In the process of applying for a patent, a patent search is often performed for the purpose of evaluating the novelty of the invention.  There are also other types of searches that serve different purposes, such as invalidation searches and market-field searches.  Novelty searches are generally the least expensive, and most commonly used, searches in the patent process.

To determine whether an invention is novel (new), the law provides that a person will be entitled to patent protection for their invention unless it “was known or used by others” in the U.S. before invention by the inventor, or was “patented or described in a printed publication” anywhere, more than one year prior to the person’s patent application date (35 U.S.C. § 102).  Prior patents or printed publications are referred to as “prior art,” and the novelty requirement is often restated in the negative; i.e., to be patentable, a claimed invention cannot have been anticipated by the prior art.  “A claim is anticipated only if each and every element as set forth in the claim is found either expressly or inherently described in a single prior art reference.”  Verdegaal Bros. v. Union Oil Co. of California, 2 U.S.P.Q.2d 1051, 1053 (Fed. Cir. 1987). That is, the invention is not novel if some other single invention somewhere incorporates each and every element.

Even if the exact invention is not identically disclosed somewhere (i.e., “anticipated”), patent protection is not available “if the differences between the subject matter sought to be patented and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art to which such subject matter pertains” (35 U.S.C. § 103).  This is the non-obviousness requirement.  For an invention to be obvious, three basic criteria must be met:

• There must be some suggestion, or motivation, either in the references themselves or in the knowledge generally available to one of ordinary skill in the art, to modify the reference or to combine reference teachings. 
• There must be a reasonable expectation of success. 
• The prior art reference (or references when combined) must teach or suggest all the   claim limitations.

In re Vaeck, 947 F.2d 488, 20 U.S.P.Q.2d 1438 (Fed. Cir. 1991); see also M.P.E.P. § 706.02(j).