According to Paragraph 2 of Article 22 of the Patent Act, an invention that is novel but can be easily made by a person having ordinary skill in the art based on prior art shall not be patented.[1] That is, an invention must involve an inventive step to be eligible for patent protection. The Patent Examination Guidelines specify that the determination of whether a claimed invention involves an inventive step should follow these steps: (1) determining the scope of the claimed invention; (2) determining the disclosure of relevant prior art; (3) determining the technical level of a person having ordinary skill in the art; (4) determining the differences between the claimed invention and the prior art; and (5) determining whether a person having ordinary skill in the art could have easily accomplished the claimed invention based on the disclosure of the prior art and the common knowledge at the time of filing.[2] The Patent Examination Guidelines also provide various factors either negating or affirming inventiveness that should be taken into account when evaluating the non-obviousness of an invention.[3] Despite these principles and considerations, the determination of inventiveness remains a complex issue that often necessitates judicial clarification.

In the 2024 Tai Shang Zi No. 459 judgment, the Supreme Court underscored the importance of identifying a primary citation, applying the could-would principle, and considering auxiliary factors when assessing inventiveness. This judgment serves as a reference for the evaluation of non-obviousness.

The case involved a patent-infringement action brought by the appellant, the patentee of Invention Patent No. 420783 titled “Commandless Programmable Controller,” against the appellee. In response to the appellant’s claim for damages, the appellee cited multiple prior art references to argue that the disputed patent claims for a method for programing a controller were invalid. The Intellectual Property and Commercial Court (IPCC) determined that the disputed patent claims lacked an inventive step based on various combinations of the citations, concluding that no infringement had occurred. However, the Supreme Court found that the IPCC’s decision was legally flawed and inadequately reasoned, thereby vacating and remanding the case for further proceedings.

In the judgment, the Supreme Court provided guidance on the principles for determining non-obviousness:
“When applying to a specific case, one should not simply disassemble the invention into individual elements or steps and then rigidly compare them with prior art in combination or patchwork. Also, the determination of whether a skilled person would have easily accomplished an invention based prior art requires considering ‘obviously willing to try’ and ‘obviously willing to perform’ (could-would principle). In other words, the key factors in determining inventiveness are not only whether it is theoretically possible to successfully carry out the invention but also whether inducements, specific factual bases or motivations existed that would have prompted a skilled person to develop and succeed. Furthermore, it should be noted that the determination of inventiveness requires: first identifying a ‘closest prior art’ (primary citation), which is a ‘single evidential document’ that could serve as the best foundation for research and development and is most likely to prompt an inventor to accomplish the invention starting from the technical information disclosed therein, and then comparing it with the technical content of the claimed invention, so as to prevent the determination of inventiveness from rigidly assessing prior art in patchwork or combination, thereby avoiding the fallacy of hindsight.”[4]

The judgment highlights the necessity of a primary citation in evaluating non-obviousness. According to the Patent Examination Guidelines, 
“Citations suitable for reasoning in the determination of inventiveness are selected from relevant prior art, and one of the citations is selected for comparison with the technical content of the claimed invention. The single citation serving as the basis for comparison is referred to as the ‘primary citation,’ and the remaining citations used in reasoning are referred to as the ‘other citations.’”[5]
A primary citation thus serves as the basis for comparison between an invention and prior art, helping to define the technical gap between the invention and the prior art, thereby preventing hindsight bias in the assessment of non-obviousness. 

The judgment also emphasized the “could-would principle,” a principle draws on the European patent practice. The Guidelines for Examination in the European Patent Office explain: 
“In the third stage the question to be answered is whether there is any teaching in the prior art as a whole that would (not simply could, but would) have prompted the skilled person, faced with the objective technical problem, to modify or adapt the closest prior art while taking account of that teaching, thereby arriving at something falling within the terms of the claims, and thus achieving what the invention achieves (see G-VII, 4). In other words, the point is not whether the skilled person could have arrived at the invention by adapting or modifying the closest prior art but whether the skilled person would have done so because the prior art provided motivation to do so in the expectation of some improvement or advantage (see T 2/83).”[6]
 
This principle reinforces the idea that when denying the non-obviousness of an invention, it is not sufficient to show that a person having ordinary skill in the art could have arrived at the invention based on prior art. Rather, the key question is whether a person having ordinary skill in the art would have been taught, guided or motivated by the prior art to achieve the invention. This would demand a more rigorous analysis when rejecting an invention for lack of non-obviousness.

Furthermore, the Supreme Court addressed the role of auxiliary factors in the assessment of inventive step:
“The so-called skilled person refers to a virtual person, and the date for determining inventiveness is often far removed from the trail of an infringement case, which leads to practical difficulties in the determination and is prone to cause subjective bias. Thus, objective facts should be used to ensure the appropriateness of the determination. Auxiliary factors considered in the examination of inventiveness help determine the degree of technical contribution of an invention from the perspective of the relationship between the invention and the market, including the invention producing unexpected effects, solving long-standing problems, overcoming technical prejudices, achieving commercial success and so forth. Where auxiliary evidence presented by litigants is likely to be explanatory, pertinent and objective for the determination of inventiveness, it should be investigated and considered so as to reconstruct the environment and reality at the time of filing of the invention as far as possible.”[7]
This reinforces the view that auxiliary factors can play an important role in demonstrating the non-obviousness of an invention. Ample evidence showing an invention producing unexpected effects, solving long-standing problems, overcoming technical prejudices and achieving commercial success may substantiate the claim that the invention was non-obvious in view of prior art.

In conclusion, the judgment rendered by the Supreme Court shows the importance of avoiding hindsight bias in the determination of inventiveness. The Supreme Court rejected the IPCC’s reasoning, which relied on combinations of prior art references, and emphasized the necessity of a primary citation, the could-would principle and the auxiliary factors in the evaluation of non-obviousness. This case highlights that the assessment of inventive step is a nuanced and hypothetical question that must be addressed with careful legal and technical considerations to avoid hindsight bias. As the litigation unfolds, further observations may be required, but the Supreme Court’s views on primary citation, could-would principle and auxiliary factors provide valuable insights for applicants or patentees seeking to defend the inventive step of their inventions.

[1]  Referring to Paragraph 2 of Article 22 of the Patent Act
[2] “The Patent Examination Guidelines,” pages 2-3-17 to 2-3-18
[3] “The Patent Examination Guidelines,” pages 2-3-19 to 2-3-26
[4] “The 2024 Tai Shang Zi No. 459 judgment,” pages 5 to 6
[5] “The Patent Examination Guidelines,” page 2-3-18
[6] “Guidelines for Examination in the European Patent Office,” pages 821 to 822
[7] “The 2024 Tai Shang Zi No. 459 judgment,” page 8