with whom Justice Marshall joins, concurring in the judgment.
I join the Court’s judgment that Justice Embry’s participation in this case denied appellant the impartial decisionmaker required by the Due Process Clause. I write separately, however, to stress that the constitutional violation in this case should not depend on the Court’s apparent belief that Justice Embry cast the deciding vote — a factual assumption that may be incorrect and, to my mind, should be irrelevant to the Court’s analysis. For me, Justice Embry’s mere participation in the shared enterprise of appellate decision-making — whether or not he ultimately wrote, or even joined, the Alabama Supreme Court’s opinion — posed an unacceptable danger of subtly distorting the decisionmaking process.
The Court states that a decision cannot be permitted to stand “when a disqualified judge casts the deciding vote. Here, Justice Embry’s vote was decisive in the 5-to-4 decision and he was the author of the court’s opinion.” Ante, at 828. In a footnote, the Court elaborates on the decisiveness *832of Justice Embry’s vote: had he disqualified himself, the decision of the trial court would not have been affirmed by an equally divided court because, under Alabama law, a special justice would have been appointed to break the tie. Ante, at 828, n. 5.
The record, however, casts doubt upon the Court’s suggestion that Justice Embry provided the most crucial vote. Justice Embry’s deposition testimony in the Blue Cross suit suggests that the initial vote of the Alabama Supreme Court was in fact to reverse the decision of the trial court in favor of the Lavoies. Accordingly, Justice Embry began work on a dissent. App. to Juris. Statement 168a-169a. After Justice Embry began writing, however, at least one justice switched his vote. Justice Embry’s proposed dissent ultimately was issued as the per curiam opinion of the court. He explained: “It’s customary a lot of times [to issue an opinion as a per curiam], if it’s been assigned to you because the other opinion didn’t prevail . . . .” Id., at 167a.
We cannot know what led each justice on the Alabama Supreme Court to the position he or she reached in this case. But we do know, from our own experience on this niné'-Member Court, that a forceful dissent may lead Justices to rethink their original positions and change their votes. And to suggest that the author of an opinion where the final vote is 5 to 4 somehow plays a peculiarly decisive “leading role,” ante, at 828, ignores the possibility of a case where the author’s powers of persuasion produce an even larger margin of votes. It makes little sense to intimate that if Justice Embry’s dissent, had led two colleagues to switch their votes, and the final vote had been 6 to 3, Aetna would somehow not have been injured by his participation.
More importantly, even if Justice Embry had not written the court’s opinion, his participation in the case would have violated the Due Process Clause. Our experience should tell us that the concessions extracted as the price of joining *833an opinion may influence its shape as decisively as the sentiments of its nominal author. To discern a constitutionally significant difference between the author of an opinion and the other judges who participated in a case ignores the possibility that the collegial decisionmaking process that is the hallmark of multimember courts led the author to alter the tone and actual holding of the opinion to reach a majority, or to attain unanimity. And because this collegial exchange of ideas occurs in private, a reviewing court may never discover the actual effect a biased judge had on the outcome of a particular case. We should not attempt the perhaps futile task of distilling Justice Embry’s particular contribution to determine whether the result would have been the same had he disqualified himself at the outset. I would not want other appellate courts to read the Court’s opinion today to suggest that such an inquiry provides an appropriate guarantee of due process.
The violation of the Due Process Clause occurred when Justice Embry sat on this case, for it was then the danger arose that his vote and his views, potentially tainted by his interest in the pending Blue Cross suit, would influence the votes and views of his colleagues. The remaining events — that another justice switched his vote and that Justice Embry wrote the court’s opinion — illustrate, but do not create, the constitutional infirmity that requires us to vacate the judgment of the Alabama Supreme Court.