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What are the different defences in a patent infringement claim?

Deqiang Zhu of CCPIT examines the different defences available in a patent infringement claim, including the invalidity defence, the non-infringement defence and the prior art defence

With the development of industry and technology, patent infringement disputes have become very common as competitors strive to occupy as big a proportion of the market share in the relative industry as possible. For a business entity, attention should be paid not only to the enforcement of its patent to stop a competitor infringing upon the patent but also to defending against the enforcement of a patent by a competitor. For a business entity involved in a patent infringement lawsuit, there are some defences to consider to protect its lawful rights and interests against the plaintiff's allegation of patent infringement. This article aims to give a brief introduction to some of the optional defences, strategies and procedures for a defendant in a patent infringement lawsuit.

Invalidity defence

The invalidity defence is one of the most commonly used defences in a patent infringement lawsuit. It is also frequently the first defence employed. Two goals may be achieved by using the invalidity defence i.e. having the patent invalidated completely or partly and making the claims of the patent further limited or narrowed down in scope and/or clarifying the protection scope of the claims of the patent.

To use the invalidity defence, an invalidation request against the patent is filed with the Chinese Patent Office, rather than simply arguing invalidity of the patent before the court handling the patent infringement lawsuit. It is better for the defendant if the invalidation request is filed within the time limit for responding to the plaintiff's complaint. With the invalidation request filed with the CPO in a timely manner, the defendant may file a request for staying the trial of the patent infringement case with the court. If necessary, the court may stay the trial of the patent infringement case in order to avoid a scenario where the court makes a finding of infringement, but later the CPO makes a decision declaring the patent invalid. According to Chinese judicial practice, if the CPO makes a decision invalidating a patent asserted by the plaintiff in the patent infringement lawsuit, the court may simply dismiss the lawsuit. However, the patent right owner may appeal the CPO's decision invalidating the patent to the Beijing Intellectual Property Court in the first instance and further appeal to the Supreme People's Court in the second instance. If the CPO's decision invalidating the patent is finally revoked by the court, the patent right holder may file the lawsuit alleging patent infringement again.

There is a list of reasons on the grounds of which a request for invalidation of a patent right can be filed. A patent right can be declared invalid for any of the following reasons: lack of novelty; lack of inventiveness; lack of practical applicability; an invention that contravenes any law or social moral or that is detrimental to public interests; violation of confidentiality examination; non-conformity with the definition of invention, utility model or design; belonging to subject matter not eligible for a patent right; amendments going beyond the scope of the initial disclosure; lack of support by the specification or failure to clearly define the protection scope; failure to record technical features indispensable for solving the technical problem; double patenting etc. Among these reasons, lack of novelty and lack of inventiveness are the most commonly used ones, but some of the remaining reasons such as lack of support by the specification, failure to clearly define protection scope, amendments going beyond the scope of initial disclosure and failure to record technical features indispensable for solving the technical problem are also useful in some cases.

Sometimes it may be difficult to find a prior art document of category X which deprives claims of a patent of novelty, and prior art documents of category Y which in combination deprive the claims of the patent of inventiveness and the claims of the patent are not declared invalid on the ground of lack of novelty or inventiveness. There is still a possibility that through the procedure of an invalidation request against the claims of a patent on the basis of the optional reasons, the claims of the patent are further clarified or narrowed down in protection scope either by amendments to the claims or observations about the invention creation claimed in the patent made by the owner of the patent right during the procedure of examination of the invalidation request.

Non-infringement defence

For the non-infringement defence, the all elements rule should be considered firstly. To find infringement of a product or a method based on a patent right necessitates that the product or method contains technical features identical or equivalent to all the technical features described in the claim of the patent. No infringement of the product or method can be found if one or more of these technical features in the claim of the patent is not identical or equivalent in the alleged infringing technical solution.

Secondly, the doctrine of equivalents should be considered. It is not unusual that the alleged infringing product or method differs from the technical solution defined in the claim of a patent and one or more technical features of the latter are not present in the former. In such a case, the doctrine of equivalents should be considered, and the crucial issue is whether there is an infringement within the framework of the doctrine of equivalents, i.e. whether the alleged infringing product or method has a corresponding technical feature which is determined as equivalent to the technical feature of the technical solution of the claim. According to the judicial interpretations on patent infringement case trials issued by the Supreme People's Court, an equivalent technical feature in an alleged infringing product or method means a feature that uses substantially identical means, realises a substantially identical function and achieves a substantially identical effect as the technical feature included in the technical solution of the claim of a patent right. Moreover, while this feature is not present in the alleged infringing product or method, an ordinary technician of the pertinent field can conceive of it easily without creative work when the alleged infringement occurs. In short four requirements i.e. triple substantial identicalness plus easy association should be met.

With the non-infringement defence, the first step is to find at least one technical feature of the technical solution of a claim of a patent right that is not used by the alleged infringing product or method. The second step is to argue that at least one of the four requirements are not met, while the plaintiff argues to the contrary. If successful, one such technical feature solves the whole lawsuit.

Thirdly, file wrapper estoppel may be considered, in arguing for non-infringement based on the doctrine of equivalents. According to the judicial interpretations of the Supreme People's Court, where a patent right holder reclaims a technical solution, which the patent applicant or patentee has abandoned through an amendment of claims or specification or through observations in the patent prosecution or invalidation procedure, into the scope of protection of a patent in a patent right infringement dispute case, the people's court shall not support it. Using this principle, if the patent right holder argues that a technical feature in the alleged infringing product or method, which differs from and corresponds to the technical feature in the technical solution of the claim of the patent and which has been abandoned during the patent prosecution or invalidation procedure, is equivalent to that particular technical feature in the technical solution of the claim of the patent, this should not be supported.

Attention should be drawn to a principle which limits the application of the file wrapper estoppel. According to the interpretations of the Supreme People's Court, where a patentee proves that any restricting modification or observations to the claims, specifications and the attached drawing that have been made by the patent applicant or patentee in the prosecution of a patent or during an invalidation examination procedure of the patent have been explicitly negated, the people's court shall determine such modification or observations do not lead to the abandonment of the technical solution. In view of this, all of the documents in the file wrapper should be studied completely and carefully when file wrapper estoppel is to be applied.

Prior art defence

According to the Chinese Patent Law, in a dispute over patent infringement, if the accused infringer has evidence to prove that the technology or design he exploits is an existing technology or design, no patent infringement is constituted. According to the judicial interpretations of the Supreme People's Court, if all the technical features which are alleged to fall into the scope of protection of a claim of a patent are identical to or are not substantively different from the corresponding technical features of an existing technical solution, the people's court shall determine the technology implemented by the alleged infringer as an existing technology. It is known that for the prior art defence, the comparison is made between the alleged infringing technical solution and the technical solution in the prior art with respect to the technical solution of a claim of a patent, rather than a direct comparison between the technical solution in the prior art and the technical solution of a claim of a patent, which is made in examination of novelty of the claim of the patent.

Prior use defence and legal source defence

Prior use defence and legal source defence are not so commonly used as the above three defences. For prior use defence, if the defendant has made or used a product or a process, respectively, which falls in the protection scope of a patent, or has made necessary preparations for making such a product or using such a process prior to the date of application of the patent, the defendant may continue to make such product or use such a process within the original scope. This is not considered infringement of the patent. However, continuing to make the product or using the process is limited to the original scope of the defendant's making and using before the application date of the patent and no expanding of operation scale is allowed. This is clearly not the most preferable defence for the defendant.

For the legal source defence, whoever uses or sells a patented product without knowing that the product was produced and sold, without permission of the patentee, or a product directly obtained from a patented process for the purpose of production and business operation is not required to bear the liabilities for compensation provided that he can prove that the product is obtained from a legal source. For this defence, the defendant should provide a complete chain of evidence to prove the products are obtained from a third party in a normal business mode and the criteria for this evidence is strict. If this defence is supported, the seller of the product should still cease to sell the product any more, but the user may continue to use the product if the user of the alleged infringing product produces evidence to prove that it has paid reasonable consideration for the product.

Given above is a basic introduction to some of the optional defences that may be considered by a defendant in a patent infringement lawsuit. In practice, the situation is usually complicated, and a comprehensive study of the case is necessary to make a strategy to defend the patent infringement lawsuit in order to achieve the best possible outcome.


Deqiang Zhu

Mr Zhu is a senior patent attorney in the patent litigation department at CCPIT and has rich experience in both patent prosecution and litigation with 20 years of experience in the IP field. His clients include both internationally well-known business entities and domestic industrial giants. Now Mr Zhu focuses on litigation, consultation, invalidation, and administrative proceedings relating to disputes regarding patents and unfair competition. He also has expertise in ADR. Among the cases Mr Zhu has handled, six were elected as key cases by the Supreme People's Court, the Higher Courts of Beijing and Tianjin, Shanghai IP Court, and the Beijing IPA from 2013 to 2018.

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