A man convicted of killing a Bristol police office is seeking a new trial. Lawyers for 36-year-old Nikolas Johnson are petitioning for post-conviction relief, arguing that his constitutional rights were violated. Johnson was convicted of murder and sentenced to death in 2007 in the killing of Bristol police officer Mark Vance, who was shot in the face in 2004 while responding to a domestic call. The petition argues that Johnson’s original attorneys were incompetent, his jury was racist, he suffered from mental illness, that there was prosecutorial misconduct and that lethal injection is unconstitutional. A hearing in the case is set for June 23.