The High Court recently examined the burden of proof to be applied by the courts in disputes over patent inventorship. The case in question, Cooke v Watermist Ltd [2014] EWHC 125 (Pat) (03 February 2014), on appeal from the intellectual property office (“IPO”), was heard in the Chancery Division of the High Court before Mr Justice Arnold.

Mr Justice Arnold upheld the IPO’s decision, ruling that:

  1. where a claimant seeks to be named joint inventor of an existing patent, he or she must prove contribution to the ‘inventive concept’ of the patent (as opposed to merely contributing to its claims);
  2. where the claimant seeks to be named as sole inventor, her or she must also prove that the patent’s named inventor did not contribute to the inventive step.

The answers to these legal questions will have to be decided on the balance of probabilities, based on the facts of the case as determined by the court. However, if the court is not provided with sufficient evidence on which establish the facts (for example, where it is one party’s word against another), it will instead ask whether the claimant has discharged the burden of proof and his or her version of the facts is more likely than not to be correct (also based on the balance of probabilities).

The facts

The case was an appeal by the Claimant, Mr Cooke, against the dismissal of his co-inventorship claim by the IPO. The patent in question related to a fire hose pressurised by its own separate pump and motor.

In 1999 Mr Cooke had been an employee of Fireworks Fire Protection Ltd (“Fireworks”). His duties had included overseeing the installation of ‘misting systems’ which suppressed building fires by generating a mist of liquid from overhead nozzles. The pressure for these nozzles was provided by a single centralised water pump. This was a sometimes expensive and not always satisfactory setup.

In 2004 Fireworks contracted Warren Services Ltd “Warren”, to supply misting systems, and Mr Cooke befriend Warren’s director. In 2005 the directors of Warren and Fireworks developed a new misting system (without Mr Cooke’s involvement), and incorporated a new company called Watermist for this venture.

Two years later, in 2007, in response to negative feedback from Fireworks’ clients, Mr Cooke invented a prototype new misting system by which each individual nozzle had an independent pump and motor, instead of relying on a single centralised pump to provide pressure. Unfortunately for Mr Cooke the prototype was faulty and failed to operate properly.  

Not long afterwards Watermist developed a hose-reel which also had on its own independent pump and motor. The product was designed for use in prison fires to be inserted through a cell door. Mr Cooke claimed this product was based on his prototype misting system’s ‘core inventive concept’ and, on that basis, he should be recorded as the sole inventor of Watermist’s new form of fire hose.

The law

According to s.7(3) of the Patents Act 1977  (the “Act”) the inventor of a patent invention is ‘the actual deviser’. The courts have refined this to mean “the natural person who 'came up with the inventive concept”. Therefore, to merely contribute to a patent’s claim is insufficient, and the contribution must go to the heart of the invention. In order to determine whether a person merely contributed to a patent claim, or to the inventive concept itself, requires a court to examine the parties’ evidence on the matter and form a view as to the facts.

Section 7(4) of the Act provides “except in so far as the contrary is established, a person who makes an application for a patent shall be taken to be the person who is entitled to… be granted a patent”. Section 7(2) provides the person ‘entitled’ to be granted the patent under s.7(4) includes the inventor (or joint inventors).

The practical effect of s.7(4) of the Act is that a person seeking to be added as a joint inventor has the burden of proving, he or she contributed to the inventive concept. Where that person seeks to be substituted as sole inventor, the test is two stage, and in addition to having to prove he or she contributed to the inventive concept, that person must also prove that the named inventor did not contribute to it.

In the majority of claims, the court will decide on disputed matters of fact relating to contributions to the inventive concept based on the parties’ evidence. However in some situations, such as in Mr Cooke’s case, there may not be sufficient reliable evidence on which to make a finding as to the facts. In these cases whether or not a claimant satisfies the tests under s.7(3) and s.(4) of the Act (thereby discharging the burden of proof) will be decided purely on the balance of probabilities (i.e. whether it is more likely than not) instead of an objectively established set of facts.

The IPO had insufficient documentary evidence before it and was left only with largely unreliable and contrasting witness testimony. Therefore the IPO was permitted to resort to the balance of probabilities test to decide whether or not Mr Cooke had proven his case, which it held, he had not.


Where patents are developed by multiple individuals outside of a sophisticated commercial context (for example by friends or through hobby projects), documenting the exact contribution made by the parties involved may not be a particular priority. As such, if question of inventorship do later arise, the evidence may be largely limited to the accounts of the parties themselves.

The High Court’s decision illustrates the extent of the burden upon a party claiming inventorship against an already named inventor and makes it clear that, where there is little credible evidence as to the facts, the defendant may simply put the claimant to proof.

To avoid such situations, any inventor who contributed to the inventive concept should ensure  they are recorded as a named inventor on patent. Further, inventors should keep proper records during the early development stages of a patented product and include details of the ideas, contributions and progress of new inventions. The provision of such documentary evidence should allow inventors to avoid being at the mercy of the courts who will otherwise have to determine the facts based only on ‘what was more likely than not to have been the case’.