Priority at the EPO

United Kingdom

This article was produced by Olswang LLP, which joined with CMS on 1 May 2017.

The priority system is at the heart of the patent system.  Most patentees rely on the right to claim priority to secure protection outside of their home country and the validity of many patents is dependent on the validity of the priority claim.  Considering the basic principles of priority were agreed in the Paris Convention in 1883 it is perhaps surprising any doubt remains as to its operation.

The European Patent Convention (EPC) specifies that priority may be claimed from the first application for protection of an invention.  This raises the question of the meaning of "invention".  Case law has developed to say that this relates to the claimed invention in the later application, and the overall disclosure of the earlier application.  That is, the later application can disclose additional subject matter and inventions, but can only claim priority for an invention in the earlier application.    However, how similar does the disclosure have to be to be "the same invention"?  For example, is priority valid if:-

  • The earlier application discloses a species, and the later application claims the genus in which that species belongs.
  • The earlier application discloses a genus, and the later application claims a species within that genus.
  • The earlier application discloses that feature A is an X, and the later application claims "where A is an X or a Y".

Generally the answer for the first two is no - the disclosure of the earlier application is different in scope to the later application and hence is for a different invention.  The answer to the third case, at least since the Enlarged Board gave its decision in G2/98, is that the "X" option is entitled to priority, but the "Y" option is not.  A claim, therefore, can have two priority dates.  This has been termed “partial priority”.

Entitlement to priority, particularly in relation to the first example, has become more critical due to the development of case law at the EPO that says family members can be prior art against their own family if they have different priority dates. For the first example above, assume a first application is filed disclosing a species, and a later European priority-claiming application is filed disclosing and claiming the genus within which that species belongs. A divisional is then filed claiming the species. The divisional application is entitled to the priority date, but the parent claim is only entitled to its filing date, as the genus was not disclosed in the original application. The divisional is then prior art under Article 54(3) EPC (which specifies that a European application with an earlier priority date than a later application, but which was not published at the later application's priority date, is prior art for novelty only). The divisional is therefore prior art against the parent, and the claim to the genus lacks novelty over the species. The danger of losing priority is not restricted to this self-collision aspect - it brings in up to 12 months of additional prior art from all sources.

However, this situation wouldn't occur in the third example above.  The claim is entitled to priority to the extent of the earlier disclosure, so "X" and "Y" each have the same priority date in all applications in the family.  The question then arises as to why the first and third options are treated differently – in the first example, why can't the species of the later claim be entitled to priority, and the other parts within the genus not be entitled to priority (i.e. the claim has a partial priority claim for the species)?

Various Boards of Appeal have reasoned that this is not possible because G2/98 specified a claim can only have more than one priority date if the claim can be split into a limited number of clearly defined alternatives.  This has been interpreted to mean a claim in the form “A" or "B" with explicit alternatives.  However, in T1222/11 and T571/10 the Board of Appeal took a different view and said the "limited number of clearly defined alternatives" should be defined in relation to the prior art, not in a general sense.  So in the first example above there are two alternatives - the species, and every other species within the genus.  Partial priority would therefore be accorded.  This conflict between decisions has now been picked up by the Board of Appeal in T0557/13 who have referred questions to the Enlarged Board of Appeal.

The appeal hearing was held in December 2014, but the Board have only just (August 2015) published their decision which includes the questions they have referred to the Enlarged Board.  The questions are:-

  1. Where a claim of a European patent application or patent encompasses alternative subject-matters by virtue of one or more generic expressions or otherwise (generic "OR"-claim), may entitlement to partial priority be refused under the EPC for that claim in respect of alternative subject-matter disclosed (in an enabling manner) for the first time, directly, or at least implicitly, and unambiguously, in the priority document?
  2. If the answer is yes, subject to certain conditions, is the proviso "provided that it gives rise to the claiming of a limited number of clearly defined alternative subject-matters" in point 6.7 of G 2/98 to be taken as the legal test for assessing entitlement to partial priority for a generic "OR" claim?
  3. If the answer to question 2 is yes, how are the criteria "limited number" and "clearly defined alternative subject matters" to be interpreted and applied?
  4. If the answer to question 2 is no, how is entitlement to partial priority to be assessed for a generic "OR"-claim?
  5. If an affirmative answer is given to question 1, may subject-matter disclosed in a parent or divisional application of a European patent application be cited as state of the art under Article 54(3) EPC against subject-matter disclosed in the priority document and encompassed as an alternative in a generic "OR"-claim of the said European patent application or of the patent granted thereon?

These questions appear to address the situations laid out above, and if answered fully should resolve at least this aspect of the priority system.  The Board of Appeal does not appear to have a strong opinion on what the answers to these questions should be, and there are good arguments in all directions.  It is very difficult to predict the outcome of this referral, and due to the importance of the topic is likely to be highly debated both within the EPO and across industry.  The Enlarged Board will in due course confirm acceptance of the questions, and it is likely at some point public comments will be invited.  Ultimately the Board will respond with answers to the questions which must then be applied by all instances at the EPO.

While we wait for the Enlarged Board's words of wisdom (which will likely be well over a year in coming), there remain some important practice points.  

  • Ensure a priority-founding application is as comprehensive as possible and includes the best-possible set of claims.  
  • Any changes between the priority application and the later application can lead to a loss of priority, which potentially fatal consequences. Ideally a priority-found application will be identical to later applications, but if this is not possible a careful consideration of priority should be made.
  • Where you are aware of differences, it may be beneficial to include explicit basis for a disclaimer to the specific disclosure of the earlier application.
  • Consider a review of priority-founding applications by a European attorney for suggestions on any points that may improve the value of the application as the basis for a priority claim by a European application.
  • The EPO can, and should, stay proceedings while an Enlarged Board responds to the questions.  It is likely to be preferable to all parties to request a stay where this case is relevant, particularly in opposition proceedings. Since the referral was first announced (without the questions) in December 2014 Olswang has been requesting stays and been successful in a number of cases.  Now that the questions are available it should become easier to obtain a stay.  Even if there is a perception that the Enlarged Board's decision will be adverse to a party it is likely to be preferable to request a stay in any first-instance cases.  The Enlarged Board decision will be available before an Appeal is concluded and so will be considered before final disposal of a case.  Staying proceedings in the first-instance will give parties more chance to work around the Enlarged Board's view, rather than be in a final corner at a Board of Appeal with fewer options when the adverse view is taken by the Enlarged Board.

The underlying message is that the EPO apply a very strict assessment to the right to claim priority, and even if the Enlarged Board takes the liberal option of allowing partial priority this will still be assessed under strictly applied rules, equivalent to the “direct and unambiguous” test applied for added matter.