A man has gone on trial in the South Australian Supreme Court charged over a 2007 murder. (Morgan Sette/AAP PHOTOS)A man has gone on trial in the South Australian Supreme Court charged over a 2007 murder. (Morgan Sette/AAP PHOTOS) Credit: AAPAlmost 20 years after a young man was fatally stabbed at a birthday party, a man is standing trial accused of his "payback" murder. "It's about a group attack on Thea Kheav allegedly committed by these four men," Mr Lesses said. "The issue in this trial … is going to be one of involvement and group criminal responsibility," Mr Lesses said.