The Uncertain Future of the Doctrine of Equivalents
Supreme Court to Review Festo Decision

Thomas J. Daly

In June of this year, the Supreme Court agreed to review the Federal Circuit's ruling in Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd. Known to practitioners as simply "Festo", the case is quite controversial because it significantly diminishes the scope of protection accorded to patent owners. Until a final ruling is made by the Supreme Court, inventors, patent owners, and patent attorneys need to adjust their approach to avoid potential limits on the scope of patent protection that would otherwise follow from the Festo decision.

The Court of Appeals for the Federal Circuit has exclusive appellate jurisdiction over all cases arising under the patent laws of the United States. In Festo, the Court held that no range of equivalents is available for a narrowing limitation to a patent claim, where the claim is amended during prosecution for a reason related to patentability. All twelve members of the Court considered the Festo appeal, with a solid majority agreeing to overturn an earlier decision in the same case by a three-judge panel of the Federal Circuit.

Utility patents end with one or more numbered sentences called "claims". A patent claim sets forth the elements or "limitations" that must be present for a product or process to be covered by the claim, and thereby defines the scope of the claimed invention. Anyone who makes, uses, imports, offers to sell, or sells a product or process that is covered by a claim without the permission of the patent owner may be liable for patent infringement. If the potentially infringing product or process literally has all of the limitations recited in a claim, it is said to literally infringe. However, even if one or more elements or limitations are not literally present, the potentially infringing product or process might still be found to infringe under an equitable doctrine developed by the courts, called the Doctrine of Equivalents.

The Doctrine of Equivalents arose to extend patent protection to products or processes not literally covered by a patent claim, where an element of the claim has been replaced by a substantially equivalent element. Thus, it removes the unfairness that could result from an overemphasis on the literal language of patent claims, and thereby expands the scope of protection accorded to claims. However, courts have also placed limitations on the Doctrine of Equivalents so that persons evaluating patent claims will have adequate notice of the scope of coverage provided by the claims and can direct their activities accordingly. The tension between avoiding undue literalism and providing adequate notice to the public runs throughout most cases dealing with the Doctrine of Equivalents, and is at the heart of the Festo decision.

One limitation on the Doctrine of Equivalents is called Prosecution History Estoppel. The process by which an application for a patent is examined by the U.S. Patent and Trademark Office for patentability is referred to as "prosecution". The course of that examination, and its documentation, which is made public once the patent issues, is known as the "prosecution history" of a patent. During prosecution, it is common for patent applicants to make amendments to proposed claims, and/or arguments, to overcome an Examiner's position that the claims are unpatentable. Such amendments and arguments are then reflected in the prosecution history of the patent. Should the patent owner later attempt to use the Doctrine of Equivalents to recapture claim scope given up during prosecution by way of amendment or argument, Prosecution History Estoppel prevents such a recapture.

Before Festo, it was clear that the doctrine of Prosecution History Estoppel would prevent a patentee from recapturing, under the Doctrine of Equivalents, a scope of claim coverage that was clearly given up during prosecution. This is illustrated in the following scenario: A patent application initially claims a chemical process that includes a temperature limitation of 20°F to 40°F. The patent examiner rejects the claim based on an earlier patent that recites a temperature range of 40°F to 50°F. To overcome the rejection, the applicant amends the claim to recite a temperature of 25°F to 35°F. Based on the amendment, the patent owner would be legally barred or "estopped" from later asserting infringement against someone who practices the process at 40°F. Before Festo, however, the patentee might still enjoy some range of protection outside the literal limits of 25°F to 35°F, under the Doctrine of Equivalents. The analysis would tend to focus on what was relinquished during prosecution, and the reasons for that relinquishment. Thus, under the above example, a patent owner might have had a reasonable possibility of using the Doctrine of Equivalents to cover a potentially infringing process operating at 22°F, because the relinquishment of the lower end of the temperature range was not needed to distinguish the prior patent. More difficult to predict would have been the likelihood of covering a potentially infringing process operating at 38°F, a temperature between the range in the ultimate patent claim and that of the prior patent.

In Festo, which involved amendment-type Prosecution History Estoppel as a limit on the Doctrine of Equivalents, the Court of Appeals held that no range of equivalents is available for a narrowing limitation made by amendment during prosecution, where the amendment is made for a reason related to patentability. Thus, in the example above, once the temperature limitation was narrowed by amendment to 25°F to 35°F, no range of equivalents would be available. The claim would thereafter only be entitled to its literal scope, i.e., a temperature range of 25°F to 35°F. Moreover, an earlier U.S. Supreme Court decision held that, if no other explanation is given, amendments made during prosecution are presumed to be for a reason related to patentability. Accordingly, narrowing claim amendments made during prosecution will now almost always trigger the Festo bar on any range of equivalents. It remains to be seen whether the reasoning of Festo will be applied to argument-type Prosecution History Estoppel such that arguments made during prosecution will also bar any range of equivalents.

The import of the Festo decision is clear: narrowing amendments during prosecution are to be avoided. How such amendments can be avoided while still preserving the ability to work with examiners during prosecution is being addressed by patent attorneys. But inventors and patent owners can also take steps to help preserve the broadest possible scope of protection for their claimed inventions. Some key steps are outlined below.

Thorough Pre-Filing Evaluation of the Prior Art

One way to minimize claim amendments during prosecution is to start with claims that clearly distinguish the prior art even though they are drafted to be as broad as they can be in view of that prior art. This is already an important goal when preparing claims. But, for the effort to be truly effective, the most pertinent prior art must be identified and evaluated before the original claims are finalized and the application is filed. Independent prior art searches are possible and should be conducted whenever the time and financial resources are available. However, inventors and/or patent owners may already be aware of or have ready access to information on prior art. Extensive knowledge of the prior art should not be feared; it is to be encouraged and should be communicated to the patent attorney. The patent attorney can use that prior art to draft claims that require fewer, if any, amendments, and take advantage of the Doctrine of Equivalents.

"Means Plus Function" Claim Limitations

The patent laws allow claim limitations to "be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof". Such a claim limitation is then literally "construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof". Therefore, the use of such built-in equivalents can appear to survive the bar of Festo. In theory, even if a "means plus function" claim limitation is narrowed during prosecution - making the Doctrine of Equivalents unavailable - the claim would still be entitled to some equivalents within its literal scope based upon what is described in the specification of the patent.

One might anticipate that patent attorneys will make greater use of "means plus function" claim limitations in view of Festo. However, for the built-in equivalents of such claims to be worthwhile, it is necessary that the description in the specification supporting such limitations provide multiple alternatives and a broad discussion of possible equivalents. Thus, inventors and patent owners should work with patent attorneys to make sure that the various features and aspects of an invention are addressed to identify potential alternatives, modifications or interchangeable components. The essential nature of the various features and aspects of an invention should also be identified so that potential equivalents can be broadly defined in the patent specification itself. Once again, these were already good ideas before Festo, but the holding of Festo makes such brainstorming exercises even more important.

Comprehensive Claim Sets

Including a comprehensive set of claims in a patent application as it is originally filed, which characterize the invention in a variety of ways, can increase the likelihood that some of the claims will not need to be amended during prosecution. Inventors and patent owners should work with patent attorneys to identify many different features, aspects, or components of an invention that are believed to be different from the prior art. This will allow claims to be presented that contain a variety of combinations or subcombinations of elements or limitations. Different ways to view the invention or think about what is new and unobvious about the invention should also be brainstormed to develop alternative approaches to claiming the invention.

By working with patent attorneys, inventors and patent owners can help secure the broadest possible scope of protection for their inventions, even in the aftermath of Festo and other decisions elevating the notice function of patent claims.