The following article appears in the journal JOM, 47 (11) (1995), p. 54. JOM is a publication of The Minerals, Metals & Materials Society

Understanding Patent Infringement Legal Opinions

The amount of patent infringement litigation has undergone a substantial increase in the United States in the last decade. In addition, it is not uncommon to see significant damages awarded to owners of patents for infringement by competitors. In one famous case, Polaroid obtained a huge damage award from Kodak for Kodak's infringement of Polaroid's patents in the instant photography field. The potential for large damage awards and other consequences that flow from patent infringement means that it is advisable to understand one of the most important aspects of evaluating the risks associated with patent infringement. This aspect is the patent infringement opinion.

Although patent infringement opinions can be obtained for many different reasons, this article focuses on the situation where another company (e.g., a competitor) has charged you or your company with selling a product that infringes one of the competitor's patents. This charge of patent infringement can be made in different ways, but most commonly it is made in a cease and desist letter that sets forth some very basic facts such as the competitor's patent (often with a copy of the patent attached to the letter) and your company's allegedly infringing product.

There are several strategic issues that must be considered carefully as soon as the charge of infringement is made. In almost every situation, a patent infringement study that leads to a patent infringement opinion should be commenced immediately in order to evaluate the risk of the patent infringement charge and also to provide a basis for avoiding a willful infringement charge by the competitor in the event of a patent infringement lawsuit. If willful infringement is found, damages can be increased by as much as three times the actual damages. It should be mentioned that patent infringement opinions often include a discussion of the validity of the allegedly infringed patent.

There are several items needed in order to produce a competent patent infringement opinion. Most obviously, a copy of the allegedly infringed patent must be obtained if not already provided by the competitor in the cease and desist letter. U.S. patents are public documents that are available from several sources, including public libraries, commercial services, and the U.S. Patent and Trademark Office.

The next item is the file history of the patent, sometimes called the file wrapper. The file history is the entire written correspondence made between the applicant for the patent and the U.S. Patent and Trademark Office. This file history includes, at a minimum, a copy of the patent application as filed, communication from the patent examiner in charge of the application, and communication from the applicant to the patent examiner. The file history remains confidential and unavailable to the public during pendency of the application, but becomes publicly available once the patent is issued. The file histories are kept at the U.S. Patent and Trademark Office and can be copied by the public.

The third main item is a copy of the prior art references cited during the prosecution of the patent application. These references are listed on the face page of the U.S. patent.

The last item is the allegedly infringing product or device itself. Preferably, a commercially sold device is best. Bear in mind that the device, during the patent infringement study, may be taken apart or otherwise rendered unsalable.

Once the information is assembled, an analysis is undertaken by first interpreting the scope of the claims. The claims of the patent are the numbered paragraphs appended to the description of the invention. The claims define the patentee's invention. If there are ambiguities, the description of the invention in the patent can be resorted in order to clarify the ambiguity or to further define a term found in the claim. Finally, the file history must be reviewed in order to determine what the patentee intends to cover by the claims.

After the scope of the claims is interpreted, each claim of the patent is compared to the allegedly infringing device. Only one claim of the patent needs to be infringed in order to have infringement of the entire patent. In analyzing each claim, each element of the claim must be contained in the infringing device in order to show literal patent infringement. If even one element of the claim is missing from the allegedly infringing device, there is no literal infringement.

The analysis, however, does not end there. Even if an element is missing, there may be another element in the allegedly infringing product that operates in the same way to produce the same result as the missing element. In this case, there is no literal infringement, but there may be infringement under the Doctrine of Equivalents.

The actual patent infringement opinion is contained in a letter. The letter will have an introduction to identify the purpose of the opinion, the patent number of the allegedly infringed patent, and an identification of the allegedly infringing product. A summary of the opinion (i.e., whether the allegedly infringing product infringes the patent) is then set forth.

After the introduction, the current law of patent infringement should be stated, with appropriate legal authority cited. The main portion of the opinion follows, which includes the analysis of the claims and possibly a table for comparing the elements of the claim to the features of the allegedly infringing product. In this main portion of the opinion, both literal and equivalency infringement should be discussed. References to the file history and other important items such as, possibly, an expert's report may also be included. The opinion will end with a closing paragraph that restates the conclusion and may also include some limitations and disclaimers.

The patent infringement opinion serves several purposes and has some important benefits. First, and most obviously, the patent infringement opinion answers the question of whether the competitor's patent is infringed by your product. If infringement is found, the patent infringement opinion may also suggest ways to minimize or eliminate the infringement risk by modifying the allegedly infringing product. Second, the patent infringement opinion can be used in devising strategies for responding to the competitor's cease and desist letter. Third, the patent infringement opinion can be used in subsequent litigation to rebut a charge of willful infringement.