What is CGK?

Australian Courts have indicated that CGK is the technical background knowledge and experience which is available to the hypothetical skilled worker in a particular field. It is accepted without question by the majority of those skilled workers and becomes part of their common stock of knowledge.

CGK is not restricted to information that may be memorised and retained. It also includes material that is known to exist and would be referred to routinely by the skilled worker even if the skilled worker is not consciously aware of the information.

CGK may include information available globally in standard textbooks, handbooks, dictionaries, industry magazines in the field and prior art acknowledged in patent specifications. CGK does not necessarily extend to information that is widely read or circulated to the skilled person or to information found by conducting searches.

The role of CGK in an inventive step determination

The Patents Act 1990 prescribes that an invention is taken to involve an inventive step unless it would have been obvious to a person skilled in the relevant art (PSA) in light of the CGK, as it existed before the priority date, alone or in combination with the relevant prior art. Accordingly, CGK is the threshold issue to be addressed in an inventive step assessment.

Evidentiary approaches to proving CGK

Determining CGK is a factual test made with the aid of a person skilled in the art. What constitutes CGK can only be established by evidence. The evidentiary approaches to proving CGK vary depending on whether the CGK is being considered before IP Australia (IPA) or the Courts.

During prosecution of a patent application before IPA, an assessment of inventive step involves the Examiner formulating an opinion of what constitutes CGK based on material such as textbooks, dictionaries, magazines and patent specifications. Examiners consider arguments against CGK on merit and apply balance of probabilities considerations.

During opposition proceedings before IPA, CGK is established through written declaratory evidence from an expert in the field of the invention. Although the rules of evidence do not apply, the Commissioner will evaluate and weigh the evidence, with hearsay evidence being given less weight than first hand testimonies and non-expert evidence.

Before Australian Courts, the Evidence Act 1995 allows the admissibility of evidence in the form of expert opinions. An expert’s opinion may be admitted if the expert has “specialised knowledge” based on training, study or experience provided the evidence is “wholly or substantially” based on that expert knowledge. The Courts will consider expert evidence from each side concurrently to establish the CGK. This is an effective way for judges to understand the technical complexities of a case. It can, however, be difficult to establish the CGK to meet the requisite evidentiary burden.

CGK failures

In Arrow Pharmaceuticals Pty Ltd v Novartis AG [2019] APO 22, the Delegate found that CGK did not extend to information included in a textbook published 17 days before the priority date of the opposed application on the basis there was not enough time for the information to be generally accepted and assimilated by those skilled in the art. It had not become part of their “common stock of knowledge”.

In Aktiebolaget Hassle and Astra Pharmaceuticals Pty Limited v Alphapharm Pty Ltd [2000] FCA 1303 the Full Federal Court noted that CGK did not equate to information that might be found by a diligent searcher and mere public availability is not sufficient to establish CGK.

CGK successes

In Minnesota Mining & Manufacturing Co v Beiersdorf (Australia) Limited (1980) 144 CLR 253, the High Court held that the claimed invention was obvious in light of the CGK alone.

In Merial, Inc. v Intervet International B.V. (No 3) [2017] FCA 21, the Federal Court considered concurrent evidence from a number of experts and utilized the joint expert reports to identify the CGK.

Practical steps that can be taken to establish CGK

  • Choose an independent credible expert with a strong command of the technical field of the invention.
  • Ensure that the expert understands their role is to assist the court, not be an advocate for either party.
  • Written in the expert’s own words and avoid legalese.
  • Substantiated by reference materials publicly available well before the priority date.

The CGK in a technical field is integral in assessing the patentability of an invention in Australia. It is therefore critically important that it is correctly determined. This may be challenging, as the state of the CGK is based on evidence which itself must be assessed for its suitability in representing what would have been known to the skilled person at the relevant time.

This article first appeared here in Managing IP and was reprinted with permission.