What is the standard of prejudice in a personal injury case?

I begin with what should be common ground. In the formulation of a standard of prejudice, "Necessarily the character of the proceeding, what is at stake upon its outcome, and the relation of the error asserted to casting the balance for decision on the case as a whole, are material factors...." (Kotteakos v. United States (1946) 328 U.S. 750, 762, 66 S.Ct. 1239, 1246, 90 L.Ed. 1557.)