After the troops came into the garden, the troops "arrested Jesus and bound Him" (18:12). Jesus then got sent to Annas, the father-in-law of high priest Caiaphas.
Caiaphas was the one who advised the Judeans that "it was expedient that one man should die for the people" (18:14). Caiaphas is mentioned way back in John 11 (the time when Jesus rose a man from the dead). His speech is basically a prophecy that Jesus would die on behalf of the Judean nation (via taking on the penalty of sin despite being right with God) and that Jesus would bring together the children of God that were scattered. Though the Judean leadership could take the words to mean that they should kill Jesus because they feel he would ruin their nation (and their status).