The EPO 's Enlarged Board of Appeal has just answered (here) the questions concerning partial priority posed to it in referral G1/15. Although the reasoning of the Enlarged Board of Appeal is not yet available, it appears that the Enlarged Board has confirmed that partial priority for a claim may not be refused in respect of subject matter embraced by that claim that is also directly (or at least implicitly) disclosed in the priority application. Provided that the disclosure in the priority application is enabling, there are no other substantive requirements in order for partial priority to be established. Thus, where a patent includes a broad claim and only some of the subject matter falling within the claim is disclosed in the priority document, then the claim will validly claim priority insofar as it relates to the matter disclosed in the priority document.
One very welcome outcome of this conclusion is that the so-called poisonous divisional problem should disappear. That is because any disclosure in the divisional application that is entitled to priority is also so entitled in the parent application, meaning that no citation under Article 54(3) EPC is possible. Similarly, there should now be no risk of self-collision between a priority application that has been published and a later European patent application that claims priority to it.
More information will be provided once the detailed reasoning of the Enlarged Board becomes available.