Prior art search as a practical, repeatable routine

The same word covers several different tasks, and the purpose changes how deep you go and which date matters. A patentability or novelty search is run before filing to see whether an invention is new and non-obvious and to help draft claims around what already exists. A validity or invalidity search targets an issued patent, usually in litigation, licensing or a sale, and looks for anything earlier than that patent's effective filing date that anticipates or renders its claims obvious. A state of the art search maps a technology field before research or investment.

A freedom to operate review is related but different. It asks whether a product infringes someone else's patents that are in force, which is a question about live claims rather than prior art. The two often run together, because prior art found during an FTO review can support an argument that a blocking claim is invalid. Our page on FTO analysis covers that side.

For applications and patents with an effective filing date on or after March 16, 2013, the America Invents Act first-inventor-to-file rules apply. Under 35 U.S.C. 102(a), prior art includes anything patented, described in a printed publication, in public use, on sale or otherwise available to the public before the effective filing date, anywhere in the world, plus US patents and published applications naming another inventor that were effectively filed earlier.

The main exceptions in 102(b) give inventors a one-year grace period for their own disclosures. A disclosure made one year or less before the effective filing date by the inventor, or by someone who obtained the subject matter from the inventor, is not prior art against the inventor's claims, and a later disclosure by others of the same subject matter after the inventor's public disclosure is also excluded. Relying on the grace period is risky in practice, because most other countries require absolute novelty and do not offer the same protection.

Patents with an effective filing date before March 16, 2013 are still judged under the earlier first-to-invent rules, which matters for invalidity work on older patents that remain in force or are litigated for past damages. Always confirm which regime applies before setting the critical date.

• Find the effective filing date, including any valid priority claims.
• Apply AIA rules on or after March 16, 2013, and earlier rules before it.
• Remember that foreign use and sale count under the AIA.
• Treat the inventor's own grace period as a US-specific safety net.

Before typing a query, write the invention as a short list of elements, the way a claim would. A good definition separates the core inventive concept from features that are routine in the field, because the search should focus on the combination that makes the invention different. For an invalidity search, the claims of the target patent are the definition, element by element.

For each element, build a list of synonyms, broader and narrower terms, and the vocabulary of adjacent industries. Patent drafters often avoid ordinary words, so a fastener may be a coupling member and a phone may be a mobile communication device. Note acronyms, older terminology and spelling variants, especially for documents translated from other languages.

• List each element of the invention or claim separately.
• Mark which elements are likely novel and which are routine.
• Build synonym sets for each element, including patent language.
• Note older terms, since earlier art often used different words.

Start with the free public databases, which together cover most of the world's patent documents. Patent Public Search is the USPTO's full text tool for US patents and pre-grant publications, with an Advanced Search that supports field searching and proximity operators. Google Patents searches US and many foreign collections with machine translation and is fast for broad first passes. Espacenet, run by the European Patent Office, covers a very large worldwide collection and groups documents into families. WIPO PATENTSCOPE covers PCT applications and many national collections, with cross-lingual search. J-PlatPat covers Japanese documents, which are important in electronics, materials and automotive fields.

Combine concept sets with Boolean logic and proximity rather than stringing all terms together. Start broad, read a sample of results, and refine by adding concepts or classification limits. Search the claims and abstract fields for focus, and the full text when you need to find a feature buried in a description. Remember that published applications that were abandoned are still prior art, and that expired patents remain prior art forever.

For practical help navigating the USPTO tools in particular, our guide to USPTO database search explains which system holds which data.

Keyword searching misses documents that describe the same idea in different words. Classification fixes that. The Cooperative Patent Classification, used by the USPTO and the EPO, assigns each document to detailed technology groups, and the CPC scheme can be browsed and searched by keyword to find the right groups. Once you find two or three highly relevant documents, look at their CPC codes and search those groups with a narrower keyword set.

Citations are the second shortcut. Backward citations are the references a document cites or the examiner cited against it, and forward citations are later documents that cite it. Following both directions from the best references often turns up the closest art faster than any query. Check the file histories too: office actions in Patent Center and in foreign offices through Global Dossier show what examiners already found.

• Collect CPC codes from the most relevant hits and search those groups.
• Follow backward and forward citations from each strong reference.
• Read examiner citations in related file histories.
• Use family information to find the best language version of a document.

Much of the closest prior art never appears in a patent. Journal articles, conference papers, theses, standards documents, technical manuals, product catalogs, archived web pages and open source repositories can all be printed publications or evidence of public use or sale. In software, telecommunications and medicine, non-patent literature is often the strongest art available.

Useful sources include Google Scholar, IEEE Xplore, the ACM Digital Library, PubMed, arXiv, standards body archives and the Internet Archive for dated web pages. The hard part with non-patent literature is proving the date and public availability, so capture the publication date, the source and a stable copy for every document you rely on. For products, look for manuals, datasheets, trade show materials and press coverage with clear dates.

• Search academic databases with the same concept sets.
• Look for product documentation with verifiable dates.
• Check standards documents for communications and electronics inventions.
• Save a dated copy of every non-patent reference you plan to use.

A search is only as useful as its record. Write down each database, query, classification group and date, and keep a table of references with their publication dates, the elements each one shows and a short note on relevance. That record lets a colleague repeat or extend the work, supports the reasoning in an opinion, and shows diligence if the search is questioned later.

For patent applicants, the search also triggers obligations. Under 37 CFR 1.56, each individual associated with the filing and prosecution of an application has a duty of candor and good faith, including a duty to disclose information known to be material to patentability. Material references found in a search are usually submitted to the USPTO in an Information Disclosure Statement. Failing to disclose known material art can lead to a finding of inequitable conduct, which can make a patent unenforceable.

• Log every query and database with dates.
• Map each reference to the claim elements it shows.
• Keep copies and proof of publication dates.
• Coordinate with counsel on which references go into an IDS.

Prior art search is usually treated as a technical exercise, but each patent reference also points to someone who owns rights. A close reference that is still in force may be a blocking patent rather than just prior art, and the owner named on its face may no longer be the owner. Patents are sold, assigned in mergers and pledged to lenders, and the original applicant can be long gone from the record.

Checking the current owner of record turns a reference list into a map of who matters. It tells you whom you might license from or acquire from, which competitors have consolidated a technology area, and whether a key reference sits with an operating company or with a licensing firm. It also tells you whether a reference has expired for nonpayment of maintenance fees, which removes it as a blocking risk while it remains prior art. Our pages on patent assignee search and patent licensing cover those next steps.

• Separate references that are expired from those still in force.
• Check the current owner of record for every live reference that matters.
• Group references by owner to see who controls the field.
• Note security interests that may affect a seller's ability to license or sell.