(CNN) A Minnesota prosecutor said Friday he has appointed an outside attorney to help him decide whether to pursue criminal charges in the July 6 shooting death of a black man by a police officer.

Ramsey County chief prosecutor John Choi told reporters that he will bring in Don Lewis , a private attorney and former federal criminal prosecutor, to join his office's deliberations on whether to file charges in the death of Philando Castile outright or delegate the decision to a grand jury.

Castile, 32, was shot during a traffic stop by St. Anthony police Officer Jeronimo Yanez in Falcon Heights, authorities say. The shooting was widely publicized after Castile's fiancée, sitting next to him in the vehicle he'd been driving, live-streamed the shooting's aftermath on Facebook.

The incident, along with the July 5 shooting death by police of Alton Sterling in Baton Rouge, Louisiana, helped spark protests nationwide and renewed debate over the relationship between law enforcement and the communities they serve.

In another controversial shooting, a former Chicago judge on Friday was appointed special prosecutor to investigate whether police colleagues lied to back up Officer Jason Van Dyke's version of the 2014 killing of Chicago teenager Laquan McDonald.

Judge LeRoy K. Martin appointed Patricia Brown Holmes -- a former federal, state and local prosecutor and state court judge -- to investigate whether charges will be filed against other officers.

Cook County State's Attorney Anita Alvarez took herself off the murder case against Van Dyke in May.

Civil rights leaders had called for a special prosecutor after dashcam video of the shooting contradicted police accounts of what happened the night of October 20, 2014.

Van Dyke has pleaded not guilty to six counts of first-degree murder in the death of McDonald, 17, whose videotaped shooting provoked anger nationwide.

In Minnesota, Choi's decision to bring in an outside attorney is something of a compromise. He said the American Civil Liberties Union and an attorney for Castile's family had been calling on him to hand off the decisions to a special prosecutor entirely to quell concerns over whether prosecutors can hold police in their own district accountable.

"I have chosen to incorporate a special prosecutor into our team to provide independent perspective bolstered by the authority of this office," Choi said at a news conference in St. Paul. "I'm not simply asking for his advice or approval. ... Don will be an integral member of our team who will review this case with me."

Choi said he thought giving the case entirely to a special prosecutor would be an abdication of his responsibility, so he decided to add Lewis -- a man who helped lead the Minnesota Association of Black Lawyers and has experience with federal civil rights cases -- to his team.

In the video of the shooting, Castile's fiancée says that the officer had pulled him over for a broken tail light, and that he had told the officer that he had a gun for which he had a concealed-carry permit.

She said he was reaching for his wallet when the officer shot him. The officer says in the video that he had "told him not to reach for it."

Castile was pulled over at least 52 times since 2002, something protesters argue is a sign of racial profiling.

An attorney for Yanez told CNN that the shooting had nothing to do with race and everything to do with a gun being present at the scene.

Video also is a key in the investigation of the McDonald shooting. A judge ordered the video's release only after a journalist filed a Freedom of Information request last year.

The dashcam video showed McDonald veering away from police as he held a knife, not lunging toward officers as police had said.

Van Dyke jumped out of his vehicle and pulled his gun, firing at McDonald six seconds after arriving on the scene. The two never faced each other in the encounter. Van Dyke continued to fire, unloading every round from his 9-mm Smith & Wesson handgun in 15 seconds.

The video appears to show McDonald's body getting hit by bullets even after he was on the ground. The video has no audio.

All 16 rounds struck McDonald.

Van Dyke, who has been suspended without pay, is free on bond.

He is the first Chicago officer charged with first-degree murder since 1980.