Acts 1:24

And they prayed, and said, Thou, Lord, who knowest the hearts of all men, show of these two the one whom thou hast chosen,

'WHO KNOWEST THE HEARTS OF ALL MEN'-(1 Chronicles 28:9; Jeremiah 2:10). 'They appealed to God himself to select one who would be true, and not bring dishonor to the cause of Christ. The apostles knew only the qualifications--but God knew the heart.' (Reese p. 29) This appears to indicate that Judas had "looked" righteous on the outside. In fact, the truth that the other disciples never caught on to his hypocrisy, until after the fact, would confirm the same suspicion.

'THE ONE WHOM THOU HAST CHOSEN'-Indicating that the apostles already knew that the Lord had made His choice.