Understanding U.S. Patent File Histories

In order to obtain a patent for an invention, the inventor (usually with the assistance of a patent attorney) files a patent application with the patent office. In the United States, the inventor files the patent application in the United States Patent and Trademark Office (USPTO). The patent application is assigned, usually on a first-come, firstserved basis, to a patent examiner who has education, training, and/or experience in the technical field to which the invention is related. Patent examiners, typically, are scientists or engineers by training, and, it may be surprising to some, most patent examiners are not lawyers.

The patent examination process is sometimes called “prosecution.” During prosecution, the patent examiner will examine the patent application to determine if the requirements for obtaining a patent are met. Broadly speaking, the patent examiner focuses on two general requirements: whether the invention is adequately described, through written text and/or drawings, so that the invention can be understood and practiced by others once the patent expires, and whether the claimed invention meets the statutory requirements of utility, novelty, and unobviousness in light of the “prior art.” In the United States, the prior art includes prior patents (whether issued in the United States or abroad) and publications made anywhere in the world.

To determine this last requirement, the patent examiner will perform a search of the prior art. The USPTO has voluminous amounts of prior patents and publications classified by subject matter, many of which are available on computer databases. The patent examiner will search the prior art relevant to the invention to determine whether the invention claimed in the patent application is novel and unobvious.

The end product of the patent examiner’s initial examination and search of the prior art is a document called an “office action.” In this document, the patent examiner can raise objections to the textual content of the patent application and/or rejections of the claims based on the prior art search. This office action is forwarded to the inventor and to his or her patent attorney. The inventor then has the opportunity to respond to the patent examiner’s office action. The patent examiner, after receiving the inventor’s response, can either issue a further office action or can allow (i.e., approve) the patent application. This communication between the inventor and the patent examiner is commonly referred to as the prosecution history of the patent application. This prosecution history is memorialized in the various writings, thus creating at the USPTO the so-called file history of the patent application.

The file history becomes extremely important and very relevant if a charge of infringement of a U.S. patent is made. In such a case, the alleged infringer will generally order the file history of the U.S. patent unless a review of the patent leads to a clear conclusion that there is no infringement. This is because under U.S. law, one of the steps in determining infringement is to ascertain the scope of the claims of the patent. The scope of the claims of the patent is determined by first looking at the claims, then the description of the invention in the patent application, and then finally at the file history. For example, statements made during prosecution by the inventor can help define or narrow a term in the claims. These statements may be used to interpret an ambiguous or unclear word or phrase in the claims.

Furthermore, the applicant’s statements in the file history as to the content and scope of the prior art can be very helpful in interpreting the scope of the claims alleged to be infringed. Also, amendments can be made to the claims of the patent application. For example, the inventor, in response to a rejection by the patent examiner, may have narrowed his claims by amendment. Under the doctrine of “file wrapper estoppel” (sometimes also called prosecution history estoppel), a patentee cannot recapture lost claim scope that the patentee gave up in order to obtain allowance of the claim. The only way to determine this is by reviewing the file history.

Other events and statements in the prosecution history can be very helpful in determining the scope of the claims. One of many examples can be the written statement made by the patent examiner after a personal or telephone interview with him or her by the inventor and/or the patent attorney. These statements can provide a unique insight into the patent examiner’s thinking about the application. Another example, which is less frequently encountered, is a written statement of the examiner’s “reasons for allowance” of the claims. This statement, if made, can also provide invaluable assistance in determining the scope of the claims.

David V. Radack is vice chair of the Intellectual Property Department and a member of Eckert Seamans Cherin & Mellott, LLC in Pittsburgh, Pennsylvania.

For more information, contact A.B. Silverman at Eckert Seamans Cherin & Mellott, LLC, 600 Grant Street, 44th Floor, Pittsburgh, Pennsylvania 15219; (412) 566-2077; fax (412) 566-6099; e-mail abs@escm.com.