Is Germany's Formstein defence to patent infringement becoming part of English law?

Briefing

Formstein is still not formally part of the English law, but if you find yourself defending against allegations of patent infringement, you may plead it just in case – or in case you make history.

However, the odds will be against you: for the third time in the history of English case law, an English judge commented favourably on the approach used in German case Formstein as a defence to patent infringement, and for the third time, they did not need to use it. So, what is a Formstein defence, why have English courts yet to employ it, and how might that happen?

The Formstein defence explained

Formstein is a German case that applies a counterbalance to the doctrine of equivalents in claims of patent infringement.

The doctrine of equivalents was established in English law by Actavis v Eli Lilly [2017]. In that case, the English Supreme Court held that you infringe a patent if your product or process varies from the patented invention in ways that are immaterial (ie it is 'equivalent').

Actavis extended the scope of protection afforded to patentees under English law. Until then, this was restricted to normal (ie literal) and purposive (ie "What would the person skilled in the art have understood the patentee to be using the language of the claims to mean?") reading of the claims.

Following Actavis, when determining whether a product infringes a patent, the judge will ask:

whether the product/process achieves substantially the same result in substantially the same way
whether the above would be obvious to the skilled person at priority date, and
whether such a skilled person would have concluded that the patentee nevertheless intended that strict compliance with the wording of the claim was an essential element of the invention.

Actavis created a perceived imbalance between the scope of protection afforded to patentees and the ability of their competitors to challenge the validity of the patent when facing infringement claims. When determining the patent's validity under English law, the judge will ask if the invention was not new or obvious to a notional skilled person considering documents (the prior art) and common general knowledge at the patent's priority date. The doctrine of equivalents does not apply. Therefore, theoretically, a situation can arise where a product/process infringes the patent as an equivalent, even though it is no more innovative than the prior art.

The Formstein defence is thought to provide a remedy for this imbalance by asking a fourth question: is the equivalent product/process, factoring in state of the art, not new or obvious to a person skilled in the art?

In other words, is the alleged infringer doing what was known or obvious before the patentee came up with their invention? If the answer is "yes", under German law, the product/process does not infringe. Dutch law adopts a similar approach.

Why is Formstein yet to be used by the English courts?

However, the existing English case law suggests that a Formstein defence is not needed. Consider three cases where it was pleaded:

Technetix v Teleste [2019]: the patent was invalid, so the matter of infringement was irrelevant to the outcome (though if the patent was valid, it would have been infringed).
Emson v Hozelock [2019]: the patent was invalid, so the matter of infringement was irrelevant to the outcome (though again, if the patent was valid, it would have been infringed).
Facebook v Voxer [2021]: the patent was invalid, and not infringed (even under the doctrine of equivalents).

This may be because the test for obviousness is flexible enough to incorporate features of the analysis under the doctrine of equivalents. When assessing the validity of a patent, the judge will consider whether the skilled person would conclude that a prior art document shows an invention that achieves substantially the same result in substantially the same way (ie equivalent). If so, it may be obvious (by referring to common general knowledge) to adapt it to arrive at the invention claimed in the patent.

For example, in Emson v Hozelock, the prior art which invalidated the patent for an expandable garden hose was a patent for a self-elongating hose to provide oxygen to crew on an aircraft called McDonald. Quite tellingly, Mr Justice Nugee (quoting a previous judgment) described it as follows:

"Therefore the hose in McDonald is supposed to expand and contract in the same way as the hose of the Blue Gentian patent and uses the same sort of combination of an elastic inner tube and a non-elastic outer tube to achieve this." (paragraph 170; emphasis added).

If that sentence rings a bell, it's because it's very close to the first Actavis question.

The invalidity case in Emson v Hozelock turned on whether it would have been obvious to adapt the hose in McDonald to a garden hose – and Mr Justice Nugee determined it would. If we apply the doctrine of equivalents to this scenario, the second question in Actavis would have been answered in the affirmative as well.

Of course, the existing rules might have been enough in three cases out of three, but as the defendant, you may not want to risk it. You may be prevented from attacking a patent for obviousness – eg because the relevant prior art document was not published until after the patent's priority date (and so only available for novelty), or other strategic considerations. If your product or process would infringe the patent under the doctrine of equivalents, a Formstein defence could be a real lifesaver.

This is particularly the case, since – as it's now apparent – the English patent judges are enthusiastic about Formstein. In the most recent case, Facebook v Voxer, Birss LJ (sitting in the Patents Court) put it in the strongest terms yet:

"However, if I did have to decide the matter, I would hold that the right approach is the Formstein approach so that the conclusion if the equivalent device lacks novelty or is obvious is that the claim scope must be confined to its normal construction in that respect. I would do so for two reasons. If the claim on its normal construction is valid, then it seems harsh to invalidate it on this ground. What else could the patentee do but write their claim in a way which, normally construed, did not cover the prior art. So that approach promotes certainty. Secondly, since it is clear that other EPC countries work that way, this is a reason in itself for this EPC state to take the same approach." (paragraph 216).

The other two English judges who considered Formstein have refrained from declaring it a feature of English law:

In Technetix v Teleste, His Honour Judge Hacon suggested it might be confirmed by the Court of Appeal or the Supreme Court (paragraph 99).
In Emson v Hozelock, Mr Justice Nugee was invited to declare that Formstein defence forms part of the English law but did not do so, suggesting it should be done in a case where it would make a difference and very probably in a higher court (paragraph 201).

Will Formstein be addressed by the English courts in the future?

So, taking inspiration from Birss LJ, we wonder if judges in the future will address Formstein as part of the answer to the third Actavis question. If extending the scope of the claim to cover the infringing product would render the invention invalid for obviousness or lack of novelty, that could be a reason for the skilled person to conclude that the patentee nevertheless intended that strict compliance with the wording of the claim was an essential element of the invention. This approach seems more likely, until a UK court decides that adding a fourth question to the Actavis analysis is required.