Swear back of a reference

In United States patent law, "swearing back of a reference" is a process where an inventor, in certain circumstances, can get a US patent even though the invention became public before the inventor filed an original patent application. This law has been substantially changed as of March 16, 2013, the effective date of the first-to-file provisions of the Leahy-Smith America Invents Act (AIA), although this procedure is still available in patent applications entitled to effective filing dates before this date.

The pre-AIA law granted a one-year grace period from when the invention became known in certain ways to when an inventor had to file their patent application. If, in the course of patent application examination, a patent examiner cites a reference that predates the filing date of the patent application by less than a year, an inventor may still get a US patent if they can swear back of the publication date of the reference.