How to determine closest prior art in patent disputes

In a patent invalidation procedure in China, inventiveness is the main point of a dispute determining whether an invention patent will be upheld. In determining inventiveness, the first consideration is whether the invention is not obvious to a person skilled in the art, and with respect to the method of determining whether an invention is not obvious, China’s Patent Examination Guidelines set out three steps.

The first step is to determine what prior art is the closest to the invention; the second step is determining the features that distinguish the invention from the closest prior art and, on the basis of such distinguishing features, determining the technical problem that the invention resolves; and the third step is determining whether any prior art contains technical teaching that would motivate a person skilled in the art to apply the distinguishing features to the closest prior art to resolve the technical problem that the invention is to resolve.

Although these rules have also been called the three-step method, the first of the three steps, namely determining the prior art that is the closest to the invention, is usually not scrutinised by the adjudicating authorities. This has resulted in a great deal of arbitrariness in the selection of the closest prior art, giving rise to unreasonable outcomes in some cases.

Zheng Feng is a senior associate at Wanhuida Peksung IP Group