5.3 Doubts about the validity of the priority claim; widening of the search 

The examining division is responsible for checking whether and to what extent the priority claim is justified. However, if its search uncovers intermediate state of the art (see B‑VI, 5.2) or potential state of the art under Art. 54(3), the search division will, if possible, check the validity of the priority claim (see B‑XI, 4, F‑VI, 1.2 to F‑VI, 1.5 and F‑VI, 2). Similarly, if it finds a document showing that a priority claim might not be justified (e.g. an earlier application or patent belonging to the same applicant and suggesting that the application from which priority is claimed may not be the first application for the invention concerned), it will cite this document in the search report (see B‑X, 9.2.8). However, it will not normally carry out any special search for such documents and will do so only if it has a particular reason, e.g. when the priority application is a "continuation-in-part" of an earlier application from which no priority is claimed (see B‑IV, 2.3 and F‑VI, 2.4.4). Sometimes the fact that the applicant's country of residence is different from the priority application's country of filing can also be an indication that it is not a first filing and so justify widening the search to some extent.

If the search is widened this way, it will cover:

(i)published patent documents filed earlier than the claimed priority date 

Example 1 (assuming that the applicant is the same for all applications)

During the search for EP1, the search division found published application GB1. GB1 was filed earlier than GB2 and so may prejudice the priority claim of EP1. The search division therefore cites published GB1 in the search report as an "L" document (see B‑X, 9.2.8(a)).

(ii)published patent documents which claim priority from an application filed before the searched application's priority date 

Example 2 (assuming that the applicant is the same for all applications)

The publication US1 was found during the search on EP1. GB1 was filed earlier than GB2 and so may prejudice the priority of EP1. The search division therefore cites US1, which claims priority from GB1, in the search report as an "L" document (see B‑X, 9.2.8(a)).