Ramsey County Attorney John Choi said Friday that he's tapped ex-Hamline University law school dean Don Lewis to be a "special prosecutor" to help him make decisions tied to the Philando Castile police shooting.

Lewis will be "an integral member of our team" and "substantially involved" in decisions tied to the case, Choi told reporters.

Local activists, however, quickly challenged Lewis' independence.

Philando Castile in an undated photo. Courtesy of Sam Castile

Full coverage: Philando Castile police shooting

Castile, 32, was shot and killed by St. Anthony police Jeronimo Yanez during a July 6 traffic stop in Falcon Heights. The bloody aftermath was captured by Castile's girlfriend, a passenger in the car, on live video streamed on Facebook, helping to fuel protests in Minnesota and across the country.

Choi, whose office will get the Castile case once the Minnesota Bureau of Criminal Apprehension completes its investigation, emphasized that no decision had been made yet on any charges in the shooting, or whether the case will be taken to a grand jury.

Police shooting cases typically go to grand juries, although Hennepin County Attorney Mike Freeman earlier this year chose not to send the Jamar Clark case to a grand jury. His office ultimately chose not to pursue charges against the Minneapolis officers, concluding the shooting was justified under state law.

Days after the Castile shooting, Choi told reporters that he'd talked to Freeman about a potential grand jury decision and acknowledged it was "a very difficult standard" to meet to bring criminal charges against a police officer in Minnesota.

Lewis, an African-American and longtime fixture in Twin Cities legal circles, vowed on Friday that his work on the Castile case would be "substantial, meaningful and visible."

Besides his years as Hamline law school dean, he also served as an assistant United States Attorney for Minnesota. He led St. Paul's outside investigation into the 2013 landslide at Lilydale Regional Park, in which two children died.

He also led an independent investigation into the 2014 arrest of community activist Al Flowers in Minneapolis. Ultimately, that investigation found no officer misconduct.

Flowers on Friday called Lewis' appointment in the Castile case "a "horrible choice. He's absolutely not neutral. When you get Don Lewis, you're getting someone to cover it up."

The Minneapolis NAACP also criticized the move.

"Don Lewis has a history of placing the interests of law enforcement ahead of the interests of justice," Minneapolis NAACP President Nekima Levy-Pounds said in a statement, adding that his appointment in the Castile case "feels like a return to business as usual."

Choi turned aside calls from Levy-Pounds and other activists who demanded that a prosecutor be appointed from outside his office. Doing that, Choi said, would be "abdicating my responsibility" and potentially creating more community mistrust.

Lewis' "independent perspective can only enhance the integrity and legitimacy of our decisions in this case," said Choi. "This is ultimately what justice requires."