"But let your communication be, Yea, yea; Nay, nay: for whatsoever is more than these cometh of evil." Matthew 5:37

Jesus was facing a terrible fate.  He knew what was to come and the agony was great, as we saw at Gethsemane where Jesus sweated blood.  Knowing what He faced, when Herod and Pilate asked him questions, Jesus said as little possible to avoid the temptation to go against the will of God.  Jesus remained obedient.  His hour had come. 

Jesus was sinless.  God needed to sacrifice a blameless man for His plan to work. The blood of the Lamb had to be pure. When Herod and Pilate, both in the highest of worldly authority and power, established His innocence, Jesus went to the cross an innocent man to take on our sin.  God used the violent crowd and their potential for revolt to move Herod and Pilate to convict Jesus to death.