The case involves the issue of the proof of evidence when defendants use public evidence to claim prior art defenses in patent infringement litigation. The defendant KAIYING Machinery Technology Co., Ltd. asserted that before the filing day of the accused patent, Company A sold a vertical VCP electroplating equipment to Company B for its use. The vertical VCP electroplating equipment was completely consistent with the allegedly infringing products, and the sale/purchase between the two constitutes a public disclosure by the meaning of the patent law, according to which the accused infringing product is the use of the existing technology, which consider as non-infringement. In the judgment of second instance, Suzhou Intermediate People's Court found that the terms of sale and purchase confidentiality stipulated in the sales and purchase contract between Company A and Company B submitted by the defendants, and remain confidential regarding the technical contents involved in the sale and purchase of both parties. In addition, from the content of the (2014) Sukun Zhengxin No. 3625 notary certificate submitted by the defendant, the equipment sold by Company A to Company B has always been in the factory of Company B, which is a closed factory, and equipped with a gate and security room, outsiders cannot enter the plant. The factory security room clearly required permission before entering, and posted a ban on the equipment for taking pictures. All of this explained that Company B has been following all the terms of confidentiality in the actual use of the equipment process and taken security measures to make the device in a confidential state, therefore the public cannot know the technical content of the device. Accordingly, the second trial of Suzhou Intermediate People's Court determined that the sale and purchase of Company A and Company B did not constitute an open disclosure in the meaning of the Patent Law, and the defendant's existing technical defense was not substantiated.