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Cortex - Life Sciences Insights

| 4 minutes read

Experimental evidence in patent litigation – Rules for fair play

The technical nature of patent litigation means that experiments are often an essential (and sometimes the only) way to prove key aspects of infringement (or, more unusually, invalidity), particularly in life sciences-related cases. Over the years, I have donned a white lab coat on many occasions and spent days with inspiring scientists as they devise and execute a suite of experiments for the purposes of preparing evidence – proving the presence of a particular gene sequence, investigating microparticles in pharmaceutical formulations, and using in vitro systems to measure the response to a drug, to name just a few. 

In the UK courts, there is a well-established procedure for introducing experimental evidence.  Rules are aimed at ensuring fair play by providing the opportunity for scrutiny of the experimental programme, and testing of repeatability. The party seeking to rely on the results of experiments serves a ‘Notice of Experiments’ which sets out in some detail the equipment, protocol, results and analysis, together with a statement of the facts to be proved and admissions sought. There is usually provision for a witnessed repetition of the experiments, which is attended by the opponent, its lawyers and its expert witness – this is often the cause of sleepless nights due to the unpredictability of experimental work. The opponent may then serve experiments in reply (with a further witnessed repetition of those experiments). 

Aside from the nail-biting witnessed repeats, two words strike fear into those developing a programme of experiments for the purposes of litigation in the UK – “Mayne Pharma”

Mayne Pharma was an action for patent revocation before the UK High Court in 2006 (Mayne Pharma Pty Ltd v Debiopharm SA [2006] EWHC 164 (Pat)). In seeking to invalidate one of Debiopharm’s patents, Mayne Pharma argued that carrying out synthetic processes disclosed in the prior art inevitably fell within the claims of the patent and so it lacked novelty. In support of this, Mayne Pharma sought to rely on experiments showing the ‘inevitable result’. 

The patentee, apparently concerned that the experiments relied upon weren’t the whole story (perhaps the inevitable result wasn’t quite so inevitable?), sought disclosure of documents relating to experiments performed during any “work up” or preliminary investigations. As experiments done for the purposes of litigation, Mayne Pharma might reasonably have expected any preliminary experiments to be entitled to legal professional privilege. However, the Court held that any privilege attaching to documents relating to workup experiments was waived by giving the Notice of Experiments, and ordered disclosure.   

Mayne Pharma was a relatively unusual case of anticipation by inevitable result. Notably, in the judgment, Pumfrey J stated, “[w]hether [the waiver] extends further, I am more doubtful and I will not express a view”. Perhaps consequently, the principles in Mayne Pharma relating to waiver of privilege laid low for a number of years. In 2017, they were aired once again in the UK, and developed further, in the case of Magnesium Elektron (Magnesium Elektron Limited v Neo Chemicals & Oxides (Europe) Ltd (No.2) [2017] EWHC 2957 (Pat)). 

Magnesium Elektron added a further class of patent cases in which privilege might be waived (in addition to cases considering inevitable result), namely those where completeness of data might be an issue. Specifically, the court held that disclosure of otherwise privileged material may be warranted where the repeatability of an experiment and any significant variation in result means that it may be critical to have information about that issue, or the failure to provide the full relevant data set may lead to unfairness. Magnesium Elektron therefore confirmed that the general principle of waiver of privilege in relation to experimental results extends beyond ‘work up’ experiments. However, the waiver was narrow and extended only to a specific experiment and runs of the same protocol for that experiment. (Indeed, a subsequent application for disclosure of further documents, including legal advice and draft evidence relating to the experiments, was refused.)

Recently, the Mayne Pharma-type waiver of privilege was asserted again in the UK, in Safestand (Safestand Limited v Weston Homes [2023] EWHC 1098 (Pat)).  This case concerned safety features of low-level access platform systems. The defendants’ allegedly infringing system was available in two different heights. They sought to rely on experiments that investigated stability of the taller system but did not disclose any results relating to the shorter system, which the claimant suspected would be more stable (as a matter of physics). 

The claimant sought disclosure of any experimental results relating to the shorter system, which the defendant objected to on the basis that (amongst other things) they were different experiments because they were performed on a different system. Notwithstanding this, the Court held that disclosure could encompass other related litigation experiments which provide materially relevant contextual information on the experiments relied upon. This was therefore arguably wider than the waiver in Magnesium Elektron, demanding disclosure of experiments beyond runs of the same protocol for the same specific experiment. 


As cases before the Unified Patent Court (UPC) gain momentum, it will be interesting to see how evidence plays out. The Rules of Procedure allow parties to deploy an armoury of written, physical and electronic evidence, including experimental evidence.

In the UPC Rules of Procedure, Rule 201 provides for experiments to be ordered by the Court and largely mirrors the UK procedure. A party wishing to prove a statement of fact by means of experiments lodges a request identifying the facts to be established, along with a detailed description of the proposed experiments and reasons for conducting them. Where appropriate, the Court may order that the experiments be carried out in the presence of the parties and their experts, allowing scrutiny of the protocol through a witnessed repetition, as in the UK. 

Further, Rule 201(2)(c) specifically provides that a party seeking to rely on experimental evidence shall “disclose any previous attempts to carry out similar experiments”, thereby codifying the Mayne Pharma waiver of privilege. It remains to be seen where the lines are drawn by the Court, but choice of the words “similar experiments” in the Rules of Procedure suggests that at least a Safestand-type approach might be adopted. 

The UK cases have recognised that legal professional privilege is a fundamental condition on which the administration of justice as a whole rests and that it may be eroded or destroyed by waiver. The UPC judges will no doubt have the same considerations at front of mind and apply a careful restrictive approach to any disclosure, with any waiver of privilege being only to the limited extent necessary. 

Many will be familiar with the old show business adage ‘never work with children or animals’ due to their unpredictable nature. I would urge the same caution when approaching an experimental programme – only do what is essential and prepare for every eventuality.