Different from U.S. Concepts of POSITA/PHOSITA, Proving “Common General Knowledge” Under German and the EPC Law: Why Proving Common General Knowledge Matters—and Why It’s Harder Than It Looks

1. Common General Knowledge in German/EPC law is narrower than U.S. POSITA knowledge: Unlike in the U.S., where the skilled person is presumed to have broad knowledge in the field, German and EPO law require strict proof that the knowledge was truly “common general knowledge” at the priority date.
   
   
2. Acceptable evidence of common general knowledge has limited scope: Only textbooks, handbooks, monographs, encyclopedias, and similar pre-priority reference works normally qualify. Journal articles, dissertations, and patents are generally NOT accepted as proof of common general knowledge (even if published earlier), unless exceptional broad dissemination over several years can be shown.
   
   
3. Common General Knowledge can only clarify prior-art disclosure, never expand it: Common general knowledge may help the skilled person understand what is implicitly disclosed in a document, but it cannot be used to add missing features or bridge gaps in the prior art.
   
   

In U.S. patent law, the direct analog to the German and EPC law concept of “common general knowledge” (CGK) is the combination of two related but distinct concepts: 

• The level of ordinary skill in the art (POSITA/PHOSITA) – “Person Having Ordinary Skill In the Art” - the hypothetical person to whom the patent specification is addressed and whose knowledge and abilities are used as the benchmark for obviousness (35 U.S.C. § 103), enablement, and other patent doctrines.
• Common general knowledge of the POSITA – U.S. courts and the USPTO attribute to a POSITA/PHOSITA an understanding of the body of technical information that is so well known in the field that it need not be explicitly cited or explained in references, and it is presumed to be known by the PHOSITA at the time of the invention. 

But, common general knowledge in German and EPC law, as a concept, is not well understood by the U.S. practitioner, and the differences can be quite surprising, especially when compared to the U.S. concept of the POSITA/PHOSITA.  

Understanding what qualifies as common general knowledge is central to patent validity proceedings in both Germany and before the European Patent Office (EPO), especially as contrasted from what is and what is not considered to be common general knowledge. Whether assessing novelty, inventive step, or the implicit disclosure of a prior art reference, courts and patent offices applying German and EPC law consistently look not only at the explicit text of a document but also at what the skilled person would implicitly understand based on their common general knowledge. Yet, defining and proving common general knowledge is often contentious—and the evidentiary standards are narrower than many practitioners expect, especially compared to U.S. law, and the understanding of the POSITA/PHOSITA. 

This article explains how German and EPO caselaw approach common general knowledge, what counts as acceptable proof, and where the boundaries and exceptions lie. 

The Legal Foundation Under German and EPC Law: Common General Knowledge Clarifies Disclosure—It Does Not Expand It 

Both German patent law and the European Patent Convention (EPC) adhere to the principle that the disclosure of a prior-art document is not confined to its literal wording. According to the well-established case law of the German Federal Court of Justice—most notably the decision Olanzapin (16 December 2008, Docket No. X ZR 89/07)—and the Boards of Appeal of the European Patent Office—for example, decision T 0786/00 of 19 December 2001— the disclosure of a prior art document also includes what a person skilled in the art would implicitly understand in light of their common general knowledge.  

However, this principle has strict limits. Common general knowledge cannot be used to broaden the disclosure of a prior art document or to introduce new technical teaching. Its function is clarifying, not augmentative: it helps interpret what is already disclosed, but it cannot fill in gaps by adding features that are absent from the document itself.  

Why Proof of Common General Knowledge Is Important in Patent Disputes 

Disputes often arise over the question of what exactly constitutes common general knowledge at the priority date. The issue plays a central role in both novelty and inventive-step assessments. The party relying on the alleged common general knowledge bears the burden of proof—sometimes a difficult task, because acceptable forms of evidence are limited.   

What Counts as Common General Knowledge? 

Common general knowledge comprises all the knowledge that a person skilled in the art possesses by virtue of their education, training and practical experience at the relevant priority date. This includes: 

• Fundamental principles and widely known techniques in the field; 
• Information a specialist would routinely know or could quickly look up in a standard reference work; and 
• Basic tools, definitions, and methodologies used broadly within the technical community. 

Acceptable Evidence: Sources That Prove Common General Knowledge 

Given this definition, the case law has consistently regarded the following as suitable evidence on common general knowledge: 

• Textbooks 
• Monographs 
• Encyclopedias 
• Standard technical handbooks 
• Reference materials  

Such sources reflect knowledge that is stable, consolidated, and widely disseminated within the technical field. Importantly, they must have been available before the priority date, which may itself require separate proof.  

What Usually Does Not Qualify as Common General Knowledge 

By contrast, the following are generally not considered adequate evidence of common general knowledge: 

• Scientific journal articles 
• Dissertations 
• Patent publications 

Even if published before the priority date, these sources typically require targeted searches to locate and are not the kind of material that a skilled person would necessarily have at hand. They can contain cutting-edge findings that have not yet been absorbed into mainstream technical teaching.  

Narrow but Important Exceptions  

Despite this general rule, exceptions exist. Case law acknowledges that scientific papers or patent literature may form part of common general knowledge if: 

• The material was published several years before the priority date,  
• The information had sufficient time to disseminate broadly within the professional community, and  
• The content was on the verge of being incorporated into textbooks or reference works.  

Such exceptions frequently arise in rapidly developing technological fields—where traditional treaties lag behind emerging technologies and the technical community relies heavily on pre-textbook publications to maintain a shared level of understanding.  

Conclusion: Winning the Battle Over What the Skilled Person Really Knew Under German and EPC Law 

Proving common general knowledge remains one of the more challenging evidentiary tasks in German patent and EPC law. Although the concept itself is well developed in case law, demonstrating it requires substantive research, careful selection of sources and close attention to what the courts consider “shared knowledge” in the field.  

For practitioners, especially those from the U.S. who may be surprised by the strict nature of common general knowledge applying German and EPC law , the key takeaway is clear: 

Common General Knowledge must be proven through stable, accessible sources that reflect what the skilled person genuinely knew at the priority date—not what they could have uncovered through specialized research. 

Understanding these nuances can significantly strengthen arguments on novelty, inventive step, and the interpretation of prior art—and, ultimately, can make or break the validity of a patent.