By: Timothy Murphy and Jessica Zilberberg

Though not required, some patent applicants choose to conduct a prior art search before filing a patent application. Prior art includes any evidence that an invention is already known—for example, other patents or patent applications, research papers, and published articles. Offers to sell an invention, using an invention in public, and presentations can also constitute prior art. An effective prior art search gives a patent application a preview of what to expect during patent prosecution. After all, once a patent examiner picks up the application, the examiner himself will conduct a prior art search. This in turn allows the patent applicant to make informed decisions about patent strategy. For instance, claims can be tailored to avoid close prior art, and ultimately streamline the prosecution process.

Examiners have available to them the same online public resources as everyone else—Google Patents, Free Patents Online, the USPTO’s website, and others. These resources are great for searching for relevant patents and patent applications. Even so, ordinary web searching should not be forgotten, as it is the easiest way to find non-patent prior art (like journal articles, existing products, etc.). Examiners also have access to a search tool called EAST (Examining and Searching Tools), which the public can access at any of the PTO’s offices. There are also subscription-based search tools, like Lexis Total Patent, which some firms may have access to.

Now that you know where to search, here are some tips for how to conduct the most effective prior art search:

  1. Use keywords to find the most relevant references. Select a few keywords that represent the invention for text-based searching—include synonyms and related terms where appropriate.
  2. Check forward and backward citations. Once your text-based search returns some relevant prior art references, check the forward and backward citations for those references. Backward citations are the prior art references that were cited in the reference. Forward citations are other patents that cite the reference. This gives you some insight into what other patent applicants and examiners in similar technology areas thought was relevant.
  3. Identify and search through relevant classes. All patents are classified according to their technology area. There are a few classification systems—USPC (US Patent Classification), IPC (International Patent Classification) and CPC (Cooperative Patent Classification). Once you have identified the most relevant references, check their classifications. Click through the other patents and patent applications in the same classes as the most relevant references uncovered in your search.
  4. Keep in mind the “why” behind the invention. Don’t just search for similar structures, keep the function of the invention in mind while searching.
  5. Searching is an iterative process. As you search, you may want to repeat one or more of the methods above. For example, as you read relevant references, you may see some keywords that you should include in a text-based search.