Defense lawyers and other opponents use this phrase when they want to knock down a patent application or weaken a patent lawsuit. Their angle is simple: dig up older patents, published articles, product manuals, public demonstrations, or other evidence showing the idea was already known, then argue the claimed invention is not new or not non-obvious.

A prior art search is the process of looking for those earlier public disclosures before filing or enforcing a patent. "Prior art" means information that was available to the public before the relevant filing date and that can be used to challenge whether an invention qualifies for patent protection. The search may cover U.S. and foreign patents, patent applications, technical publications, websites, catalogs, and sometimes products already on the market. The goal is to spot problems early and measure how strong a proposed patent claim really is.

Practically, a good search can save time, filing costs, and a lot of false confidence. It can help an inventor narrow claims, redesign the invention, or decide not to pursue a weak application. It also helps businesses avoid stepping into someone else's rights.

In a dispute, prior art can shrink the value of an injury-free business claim by undercutting damages tied to a patent, licensing deal, or infringement case. There is no South Dakota-specific filing deadline unique to a prior art search; patent rules are mainly federal and handled through the U.S. Patent and Trademark Office.