Before us is Mishnah 10 in the first chapter of Maseches Makkos, which deals with the law of one whose verdict was rendered and who then fled, with the authority of the Sanhedrin in the Land of Israel and outside it, and with the question of how frequent capital punishment ought to be in Israel.
"Mi shenigmar dino uvarach":
The Mishnah opens: "Mi shenigmar dino uvarach uva lifnei oso beis din - ein sosrin es dino" - one whose verdict was rendered and who fled, and who then came before that same court, his verdict is not overturned. A person whose case was concluded in court and who was convicted of murder, and who fled, and was afterward brought once again before that very same court - the case is not retried and the verdict already reached is not annulled; rather, they proceed to carry out the sentence that has already been decided.
The Mishnah continues: "Kol makom she'amdu shenayim ve'yomru: me'idin anu b'ish peloni shenigmar dino b'veis din shel peloni, u'peloni u'peloni eidav - harei zeh yehareg" - anywhere that two men stand up and say: we testify concerning so-and-so that his verdict was rendered in the court of so-and-so, and so-and-so and so-and-so were the witnesses, this man is put to death. It is enough that two witnesses report the existence of the verdict and identify who the witnesses were who testified about his crime, and on the basis of that report alone he is executed.
The Gemara's precise reading of the two halves of the Mishnah:
The Gemara notes the shift between the two statements: in the first half the Mishnah specifically says "that same court," while in the second half it broadens the language and says "anywhere." The Gemara explains (and so Rashi comments) that there is no contradiction here, but rather two different situations:
From outside the Land to the Land of Israel: The first half speaks of someone who was originally tried outside the Land of Israel and then came to the Land of Israel. If he was brought before that very same court, they do not trouble themselves to try the matter again. But if he came before a different court, the case is reopened, since it is possible that the merit of the Land of Israel will stand him in good stead and he will be judged favorably.
From the Land of Israel to outside the Land, or entirely outside the Land: Here the Mishnah says "anywhere" - in any place where it is reported that he was already tried and sentenced to death, he is put to death on the basis of that verdict.
"Sanhedrin noheges ba'aretz uv'chutz la'aretz":
This ruling is necessary in order to understand the above: the Sanhedrin can impose capital punishment both in the Land of Israel and outside the Land. There is, however, a condition: the Sanhedrin itself must be seated in the Land of Israel. As long as it sits in the Chamber of Hewn Stone in the Beis HaMikdash, there is authority to judge outside the Land of Israel at that time; and if not, there is not.
The frequency of capital punishment:
From here the Mishnah turns to discuss the question of how common capital punishment ought to be:
"Sanhedrin haHoreges echad b'shavua nikreis chavlanis" - a court that puts even one person to death once in seven years is considered a destructive court.
Rabbi Elazar ben Azaryah takes a more extreme position: "echad l'shivim shanah" - even a court that executed once in seventy years is considered destructive.
Rabbi Tarfon and Rabbi Akiva say: "ilu hayinu b'Sanhedrin lo neherag adam le'olam" - had we been on the Sanhedrin, no person would ever have been put to death. How is that possible? The Gemara explains that they would put questions to the witnesses that are extremely difficult to answer - a detailed interrogation about every peripheral detail, such as what the people were wearing and the like, and in this way no witness could withstand the examination.
Rabban Shimon ben Gamliel responds to them: "af hen marbin shofchei damim b'Yisrael" - they too would increase the number of murderers in Israel. If imposing capital punishment is made so difficult, murderers will multiply in Israel, because the deterrence that stems from the very possibility of a death sentence will have been removed.
In summary: In this Mishnah we learned that a case which has been decided is not reopened when the litigant comes back before that same court, and that the testimony of two witnesses as to the existence of the ruling is enough to carry it out. We noted the Gemara's distinction between one who comes from outside the Land to Eretz Yisrael (where another court does reopen the case, because of the special standing of Eretz Yisrael) and all other places. We saw that a Sanhedrin functions both in the Land and outside it, provided that it sits in the Land. And finally we examined the dispute among the Tannaim about how often the death penalty should be imposed: between the aspiration to minimize it as far as possible and the concern about multiplying those who shed blood in Israel.