Under U.S. patent law, an invention lacks novelty if it was diligently completed in the U.S. by another (who has not abandoned, suppressed or concealed it) prior to its invention by the applicant for patent. [35 U.S.C. 102(g)]. This rule is an exception to the "first to invent" concept in that a prior art invention that is abandoned, suppressed or concealed will not anticipate (defeat the patentability of) the same invention when it is "rediscovered."
Rejections under 35 U.S.C. 102(g) are rare during patent prosecution because knowledge about inventions that have been completed (i.e., conceived and reduced to practice) that have not been made public is typically not available to Examiners. The issue can, however, arise during prosecution and during court challenges of the validity of issued patents. The rule applies even when the prior invention is not known to the public or to the applicant.
The prior art invention must have been completed in the U.S. (or its territories or possessions) by someone other than the applicant (i.e., by an inventive entity other than the inventive entity that filed the U.S. patent application). Finally, the prior art invention must have been completed before the applicant(s) completed the same invention.
A finding of abandonment, suppression or concealment is based on equity principles (e.g., what is fair) and public policy (e.g., encouragement of disclosure of new inventions) in the light of the facts of each case. For this reason, it is difficult to state hard and fast criteria for making such a finding. In general, for abandonment of a prior art invention to be found, the prior inventor(s) must have voluntarily ceased or unreasonably delayed his/her/their efforts to exploit a completed invention that he/she/they have maintained in confidence. Abandonment, suppression or concealment can be found if, within a reasonable time after completion of the invention, a patent application is not filed on the invention, the invention is not described in a publication or the invention is not used publicly. A first inventor who has unreasonably delayed exploitation of his/her/their invention, resulting in an inference that the invention was abandoned, suppressed or concealed, can "reclaim" the invention by resuming a diligent effort to exploit the invention.