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Estoppel Doctrine in China's Patent System



When I was participating in a webinar as a speaker recently, a listener asked me, is there "Estoppel" in China? I think this question is representative, so I have summarized this short article to introduce the estoppel doctrine in China.

In China, we indeed have estoppel doctrine, but it is not provided in the Patent Law. However, in the Judicial Interpretations of the Supreme People's Court (SPC) about hearing the patent infringement litigation, the estoppel doctrine has been stipulated many times.

The Judicial Interpretation stipulates that "where patent applicants or patentees have abandoned technical solutions through amendments to claims, descriptions or through statements of opinions (responses) in the patent granting or invalidation procedures, the patentees include them in patent infringement disputes, the people's court shall not support."

The Judicial Interpretation also stipulates that the court may use other patents that have a divisional application relationship with the asserted patent, their patent file wrappers, and their effective patent granting and post-granting decisions to construe the claims of the asserted patent.

Patent file wrapper includes written responses submitted by patent applicants or patentees during the patent prosecution or post-granting proceedings, office actions and effective decisions issued by the CNIPA and its Patent Reexamination and Invalidation Department (PRID), meeting records, oral hearing records, etc.

When determining whether to grant a patent right, whether the patent right is valid, and whether it constitutes a patent infringement, the patent applicant or patentee's interpretation of the technical features in the claims should be consistent. The applicants or patentees are not allowed to make narrow interpretations of claims in the process of patent prosecution and invalidation procedure in order to obtain patent rights or maintain the validity of the patent, and then make broad interpretations of claims in the litigation in order to prove the infringement.

In patent infringement litigation, the patentee should be prohibited from re-incorporating the explicitly abandoned technical solutions into the scope of patent protection.

The core concept of the estoppel doctrine is based on the principle of honesty and trustworthiness, to prevent the patentee from "benefiting at both ends" in the prosecution and litigation procedures, thereby protecting the public's interests.
The Judicial Interpretation also stipulates that if the right owner proves that the applicant's or the patentee's restrictive amendment or statement to the claims, descriptions, and drawings in the patent granting and post-granting proceedings are explicitly denied, the people's court shall affirm the amendment or statement did not lead to the abandonment of the technical solution.

The application of the estoppel doctrine has been reflected in many judicial precedents in China. E.g.

In the infringement case of " Deepquant Ai Technologies (Deepquant) and Jiugong Audio Mixing Company(Jiugong) v. Beijing Sogou Technology (Sogou)" concluded by the SPC in 2019, the court held that the assertion of Deepquant and Jiugong that the technical features (d) contains the situation of partly display is to include the technical solution abandoned in the patent prosecution into the scope of patent protection, which is contrary to the "estoppel doctrine" stipulated in the judicial interpretation, and thus the court does not approve it. The court did not support the patentee's assertion.

In the patent infringement litigation case of "Shanghai Haohe Electric Appliance (Haohe)and Shanghai Mingwei Electronics (Mingwei) v. Zhongshan Towel Butler Technology (Towel Butler)" concluded by the SPC in 2020, the SPC referred to the relevant content of the previous invalidation decision on the asserted patent and ruled that" the face cover is provided with vent holes" and "the middle cover is provided with a number of vent holes" of the asserted patent should not be regarded as equivalent features according to the doctrine of estoppel. Therefore, the SPC concluded that the alleged infringing technical solution did not fall into the protection scope of claim 1 of the asserted patent.

In summary, there are three conditions for the application of the estoppel doctrine in China.

1. The patentee has abandoned one or several specific technical features in the patent granting or post-granting procedure.

2. The technical features abandoned by the patentee in the patent granting or post-granting procedure are those that constitute the “same” or “equivalent” technical features to the alleged infringing product in the infringement litigation.

3. The restriction or abandonment of the technical features made by the patentee has not been explicitly denied and has been recorded in the patent file wrapper (for example, recorded in the responses to the Office Actions).

Ok, above, we discussed the estoppel doctrine in China’s patent litigation. It is worth noting that estoppel doctrine is also applicable in the invalidation procedure after granting, that is, in the invalidation stage, the interpretations of the patentee should be consistent with those in the prosecution stage. Therefore, the applicant must consider the influence of the estoppel doctrine on the subsequent procedure when making responses or amendments during patent prosecution.

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