In 2007, Mirowski provided Medtronic with a notice of infringement alleging that seven new Medtronic products violated two Mirowski patents. Medtronic responded by bringing a declaratory judgment action seeking a declaration that Medtronic’s products did not infringe Mirowski’s patents and that the patents were invalid.

The District Court held that the burden of proof in a declaratory judgment action falls on the patentee to prove that its patent rights have been infringed upon. The Court of Appeals for the Federal Circuit held that the burden should shift to the moving party because when a patentee is the defendant they are unable to bring an infringement action.

The Supreme Court reversed, specifically noting the extensive case law supporting the patentee’s burden of proof, stating that it was “well established that the burden of proving infringement generally rests upon the patentee”.

In addition, Justice Breyer noted that shifting the burden of proof away from the patentee could create “unnecessary complexity” and cause confusion as to what theory a patentee’s infringement claim lays upon because the patentee is best equipped to state how an alleged infringer has infringed on an existing patent, whereas the alleged infringer would need to “negate every conceivable infringement theory” as part of their proof that they did not violate the patent.

In addition, the Court stated that shifting the burden away from the patentee would move against the basic purpose of the Declaratory Judgment Act. The Court held that were it not for the declaratory judgment procedure, the alleged infringer would be forced to either continue the alleged breach, forcing the patent holder to bring an infringement action, or cease the alleged breach and cure.