A case taken in which the plaintiff is seeking from the court a declaration that the plaintiff is not liable to the defendant. A DJ action is best described as “a lawsuit in reverse,” where the putative defendant sues the putative plaintiff rather than waiting, in uncertainty, for a case to be filed. Usually to bring a declaratory judgment case the plaintiff has to show reasonable grounds to believe that the defendant may make a claim against the plaintiff. This is usually achieved by showing that warning letters have been sent to the plaintiff or the plaintiff’s customers, or that other threats of litigation have been made.
Declaratory judgment cases are more common in patent infringement litigation, where they can convey considerable advantages on the purported infringer. Indeed, some statistical studies have shown that, in the United States all things being equal, an alleged infringer may be twice as likely to win a declaratory judgment as an ordinary infringement case.
Among the advantages a DJ gives the accused infringer is the ability to choose the court in which the case is filed, because the lis pendens rule will usually preclude the same issues being heard by a second court. Because perceived jury bias and local or anti-foreigner chauvinism in the United States varies on a court-by-court, state and district basis, while some districts have more educated and cosmopolitan jury pools than others, as does time to trial, and because of procedural differences in different European court systems, this choice may result in a considerable advantage. Despite these advantages, DJ cases are rare, primarily because of the difficulty in persuading a potential defendant to act first, despite the advantages.
Moreover, bringing a DJ case presents an image of forthright confidence and innocence on the part of the alleged infringer, which presents a more positive image to a jury or judge, than that of a reluctant defendant, haled as an alleged miscreant into court. Declaratory Judgment in the United States is generally only available in patent cases because of the so-called “case or controversy” requirement in the U.S. constitution limiting the courts to hearing actual as opposed to hypothetical disputes. See Warning Letter, Italian Torpedo, Forum Shopping.