All U.S. patent applications must include a description that is sufficiently detailed to empower a person having ordinary skill in the technical field of that application’s claimed concept(s) to successfully make and use (“implement”) the full scope of each of those claimed concepts (without undergoing undue further research, experimentation, or training).
All U.S. patent applications also are required to describe, from the perspective of each inventor of each claimed concept, that inventor’s “best mode” (sometimes referred to as “preferred embodiment”) for implementing the claimed concept at the time of filing the application. The requirement is excused only if that inventor had no particular best mode. Historically, a failure to describe the best mode could (and occasionally did) serve as grounds for invalidating the corresponding claim, or even the entire patent.
Although USPTO examiners are still required to reject any patent application that fails to fulfill the best mode requirement for each claimed concept, in 2013, Congress eliminated the best mode defense to an allegation of patent infringement. As a result, a court can no longer find a U.S. patent either invalid or unenforceable for a failure of the application that led to that patent to describe the inventor’s best mode for implementing the claimed concept.
The potential impact of this change is profound. Now, so long as a patent application describes how to even barely successfully implement the full scope of its claimed concepts, the patent applicant can retain optimization details for implementing those concepts as trade secrets. This can allow a patent owner to prevent competitors from implementing the patent’s claimed concepts in any manner and avoid teaching competitors the hard-learned details of how best to implement those concepts.
On the other hand, if the best mode is non-obvious in light of the teachings of the patent, then competitors who later discover that best mode can themselves patent it, potentially positioning the first patent owner as an infringer. So retaining the best mode as a trade secret is not always the best choice.
Even with this change, patent applicants should continue to include in each patent application a description of their best mode, if any exists at the time of filing that application, for implementing each claimed concept. Keep in mind that there never has been a requirement to identify which specific described implementations are considered the “best” or “preferred”. Also, after an application is filed, there is no requirement or ability to “update” the application to describe a newly discovered best mode. Instead, if the innovative concept has changed to the point that the original application’s description is not broad enough to cover it, consider filing a new patent application to describe and claim that changed concept.