The America Invents Act significantly expanded the “Prior Use” defense under 35 U.S.C. § 273 to patent infringement. Prior thereto, the defense was limited to use against claims of business method patents. Now, a litigant may assert this affirmative defense if it commercially used, in good faith, a process, machine, manufacture, or composition of matter that is asserted to infringe the patent-at-issue. While this sounds good on paper, there is a catch. If it is shown that a defendant failed to have a “reasonable” basis for asserting this defense, the “court shall find the case exceptional for the purpose of awarding attorneys’ fees under section 285.” 35 U.S.C. § 273(f)(emphasis added). The problem is that the Courts have failed to address what “reasonable” means. Thus, companies facing patent infringement claims must decide whether it’s worth the risk. If they don’t produce enough information to sustain the defense, they might have to pay the patentee’s attorneys’ fees- a remedy generally available only in instances of willful infringement.