Insights: Public Prior Use: What Can the Skilled Person See?

It is a well-known principle under UK patent law that any subject matter that the public can access without breaching a duty of confidentiality is considered to have been publicly disclosed, irrespective of whether anyone has actually accessed that subject matter. A disclosure which is in reality seen by no-one can therefore invalidate a subsequent patent application. A recent case in the Intellectual Property Enterprise Court (Claydon Yield-O-Meter Ltd v Mzuri Ltd [2021] EWHC 1007 (IPEC)) has provided some further applications of this principle.

As discussed in Lux Traffic Controls Ltd v Pike Signals Ltd ([1993] RPC 107) a book on a shelf of a library which is open to the public is considered a public disclosure. The contents of the book are considered disclosed “whether or not anybody read the book and whether or not it was situated in a dark and dusty corner of the library”. More recently though, in E. Mishan & Sons Inc v Hozelock Ltd [2019] EWHC 991 (Pat) it was decided that the inventor’s testing of a prototype garden hose in his garden, the garden being visible from a public road, was not an enabling disclosure because the judge accepted that the inventor would have hidden the prototype from view if anyone had tried to observe him. The questions of what the inventor would have done and what the skilled person could have seen if they were actually present were therefore key in that case to determining whether the subject matter had been disclosed.

In Claydon Yield-O-Meter Ltd v Mzuri Ltd., similarly to E. Mishan & Sons Inc v Hozelock Ltd, the inventor had tested a prototype of their invention, before filing their patent application, on private land that was visible from a public footpath. However, in this case the testing was of a large piece of agricultural machinery pulled behind a tractor in a field.

Amongst other things, the arguments in this case considered whether or not the inventor would have been able to effectively hide the relevant parts of the prototype from a person appearing on the public footpath and what the skilled person would have been able to determine about the invention from the marks left in the soil by the prototype, The judgement noted: “preventing a member of the public from seeing a prototype seed drill would have been a good deal more difficult than hiding a prototype garden hose….” The judgement also questioned whether the inventor could accurately state what they would have done if a member of the public had appeared given the length of time (nearly 20 years) since the testing had occurred. Ultimately, the testing of the prototype was considered to be a prior public use constituting an enabling disclosure of the invention, and so the claim in question was deemed invalid.

This case highlights the dangers inherent in testing prototypes in publicly-visible locations. It is clear that it will not always be possible to rely on an assertion that the device would have been hidden if a member of the public had been present. It seems that UK courts will take a practical view of what the skilled person could have seen in the specific circumstances in question, not only of the tested prototype itself but of any results of that test which would be visible to the skilled person had they passed by at the right moment.

If you have any questions, your usual Boult Wade Tennant advisor will be happy to assist you.