Hacon HHJ and the Seed Drill: Intentionality in prior use (Claydon v Mzuri, [2021] EWHC 1007)

Does a tree falling in a forest make a sound? The answer to this epistemological cliché (and whether or not you care) depends on your philosophical leanings. Patent law has its own clear answer to the question. In UK patent law, the mere potential for prior public use to have been observed can deprive an invention of novelty. This principle can be a problem for inventors seeking to test prototypes of their inventions, and raises the question of how large, mechanical inventions can be tested without creating the potential (however small) for the invention to have been observed. The recent case of Claydon v Mzuri ([2021] EWHC 1007 (IPEC)) is a particularly harsh example of the application of the prior use case law. The patent was deprived of novelty in view of the inventor's prior use of a prototype of the invention (a seed drill) in a secluded field on his own land. 

Legal Background: Expandable hose pipes and the potentiality of disclosure

A general principle of UK patent case law is that disclosures in a publicly visible place are prior art even if no one was there to observe the disclosure. The classic example of such a disclosure is the unread PhD thesis languishing in a publicly accessible library. In Emson v Hozelock, Mr Justice Nugee (as then was), considered whether the development of a new garden hose by an inventor in his garden should be considered prior public use (IPKat: Mr Justice Nugee and the Superhose: The potentiality of disclosure). 

Audience of potential observers

In Emson v Hozelock the Judge was clearly conscious that categorising as "public disclosure" the private activities of an inventor in his garden, just because the garden was visible from the road, would not necessarily correspond to a common sense view of things. To rescue the situation, Mr Justice Nugee (as then was) focused on the effect of the inventor's intention on the potentiality of disclosure. In the case in question, the Judge observed that, if the inventor had seen anyone peering into his garden, he would have packed up the garden hose and gone inside. Thus, no potentiality of disclosure existed. 

By way of example, the Judge noted that a publicly advertised talk to which no-one turned up, but which nonetheless went ahead, would be public disclosure. However, an inventor talking to themselves on a deserted moor would not be public disclosure. The Judge reasoned that the soliloquising inventor on the moor could have been expected to stop speaking if they happened to have noticed someone walking behind them. 

To this Kat, the High Court's reasoning in Emson v Hozelock had its problems. Surely there would still be the potential for disclosure by the inventor hiking on the moors to a very soft-footed hiker creeping up behind them? Similarly, what if the inventor of the garden hose in Emson v Hozelock had been too wrapped up in his inventive activities to notice any observers?

You might think the field is empty

The question of when a prior use should be categorised as a public disclosure was again considered in the recent case of Claydon v Mzuri. The case related to the alleged prior public use of a new seed drill. The alleged infringers and defendants, farm equipment suppliers Mzuri, argued that Claydon's UK patent claiming the invention (GB 2400296) were invalid in view of a prior public use by the inventor, Mr Claydon. 

The inventor of the seed drill tested a prototype of the invention in a field on his own farm before the patent application was filed. This fact was not in dispute. The question before the Judge was whether this prior use constituted public disclosure of the invention, given the potential for a skilled person to have observed the prototype seed drill. 

Mzuri argued that the prototype in the field could have been observed from a public footpath. The footpath in question was on the edge of the field, and was unmarked and unmaintained. There was a six foot high hedge between the footpath and the field. Crucially however, there were three gaps in the hedge through which the field could be seen by an intrepid countryside rambler. 

Mr Claydon argued that he was aware that prior public use of his invention could jeopardize his ability to get patent protection. He also had a good vantage point from his tractor cab. If he had seen someone on the footpath when he was testing the prototype, Mr Claydon submitted, he would have manoeuvred the tractor so that the drill prototype was not visible. 

Testing the prototype

Unfortunately for the patentee, the Judge, His Honour Judge Hacon (Hacon HHJ), was not convinced that Mr Clayton could have successfully hidden the large seed drill from a potential observer. As the Judge noted, large pieces of agricultural machinery are not as easy to hide as garden hoses. On the basis of expert witness testimony, the Judge also concluded that a hypothetical skilled person would have been able to deduce all of the claimed features of the invention from their vantage point at the edge of the field (para. 101). 

For Hacon HHJ, there had thus existed the clear potential for disclosure of the invention to a skilled person. The patent was thus found to lack novelty in view of the prior public use. 

The potentiality rabbit-hole

To this Kat, the outcome of this decision raises the question of the suitability of the potentiality of disclosure test for prior use. The patentee was deprived of their patent because the inventor had tested, unobserved, a prototype of his invention on his own land, just because there had been the potential (how every small) for a skilled person to look through a gap in the hedge from an overgrown and unmarked footpath. This does not feel like a wholly fair outcome. Indeed, despite his final decision, Hacon HHJ himself was obviously sympathetic to the plight of the patentee: "Mr Claydon had to test his prototype, nobody saw any of the testing and I entirely understand why he believed that his invention was not publicly disclosed" (para. 102) [Merpel: Indeed, what was the inventor expected to do, test his seed drill indoors?]

The concept of "intentionality" in prior use was arguably introduced in Emson v Hozelock as a way to avoid outcomes of patent invalidity based on prior use that would seem obviously unfair to the layman (IPKat). However, the decision in Claydon v Mzuri now reveals the limitations of the intentionality argument, and particularly the difficulty of building a case around the intentions that inventors may or may not have had many years ago. Hacon HHJ noted that he found "it hard to believe that nearly 20 years later Mr Claydon could accurately say with any certainty what he would have done" at the time the invention was conceived and tested (para. 92). 

Drone swarm

The Judge raised (but did not address) the question in Claydon v Mzuri of whether a potential observer could be afforded technical equipment in the form of binoculars, video recorder or even a swarm of drones (para. 80). The Judge steered away from the possibility of permitting most forms of skilled person the use of a drone swarm, believing that "it will not be often that evidence will establish" a skilled person to have access to a drone swarm at hand at the relevant time and place. Although, notably, the Judge doesn't completely rule this out. Nonetheless, discriminating between what (if any) technical equipment may be afforded a potential observer is a step away from the absolute principle that if a member of the public could have gained access to the invention (however unlikely), the invention should be considered disclosed. After all, there still remains the possibility for a member of the public to walk the fields of England with a drone or even a swarm of drones. 

It is thus perhaps in Hacon HHJ's reasoning on what technical equipment may be afforded to the skilled person that we find a possible escape from the "potentiality of disclosure" rabbit hole. Perhaps the answer is a more focussed assessment of the probability that a prior use could have been observed by a skilled person at a particular place at that time (e.g. more than negligible), as opposed to the existence of an absolute possibility, however small.