Co-pending applications: Collision course

It is a well-established legal concept in Europe that ‘co-pending’ patent applications are available for the purpose of assessing the novelty of a European patent application that
has been filed between the priority/filing date (the effective date) and publication date of an earlier application. Normally, both a parent application and its related divisional application possess the same effective date for the assessment of patentability and so cannot be cited against one another.

However, the European Patent Office’s (EPO) boards of appeal held, in T1496/11, that a divisional application may, in certain circumstances, be considered to be a co-pending patent application for the purpose of assessing novelty of its own parent application (or vice versa). These applications can be described as ‘self-colliding’ (also commonly referred to as ‘poisonous divisionals’).

How does self-collision occur?