The Torah says that an unintentional murderer who is sent to an ir miklat (city of refuge) must stay there until the death of the kohen gadol (Bamidbar 35:28). The gemara (Makkot 11b) explains the connection as follows. The kohen gadol bears some responsibility for what happened because he should have prayed that such deaths not occur. The gemara continues that if the kohen gadol was appointed between the murder and the sentencing to ir miklat, the murderer goes free with the kohen gadol’s death. The gemara wonders: what could the kohen gadol have done in this case? It answers that he could have prayed that the sentencing would not have ended with a sentence to go to ir miklat.
This is a very strange halacha. Once the action upon which his conviction is based already took place, what point is there to pray for a positive outcome? Perhaps he really deserves conviction, and there is nothing to do! The answer seems to be based on Tosafot (Makkot 7a). Tosafot posits that there are questions beit din does not have to ask witnesses, but if they ask and the witnesses do not know the answer, the defendant is not sentenced. The rationale behind this halacha is the idea of "the congregation will save him" (Bamidbar 35:25), based on which even with a small possibility of merit, we do not sentence a defendant in capital cases.
We can now understand the statements of Rabbi Akiva and Rabbi Tarfon and Rabban Shimon ben Gamliel (Makkot 1:10). The former two said that had they been in Sanhedrin, no one would ever have been convicted [because they would have found remote grounds for dismissing the conviction]. The latter said that had they done so, they would have increased murderers in Israel. Rabbi Akiva did not mean to invalidate convictions made by Sanhedrin. Rabban Shimon did not think that Rabbi Akiva’s system of exempting was invalid, for, if so, he would not have had to given a side reason of increasing murderers. So what was their dispute about?
Rabbi Akiva felt that one could ask questions that the witnesses would not be able to answer and in that way force an acquittal. Rabban Shimon reasoned that while one could force an acquittal in that way, it would be detrimental to society to make that happen. Rabbi Akiva probably agreed that if the state of society were such that creating acquittals would increase murderers he would have agreed not to do so. He just believed that Sanhedrin could improve the situation in a manner that precluded the danger of increased murder. We see then that only in societies where bloodshed is taken as seriously as it should would we encourage extricating the accused from punishments.
Now we can understand the gemara about the kohen gadol’s prayers. The fact that the effort was not made to get the murderer off on a loophole is an indication that the moral standing of the nation at the time of the sentencing was not what it should have been. For that we hold the kohen gadol responsible enough that his death is needed to free the unintentional murderer. How powerful is the message of a leader’s responsibility?!