By Fiona Ortiz
CHICAGO (Reuters) - Politicians, pastors and civil rights lawyers petitioned Cook County's chief judge on Tuesday to assign a special prosecutor to the murder trial of a Chicago police officer who fatally shot a black teenager, saying the state's attorney was biased.
Officer Jason Van Dyke, who is white, faces six counts of first-degree murder after shooting 17-year-old Laquan McDonald 16 times in October 2014.
Patrol car dashboard-camera videos of the shooting were released a year later, setting off weeks of protests calling for the resignations of Mayor Rahm Emanuel and of Anita Alvarez, the top prosecutor in Cook County, which includes Chicago.
Alvarez has been criticized for taking more than a year to bring charges in the case, which has become a key issue in her campaign for re-election to a third term next month.
"This is an extraordinary measure that is necessary to restore public confidence," Cook County Commissioner Jesus "Chuy" Garcia said at a news conference on the petition.
The petition, which a judge will hear on Friday, says Alvarez only filed the murder charges because she was under pressure after videos of the shooting were made public.
The petition says Alvarez repeatedly failed to charge police officers who committed crimes because she has a conflict of interest. It says the Fraternal Order of Police union endorsed her and donated to her campaigns when she was elected in 2008 and 2012.
Alvarez said in a statement that her office had built a meticulous case against Van Dyke and that highly skilled prosecutors would handle it. She defended her record, saying she had brought charges against 96 law enforcement officers in the past.
State Senator Kwame Raoul, U.S. Representatives Danny David and Bobby Rush, five Chicago aldermen and a number of pastors supported the petition.
Alvarez decried the petition as politically motivated, noting that people who have endorsed her campaign rival, Kim Foxx, have backed it. But Locke Bowman, one of the lawyers who filed the petition denied there was any political element.
The U.S. Justice Department is investigating the use of force by Chicago police, who over the past eight years have shot an average of 50 people a year, 74 percent of whom are black.
During last year's protests over the McDonald killing, Mayor Emanuel fired the police chief and replaced the head of the police oversight agency.
(Editing by Lisa Von Ahn)