Immediately after the flood in Noah's day, God instituted human government by placing the authority of capital punishment into the hands of men. Man would be responsible to put murderers to death, and thus human government was born (Gen 9:6).
This passing of judgment to allow the death sentence has been a symbol of a government's authority over its people. Throughout the history of Israel, they were conquered many times but still allowed to govern their own people who remained in the land. In about 4 AD, King Herod (who had tried to kill the young Jesus by wiping out a large number of babies) had died, and his son, Herod Archelaus, replaced him. He was very unpopular, and he was removed in 6 AD.
A Roman procurator, Caponius, came into power and removed the authority of Jewish leadership, particularly the power of the Sanhedrin (Jewish Religious leaders) to sentence people to death. (This is why they had to get Roman permission to crucify Jesus.)
The entire Sanhedrin began to wail, covering their heads with ashes and wearing sackcloth. They went around Jerusalem crying “Woe unto us for the scepter has departed from Judah and the Messiah has not come!” (Babylonian Talmud Chap 4, folio 24). Had they only believed their Bibles, they should have rejoiced that the scepter HAD departed, because that could only mean the Messiah had arrived and they just needed to find Him.
God’s Word cannot be broken. A few miles away a young boy named Jesus was being raised by his mother and adoptive father, growing in grace and truth. Shiloh had arrived.
Too many people who supported Jesus were present in the temple. Since he had just ridden into Jerusalem to the praise of all the people, a riot would have broken out to defend Him if the Sanhedrin had stood against him.
Instead of standing against Jesus publically during the day, they had to convict him secretly at night, since holding trials at night was illegal. Moreover, they had to use false witnesses to convict Jesus of His crimes. They then had to threaten riots if Pilate did not rule in their favor against Jesus.
In conclusion, Jesus could have defended Himself. However, he was on trial in our place, so to speak, and found guilty in our stead.