I think it should be pointed out as well that the Mishnaic vision of a formal ‘Sanhedrin’, somethng which is admittedly the majority opinion, is probably yet another historical anachronism. What we do have (based on a reading of Josephus) is this: in the 1st century there was a formal institution called a
boulē which acquired the character of a national institution and which discussed issues pertinent to the city of Jerusalem. This is
not the Sanhedrin of the Tannaitic and Christian texts, but rather a consultative body most likely made up of people of wealth and influence, similar to local councils present in Hellenistic cities. In addition, there were two further institutions described the same Greek term,
synedrion (where the Aramaic ‘sanhedrin’ comes from), which were not standing institutions but functioned only for specific tasks, either consultative, where a Roman official called on specific Jewish groups to assist in determining a course of action, or judicial, a place of arbitration, a court, which was convened usually by a leading official such as the serving high priest. Capital cases could be tried in the second type of
synedrion. (Josephus in fact also uses
synedrion to refer, not just to the council convened by the high priest, but also to the advisory council of Agrippa II and even of the emperor Augustus, which may show that an advisory council was all the term implied.)
In fact, you could see a pattern emerging: the high priest, with the support and assistance of the chief priests and some of the powerful lay people, handled local government; the
boulē, meanwhile, normally did very little, if at all. At least, only in the last, fatal crisis under Gessius Florus (AD 64-66) does this city council appear, and similarly only this one time did the chief priests feel compelled to call on the Pharisees for help.
Lastly, there is no lack of evidence both in the Christian scriptures and in Josephus that the Sanhedrin could perform executions during the Roman occupation contradicting the claim in Mark and Matthew that the Sanhedrin turned Jesus over to the Romans because they wished to kill him but were prohibited from performing executions. Why then does the Christian scripture say that the Sanhedrin could not perform executions?
I’ll address this one first. As mentioned earlier, the Romans seldom granted anyone capital power, much less provincial courts, and for a good reason: in decidedly anti-Roman areas, it could be used to deal with local Roman sympathizers. If it was to be granted anywhere, it would be to free states that had shown special loyalty to Rome - which would put Judaea out of the question. A decree of Augustus to the proconsul of Cyrene, dated 7-6 BC, which made provision for provincial courts to practice “delegated jurisdiction except in capital cases,” which are to be kept in the hands of the proconsul himself, shows just how picky the Romans were about restricting the power.
Yes, Josephus does write that in 62, then high priest Ananus son of Ananus (aka Annas) convened a
synedrion and had James the brother of Jesus and probably others executed (
Antiquities 20.200-201). But guess what? Ananus was deposed precisely because he took advantage of the brief period in between procuratorial assignments to violate the rule.
But this younger Ananus, who, as we have told you already, took the high priesthood, was a bold man in his temper, and very insolent; he was also of the sect of the Sadducees, who are very rigid in judging offenders, above all the rest of the Jews, as we have already observed; when, therefore, Ananus was of this disposition, he thought he had now a proper opportunity [to exercise his authority]. Festus was now dead, and Albinus was but upon the road; so he assembled the sanhedrim of judges, and brought before them the brother of Jesus, who was called Christ, whose name was James, and some others, [or, some of his companions]; and when he had formed an accusation against them as breakers of the law, he delivered them to be stoned: but as for those who seemed the most equitable of the citizens, and such as were the most uneasy at the breach of the laws, they disliked what was done; they also sent to the king [Agrippa], desiring him to send to Ananus that he should act so no more, for that what he had already done was not to be justified; nay, some of them went also to meet Albinus, as he was upon his journey from Alexandria, and informed him that it was not lawful for Ananus to assemble a sanhedrim without his consent. Whereupon Albinus complied with what they said, and wrote in anger to Ananus, and threatened that he would bring him to punishment for what he had done; on which king Agrippa took the high priesthood from him, when he had ruled but three months, and made Jesus, the son of Damneus, high priest.
The stoning of Stephen is not so much an official execution as a lynching: there was no verdict and no sentence (Acts 7:57-58).
The
only exception to this rule I can think of is the Temple Court warning, wherein any gentile who entered the sacred inner court - even if they were a Roman citizen - could be put to death. This is keeping in line with the Roman custom of granting provincial subjects as much freedom as possible in practicing their religion, and besides, the Jews would wish to maintain the purity and sanctity of the Temple hence, the special exception.