What is the test for a constructive amendment to an indictment?

The Fifth Amendment prohibits the trial of a "defendant ... on charges that are not made in the indictment against him." Stirone v. United States, 361 U.S. 212, 217, 80 S.Ct. 270, 273, 4 L.Ed.2d 252 (1960). A constructive amendment of an indictment occurs when "the terms of the indictment are in effect altered by the presentation of evidence and jury instructions which so modify essential elements of the offense charged that there is a substantial likelihood that the defendant may have been convicted of an offense other than that charged in the indictment." United States v. Mollica, 849 F.2d 723, 729 (2d Cir.1988) (quoting United States v. Hathaway, 798 F.2d 902, 910 (6th Cir.1986)). Constructive amendments to an indictment are generally considered prejudicial per se, thereby requiring a new trial. United States v. Weiss, 752 F.2d 777, 787 (2d Cir.), cert. denied, 474 U.S. 944, 106 S.Ct. 308, 88 L.Ed.2d 285 (1985).