But how would telling the truth get him released?
That I don't know, but I can see her visiting him, crying and saying, "Please just tell the truth - I know you didn't do anything wrong.
We know she is deluding herself about this, but her crying and pleading with him would be another pressure on him.
Another thing that occurs to me, is he has had a compulsion to brag about his nefarious lifestyle. Keeping his mouth shut about Natalee for the rest of his life will be torture for him.