PCT International Search and Preliminary Examination Guidelines
PART III EXAMINER CONSIDERATIONS COMMON TO BOTH THE INTERNATIONAL SEARCHING AUTHORITY AND THE INTERNATIONAL PRELIMINARY EXAMINING AUTHORITY
Documents Casting Doubt on Priority Claim Made in the International Application
11.06 Documents showing that a priority claim in the international application might not be justified (for example, an earlier application or patent resulting therefrom, by the same applicant, indicating that the application from which priority is claimed may not be the first application for the invention concerned) should be mentioned in the international search report and explained in the relevant portion of the written opinion. No special search is normally made by the International Searching Authority to determine whether the priority claim made in the international application is justified, except when there is a special reason to do so, for example, when the priority application is a “continuation-in-part” of an earlier application from which no priority is claimed; also sometimes the fact that the country of residence of the applicant is different from the country of the priority application may be an indication of possible lack of first filing, justifying a certain extension of the international search.