Missouri Gov. Jay Nixon will not remove St. Louis County Prosecutor Robert McCulloch from the investigation of the police killing of unarmed teenager Michael Brown. Prosecutors will be presenting preliminary evidence to a county grand jury Wednesday which will determine the fate of a Ferguson police officer who fatally shot Brown on Aug. 9. There have been calls for McCulloch to recuse himself because of his purported close ties to police. Grand juries are secret, and potential defendants usually don't appear. But a McCulloch spokesman told NBC News that Officer Darren Wilson would be given an opportunity to testify.