A trial court's error in an evidentiary ruling only rises to the level of harmful error if a party's substantial right is affected. See 28 U.S.C. § 2111; Fed. R. Evid. 103(a); Lubanski v. Coleco Indus., Inc., 929 F.2d 42, 46 (1st Cir. 1991). 'In determining whether an error affected a party's substantial right, 'the central question is whether this court can say with fair assurance . . . that the judgment was not substantially swayed by the error.'' Espeaignnette v. Gene Tierney Co., 43 F.3d 1, 9 (1st Cir. 1994) (quoting Lubanski, 929 F.2d at 46 (internal quotations omitted)). Factors a court must consider in determining whether substantial rights are implicated include both the centrality of the evidence and the prejudicial effect of its exclusion or inclusion. Lubanski, 929 F.2d at 46. A court must weigh these factors in ''the context of the case as gleaned from the record as a whole.'' Id. (quoting Vincent v. Louis Marx & Co., 874 F.2d 36, 41 (1st Cir. 1989)). Courts have repeatedly noted that 'no substantial right of the party is affected where the evidence omitted was cumulative as to other admitted evidence.' Doty, 908 ...