Date: 26 June 2019
In Technetix BV v Teleste Ltd, the question of infringement was considered hypothetically on the basis that the Formstein defence existed, and the English court concluded that it could apply in the given circumstances.
The Intellectual Property Enterprise Court (IPEC) found that a patent related to a cable tap unit used to modify a cable TV or internet signal was invalid over prior art. Had the patent been valid, HHJ Hacon held that Teleste’s product would have infringed pursuant to the “doctrine of equivalents”. However, he also found that Teleste might have been able to rely on a “Formstein defence”.
Under German law, defendants can rely on the Formstein defence in order to limit the scope of a patent under the doctrine of equivalents: if a product or process is found to infringe a patent in suit by “equivalent means”' under the doctrine of equivalents, but the equivalent would have lacked novelty or inventive step over the prior art at the priority date, then it is deemed to fall outside the scope of the claim. Although not currently available in English law, the judge said he could not rule out the possibility that a Formstein defence might be introduced in the future.
The English courts have not yet decided how the doctrine of equivalents should be applied when considering the validity of a claim, but this decision illustrates how a Formstein defence could provide a squeeze on patent infringement.
Our full article will be published in Computer and Telecommunications Law Review  Issue 5, pages 138 to 140.