‘Clear and convincing evidence standard’ applies to prior art taking the form of physical objects

On 2 September 2019 the IP Tribunal of China Supreme People’s Court handed down Judgment Zui Gao Fa Zhi Xing Zhong No 1 (2019), confirming that a physical mobile phone is an eligible prior art in assessing the novelty and inventiveness of litigious patent ZL200810116190 8, titled “a method and a device for deleting information during an input process”. The IP Tribunal clarified that a party that asserts a physical object as prior art is obligated to specify the asserted prior technical solution and the relation between this and the physical object, and to prove or demonstrate that the public can intuitively obtain the technical solution from the physical object.

This is the first patent administrative case appealed before the Supreme People’s Court IP Tribunal and has been selected as one of 36 exemplary cases concluded by the tribunal in 2019.


Beijing Sogou Technology Development Ltd filed a civil lawsuit before the Beijing IP Court, in which it claimed that Baidu Network Ltd’s input method software infringed Sogou’s Patent ZL200810116190 8.

In response, Baidu filed an invalidation petition before the Patent Reexamination Board (which was later incorporated into the China National IP Administration) against the patent at issue, arguing that the patented claims were devoid of novelty or inventiveness over the physical mobile phones launched before the application date on 4 July 2008, among other things. In the hearing, Baidu demonstrated the operation and function of mobile phones acquired through notarised purchase.

Claim 1 of the patent at issue included the following internal steps performed by the background program:

“1. A method for deleting information during an input process, characterized in that the input area includes a code input area and a character screen area, and the method includes:

When the input focus is in the code input area, receiving the instruction of the delete key to delete the code that has been entered;

When all the codes have been deleted, suspending the receiving of the instruction of the delete key; and

When the key state of the delete key meets a preset condition, continuing the receiving of the instruction of the delete key to delete the character in the character screen area.”

On 2 February 2018 the Patent Reexamination Board maintained the validity of the patent at issue. The decision held that the mobile phones that Baidu had cited were not eligible prior art, and therefore refused to further evaluate the novelty and inventiveness over them. The decision reasoned that notwithstanding the demonstration of input function through user interface, the mobile phones failed to prove how the background program cooperates with the phone hardware and what definite solution is adopted to achieve the input function.

On 29 May 2018 Baidu initiated an administrative lawsuit before the Beijing IP Court.

Court decision

On 28th January 2019 the first-instance court revoked the Patent Re-examination Board’s decision, holding that there is no strict requirement on how definitely prior art should be disclosed, thus the board should not cite indefinite disclosure to deny the eligibility of a mobile phone as prior art.

The second-instance court (the IP Tribunal of the Supreme People’s Court) upheld the conclusion of the first-instance judgment, finding that the mobile phones were eligible prior art in assessing the novelty and inventiveness of the patent at issue. The IP Tribunal added that, during the course of the operation, the phone’s user interface indicated that the background program inevitably included the step of receiving the delete key instruction, so as to delete the input code in response to the instruction of the delete key. Here, the user interface could uniquely correspond to the background program. The IP Tribunal underlines that any party citing a physical object as prior art is obligated to specify which technical solution is cited as prior art, among the solutions reflected in physical object, and to prove or to demonstrate that the asserting technical solution could be intuitively obtained from the physical object.


The ‘direct and beyond all doubt’ criteria that the Patent Re-examination Board used in its fact-finding proceeding for prior documentary evidence is analogous to the ‘beyond reasonable doubt’ standard applied in criminal procedure. The Patent Examination Guidelines provide that the technical content disclosed by a reference document “includes not only those technical contents expressly described in the reference document, but also those implied technical contents that can be derived directly and unambiguously from the disclosure by a person skilled in the art”, and “the contents inferred from the drawings, and the dimensions with their relations measured from the drawings without any written description cannot be taken as the contents of disclosure”.

Prior use evidence has come into the spotlight in patent invalidation procedures that involve invention patents, especially in the software industry. The petitioner of the invalidation proceeding – usually the accused infringer in the associated civil suit – would be overburdened with arduous burden of proof, if the proof standard for documentary evidence is applied for the physical object. In order to meet the “direct and beyond all doubt” criteria, the accused infringer Baidu had to determine the internal step of the physical cellphone, which could be technically impracticable or expensive, if possible at all. However, in the associated civil suit, according to the high probability proof standard, the burden of proof would shift to Baidu if Sogou preliminarily proved the infringement of the patent by deducing the internal step of the background program from the user interface of the accused software.

The final judgment found patent infringement of the Baidu input method software, based on the reasoning that the patentee proved that the Baidu software shares the same function of the patent and possibly includes the internal step recited in patent claim, yet Baidu failed to prove the difference between the internal step of the accused software and the patent.

Addressing the burden of proof allocated to the accused infringer in the patent invalidation procedure, the IP Tribunal clarified the clear and convincing evidence standard for prior arts taking the form of physical objects. Still, this standard is stricter than the high probability proof standard adopted in civil proceedings, probably weighing up the impact of patent invalidation procedure over public interests.

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