In Luke 20:1-2 Jesus gets a visit from members of the Sanhedrin. There were many sanhedrins throughout Judea and Galilee. They were the local courts of the land, composed of three or twenty-three members, populated by the Jewish leaders in each town. The chief court in Jerusalem, THE Sanhedrin, or the Supreme Court of the Jews, seems to have been composed of the three, twenty-three member courts at Jerusalem. It was made up of Pharisees, Sadducees and Jewish elders (considered to be the Jewish nobility). The high priest would preside over the assembly as its president or nasi, i.e. prince (cf. cf. Numbers 11:16; ).
During the days of Moses and immediately afterward, there wouldn’t have been a need for an elaborate judicial system. Rather, it would have been sufficient to set up a system of elders and judges (Exodus 18:21; Deuteronomy 1:15). It was David who first expanded Israel’s judicial system by appointing 6000 Levites to be judges of the land (1Chronicles 23:4), not that the judicial system was composed of Levites only, but this scripture shows the Levites would form a substantial part of that system.
It wasn’t until King Jehoshaphat’s day that the Jewish Supreme Court was formed at Jerusalem:
Moreover in Jerusalem did Jehoshaphat set of the Levites, and of the priests, and of the chief of the fathers of Israel, for the judgment of the LORD, and for controversies, when they returned to Jerusalem. And he charged them, saying, Thus shall ye do in the fear of the LORD, faithfully, and with a perfect heart. And what cause soever shall come to you of your brethren that dwell in their cities, between blood and blood, between law and commandment, statutes and judgments, ye shall even warn them that they trespass not against the LORD, and so wrath come upon you, and upon your brethren: this do, and ye shall not trespass. And, behold, Amariah the chief priest is over you in all matters of the LORD; and Zebadiah the son of Ishmael, the ruler of the house of Judah, for all the king’s matters: also the Levites shall be officers before you. Deal courageously, and the LORD shall be with the good. (2 Chronicles 19:8-11 KJV)
Notice that the court was made up of Levites, priests and the chief of the fathers (verse-8), and the king set them over matters of the Lord (theological matters and matters of worship), and over matters of the state or civil matters (verse-11). He also set up a very elaborate lower court system throughout the fenced or walled cities of Judah (2Chronicles 19:5). The lower courts or sanhedrins decided the easier matters of law, but the greater matters were taken to the Sanhedrin at Jerusalem (cf. Deuteronomy 17:8).
The Sanhedrin is mentioned in the New Testament under the name, council (G4892 – sunedrion, see Acts 5:21; 22:30; 23:1), and the council of elders (G4244 – presbuterion see Acts 22:5 and Luke 22:66). Josephus uses the term, senate (gerousia – G1087), which is used with G4829 (sunedrion) at Acts 5:21. He also uses the term council (boule – G1012), but it is not so used in the New Testament. Instead G1012 is used to describe the counsel of God (Acts 2:23) or of men (cf. Luke 7:30), but the term councilor (bouleutes – G1010) is used of Joseph of Arimathaea (Luke 23:50; cf. Mark 15:43) and infers that he was a member of the Sanhedrin.
The New Testament records three trials conducted by the Sanhedrin at Jerusalem and all were conducted by the high priest and his family. They were to try Jesus (Mark 14:53-65; John 18:12-24), but notice that in Mark 15:1 that the whole council met in the morning, which may imply that only a 23 member portion met at night to establish the accusation that would condemn Jesus to death before the whole council in the morning. The second trial was conducted against Peter and John in Acts 4:3-22, and the third was against Paul in Acts 22:30 and 23:1-9. The court was dissolved by the order of Rome in 70 AD after the Romans defeated the Jews in the war of 66-70 AD.
 See Babylonians Talmud, Sanhedrin – Mishnah, 2a
 Josephus: Antiquities of the Jews 12.3.3.
 This same term (G1087 is used in the Apocrypha books 1Maccabees 12:35 and 2Maccabees 11:27.
 Josephus: Wars of the Jews 5.4.2.