Paul Callan : Justice Department made a mistake with its new investigation of Ferguson police . Callan : He says the probe is politically inspired and risks prejudicing the Michael Brown case . Prosecutors and grand jury seeking to decide if criminal charges are warranted , he says . Callan : ( CNN ) -- The U.S. attorney in St. Louis has said that his office will not be involved in any decision on whether or not to charge Darren Wilson for killing unarmed teenager Michael Brown.
Paul Callan : Justice Department made a mistake with its new investigation of Ferguson police . Callan : He says the probe is politically inspired and risks prejudicing the Michael Brown case . Prosecutors and grand jury seeking to decide if criminal charges are warranted , he says . Callan : The U.S. attorney in St. Louis has said that his office will not be involved in any decision on whether or not to charge Darren Wilson for killing unarmed teenager Michael Brown.