advice-of-counsel defense. Patents. In an action for infringement, an assertion that after learning of the owner’s rights, the defendant sought, obtained, and relied on an attorney’s well-reasoned opinion before continuing the challenged act. • Courts treat the assertion as a factor in determining whether an act was willful (to support en-hanced damages). It is not a true defense. Cf. willful infringement under INFRINGEMENT. [Cases: Patents 227. C.J.S. Patents § 403.]