Billy Desmond is a smart, politically motivated ADA, and hadn't lost a case during his three years at the DA's office. Initially, he appeared to care more about winning cases and his political stature, but over the course of the series, it become evident that Billy will not compromise the law or the DA's office for either his track record or his aspirations. Billy appears to be closest to Finn and Peluso, who he is seen to go out with after hours, but he also has hit a club or two with new co-worker, Potter. The Cast of Conviction.