Two major defences in patent infringement cases

By Chen Jianmin, Gaowo IP Law Firm
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Can a defendant use the ‘prior art defence’ and the ‘patent invalidation defence’ interchangeably?

When the patentee files a patent infringement lawsuit against a defendant, the defendant often adopts a “prior art defence” or “patent invalidation defence”. This raises the question of whether the two different opinions can be replaced by each other, or whether the court can determine that the plaintiff’s patent can be invalidated directly after the defendant filing the prior art defence.

陈建民, Chen Jianmin, Senior consultant, Gaowo Law Firm
Chen Jianmin
Senior consultant
Gaowo IP Law Firm

“Prior art defence” usually means that once the patentee files a patent infringement lawsuit before the court, the defendant files a defence claiming that the technology they used in its own product or the method is a prior art that was public before the date of the patent application, and thus the technology used in its own product or scheme is consistent with the prior art. This is generally called the prior art defence.

“Patent invalidation defence” means that after being sued for patent infringement, the defendant claims that the plaintiff’s patent does not meet the conditions for granting patent right as provided in the Patent Law, and then files a patent invalidation with the China National Intellectual Property Administration. If the invalidation request can be supported after the examination by the administration, the patent right will be invalidated in whole or in part, thus the patentee’s infringement lawsuit will fail.

As long as one of these two arguments can be supported, the defendant’s defence against the patentee will win.

However, when adopting the two mentioned defences, attention should be paid to the difference between them. First, the prior art defence compares the defendant’s product or method with the prior art in order to prove that the defendant’s product or method is the same, or substantially the same, as the prior art; while the patent invalidation defence compares the literature of the plaintiff’s patent and the prior art, which aims to prove that the plaintiff’s patent does not meet the conditions for granting a patent right and should not be protected.

Second, the prior art defence is used to prove that the defendant’s product does not fall into the scope of the patentee’s patent protection, while the patent invalidation defence is used to prove that the plaintiff’s patent should not be protected.

Therefore, when filing the non-infringement defence, the defendant should determine the defence means according to their evidence.

Recently, the Supreme People’s Court (SPC) made a second-instance ruling on the utility model patent infringement case of Qingdao Bellinturf v Jiangsu CCGrass (2020), which drew a lot of attention. In the first instance of the case the defendant, Jiangsu CCGrass, claimed that the plaintiff’s patent had been publicly used before the application date, and that the user was the defendant itself. Therefore, the patent right should not be approved. The defendant also submitted the literature of the prior art.

Meanwhile, because the product sold by the defendant was older than the plaintiff’s, both the prior art defence and the patent invalidation defence were put forward. In the first instance, the judgment held that the plaintiff’s patent was not creative compared with the comparison literature, thus the plaintiff’s patent right was unstable, and the plaintiff could not file an infringement litigation based on it. Therefore, all the claims of the plaintiff were rejected.

The plaintiff refused to accept the first-instance judgment and appealed to the SPC. In the second instance, the SPC held the opinion that if the defendant had enough evidence to prove the plaintiff’s patent right was obviously invalid, the court did not mean not to examine it in any sense.

However, under the current legal framework, the patent administration department has the right to examine whether the patent right is valid or invalid. In the trial of patent infringement cases, the court only carries out limited examination on the specific challenge or defence against the patent validity that has been put forward by the accused infringer, the purpose of which is to examine whether the patentee has the basis to appeal, but the court could not make a judgment on the validity of the patent right.

However, the first-instance judgment made a decision directly, which recognised that the plaintiff’s patent was invalid and rejected the plaintiff’s claim, which is beyond the current trial authority. The first instance court shall examine the evidence of the prior art defence that has been put forward by the defendant, and determine whether the prior art defence is established or not. Therefore, the SPC made a second-instance ruling revoking the first-instance judgment, and made a new judgment for its retrial.

Based on this case, it can be seen that after being accused of patent infringement, if the defendant has sufficient evidence to prove that the plaintiff’s patent should be declared invalid, it can put forward a defence to the court. Meanwhile, the defendant should also file a patent invalidation with the administration. Otherwise, the defendant can only compare the prior art with its own product or method, and prove that its usage is the prior art. Although the prior art defence and the patent invalidation defence are both means of defending non-infringement, their purposes are different and cannot be replaced by each other.


Chen Jianmin is a senior counsel at Gaowo IP Law Firm. She can be contacted on +86 10 8287 3665 or by email at jianminchen@gaowoip.com