DNA evidence showing a man had sexual contact with a murder victim within three days of her death is not enough to prove he was the killer, a divided panel ruled.A majority of the 1st District Appellate Court panel in an unpublished order Friday reversed Michael Johnson’s first-degree murder and aggravated sexual assault convictions and sentences.Cook County jurors found Johnson guilty of sexually assaulting and strangling L.B. to death. He was sentenced to 40 years in prison for the murder charge and 30 years in prison …