Introduction

During substantive examination of a patent application, the patent examiner needs to make a search, and find out the closest prior art as the basis for determining whether a claimed invention has prominent substantive feature.  The closest prior art is important for obtaining a conclusion of inventiveness.  When the patent examiner obtains a conclusion that an invention as claimed is obvious over the closest prior art, as a patent applicant or an agent for a patent applicant, do we need to study whether the selection of the closest prior art is right?  That is a question this article intends to solve. 

Role of closest prior art in three-step method for evaluating inventiveness

Three steps are usually followed to determine whether a claimed invention is obvious as compared with the prior art.  The first step is to determine the closest prior art.  The closest prior art is defined in Chinese Guidelines for Patent Examination as “a technical solution in the prior art which is the most closely related to the claimed invention”, it is the basis for determining whether or not the claimed invention has prominent substantive features.  So the closest prior art is certainly important for evaluating inventiveness. 

When an examiner estimates whether a claim has inventiveness, he/she would firstly make a search and find the closest prior art, and would then follow the next two steps to study whether the claimed invention is obvious.  The next two steps are: determining the distinguishing features of the invention as compared with the closest prior art and the technical problem actually solved by the invention on the basis of the technical effect of the distinguishing features; and determining whether or not the claimed invention is obvious to a person skilled in the art. 

The selection of the closest prior art is of significance, since it is the starting point for determining the obviousness.  If the examiner incorrectly takes another prior art as the basis, which is not the closest, he/she may obtain an incorrect conclusion of a claimed invention possessing inventiveness. 

Relationship between closest prior art and obviousness

Inventiveness actually depends, to some extent, on the distance from the closest prior art to the claimed invention.  The shorter the distance from the closest prior art to the claimed invention, the easier a person skilled in the art could obtain the claimed invention, and accordingly the easier the conclusion of obviousness is obtained. 

Since the closest prior art is a technical solution which is most closely related with the claimed invention, if using another prior art rather than the closest prior art as the basis, the distance from the starting point to the claimed invention may be extended, and thus it may be easier to get a conclusion of possessing inventiveness, compared with using the closest prior art as the basis. 

Specifically, if an examiner uses another prior art rather than the closest one as the basis and get a conclusion of the claimed invention being not obvious, it is possible that the claimed invention is actually obvious on the basis of the closest prior art. 

However, if an examiner uses another prior art rather than the closest one as the basis and get a conclusion of the claimed invention being obvious, the claimed invention would generally be still obvious on the basis of the closest prior art. 

From the above analysis, we can conclude that the selection of the closest prior art is important for obtaining the conclusion of inventiveness.  Nevertheless, if a conclusion of a claimed invention being obvious can be obtained on the basis of another prior art (although not the closest prior art), the claimed invention would be also obvious based on the closest prior art.  In other words, if a claimed invention is obvious on the basis of another prior art which is relevant with the claimed invention, we could get a direct conclusion that the claimed invention is obvious on the basis of the closest prior art. 

Would arguments for changing closest prior art help?

As per our patent practice, a circumstance often occurs – the examiner uses two prior arts relevant with the claimed invention to get a conclusion of the claimed invention being obvious.  For example, the conclusion of obviousness is obtained on the basis of prior art A (considered by examiner as the closest one) in combination with prior art B.  However, if we note that prior art B is more closely relevant with the claimed invention compared with prior art A and should be considered as the closest prior art, can we argue the selection of the closest prior art by the examiner is incorrect?  Do you think such arguments would be helpful for inventiveness?  

It is a pity that the answer may be negative.  For such a situation, we just have a real case receiving a court decision.  In the court decision, the court does not pay attention to which one (prior art A or prior art B) is “the most closely related” to the claimed invention, but only focuses attention on whether the conclusion of obviousness is correct or not based on prior art A. 

Why do we hope to change the closest prior art?

Before introducing the court decision, let’s see why we hope to change the closest prior art.  Of course, there may be several different reasons, for example, the closest prior art selected by the examiner is not in the same or similar technical field with the claimed invention, or it is not technically related with the claimed invention at all.  Our article is to only discuss such a situation - two cited prior arts are both in the same technical field and technically related with the claimed invention, we hope to use another prior art, rather than the one selected by the examiner, to be the closest prior art. 

For example, as shown in the following table, a claimed invention is composed of two technical features, i.e., technical feature 1 and technical feature 2, which are separately disclosed by prior art A and prior art B. 

The examiner selects prior art A as the closest prior art, and comparing the invention with the closest prior art A, the distinguishing feature of the invention is thus technical feature 2.  When prior art B discloses the feature 2 and the function thereof, the examiner could conclude that the claimed invention is obvious. 

However, we hope to take prior art B as the closest prior art.  Based on the closest prior art B, the distinguishing feature of the invention is technical feature 1.  And, if prior art A only discloses technical feature 1 and does not disclose the function thereof, it would be not obvious to obtain the claimed invention. 

Please see the following illustrations.  The examiner follows the evaluation process I and we follow the evaluation process II. 

Comparing the two processes of evaluation, we could find that there are some differences therebetween.  What most interests us is that even if prior art A does not disclose the function of feature 1, a conclusion of obviousness could be obtained by the first evaluation process; However, only if prior art A discloses the function of feature 1, a conclusion of obviousness could be obtained by the second evaluation process.  In other words, when prior art A does not disclose the function of feature 1, we could get two, opposite, conclusions through the evaluation processes I and II, and obviously the second evaluation process may be beneficial for the applicant.  That is why we hope to use prior art B as the closest prior art. 

However, in patent practice, if the examiner already gets a conclusion of obviousness on the basis of a relevant prior art, it would be almost impossible to convince him/her to use another prior art as the closest prior art so as to get an opposite conclusion. 

What is opinion of court for changing prior art?

As mentioned above, the court believes that if a claimed invention is obvious on the basis of a relevant prior art (no matter whether it is the closest one), a conclusion of the claimed invention being obvious can be directly obtained.  The court provides a powerful explanation to support its opinion, which is summarized as below. 

The three-step method is used for estimating inventiveness, which essentially lies in matching the judgment of inventiveness with the objective law of creating an invention in practice.  The closest prior art identified in the first step corresponds to the starting point in creating an invention in practice.  Since it is only the starting point for invention, it is not a necessary condition itself for granting a patent.  Therefore, it is only possible for the closest prior art to play an indirect role by influencing the conclusion of inventiveness judgment.  That also means even if the closest prior art identified for a specific case is not “the most closely related to” the claimed invention, as long as the conclusion of inventiveness judgment based on this prior art is not inappropriate, the conclusion of the claimed invention being obvious would be correct. 

Under realistic circumstances, an invention is generally created by a technician following a process of: discovering certain defects in the existing technology and getting a motivation for improving the existing technology, and on this basis, obtaining the technical solution of the invention through intellectual labor.  The three-step method of inventiveness judgment just corresponds to the above process.  The closest prior art identified in the first step corresponds to the starting point for creating an invention in practice.

The Guidelines for Patent Examination stresses that the starting point for inventiveness judgment should be the "closest" prior art (that is, a technical solution most closely related to the claimed invention), because the purpose of the inventiveness system lies in ensuring, as far as possible, only the inventions having a technical contribution to the existing technology as a whole could be granted.  The extent, to which the purpose of the inventiveness system is achieved, is closely related to the selection of the prior art as a starting point for inventiveness judgment.  In general, the closer the relationship between the selected prior art and the claimed invention, the easier the person skilled in the art will get the claimed invention from this prior art, accordingly, the more likely the claimed invention is deemed not to have inventiveness.  Just because of this, the Guidelines for Patent Examination provides the relevant reference factors for the determination of the closest prior art, the purpose of which is to provide a valuable guidance for examiners to ensure as far as possible that only those inventions that truly have a technical contribution to the existing technology as a whole could be granted, and thus to improve the quality of the granted patents.

The reason, why the applicant argues that the determination of the closest prior art is incorrect, is that the applicant intends to prove that the claimed invention has inventiveness by replacing the closest prior art.  But in fact, as above mentioned, the purpose of the inventiveness system is to ensure that the claimed invention has inventiveness over the “whole” of prior art, rather than one or more specific prior arts.  Thus, even if the claimed invention is inventive on the basis of prior art B combined with prior art A, the application should not be granted, as long as the conclusion of the claimed invention being obvious on the basis of prior art A and prior art B is correct.  Based on this, the Court does not pay attention to which one (prior art A or prior art B) is “the most closely related” to the claimed invention, but only focuses attention on whether the conclusion of obviousness is correct or not based on prior art A as the closest prior art. 

Suggestions

From the above discussions, we suggest that when an examiner obtains a conclusion of a claimed invention being obvious on the basis of a relevant prior art, we could focus our attention on whether the examiner’s analysis on obviousness is right or not.  Particularly, we could pay more attention to the second and third steps in the three-step method, but there seems no need for us to analyze whether the selection of the closest prior art by the examiner is right or not.