In Burke v. Pittsburgh Limestone Corporation, 375 Pa. 390, 100 A.2d 595 (1953), our supreme court stated the law of the case doctrine as follows: The doctrine of the 'law of the case' is that, when an appellate court had considered and decided a question submitted to it upon appeal, it will not, upon a subsequent appeal on another phase of the same case, reverse its previous ruling even though convinced that it was erroneous... It is not, however, inflexible. It does not have the finality of the doctrine of res judicata.... the rule of 'the law of the case' is one largely of convenience and public policy, both of which are served by stability in judicial decisions... Thus there is an abundance of authority to the effect that where a prior decision is palpably erroneous, it is competent for the court, not as a matter of right but of grace, to correct it upon a second review ... where, following the decision on a former appeal, the court in another case has laid down a different rule either expressly or by necessary implication overruling the previous decision. Burke, 375 Pa. at 394-95, 100 A.2d at 598 quoting Reamer's Estate, 331 Pa. 117, 122-23, 200 A. 35, 37-38 (1938)).