The issue of partial priority and so-called 'poisonous divisionals' has been a recent topic of interest in European patent case law.
The key argument relates to how a previous decision of the Enlarged Board of Appeal (G 2/98) should be interpreted when considering the priority entitlement of claims directed to generic subject matter that is supported in the priority document by a somewhat more limited example falling within the generically worded claim. Two different Technical Board of Appeal decisions (e.g. T 1222/11 and T 1877/08) have taken different approaches. As a result, some inconsistency in the case-law has developed.
However, recently, an appeal hearing was held in connection with appeal T 557/13 (relating to European patent application 98203458) and the minutes of that hearing indicate that questions are to be referred to the Enlarged Board of Appeal on the topic of partial priorities, to resolve the inconsistency that had developed. The exact form of those questions will not be known until the written decision in connection with T 557/13 is issued. Nevertheless, the prospect of future clarification on this issue comes as welcome news, as it will ultimately provide greater legal certainty as to the validity of many patents.