U.S. Court of Appeals Case No: 061571P.pdf 02/09/2007 U.S. District Court for the District of Minnesota Plaintiff wins Minnesota prejudgment interest. Although interest is an Erie ( 304 U.S. 64, 78 (1938)) substantive issue ( Emmenegger v. Bull Moose Tube Co ., 324 F.3d 616, 624 (8th Cir. 2003)) , so