Critical Date for Invalidating a Patent

The Bard’s way of questioning “What’s there in a date?” would have serious repercussions if you are thinking of invalidating a patent because in the field of IP activity date is what forms the basis for everything. That is why it is of utmost important to understand and establish the critical date of the patent before you actually start to invalidate/validate. A critical date can have different nomenclature, viz. the effective filing date, priority date, cut-off date, etc., but eventually, it means the same – the date before which the prior art will be effective. Though USPTO and the Federal Circuit had at many occasions tried to clear the misunderstanding through definite legal statutory and judgments, yet there remains a sort of confusion, which we attempt to sort out.

In US patent law, 35 U.S.C. 102(a) talks about the conditions of novelty, whereas 102(b) deals with the exceptions in its preceding section and its sub-sections. However, these sections only highlight the documents which can be considered as prior art and does not mention anything about the date for a patent application. Section 102(e) explains the effective date for a US patent/published application or an international patent application designating the US. We will walk through these sections and related MPEP regulations to establish a proper understanding of a critical date of a patent.

The Critical date in simple words could be either of the two:

actual filing date of the patent or published application
effective filing date or the priority date to which the patent or application is rightly entitled to.

The idea of a critical date varies in the two phases of US IP regime: Pre-AIA and Post-AIA. Though there is a majority of overlap, yet there are some contrasting objectives which are reflected in the way critical dates are established, especially for foreign patents/publications. Post-AIA caters to IP homogeneity throughout the world and thereby makes room for allowing foreign references to be at par with its US counterpart. Also, the priority date which was earlier varying from application to application now varies from claim to claim for the same document. Let’s discuss these in specific categories.

i) Priority from US family only

If an application is a continuation or divisional application of one or more earlier filed US application, subject to satisfaction of certain provisions, the critical date (effective filing date) is the filing date of the earliest US application.

If an application is a continuation-in-part (CIP) of an earlier US application, and claims subject matter which were not disclosed earlier in the parent US application then the critical date is the filing date of the CIP application. On the other hand, if the subject matter was previously disclosed in the parent application then the filing date of parent application becomes the critical date of the CIP application.

If an application is a subsequent non-provisional filing of a provisional application and the claimed subject matter is completely discloses in the provisional application, then the date of filing of a provisional application becomes the critical date of the application.

ii) International application or priority from International application

International Application filed before November 29, 2000

These applications are subject to the pre-AIPA version, and the publication date is considered as the critical date for these applications.

For US patent/published application claiming priority from such application, the filing date of the US patent/application (371(c) – commencement of national stage) is considered as the critical date.

For US applications published directly resulting from the international application, the publication date of the US application is considered the critical date.

International Application filed on or after November 29, 2000

If the international application is published in English and designates US, then the international filing date or earlier filing date, considering proper priority claimed, is the critical date for such application. Else, the publication date of the international application is considered as the critical date for such an application.

For US patent/published application claiming priority from such application, wherein the publication was not in English, the US filing date is considered the critical date.

iii) Foreign patent/ published application or priority from foreign patent/ published application

Pre-AIA

The critical date for the foreign patent/published application is its publication date or the grant date, whichever is the earliest.

For US patent/published application claiming priority from the above-mentioned application, the critical date will be the filing date of the US application. The effective filing date is not the filing date of the foreign priority document; although the filing date of the foreign application can be used to overcome certain prior art rejection.

Post-AIA

The filing date of the foreign patent/published application is considered as the critical date of the patent/published application, provided the subject matter is adequately disclosed in the foreign document and the priority is timely claimed (4 months from the actual filing date of the application/ 16 months from the date of priority – this can be extended up to 2 months on discretion of the Director when the delay made was unintentional).

The above benefit is given to those countries only which affords similar privileges in the case of applications filed in the United States or to citizens of the United States.

The USPTO has also provided a flowchart that tries to simplify the 102(e) aspect of the 35 USC guidelines related to International applications. The rationale is to understand in which category does the validating/invalidating patent belong to and thence the critical date is established to uncover potential prior art.