In the federal system, parallel suits are defined as those actions in which "substantially the same parties are litigating substantially the same issues simultaneously. . . ." Schneider Nat'l Carriers, Inc. v. Carr, 903 F.2d 1154, 1156 (7th Cir. 1990).
Once a determination is made that two suits are parallel, the party seeking abstention has the burden to establish that "exceptional circumstances" warrant dismissal or a stay. Madanes v. Madanes, 981 F. Supp. 241, 264 (S.D.N.Y. 1997); Herbstein v. Bruetman, 743 F. Supp. 184, 188 (S.D.N.Y. 1990).
The placement of the burden of proof on the party challenging parallel litigation flows from federal abstention cases and emphasis on concurrent jurisdiction, which is derived from the federal courts' obligation to hear controversies under Article III of the United States Constitution. James P. George, Parallel Litigation, 51 BAYLOR L. REV. 769, 906 (1999) (citing Colorado River Water Conserv. Dist. v. United States, 424 U.S. 800, 817, 96 S.Ct. 1236, 1246, 47 L. Ed. 2d 483, 498).