at the conclusion of the inter partes reexamination proceedings.  Thus, as recommended in part 1 of this series, a third-party requester is well-advised to perform an exhaustive search for prior art prior to requesting inter partes reexamination or risk being estopped from relying on late-discovered prior art in litigation.

Estoppel does not apply until a claim is finally determined to be valid and patentable.  The statutory phrase “finally determined” is subject to interpretation because § 315(c) does not expressly state whether estoppel attaches when a final office action issues or when a certificate of reexamination issues, for example.  Because a final office action does not necessarily preclude a patent owner from amending claims, the practical application of the phrase “finally determined” will most likely mean when a certificate of reexamination issues, or after a notice of intent to issue a certificate of reexamination issues and all appeals have been exhausted.  See, e.g., Safoco, Inc. v. Cameron Int’l Corp., No. 05-0739 (S.D. Tex. July 31, 2009) (concluding that § 315(c) estoppel does not attach until the Office issues a reexamination certificate).  Thus, when patentability is not “finally determined,” a third-party requester may be able to present in a parallel litigation the same invalidity arguments that it has presented in a parallel inter partes reexamination proceeding.


The estoppel provision of § 315(c) should not, by itself, scare a party away from inter partes reexamination.  A party must give thorough consideration to all of the potential exceptions to estoppel and whether they apply in any particular situation.  Lastly, if an exhaustive search of prior has been performed, then inter partes reexamination proceedings should be viewed as an alternative to litigation for having issues of invalidity determined.

The estoppel consequences of inter partes reexamination are set forth in 35 U.S.C. §§ 315(c) and 317(b) as well as the uncodified provision of § 4607 of P.L. 106-113.  This blog entry will focus on § 315(c).  A third party is estopped from asserting in litigation the “invalidity of any claim finally determined to be valid and patentable on any ground which the third-party requester raised or could have raised during the inter partes reexamination proceedings.” 35 U.S.C. § 315(c).  A few basic considerations can help an accused infringer minimize, if not eliminate, the negative effects of estoppel and still reap the benefits of inter partes reexamination. The foundation of a strong request for inter partes reexamination is a thorough search of the prior art before the request is filed.  The statutory language of § 315(c) is intended to limit the third-party requester to a single bite at the invalidity apple.  Any prior art patents and printed publications discovered after the request for reexamination is filed may be excluded as a basis for invalidity in litigation if that prior art was publicly accessible when the request for inter partes reexamination was filed.  Thus, the party contemplating inter partes reexamination must be confident that an exhaustive prior art search was performed before filing a request for reexamination.  In view of the high stakes nature of patent litigation, an exhaustive search for prior art typically does not pose a significant additional burden upon the accused infringer because a litigation budget can normally absorb the cost of multiple searches. Once an exhaustive prior art search has been performed, the next thing to consider is whether the prior art provides a compelling basis for invalidity.  If the prior art supports strong invalidity arguments, then inter partes reexamination may be the most efficient and effective way to cause significant damage to a patent that should never have been allowed.  On the other end of the spectrum, if the grounds for invalidity are weak, then inter partes reexamination is rarely, if ever, the best option for the accused infringer.  A reexamination request with weak invalidity arguments will likely result in the worst of all scenarios for the accused infringer – a reexamination certificate confirming the original claims and giving the patent owner justification to proclaim that the patent is now “gold plated.” The fact that 95% of inter partes reexamination requests are granted only makes it more likely that a weak request for inter partes reexamination will merely gold-plate the original patent.  Statistically speaking, even a weak request for inter partes reexamination that raises a substantial new question of patentability but falls short of establishing prima facie invalidity of patent claims is likely to be granted.  This can be attributed to the relatively low important to a “reasonable examiner” threshold for establishing a substantial new question of patentability and to the fact that the patent owner cannot file a patent owner’s statement opposing the request prior to the Patent Office’s decision to initiate inter partes reexamination proceedings.  Once inter partes reexamination is underway, however, the patent owner can actively participate in exposing the deficiencies of weak prior art.  If the prior art does not support a sound basis for invalidity, then the Patent Office is likely to acknowledge deficiencies in the prior art and confirm the original patent claims under reexamination. Thus, the ability of the accused infringer to identify strong evidence in support of invalidity is a critical factor when contemplating inter partes reexamination. Once strong prior art is identified, the ultimate question to the accused infringer is whether the prior art is best presented to the Patent Office’s Central Reexamination Unit (“CRU”), which specializes in conducting reexamination of patents, or a jury of laypeople. (Most patent owners exercise their constitutional right to a jury trial, so a bench trial is normally not an option for the accused infringer.)  Historical data suggests that the CRU is more likely than a jury to find invalidity.  This is not surprising because the CRU does not presume a patent valid and applies a “preponderance of the evidence” standard in determining patentability of a claim under reexamination, whereas a jury must presume a patent valid and apply a “clear and convincing” evidentiary standard in determining invalidity issues.  In any event, the unique strategic considerations of every case must always be taken into account when choosing the best audience for invalidity arguments.  For example, some invalidity arguments are strengthened when presented simultaneously with other defenses or bases for invalidity that are not the subject of reexamination proceedings (e.g., noninfringement, prior public use, etc.). Moreover, the Patent Office rules anticipate the possibility that a third-party requester may discover new patents and printed publications after an order for inter partes reexamination issues.  Under 37 C.F.R. § 1.948, a third-party requester can submit newly discovered prior art in connection with comments on a patent owner’s response to an Office action on the merits.  Although § 1.948 is not a substitute for performing a diligent search for prior art prior to requesting reexamination, it can provide a vehicle for testing the validity of a patent against prior art that is discovered during reexamination proceedings. In sum, the § 315 (c) estoppel effect of inter partes reexamination should not be a concern if an exhaustive prior art search has been performed and the prior art patents and publications support strong invalidity arguments.  Under these circumstances, the appropriateness of inter partes reexamination distills to a decision by the accused infringer whether the strong invalidity arguments are more likely to prevail in the CRU or a jury room.  The fact that inter partes reexamination estoppel may prevent the accused infringer from getting two bites at the invalidity apple is not, in itself, a reason to dismiss inter partes reexamination as an alternative to district court litigation.  When the accused infringer has identified strong prior art that is presumably as good or better than any prior art likely to be uncovered in the future, inter partes reexamination provides the accused infringer with a lower burden in proving invalidity and an extra choice as to who will determine whether the patent is invalid.  Moreover, later discovered patents and printed publications can be used by the third party as a basis for filing an ex parte reexamination request against the same patent.  Such a request is not precluded by law and if made early enough in the inter partes reexamination proceedings may be a basis to have such prior art considered in merged ex parte and inter partes reexamination proceedings.  This is not considered to be a second bite at the apple and the ex parte reexamination request can be filed anonymously. The next blog entry in this two-part series will focus on possible exceptions to the estoppel effect of inter partes reexamination.
Any requested reexamination filed while an earlier filed reexamination is pending must raise an SNQ different than that raised in the pending reexamination. Each request for reexamination must raise its own SNQ, as compared to the pending reexamination proceeding for the same patent. Previously, one could use the same SNQ as in the pending reexamination. A TPR was able to provide continued input during the reexamination proceeding by filing multiple ex parte reexamination requests and having them merged, thus resulting in an essentially inter partes reexamination, without the statutory estoppels. Patent owners or TPR, depending on who was losing in the pending reexamination proceedings, could delay the proceedings indefinitely. Extensions of time in reexamination proceedings are difficult to get granted. They must include a statement of what action the patent owner has taken to provide a response as of the date the request for the extension of time. The Patent Owner must provide a factual accounting of reasonably diligent behavior by all those responsible for preparing a response to the Office action within the time period for filing a response. A statement of why, in spite of the actions taken so far, the requested additional time is needed. If a second request for reexamination is filed after an action closing prosecution in an inter partes reexamination the proceedings will generally not be merged. Merger would run contrary to the statutory “special dispatch” requirement of 35 USC 314. If prior art is cited to the USPTO after an action closing prosecution the patent owner must submit a 37 CFR 1.182 petition, including a factual accounting providing a sufficient explanation of why the information could not have been submitted earlier and an explanation of the relevance of the information submitted with respect to the claimed invention.
On March 7, 1912, the Commissioner of Patents decided in Ex parte Bayles, 176 O.G. 749 that “[u]ntil a[n] [reissue] application is ended in all its divisions the vitality of the original patent continues so far as required to support that portion of the [reissue] application which remains undecided.” This would be true even if the parent reissue patent were to issue during the pendency of the divisional application. On August 31, 1911, the petitioner in Bayles filed a reissue application containing both method and apparatus claims found in the original patent. Subsequently, by amendment, the petitioner canceled the method claims for the purpose of filing a divisional reissue application. The divisional reissue application claiming the method was filed prior to issuance of the parent reissue application claiming the apparatus. The Commissioner relied on the August 31, 1880 decision of the Acting Attorney-General in the case of ex parte Greaves (C.D., 1880, 213; 18 O.G., 623; 16 Op. Atty. Gen., 560) holding that the good sense of the maxim pendente lite nihil innovator applied. The purported surrender of the original patent when the parent reissue patent issued after the filing of the divisional reissue application did not prevent a division of the reissue from issuing. In MPEP § 1451 (II) states that “[t]he decision of In re Graff, 111 F.3d 874, 42 USPQ2d 1471 (Fed. Cir. 1997) interprets 35 U.S.C. 251 to permit multiple reissue patents to issue even where the multiple reissue patents are not for "distinct and separate parts of the thing patented." This section further cautions that “[a]s is true for the case of multiple divisional reissue applications, all of the claims of the patent to be reissued must be presented in both the parent reissue application and the continuation reissue application in some form, i.e., as amended, as unamended, or as canceled. The same claim of the patent cannot, however be presented for examination in both the parent reissue application and the continuation reissue application, as a pending claim, in either its original or amended versions. …Where the parent reissue application issues **>before< the examination of the continuation >reissue application<, the claims of the continuation >reissue application< should be carefully reviewed for double patenting over the claims of the parent >reissue application<. Where the parent and the continuation reissue applications are examined together, a provisional double patenting rejection should be made in both cases as to any overlapping claims. See MPEP § 804 - § 804.04 as to double patenting rejections. Any terminal disclaimer filed to obviate an obviousness-type double patenting rejection ensures common ownership of the reissue patents throughout the remainder of the unexpired term of the original patent.” However, the MPEP is silent as to the effect of the language of 35 U.S.C. § 252 which indicates that “[t]he surrender of the original patent shall take effect upon the issue of the reissued patent, and every reissued patent shall have the same effect and operation in law, on the trial of actions for causes thereafter arising, as if the same had been originally granted in such amended form, but in so far as the claims of the original and reissued patents are substantially identical, such surrender shall not affect any action then pending nor abate any cause of action then existing, and the reissued patent, to the extent that its claims are substantially identical with the original patent, shall constitute a continuation thereof and have effect continuously from the date of the original patent.” Do the principles announced in ex parte Bayles apply? Namely, because a continuation reissue was filed prior to issuance of the parent reissue patent does surrender of the original patent not take place until issuance of the last continuation reissue patent? Suppose that the original patent claimed an invention AB. Within two years of the grant of the original patent a broadened reissue application was filed claiming the invention as AB, AbrBsp and AspBsp. During examination applicant facing a rejection of claims to AB, and AbrBsp, chooses to file a continuation reissue as to these claims, while thereafter letting the parent reissue application claiming only AspBsp issue. Putting aside the obviousness-type double patenting issue that can be obviated by filing a terminal disclaimer in the continuation reissue application, what effect, if any, does section 252 have on the examination of claims AB in the continuation reissue application. Are claims to AB surrendered by operation of section 252 or do the Bayles principles apply to avoid the surrender of original patent claims to AB? We are unaware of any Federal Circuit precedent directly on point. We leave it to you to decide.