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Patents Court considers Formstein defence to patent infringement in Facebook v Voxer

Posted on 9 June 2021

In Facebook v Voxer, Lord Justice Birss has provided guidance in relation to the use of a 'Formstein' defence to patent infringement established on the basis of the doctrine of equivalents. The proceedings concern an action for revocation brought by Facebook against a patent entitled "Telecommunication and multimedia management method and apparatus" owned by Voxer, the developers of the Walkie Talkie app. Voxer's invention enables users to review messages of conversations in either a live mode or a time-shifted one, and to transition the conversation back and forth between those modes.

Voxer had counterclaimed that Facebook's live broadcast feature via its website and Facebook/Instagram apps on Apple devices infringed the patent, but the Court rejected its infringement claim, both on the basis of a normal interpretation of the patent, and also on the basis of the doctrine of equivalents. The Court also found that the patent, as proposed to be amended by Voxer, was invalid on the grounds of lack of inventive step over a prior US patent.

Of particular interest in the decision is Lord Justice Birss' discussion – which was not needed to determine the case, given his finding of non-infringement on both a normal construction and on the basis of the doctrine of equivalents, and so is obiter – of Facebook's argument that a 'Formstein defence' exists in UK law, as an extension of the well-established Gillette defence. The Gillette defence arises where the allegedly infringing product or process is not new or was obvious as at the priority date of the patent alleged to be infringed. The question for the Court to consider in this case was how to apply this principle in the context of cases where infringement is established on the basis of the doctrine of equivalents.

Birss LJ identified that, where a claim on its normal construction is valid and not infringed, but the Defendant's device is found to infringe by the doctrine of equivalents but is also found to be obvious over the prior art, there are two possible options:

  1. The claim could be found infringed but invalid because its proper scope, taking into account equivalents, encompasses something obvious over the prior art; or
  2. The claim could be found valid but not infringed on the basis that the law of equivalents mandates that the equivalents doctrine does not expand the claim in such a factual scenario.

Whilst both answers could be a logical response and, if there were no authority on the point, he thought the invalidity approach could be seen as a "purer application of the letter of the law", Birss LJ decided to follow the approach of the German courts in the Formstein case itself. Notably that approach has also been followed in the Netherlands (in Eli Lilly v Fresenius), with the same outcome applying also in US case law, albeit on a different doctrinal basis. Accordingly, he concluded that, where an equivalent device lacks novelty or is obvious, the claim scope must be confined to its normal construction, and so the claim would be valid but not infringed. As Birss LJ stressed, this approach promoted certainty and he thought it appropriate for the approach taken in other European Patent Convention states to be adopted in the UK.

The possibility of relying upon a Formstein defence in an infringement case based on equivalents was first raised in a 2019 decision of HHJ Hacon in the Intellectual Property Enterprise Court, Technetix v Teleste. Again, the Court's observations on the Formstein defence were obiter, but there now appears clear guidance from Birss LJ as to the applicability of the defence in future relevant cases, and how it will operate.

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