Tracing the roots of UK contributory infringement in Patent law

Understanding the ‘essential element’

To those used to the US definition of contributory infringement one feature of the UK definition appears particularly alien. The ‘essential element’. To explain this difference in the UK definition we must examine one of the earliest cases of contributory infringement – Innes v Short (1898).

 

The patent at the heart of the dispute

In 1895 Innes’ was granted a patent for the process of the introduction of metallic zinc powder into steam boilers to prevent corrosion. The claimed invention was as follows:

 

“The introduction of metallic zinc in a powdered state either alone, amalgamated with alkali metals or mechanically mixed with alkalis, alkaline earths or the like, into steam boilers or the like.”

 

From agent to alleged infringer

In May of the same year Innes’ began using Short as an agent to supply his powdered zinc to steam ship owners. Short supplied each packet of powder with directions for use entitled ‘Innes’ Patent Metallic Zinc “Powder”.

 

In 1897 Short began to suspect that the zinc powder itself was not protected by Innes’ patent which only claimed the process of introduction to the boiler. Additionally, he believed that the patent was invalid. He terminated his role as Innes’ agent and continued to sell the zinc powder with the directions for use.

 

In response Innes’ brought an infringement action against Short arguing that selling the powdered zinc with instructions for use amounted to infringement. Short alleged that they did not infringe as they were selling a material they were allowed to sell and that knowing it would be used to infringe a patent did not make them infringers. The defence additionally argued that the patent was invalid due to lack of inventive step.

 

The court’s decision – intent and expectation matter

The case was decided in Innes’ favour with Justice Bingham commenting on the difference between selling a product knowing it was possible to use for infringement and selling a product and expecting it to be used for infringement. He decided that Short’s supply of directions for use actively invited buyers to infringe Innes’ patent and so it would only be logical for him to expect buyers to use the powdered zinc to infringe. 

 

While the judgement that Short directly infringed Innes’ patent was questioned at the time, it is obvious to the modern reader that the circumstances meet all the criteria for what would later be defined as contributory infringement. But this does not explain how ‘an essential element’ became part of the definition for contributory infringement in the UK. This feature instead comes from Bingham’s discussion of the validity of the patent.

 

The origins of the ‘essential feature’

To determine the validity of the patent Bigham’s highlights the ‘essential element’ of the patent. In this case that the zinc introduced to the boiler was in powdered form so could be held in suspension which was more effective than the previous granulated or block forms. Bingham determined that it was this ‘essential element’ which embodied the novelty and inventiveness and therefore is the feature that the patent aims to protect.

 

While the ‘essential element’ was not used as part of the infringement judgment, Bingham’s comments influenced how judges later viewed scope of a patent’s protection.

 

Therefore, this discussion of an ‘essential element’ in one of the first cases of contributory infringement has influenced the current definition used in the Patents Act.

 

How we can help

For advice on protecting your inventions, please contact Kelda Style.

 

This briefing is for general information purposes only and should not be used as a substitute for legal advice relating to your particular circumstances. We can discuss specific issues and facts on an individual basis. Please note that the law may have changed since the day this was first published in June 2025.