They were hoping to find Jesus guilty of being a false prophet or of enticing secretly (Deut 13:1-5) so they could have legitimate reason to pronounce the verdict they already had decided upon. The high priest starts by interrogating Jesus, which was strictly prohibited by Jewish law because it did not allow the accused to incriminate himself. The case had to be established by the testimony of witnesses and it was the responsibility of His accusers to find them and bring them forth.

Deuteronomy 13:1-5  If a prophet, or one who foretells by dreams, appears among you and announces to you a miraculous sign or wonder,  and if the sign or wonder of which he has spoken takes place, and he says, “Let us follow other gods” (gods you have not known) “and let us worship them,”
you must not listen to the words of that prophet or dreamer. The LORD your God is testing you to find out whether you love him with all your heart and with all your soul.  It is the LORD your God you must follow, and him you must revere. Keep his commands and obey him; serve him and hold fast to him.  That prophet or dreamer must be put to death, because he preached rebellion against the LORD your God, who brought you out of Egypt and redeemed you from the land of slavery; he has tried to turn you from the way the LORD your God commanded you to follow. You must purge the evil from among you. 

Annas first questions Jesus about His disciples and then about what He was teaching them. Hendriksen finds this order significant: “That is exactly what one can expect from Annas! He was far more interested in the ‘success’ of Jesus – how large was his following? – than in the truthfulness or untruthfulness of that which he had been teaching. That is ever the way of the world.”

It is uncertain exactly what questions Annas was asking about Jesus’ disciples: their number, who they were, or what they did and what was expected of them.