A patent examiner (or, historically, a patent clerk) is an employee, usually a civil servant with a scientific or engineering background, working at a patent office. Major employers of patent examiners are the European Patent Office (EPO), the United States Patent and Trademark Office (USPTO), the Japan Patent Office (JPO), and other patent offices around the world.
Patent examiners review patent applications to determine whether a claimed invention should be granted a patent. In general, the most important task of a patent examiner is to review the technical information disclosed in a patent application and to compare it to the state of the art. This involves reading and understanding a patent application, and then searching the prior art to determine what technological contribution the application teaches the public. A patent is a reward for informing the public about specific technical details of a new invention, so the work of a patent examiner includes searching prior patents, scientific literature databases, and other resources for prior art. Then, an examiner reviews a patent application substantively to determine whether it complies with the legal requirements for granting of a patent. A claimed invention must meet patentability requirements of novelty, inventive step or non-obviousness, industrial application (or utility) and sufficiency of disclosure.