The presence of alternative grounds presents appellate practitioners with additional issues to evaluate. The most frequently encountered alternative ground situation involves appeals from general verdicts where at least one of the bases for liability decided by a jury is invalid. The rule for such cases changed relatively recently. Historically, when a general jury verdict could have been based on either valid or invalid grounds, a new trial was required. See Izzi v. Philadelphia Transportation, 195 A.2d 784, 789 (Pa. 1963). In such situations, the jury "may as readily have followed the incorrect as the correct theory, and it is impossible to know which they accepted." See Pedretti v. Pittsburgh Railways, 209 A.2d 289, 292 (Pa. 1965). Reviewing courts "would have had to speculate" on whether verdicts were based on grounds "erroneously submitted to the jury." See Mendralla v. Weaver, 703 A.2d 480, 486 (Pa. Super. 1997) (en banc).