When Jesus was arrested in the Garden of Gethsemane by the temple guard, they led him to the High Priest, Caiaphas (26:57). This is often called a trial before the Sanhedrin as if the full ruling council of the Jews came together in the middle of the night for a formal trial. This is not the case. Rather than a meeting of the whole Sanhedrin, this is a hearing at the home of the High Priest, Caiaphas.
What is the Sanhedrin? The word refers to a Jewish council that met in Jerusalem and was something like a city council. The word comes from the Greek συνέδριον (synedrion). However, there are several possible Hebrew or Aramaic phrases used for the council (for example, term בֵּית דִּין (beit din, “house of judgment”). Sometimes it is simply called “the Great Assembly,” כְּנֶסֶת הַגְּדוֹלָה, keneseth haggedolah).
There is some question as to whether the Sanhedrin had an official meeting place in Jerusalem at this time. Josephus says there was a βουλή (boulē ) or βουλευτήριον in Jerusalem (JW 5.144; 6,354), referring to an official meeting place for the Sanhedrin. But Josephus uses the terms Sanhedrin and boulē quite loosely. It is an anachronism to think of the Sanhedrin as something like the US Congress. Based on the later and idealized Mishnah tractate Sanhedrin, the Sanhedrin had seventy members, but as few as twenty-three could make a quorum. Since only a few members are likely present, this is an informal hearing rather than a formal trial.
The meeting is at Caiaphas’s home, possibly in his courtyard with “the scribes and the elders.” This is a small group of Caiaphas’s close supporters gathered to figure out how to get rid of Jesus without getting blamed for it! This is not an official trial. It is more like politicians making a shady backroom deal.
They did not meet in an official meeting place (if there was one) or call all the council members together because that would give the meeting (and decision) an official look. This meeting is “off the record” to give the political leaders “plausible deniability” when Jesus is executed. Remember, they fear the crowds and seek to arrest him quietly (Matthew 26:3-5).
They do not pretend this is a trial to determine if Jesus is guilty or not; 26:59 says they are looking for false testimony to put Jesus to death. They are not looking for facts, but for a pretext to do what they have already decided must be done.
It is possible this secret trial with no real witnesses alludes to Psalm 27:12 (LXX 26:12) and/or Psalm 35:11 (LXX Psalm 34:11).
Psalm 27:12 (ESV) Give me not up to the will of my adversaries; for false witnesses have risen against me, and they breathe out violence.
Psalm 35:11 (ESV) Malicious witnesses rise up; they ask me of things that I do not know.
When Jesus was arrested and led to the high Priest, Peter followed at a distance and remained in the courtyard of Caiaphas’s home “to see the end” (26:58). This is ironic: Peter was called to follow Jesus. He is still doing so, but not as disciple willing to die alongside his master.