Under U.S. patent law, an invention lacks novelty if it was publicly used by others in the U.S. prior to the date it was invented by the applicant for a patent [35 U.S.C. 102(a)]. This situation typically occurs when someone other than the applicant(s) independently invents the invention before the applicant(s) do and uses it in public. It can also occur when the applicant(s) do not make deliberate attempts to keep information about their incomplete invention a secret during its development and someone else grasps the reason the invention is incomplete, completes it before the applicant(s) do(es) and uses it in public in a way that teaches the invention.
The use which is accessible to the public must be performed by other than the inventor(s). Thus, the user can be one of the joint inventors named in an application, the implication being that one of the joint inventors was actually the sole inventor because the use must have occurred before the date that the joint inventors completed their invention. The use must be in the U.S. (or in its territories or possessions) and, for that reason, even widespread use in another WTO or NAFTA member country (or any other country, for that matter) does not destroy novelty under 35 U.S.C. 102(a).
As is the case with 35 U.S.C. 102(b), the public use can be a single public use of a single article by a single person, but here the use must be by "another." Public use or public accessibility of a machine that embodies the invention invokes the bar, even if the invention is a part of the machine that is hidden from view. Public use also occurs when someone other than the applicant (that "someone" being the true first inventor) allows public use of an invention without restriction or obligation of secrecy to the inventor. Making a product of a secret machine or process accessible to the public can be a public use of the machine or process if "how to make" and "how to use" the machine or process are ascertainable by inspection or analysis of the product. Patent Partner explains the experimental exception to this rule in another evaluation element.