He didn't want to bother with testifying. I think either in his zeal to see AG convicted, or as a result of collecting reward money, (I don't know which, but something made this drug dealer come forward) he gave a statement. Then when it came time to testify, he didn't want to be there. He was in California prior to the day of his testimony. So, he didn't want to be there and couldn't be bothered with dressing appropriately for court. The judge glared at him when he asked to be excused or if he could leave, and she remarked, "Surprised he even bothered to show up." (Per YouTube video of trial.) He met in chambers with the Judge prior to giving his testimony. Whatever he said was not well received by the Judge.
And it's been alleged in articles that the prosecution had to threaten him with arrest and contempt if he didn't show up.
I don't think he was afraid. I think he just couldn't be bothered. moo