The Supreme Court affirmed that inventors have the rights to versions of their inventions that use ‘equivalent’ elements.
On 05/28/02, the Supreme Court published its decision in the case of Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co. (aka SMC). The case affirmed that inventors have the rights to not only the literal versions of the inventions claimed in their patents but also to inventions that use “equivalent” elements, unless the equivalent element was abandoned by the patentee during the patent process in order to secure a patent. Consider the following hypothetical. A patentee’s invention includes elements A, B, and C. A competitor’s product includes elements A, B, and D. Element D is the functional equivalent of element C. The competitor’s product is within the scope of the patentee’s rights. If, however, the patentee claimed element D during the patent process but abandoned it in favor of the narrower element C, then the competitor’s product would not be within the scope of the patentee’s rights.
What does Festo mean for inventors? The so-called “Doctrine of Equivalents” (DOE) that the Festo decision upholds is, in some respects, a line of last defense (or offense, as the case may be) in a patent dispute. It would be better not to have to rely on the DOE at all. Instead, when you are drafting your patent applications, you should review them from the point of view of your competitor. You should imagine every possible way to get around your future patent, and then you (or your trusty patent attorney) should rework the patent application to fully protect your invention. On the other hand, if you have really deep pockets and a lot of time to spare, you could try litigation. For those scoring at home, Festo has over 10,000 employees and SMC has over 5,000. Since the Supreme Court ruled on the law and not on the merits of the case, the lower courts are still chugging along on the case, which has been going on for 14 years!
[EDITOR’S NOTE: In the summer of 2025, Clocktower Intern Mark Magyar used artificial intelligence (AI) software to shorten over 100 Clocktower articles by 17%. The shortened articles are included as comments to the original ones. And 17 is the most random number (https://www.giantpeople.com/4497.html) (https://www.clocktowerlaw.com/5919.html).]
* Festo – The Supreme Court’s Latest on Patent Law
On 05/28/02, the Supreme Court decided Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co. (SMC), affirming that inventors have rights not only to literal claims but also to inventions with “equivalent” elements—unless the patentee surrendered that element during prosecution.
Example: if a patent claims A, B, and C, and a competitor makes A, B, and D—where D is the functional equivalent of C—the competitor’s product infringes. But if the patentee once claimed D and abandoned it for C, then no infringement exists.
This Doctrine of Equivalents (DOE) is often a last line of offense or defense in disputes. Ideally, you shouldn’t rely on DOE. Draft patent applications as if you’re your own competitor: imagine every possible workaround, then revise to close those gaps.
For those with deep pockets, litigation remains an option. Festo has 10,000+ employees and SMC over 5,000. Since SCOTUS ruled only on the law—not the facts—the lower courts continue their battle. This case has already lasted 14 years and counting.