Designing Around Patents


The Concept of Infringement. A patent contains one or more claims, which constitute the scope of the invention. If someone has an application that uses each and every element of any claim in a patent, then that application literally and directly infringes on the patent.

How Can a Patent Be Infringed? A patent can be infringed either directly or contributorily.

1) Direct patent infringement is covered under 35 USC 271(a) and applies when:

  • The claim language is legally defined and interpreted by a judge.
  • Then, a jury (or a judge when a jury is not requested) determines whether the legally- defined and interpreted claims cover the accused device or process.

Note that there is no intent or knowledge element required to prove direct infringement. Direct infringement is analogous to a strict-liability offense because it requires no more than the unauthorized use of a patented invention: knowledge or intent is legally irrelevant. However, direct infringement is only available against those who practice each and every element of the claimed invention.

2) Contributory patent infringement is covered under 35 USC 271(c) and applies when someone encourages someone else to directly infringe a patent plus two other conditions are present:

  • that the allegedly infringing device is not a staple article or commodity of commerce suitable for a substantial non-infringing use; and,
  • that the alleged contributory infringer knew of the asserted patent and that its activities would cause infringement of that patent.

To be liable for induced infringement, the accused infringer must have knowingly induced the infringement. The accused infringer must have knowledge that the steps being encouraged are covered by the patent. One can defeat a charge of induced infringement if the alleged infringer has “a good-faith belief of invalidity [of the patent because such belief] may negate the requisite intent for induced infringement.” Commil USA v. Cisco Systems Inc., Fed. Cir., No. 2012-1042, 25-JUN-2013.

Statutory Law.  Section 271(a) of title 35 of the United States Code defines direct infringement:  “whoever without authority makes, uses, offers to sell, or sells any patented invention, within the United States or imports into the United States any patented invention during the term of the patent therefor, infringes the patent.

Equivalents.  In addition, the doctrine of equivalents expands the scope of a patent beyond its literal terms to equivalents of what was claimed. The notion of the doctrine of equivalents in patent law is that unimportant substitutes for certain elements will not evade the protection offered by a patent because otherwise such substitutions would unfairly destroy the value of a patent.

The Federal Circuit explains in its now famous 2002 Festo decision, “The doctrine of equivalents allows the patentee to claim those insubstantial alterations that were not captured in drafting the original patent claim but which could be created through trivial changes.

The Federal Judicial Center publishes a 17-minute video (QuickTime, Real Media and Windows Media Player formats) “designed to be shown to jurors in patent jury trials. It contains important background information intended to help jurors understand what patents are, why they are needed, how inventors get them, the role of the Patent and Trademark Office, and why disputes over patents arise.” It is about 65 megabytes in file size.

Applying the Doctrine of Equivalents. In applying the doctrine, the invention as a whole is not the focus of an equivalents determination. Rather, this doctrine is applied by examining each element contained in a patent claim to determine equivalency of an element or part of the invention with the one that is substituted in the accused product or process. This is important because a focus on the elements of a claim ensures that the application of the doctrine does not result in the vitiation or elimination of any such element. The important thing to remember is that the doctrine of equivalents extends protection beyond the literal terms in a patent and no matter how careful one is, such expansion can create uncertainty about what the patent protects.

Court Decisions Narrow Doctrine of Equivalents. The doctrine of equivalents has been scaled back in recent times. Legal principles of “prosecution history estoppel” and “file wrapper estoppel” can eliminate the doctrine when amendments to a patent application were made to avoid prior art, or otherwise to address a specific concern–such as obviousness–that arguably would have rendered the claimed subject matter unpatentable. The legal concept is that if the applicant responds to patent office action on his application by narrowing the claims, then this prosecution history precludes the applicant from later reclaiming the subject matter by arguing it is an equivalent.

Nonetheless, one must be careful when attempting to design around a patent so as to avoid both literal patent infringement and infringement under the doctrine of equivalents. The Supreme Court said in its 2002 Festo decision, “Though prosecution history estoppel can bar challenges to a wide range of equivalents, its reach requires an examination of the subject matter surrendered by the narrowing amendment. Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd., 535 U.S. 722, 737, 122 S.Ct. 1831, 1840, 62 USPQ2d 1705 (2002),

Designing Around, A Good Thing? Designing around a patent is considered an important public benefit of the patent system.  A competitor’s designing around a patent’s claims “is the stuff of which competition is made and is supposed to benefit the consumer. State Indus., Inc. v. A.O. Smith Corp., 751 F.2d 1226, 1236, 224 USPQ 418, 424 (Fed. Cir. 1985). In a trial for infringement, the “fact-finder may infer that the competitor, presumably one of skill in the art, has designed substantial changes into the new product to avoid infringement. . . .Evidence of designing around therefore weighs against finding infringement under the doctrine of equivalents. Hilton Davis Chemical Co v. Warner-Jenkinson Company, Inc., 93-1088 (Fed. Cir. 1995).


  1. Designing around an existing patent may require a review of more than the literal terms of a patent.
  2. An infringement determination should be made only after considering the law that is applicable.
  3. If you think someone has infringed your patent, Attorney Louis Ventre, Jr. would be pleased to discuss legal representation with you on an hourly or fixed-price, fixed-tasking retainer basis. Please contact Attorney Louis Ventre, Jr. to discuss this in a free initial consultation.
  4. If you are worried about whether your existing design around was adequate, it is not too late to get a second opinion.
  5. If you have received a letter demanding you cease and desist infringement, read on.

Other related pages that may be of interest are patent infringement opinions | infringement damages | and pharmaceutical importation and infringement.

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