Prosecution History Estoppel: Differences in Regulations between U.S., China, and Taiwan and Suggested Strategies

George Jui-Hsien Huang

While prosecution history estoppel (“PHE”) is common in patent infringement litigation in many countries, each country has different regulations and court practices in regard to claim interpretation in view of the prosecution history, limitations of PHE on the doctrine of equivalents (“DOE”), and the effects of the prosecution history of related cases, etc. We discuss in this article how PHE operates and how it is applied in the U.S., China, and Taiwan, and offer our suggestions.

U.S.

U.S. precedents state that the prosecution history of a patent serves different functions in claim interpretation and in acting as limitation on the DOE, respectively. In Southwall Techs., Inc. v. Cardinal IG Co., 54 F.3d 1570, 1578 (Fed. Cir. 1995), it is confirmed that claim interpretation in view of the prosecution history is a preliminary step in determining literal infringement, while prosecution history estoppel applies as a limitation on the range of equivalents if, after the claims have been properly interpreted, no literal infringement has been found. That said, there is no substantial difference between the theoretical basis of the two, and they have come to be nearly identical in practice in recent court decisions.

1. Claim interpretation in view of the prosecution history

In the U.S., any amendment and response made in the prosecution history of a patent may affect the future claim interpretation and is subjected to close scrutiny. For instance, in UCB, Inc. v. Yeda Rsch. and Dev. Co., 837 F.3d 1256 (Fed. Cir. 2016), the patentee’s amendments, though rejected, caused limitations on future claim interpretation, since the patentee’s interpretation of certain terms was apparent from his motivation for the amendment. This also shows that prosecution history is taken very seriously in the U.S. Any action the patentee takes during examination may be seen as admitting how he interprets his claims.

2. Limitation of PHE on the DOE

Similarly, any explicit argument, including amendments and mere responses, submitted to the USPTO during examination may bar the patentee from recapturing the scope that was previously surrendered. This is essentially the same in China and Taiwan.

3. Effects of prosecution history of related cases

With regard to claim interpretation, the prosecution history of the parent application in a divisional application is eligible as intrinsic evidence for the claim interpretation of the child application. Moreover, accounts submitted to foreign IP offices in equivalent foreign applications may also affect the interpretation of claims in the U.S. application.

 As for the DOE, the Federal Circuit clearly pointed out that in determining the applicability of PHE, accounts made to foreign IP offices may also be taken into consideration[1]. PHE resulting from the contention and amendments directed to one claim is applicable to the ranges covered by other claims in related patents.

China

1. Effects of prosecution history on claim interpretation and equivalent expansion

Article 61 of “Patent Infringement Determination Guide (2017)” published by the Beijing High People’s Court in China states PHE as a limitation on the DOE. Furthermore, according to Article 6 of “Interpretation of the Supreme People's Court on Several Issues Concerning the Application of Law in the Adjudication of Patent Infringement Dispute Cases (II)” (“Interpretation”)[2], the prosecution history of a patent and its divisional patents also serves as the basis for claim interpretation. Thus, any history of a patent, including substantive amendment and accounts, will limit future claim interpretation and equivalent expansion. Plus, the distinction between the role of prosecution history in claim interpretation and limitation on the DOE is not as clear as that in the U.S.

2. Effects of prosecution history of related cases

Article 6 of “Interpretation” stipulate that the history of a divisional application may be the basis for claim interpretation. However, other than divisional applications which are clearly stipulated therein, any case that is relevant to a patent, including patents in the same patent family, the specification of other related patents the patentee applies for in the same time period, and the specification of patents applied for by companies related to the patentee at a later time may all be possible basis for claim interpretation. In this regard, China has a broader explanation than the U.S.

 For example, in the invention patent infringement dispute between Dyson Technology Limited and Suzhou Su-Vac Electric Motor Co., Ltd., the China’s Supreme People’s Court found there was a close connection between the disputed patent and patents of the same family, and therefore held that the accounts made during the examination stage of the patents of the same family could be used to interpret the claims of the disputed patent.

 As can be seen, even if no priority is claimed between two applications, the mere fact that they share the same applicant or the applicants are related entities may suffice for one to be the basis for claim interpretation for the other. This rule is strictly implemented in China and should be well noted.

3. Defense strategy for patentees

According to Article 13 of “Interpretation”, if the patentee has attempted to amend and limit the scope or submit responses during examination and such amendments or responses have been rejected, then it is deemed that the amendments or responses do not result in the surrender of the technical means in question. This is slightly different from the U.S. where any action the patentee takes might be used to deduce his true intent. In China, when an action is rejected by the China National Intellectual Property Administration, the technical means is not considered to be surrendered.

4. The Court may invoke PHE of its own accord

Lastly, even if the alleged infringer does not argue for the application of PHE, the Chinese courts are entitled to make necessary limitations on the range of equivalents by invoking PHE of its own accord based on the facts that have been established and reasonably determine the scope of protection. This is a distinct difference compared with the U.S. and Taiwan.

Taiwan

1. Effects of prosecution history on claim interpretation and equivalent expansion

According to the most recent “Key Points for Patent Infringement Determination (2016)” (“Key Points”)[3], if any pre- or post-grant amendment or response made by the patentee during prosecution or enforcement of a patent limits the scope of protection, he may not recapture the surrendered rights using the DOE. Therefore, PHE is one of the limitations on the DOE.

 Furthermore, according to the “Key Points”, if an applicant or a patentee makes a limiting interpretation of the terms or technical features in the claims in order to overcome office actions or reasons for invalidation during prosecution or enforcement, then the file wrapper could also serve as the basis for claim interpretation.

2. Effects of prosecution history of related cases

With regard to claim interpretation, the “Key Points” provide that the intrinsic evidence for interpreting claims include the description, claims, drawings and file wrapper of the application, as well as the related cases and file wrappers thereof[4]. This is similar to the provisions in the U.S., illustrating that the basis for claim interpretation includes other cases with direct connection with the patent, but excludes other applications filed by the same applicant at the same or a different time.

 However, with regard to the DOE, according to Section 1.4, Chapter 4 of the “Key Points”, if a patentee applies for patents of the same invention in different countries, different scopes of protection might be obtained in different IP offices due to different examination system and guidelines in each jurisdiction. The limitations of PHE on patent rights may also vary based on the pre- or post-grant amendments or responses made in each jurisdiction. As a result, when determining whether PHE applies, in principle, the file wrapper of the corresponding foreign applications shall not be considered unless under special circumstances. This is different from the provision in the U.S.

 Accordingly, if the amendments or responses made in other jurisdictions are for the purpose of overcoming office actions in that particular jurisdiction and are not submitted to the Taiwan Intellectual Property Office (TIPO), then the file wrappers of those applications shall not be considered. If the same amendments are submitted to TIPO, however, it would be obvious that the applicant intents to expedite the examination process of the Taiwanese application by adopting the same reasons for amendment as the corresponding foreign applications. Hence, even if the applicant does not provide clear reasons for amendment for the Taiwanese application, PHE would apply.

Wisdom Suggested Strategies

To sum up, both the U.S. and China have more stringent regulations for patentees regarding PHE than those in Taiwan, and currently there have been fewer Taiwanese court decisions on the applicability of PHE.

 Patent owners are advised to carefully craft their response to IP offices only to the extent that office actions may be overcome, instead of explaining in full detail the other technical means of the invention. An excess amount of explanation on the technical contents that are not pertinent to the office action would possibly result in PHE in the subsequent enforcement actions. In addition, if the amendments are unrelated to patentability requirements such as the novelty, non-obviousness or clarity of the application, it should be clarified in the response lest PHE be invoked based on the reasoning that such amendments are for the sake of patentability.

For alleged infringers, invoking PHE is a useful defense strategy. Aside from obtaining the detailed prosecution history of the disputed patent, it is recommended to inspect the history of related cases as well, i.e. patents of the same family, the parent application of a divisional application, and the corresponding foreign applications. For applications in China, one could even take one step further and look into the patentee’s other cases in order to limit the claim interpretation of the disputed patent and the application of the DOE.