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T 1983/14: The inescapable trap, but not as we know it


Patent practitioners are familiar with the so-called ‘inescapable trap’. This is a situation in which a granted patent is inescapably invalid because an amendment to the claims that is required to overcome an added matter issue would contravene the prohibition against broadening the scope of the claims post-grant.

The European Patent Office’s (EPO) Board of Appeal decision in T 1983/14 illustrates a somewhat different and less familiar form of the inescapable trap. It demonstrates the importance of considering the validity of a patent application’s claim to priority before it is granted.


Like other patent systems, the European Patent Convention (EPC) prohibits post-grant amendments that broaden the scope of the claims. This is to improve commercial certainty for third parties, who can rest assured that if their actions do not infringe a patent at the time it is granted, those same actions will never infringe the patent, even if its scope of protection is amended post-grant.

While this prohibition applies in all situations, it is best known in Europe for its interaction with the prohibition against adding subject matter that extends beyond the disclosure of the application as filed. This interaction was considered by the EPO’s Enlarged Board of Appeal in G 1/93: if a patent as granted includes a limitation to claim 1 that adds matter, unless the added matter issue can be overcome by a further limitation to claim 1, the patent is inescapably invalid. This is because the only means of addressing the added matter issue would amount to prohibited post-grant claim broadening.

The inescapable trap is especially significant in Europe because of the EPO’s strict assessment of added subject matter, and patent practitioners are well aware of the risk of adding matter during the examination of European patent applications.

The Decision

The decision under appeal was the Opposition Division’s decision to revoke European Patent EP 1560142 for lacking novelty.

The invention related to an electronic point of sale (EPOS) terminal that allows a shop cashier to sell mobile phone credit (“top-up vouchers”) using the same EPOS terminal used for other goods and services, such as groceries and fuel. Claim 1 of the granted patent included the following limitation:

“An electronic point of sale (EPOS) multi-task apparatus for the purchase of mobile telephone credit and other products in a retail environment…operable to…invoice the purchase of the mobile telephone credit product and other products on the EPOS as one transaction”.

All parties accepted that claim 1, including the underlined feature, had basis in the application as filed. The claims therefore did not add matter, and the conventional inescapable trap could not rear its ugly head.

However, EP 1560142 claimed priority from an earlier filed Irish national patent application and, as it transpired, the only explicit basis for the underlined feature was contained in some passages and figures of the application that had not been included in the priority application. The opponents therefore questioned whether claim 1 was entitled to its claimed priority date.

This was bad news for the owner of the patent because they had, by their own admission, publicly used the invention between the priority date and the filing date. This meant that if the priority claim was invalid, their own public use would be novelty destroying prior art.

In fact, it was even worse news than it first appeared. If the underlined feature was not disclosed in the priority application, the only way the validity of the priority claim could be restored would involve broadening the claims, which is prohibited. On the other hand, the nature of the public use was such the owner could not make any claim limitations that would restore novelty over the public use. The patentee would therefore find themselves in an inescapable trap, unable to restore the novelty of their claims without broadening the scope of protection.

Despite the missing passages and figures in the priority application, the patentee could be forgiven for believing that their priority claim was valid. The priority application included the following statement:

“the top-up software control module has means for printing the top-up code onto a customer receipt and adding the value of the top-up to the total receipt”.

At face value the underlined text seems to support the invoicing of the purchase of mobile telephone credit and other products as one transaction, as was claimed. Unfortunately for the patentee, when the EPO assess priority entitlement they apply the same strict test that they use for assessing added matter.

This test, set out in G 2/98, requires that the claimed subject matter is “directly and unambiguously derivable” from the priority application. The Board of Appeal accepted that the statement in the priority application could be interpreted as disclosure of the claim feature in question, but this was not good enough. The Board felt that other reasonable interpretations were possible, such as the printing of the top-up code and top-up value on the same physical receipt. Since other reasonable interpretations were possible, the Board decided that the statement was not direct and unambiguous disclosure of the claim limitation.

The Board therefore decided that claim 1 of the patent was not entitled to its claimed priority date, and that it therefore lacked novelty over the admitted prior use. They further decided that there was no means of addressing the lack of novelty by amendment: the patentee was caught in an inescapable trap, analogous to the added matter trap considered in G 1/93.


This case illustrates the importance of considering the validity of a European patent application’s priority claim before grant, especially if there may have been a public disclosures of the invention in the time between the priority date and the filing date. If an issue is spotted before grant, it may be possible to craft a claim that is both entitled to its claimed priority date and is novel and inventive over the other prior art. Post-grant, however, it is possible to find yourself in an inescapable trap.

It is also worth remembering that while the EPO will always assess whether amendments add matter, they will only assess a claim’s priority entitlement if they are aware of disclosures made between the priority date and filing date. Since the EPO will often be unaware of public use in the priority year, the onus is on applicants and their advisers to consider priority entitlement before grant. In particular, care needs to be taken where material has been added to the priority application, and where there has been a public disclosure in the priority year.

This article is for general information only. Its content is not a statement of the law on any subject and does not constitute advice. Please contact Reddie & Grose LLP for advice before taking any action in reliance on it.

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