Then when Judas, his betrayer, saw that Jesus was condemned, he changed his mind and brought back the thirty pieces of silver to the chief priests and the elders,
Now on the face of it, the phrase "changed his mind", which is also translated by the King James as, "repented himself" and the CEV translation renders this as, "he was sorry", seems to lend itself in our American thinking that Judas was truly sorry. Therefore Judas is now in heaven.
The problem here is with our American thinking about human nature and ability. We seem to think that a man's conscience which is pricked somehow means that the Holy Spirit intends to do something salvific. Listen to Paul's words from 2 Corinthians 7 as the Holy Spirit has given them to us.
2Co 7:9 Now I rejoice, not that you were grieved, but that you were grieved to repentance. For you were grieved according to God, that you might suffer loss in nothing by us.
2Co 7:10 For the grief according to God works repentance to salvation, not to be regretted. But the grief of the world works death.
Notice that the Spirit of God explains to us that natural man and the spiritual man both may feel sorrow. Shouldn't that be obvious? This comports with our everyday experience. But the assumption by many is that all men are capable of working up in themselves a true repentant heart, or it assumes that God gives everyone an equal chance through some kind of prevenient grace. This is all just assumed.
Anecdotally, just the other day, I had to assist a female that was involved in a car accident. She felt extremely guilty about what she had done. She probably will never do whatever she was doing that caused her to have the accident again. Yet she is still fully culpable for what she had done and will pay for it via insurance or whatever. The range of human ability and emotions is wide, but to assume it is able to produce within itself godly sorrow is simply, again, an assumption that we shall see does not fit with all of the Biblical text.
We must understand that there is a godly sorrow that leads to repentance of salvation. It is a Spirit borne sorrow that causes a person to look outside of themselves and to Christ. Is this what Judas did? Let's read the rest of the verse.
Mat 27:5 And tossing the silver pieces into the temple, he left. And going away he hanged himself.