Here are the scriptures that whitjm5 provided in MKJV

Joh 6:64 But there are some of you who do not believe. For Jesus knew from the beginning who they were who did not believe, and who is the one betraying Him.

Joh 6:70 Jesus answered them, Have I not chosen you, the Twelve? And one of you is a devil?

Joh 17:12 While I was with them in the world, I kept them in Your name. Those that You have given Me I have kept, and none of them is lost, but the son of perdition, that the Scripture might be fulfilled.

2Th 2:3 Let not anyone deceive you by any means. For that Day shall not come unless there first comes a falling away, and the man of sin shall be revealed, the son of perdition,

Let's not forget that Peter denied Christ three times to save his own skin. If he believed at the time that Christ was the Son of God why would he deny him? (not really looking for an answer here, just some food for thought concerning Judas)

The fact is, we do not no what was the reasoning behind Judas's motives for betraying Jesus, but it's clear that he did not want to see Jesus killed. He was remorseful. So remorseful that he killed himself for what he had done. Who are we to think we can see into a man's heart? Only God can. Many theories have arised concerning Judas, but let's not loose the real message. Judas must of believed in Jesus, but the extent of that belief is not known.

Oh yay, let's not forget about "Doubting Thomas". Joe, thanks for you explanation. What you said is very true. But, how many of the disciples were true believers, and how many understood the whole picture of Jesus' ministry while Jesus was still with them? This isn't a question directed to you Joe, it's just a question I thought I would put out there. By the way, the definition of devil as used by Jesus was meant as accuser and not the literal devil we know as Satan. Judas obviously wasn't Satan, but Judas did have his own agenda.