Prior art is a legally complex concept, but one that is important for patent applicants to understand. In order to obtain a patent from the U.S. Patent and Trademark Office (USPTO), the existence of "prior art" can be a roadblock. The USPTO will not ordinarily grant a patent over an invention that already exists. What exactly is "prior art" and how can you overcome it in order to secure your patent?
In order to qualify for a patent in the U.S., an invention must be "novel." Under 35 U.S.C. § 102 of the Patent Act, an inventor is entitled to a patent unless "the claimed invention was patented, described in a printed publication, or in public use, on sale, or otherwise available to the public before the effective filing date of the claimed invention...."
In other words, the USPTO will not issue a patent when the claimed invention is already public knowledge in some form or fashion. While there are certainly some complexities and exceptions to this rule, the basic principle is important: An invention must not already exist in order to receive protection.
Moreover, under 35 U.S.C. § 103, one cannot get a patent if "the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains."
Thus, the USPTO examiner will compare the claimed invention to prior art (other existing inventions) and determine whether the differences in the new invention are sufficiently 'new' that they would not be obvious to a person of "ordinary skill" in the relevant field (such as chemistry, medicine, coding, and so forth.).
Importantly, the prohibition on prior art is not limited to merely existing patents; rather, it includes any written description or patent anywhere in the world. If the proposed invention is already the subject of a patent in another country, that precludes the issuance of a patent in the United States. Moreover, if the proposed invention is described in a written publication anywhere in the world (even if it is not formally patented), this still precludes the issuance of a patent in the United States.
For inventors, the existence of prior art can clearly frustrate the attempts to obtain a patent. How can you avoid this problem? The best approach is to perform a comprehensive search for potential prior art. Doing so could help you to avoid protracted dispute with the USPTO's patent examiner—or worse, rejection of your application.
Many public resources will help you to search existing patents. Google Patent Search, for example, allows you to search by keyword and category. You can also use the USPTO's Public Patent Application Information Retrieval (known as PAIR) to conduct searches of filed or existing patents. While these sorts of do-it-yourself searches will not replace a professional search by an attorney, they will give you a sense of existing prior art, and hopefully allow you to focus on the elements of your invention that are truly unique.
Note that patent law and patent searching can be complex. Depending on the nature of your potential invention, it might also be highly technical. For these reasons, you may wish to speak with a patent attorney before proceeding with an application. An experienced attorney can guide your search and help you to frame your application in a way that is most likely to be successful.