After claiming

After claiming (also "late claiming") is the practice of filing a US patent application after the publication by a third party of a description of the same invention. This is possible in US patent law since an inventor has one year after the publication of the description of an invention to get a patent application on file.

In order to get the patent, however, the inventor must submit a declaration supported by evidence that he or she conceived of the invention before the third-party publication. The inventor must also provide evidence that he or she was diligent in either reducing the invention to practice or in filing the patent application.

Example

On December 28, 1995, a Synteni (now Incyte Genomics) patent application WO/95/35505 was published describing a new microarray invention. A Synteni competitor, Affymetrix, filed a patent application describing almost exactly the same invention within six months. This patent application issued as U.S. Patent 5,800,992. Affymetrix then sued Synteni for patent infringement. The case was eventually settled with both parties cross-licensing their patents to each other.