The Federal Circuit has long held that a patent can be held unenforceable under the equitable doctrine of prosecution laches if the patent applicant engaged in “unreasonable and unexplained delay in prosecution” and others who have used the patented technology during the period of delay are prejudiced. In Hyatt, the Federal Circuit went further and held that applicant’s prosecution lasting more than six (6) years at the USPTO is presumed to be “unreasonable and prejudicial,” shifting the burden to the patent holder to rebut the presumption in order to enforce the patent. In the Amicus brief, USI argues that the Federal Circuit should grant rehearing by the full Court to correct its prior decisions because equitable doctrines cannot be available where an applicant seeks a legal right — to obtain a patent right. It is shown that an applicant’s claim to a patent, both during prosecution at the USPTO and later in a § 145 civil action, is not contingent on privilege, fairness, or judicial discretion; it is a statutory claim to a defined legal property right, which cannot be defeated by equitable claims such as laches.