The head of Dallas’ largest police union says due process was followed in the trial of a former Balch Springs Police officer convicted of murder for killing a 15-year-old boy. Sgt. Michael Mata, who heads the Dallas Police Association, said Thursday that a large percentage of officers thought former Balch Springs officer Roy Oliver committed a crime by killing 15-year-old Jordan Edwards. The officers differed on whether the crime was murder or manslaughter