When a person applies for a patent, they are supposed to disclose the "best mode" of carrying out the invention. The idea is that a person cannot gain the monopoly of a patent without letting the public know how their invention works. If they were allowed to keep the best mode secret, they would be getting something for nothing.

In Bayer AG v. Schein Pharmaceuticals, 301 F.3d 1306 (2002), the Federal Circuit established a two-prong test for finding best mode violations:

1. The factfinder (i.e. the judge or jury) determines whether the inventor had a best mode of practicing the invention at the time they filed for the patent. If they didn't know of, or believe in, a best mode at that time, then there is no best mode violation.
2. The factfinder then decides whether the disclosure in the patent specification is adequate to enable a person having ordinary skill in the art to practice the best mode of the invention.