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Patents secure rights for inventions that are "new" or "novel." This means that before a patent can be granted, patent examiners must determine whether the invention can be found in the "prior art." Thus, it is prudent to search for prior art before applying for a patent to determine what part of the invention can be claimed under a patent. This article will discuss some of the basic concepts of prior art and performing prior art searches.

What is Prior Art?

So, which kinds of information are considered by patent examiners when they determine whether a patent claim is to a "novel" idea. The answer technically depends on which jurisdiction the patentee is considering filing in. For instance, the European Patent Office (EPO) defines prior art as "any evidence that your invention is already known." In contrast, the United States Patent and Trademark Office defines prior art as "those references or documents which may be used to determine novelty and/or non-obviousness of the claimed subject matter in a patent application. As the definition implies, the United States patent laws explicitly define what references may be used to determine novelty and non-obviousness. Before the passage of the America Invents Act (the AIA), certain foreign references were excluded from the body of prior art. However, the new laws essentially include any publicly available information as prior art.

35 U.S.C. Section 102(a)-(b) defines the conditions required for patent claims to be novel. While the "grace period exceptions" under 102(b) are crucially important to a formal understanding of personally-generated prior art (such as, for instance, marketing disclosures), this article will focus on Section 102(a), which state that "[a] person shall be entitled to a patent unless—

(1) the claimed invention was patented, described in a printed public, or in public use, on sale, or otherwise available to the public before the effective filing date of the claimed invention; or

(2) the claimed invention was described in a patent issued under section 151, or in an application for patent published or deemed published under section 122(b), in which the patent or application, as the case may be, names another inventor and was effectively filed before the effective filing date of the claimed invention.

Section 102(a)(1)

Essentially, 102(a)(1) boils down to five fundamental types of priors art.

1. "...described in a printed publication,"

According to Federal Circuit case law, '"printed publication" has been interpreted to mean that before the critical date, the reference must have been sufficiently accessible to the public interested in the art; dissemination and public accessibility are the keys to the legal determination whether a prior art reference was 'published.'"1 This does not mean that prior art must be indexed in a publicly available library or web engine to be considered. For instance, slides displayed at a scientific conference may be considered "sufficiently accessible to the public interest in the art."

2. "...patented"

The patented category in 102(a) is somewhat of a red herring, and that is why it is worth addressing specifically in this section. When an examiner reviews your application for a patent, there is a statistically-likely chance that it will be based on a previous patent if the original claims are rejected. However, it is important to note that the patent itself is almost surely NOT the reference they are using to reject your patent in this case. The application that the issued patent is based on is more likely the reference under which the Office Action is issued (based on section 102(a)(2)).

If you happened to jump ahead to the section about 102(a)(2), you might have noticed that it only addresses U.S. filed applications. Therefore it would seem like foreign patents may sometimes qualify under this category. However, even a foreign application will be published before a patent issues based on the application. And even if a patent were to issue before the application was published, the issuance would simultaneously be a printed publication.

3. " public use"

Even if there is no documentary evidence that an idea you have for a patent has already been invented, the existence of the invention in public is a prior art reference. For instance, if your patent is directed to a scheme for attaching wires to telephone poles, and a company is practicing the invention in their own business on public telephone poles, then that is a prior art reference.

The public use exception applies to use anywhere in the world. MPEP Section 2152.02(c). However, it should be noted that for the public use exception to apply, the use must be public so that a person having ordinary skill in the art (a PHOSITA) would know from the use how to practice the invention. So in certain situations where an end product cannot be reverse-engineered, and the inventive part of making the product is sufficiently confidential, there would be no prior art reference.

4. "...on sale,"

A sale anywhere in the world of the same invention as you are claiming will defeat the novelty of your invention. Unlike other types of prior art in this section, the prior art references that are "on sale" do not need to be enabling to the public in order for them to be a barring reference under this section. So, returning to the previous example of an invention for attaching wires to telephone poles, if a company were to sell the invention to someone to use it completely privately, in an area that was not publicly-accessible, this would still be considered a prior art reference under 102(a)(1). The legal standard is that "on sale activity will bar patentability if the claimed invention was: (1) the subject of a commercial sale or offer for sale, not primarily for experimental purposes; and (2) ready for patenting."2

5. "...or otherwise available to the public"

The last type of reference covered in Section 102(a)(1) is a "catch-all" provision meant to cover types of prior art that do not neatly fit into any other category but which still bar patentability. A common situation that arises is when a scholar or student displays a poster or other information at a scientific meeting for like-minded peers.3


102(a)(2) includes U.S. patent documents that have a 102(a)(2) "effectively filed" prior art date. There are three types of U.S. patent documents that would fall into this category:

  1. U.S. patents
  2. U.S. patent application publications
  3. World Intellectual Property Organization (WIPO) publications of PCT applications that designate the U.S.

Examiners are best tuned to find prior art in patent databases where they can perform text searches of issued patents and patent application publications. Therefore, it can be quite helpful to search for prior art patent publications to find critical references that will need to be considered in drafting patent claims to your invention. The next section will discuss some of these resources in more detail.

How to Search for Prior Art

There are many tools, methodologies, and professional search agencies that can be utilized to uncover prior art references. This article will discuss a general approach for thinking about the prior art search process but is not a comprehensive guide on the subject. There are many other helpful resources that an inventor should consider in the process of searching for prior art.

1. Develop a List of Keywords

To effectively search for prior art it is important to read the invention disclosure and determine the words that will be the most important for finding relevant work that could defeat or narrow the novelty of the invention.

2. Read Related Scientific Literature to Generate Alternative Keywords

After determining what keywords will be the most relevant for the prior art search, a prudent next step is to do some research about the concepts that the prior art is related to in order to find alternative ways of phrasing the keywords. I find this particularly relevant when working with a technology that one is not deeply familiar with. In many cases, inventors will discuss their inventions with you in terms of industry jargon. In some instances, the jargon may even be specific to their company.

3. Consult a Prior Art Database

There are many prior art databases out there in which you can find prior art references. One to consider is Google Patents, which is publicly available and contains a massive amount of issued patents and published patent applications. Another resource that is commonly-utilized, particularly internationally, is Espacenet. While there may some small differences in what is available between the two platforms, I would say that the difference is more a matter of style. Espacenet has some more advanced features for searching, but Google Patents is probably more accessible for beginners. Another useful resource is PatFT (which stands for Patent Full-Text Databases). I find PatFT particularly useful when I find a good prior art reference but I want to work with it in a more convenient manner than in a prior art database. It allows you to access plain text versions of the applications and patents, which you can put into a word document to perform more sophisticated highlight and search functions.

Getting in the Weeds with Google Patents

When it comes to prior-art searching with the Google Patents database, there is a lot more there than may meet the eye at first glance. When you go to the home page of the search tool, it presents you with a search box similar to the one on Google's own home page. From there, you can simply type relevant keywords that you want to search for in patents and patent applications. But there are also more advanced settings that can be leveraged by the tool. This article does not claim to provide all of the options available within Google Patents (because I do not know them all), but it should give you a good feel for some of the basic functionality of the tool.

Using Boolean Operators in Google Patents

Like other legal search tools, the heart of Google Patents is the option to perform boolean searches. Boolean searches allow you to combine words and phrases using the words AND, OR, NOT, and others to limit, broaden, or further define your search.4 Here is a list of how some of these functions work:

  • AND – this operator will retrieve results that contain both words that are joined thereby. For instance, a search for (airplane AND motor) will only retrieve results that include both of the terms within the text of the patent.
  • OR – this operator will retrieve results that contain either of the words that are joined thereby. For instance, a search for (airplane OR motor) will retrieve results that include either of the terms within the text of the patent.
  • ! or * – these operators, sometimes referred to as "wildcards," can be used to search for different forms of a root word. For instance, a search for (throttl!) would return results for "throttle" or "throttling" or any other derivative of the root word.

There are also "proximity operators" including WITH, SAME, and ADJ/x which will find words that are within a search number of terms of each other.

Searching Different Parts of the Patent

One thing that I think is particularly helpful in doing a patent search with Google Patents is being able to search within different parts of the patent. It allows you to narrow down to either the Title (TI), the Abstract (AB), or the Claims (CL). For example, you can search CL=(airplane AND motor) to find patents and applications that only contain both of these claim terms within the claims of the patent. This can be particularly helpful if using the tool to do a freedom to operate (FTO) search.

[1] In re Cronyn, 890 F.2d 1158, 1160 (Fed. Cir. 1989) (quoting Constant v. Advanced Micro-Devices, Inc., 848 F.2d 1560, 1568 (Fed. Cir. 1988)).

[2] MPEP Section 2152.02(d) (citing Pfaff v. Wells Elecs., Inc., 525 U.S. 55, 67 (1998).

[3] See, e.g., In re Klopfenstein, 380 F.3d 1345 (Fed. Cir. 2004).

[4] What is Boolean Search?, New York Public Library: Blogs (Feb. 22, 2011),,broaden%2C%20or%20define%20your%20search.