Patents – aren’t they obvious?

read time: 5 mins

Readers may be aware that when a person or business is confronted with allegations that they are infringing another’s patent one option (in addition to denying infringement) is to apply to invalidate the patent in question.

Probably the most common ground on which a patent’s validity is contested is to assert that the invention claimed in the patent does not involve an inventive step. In other words, the invention was obvious to a person skilled in the art, having regard to any matter which formed part of the state of the art, at the time of the filing of the patent application (or its priority date, if earlier) (“the relevant date”).

But what does this mean in practice? 

First, it is important to understand what certain terms mean.

The “state of the art” comprises all matter (whether a product, a process, information about either, or anything else, for example an earlier filed patent application or granted patent) which has been made available to the public (whether in the United Kingdom or elsewhere) by written or oral description, by use or in any other way. This is otherwise known as the “prior art”.

When asserting that an invention claimed in a patent is obvious in light of the state of the art, reliance is usually placed on one or more pieces of prior art (often earlier filed patent applications or granted patents), sometimes in combination with common general knowledge, or sometimes in light of common general knowledge alone. 

A “person skilled in the art” means a person (or, in some cases, a team) skilled in the relevant field of technology covered by the problem deemed to have been solved by the invention claimed in the patent (“the relevant field”). They are deemed to have no inventive capacity, but to have read all the prior art relied upon to challenge the validity of the patent and to be abreast of what was the common general knowledge at the relevant date in the relevant field.

“Common general knowledge” is that which was generally known by the majority of persons skilled in the relevant field. It is knowledge they would keep in mind when reading the prior art. 

Second, the Courts in this country have established various principles which are to be applied when assessing the alleged ‘obviousness’ of an invention claimed in a patent. In particular:

  • Obviousness involves a multi-factorial evaluation
  • What matters is whether something was technically (not commercially) obvious
  • If (in light of the prior art and what it teaches the person skilled in the art) something was obvious to try and there was a fair expectation of success, then the invention may well lack an inventive step and is obvious.
  • If there were a number of avenues of research suggested by the prior art, which could have been followed to try to get to the claimed invention, and they would have required extensive effort, this points away from the invention being obvious. If the research would have been routine in nature this points towards the invention being obvious.   
  • Hindsight (as to knowledge of the successful invention claimed in the patent under challenge) must be avoided when assessing whether the invention is obvious
  • The English Courts will ask four questions:
    (1) Identify the notional person skilled in the art and identify the relevant common general knowledge of that person;
    (2) Identify the inventive concept of the claim in question (as set out in the patent) or if that cannot readily be done, construe it;
  • Identify what, if any, differences exist between the matter cited as forming part of the state of the art (i.e. the prior art) and the inventive concept of the claim or the claim as construed;
  • Viewed without any knowledge of the alleged invention as claimed, do those differences constitute steps which would have been obvious to the person skilled in the art or do they require any degree of invention?

So how do you prove obviousness?

Typically, parties to a patent dispute primarily rely on independent expert witness evidence to try to prove their case. 

This is usually given by experts in the technical field covered by the patent, who purport to say whether or not (and, more importantly, explain why) the invention claimed in the patent would have been obvious to the person skilled in the art, in light of the state of the art at the relevant date.  

Expert witness evidence is sometimes supplemented with other evidence, for example, evidence that there had been a ‘long felt want’ for a solution to the problem solved by the invention claimed in the patent, and that many people had tried and failed previously to solve the problem. Other evidence might assert that the product or process claimed in the patent has enjoyed commercial success since launch, although this is often discounted as there can be many reasons why success arises (e.g. marketing campaigns; the strength of the brand name under which the product/process is sold, etc., rather than because the product/process was inventive). 

A common argument made is that if the invention was obvious why was it not done before? The facts of the case may require this question to be answered.


Whilst “obviousness” is (according to the law) to be assessed objectively, when making that assessment some subjectivity on the part of the judge or hearing officer is inevitable. It is often possible for two Courts to reach opposing conclusions. 

In broad terms, the more trivial the differences between the invention claimed in the patent and what came before it, the more likely the invention will be deemed obvious  - and thus the patent invalidated. However, hindsight must be avoided and just because the invention claimed is simple in design and concept does not automatically mean it was obvious.

For more information or assistance with any patent matter please contact Carl Steele or your usual contact at Ashfords LLP.

Sign up for legal insights

We produce a range of insights and publications to help keep our clients up-to-date with legal and sector developments.  

Sign up