Sanhedrin was the name applied to the higher courts of law which in the later period of the Second Temple administered justice in Palestine according to the Mosaic Law, involving criminal and capital offenses. Sanhedrin is also the name of a tractate in the Talmud which fully describes the composition, powers, and functions of the court.
At one time two types of Sanhedrin coexisted simultaneously, the Great Sanhedrin with seventy-one members, and several lesser Sanhedrin with twenty-three. According to tradition, both were instituted by Moses, but the former is a reference to a functioning Sanhedrin formed in 57 BC. Some scholars claim that there was another Sanhedrin possessing more political powers. Its president was known as the nasi; the deputy, the ab bet din; the expert or specialist of any case, the mufla. The Great Sanhedrin met in the Chamber of Hewn Stone in the Temple of Jerusalem. The Sanhedrin organized in Yavneh following the destruction of the Second Temple was purely religious in character.
It is known the local courts were in session on the second and fifth (Monday and Thursday) days of the week, but whether this was the practice of the Sanhedrin is unknown. However, tannatic sources describe it as a permanent assembly of sages who met daily between the first and second sacrifice. It was the place «where Law went forth to all Israel» (B.Sanh. 11. 2). There were no sessions conducted on festival days, or the Sabbath. In cases which did not admit for delay it assembled in the high priest’s house (Matthew 26:3, 57; Mark 14:53). A.G.H.
Sources:
Schreiber, Mordecai,The Shengold Jewish Encyclopedia, Rockville, Maryland, Schreibe Publishing, 2nd. ed., 2001, pp.230-231
Unger, Merrill F., Unger’s Bible Dictionary, Chicago, Moody Press, 1966, pp.967-9683
Bowker, John, The Oxford Dictionary of World Religions, New York, Oxford University Press, 1997, p. 854