What is the relationship between conception and diligence in patent law?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

In patent law, there is a crucial relationship between conception and diligence. According to the MPEP, Where conception occurs prior to the date of the reference, but reduction to practice is afterward, it is not enough merely to allege that the inventor or inventors had been diligent. Rather, applicant must show evidence of facts establishing diligence.

This means that when an inventor claims to have conceived an invention before a prior art reference but reduced it to practice after, they must provide evidence of diligence in the interim period. The MPEP further clarifies, In determining the sufficiency of a 37 CFR 1.131(a) affidavit or declaration, diligence need not be considered unless conception of the invention prior to the effective date is clearly established.

Therefore, the process typically follows this order:

1. Establish conception prior to the effective date of the reference
2. If conception is established, then demonstrate diligence from just before the reference date until reduction to practice

This relationship ensures that inventors who conceive an idea early but take time to reduce it to practice can still establish priority, provided they were diligent in their efforts.