Doctrine of Equivalents Is Strong Patentee Tool, but Needs Care

26 Jan 2026
Client Alert

Todd Krause and Alyssa Monsen wrote an article entitled "Doctrine of Equivalents Is Strong Patentee Tool, but Needs Care" for Bloomberg Law, which discusses the doctrine of equivalents (DOE) as a means for patentees to assert infringement when claims are not literally infringed. The article reviews recent Federal Circuit and district court decisions, highlighting common pitfalls such as failing to tie DOE theories to specific claim limitations, providing insufficient evidence, and untimely assertion of DOE claims. It emphasizes the importance of particularized testimony, careful claim interpretation, and awareness of prosecution history estoppel and vitiation defenses. Ultimately, the authors advise that DOE remains a powerful tool when applied with precision and supported by robust evidence.

Read the full article (subscription may be required).

We are Morrison Foerster — a global firm of exceptional credentials. Our clients include some of the largest financial institutions, investment banks, and Fortune 100, technology, and life sciences companies. Our lawyers are committed to achieving innovative and business-minded results for our clients, while preserving the differences that make us stronger.

Because of the generality of this update, the information provided herein may not be applicable in all situations and should not be acted upon without specific legal advice based on particular situations. Prior results do not guarantee a similar outcome.