By Carey Gillam
(Reuters) - The parents of Michael Brown, the unarmed black teenager shot dead in August by a white police officer in Ferguson, Missouri, on Monday asked Missouri's governor to reconsider his decision not to appoint a special prosecutor in the case, according to the family's attorney.
In a letter addressed to Missouri Governor Jay Nixon, lawyers representing Lesley McSpadden and Michael Brown Sr. said there were "compelling and rising concerns of conflict that now exist" between St. Louis County Prosecutor Robert McCulloch and the Ferguson Police Department.
McCulloch has been overseeing a grand jury probe into the Aug. 9 shooting by police officer Darren Wilson of 18-year-old Brown. His office has been presenting evidence to the grand jury, and has said a decision on whether or not Wilson will be indicted could come by mid-November.
McCulloch's office has also said that criminal cases involving Wilson as a witness have been put on hold.
The Brown family lawyers, who provided a copy of the letter to the media, said that the decision to put those cases on hold "clearly raises an issue of concern." The "potential for bias is present" because Wilson is both a possible defendant and a witness for the prosecutor, they added.
"Officer Wilson... has developed a special working relationship with Mr. McCulloch and his office," they wrote in the letter, dated Oct. 6.
Brown's parents and protest groups have asked for a special prosecutor before but Nixon has declined.
Representatives for the county prosecutor and the governor had no immediate comment on the latest request.
Brown's death has sparked weeks of sometimes violent protests in Ferguson, a St. Louis suburb, prompting the governor at one point to call out the National Guard.
Several witnesses have said Brown was trying to surrender to Wilson, holding his hands in the air, when Wilson shot him multiple times. Federal officials are also investigating the incident.
Wilson has been in hiding since the incident, and has not told his version of events publicly, though police officials have said there was an altercation between Wilson and Brown before Brown was shot.
On Saturday night, a group of protesters interrupted a performance of the St. Louis symphony by singing a "justice for Mike Brown" song and chanting "black lives matter." A video of the incident shows the group unfurling banners over the symphony balcony, including one that read "racism lives here."
(Reporting by Carey Gillam in Kansas City, Mo.; Editing by Susan Heavey)