Since being established in 2007, the police review board has faulted officers in only two of the more than 400 shootings it has examined. Mayor Rahm Emanuel said last year that those statistics seemed to “defy credibility,” and a former investigator for the agency, Lorenzo Davis, said he was fired after he found some shootings to be unjustified, only to be overruled by his supervisors.

Among the cases where Mr. Davis said he faulted the officer, but where the final report found no wrongdoing, was the fatal shooting in 2013 of Cedrick Chatman, a black 17-year-old shown on video running away from the police. The officer who shot him said he mistook the iPhone box Mr. Chatman was carrying for a gun.

The review of past shootings comes at a time of upheaval in the Chicago Police Department. The Justice Department is investigating police practices here, murders have increased 84 percent over the same period in 2015 and Mr. Emanuel is considering three finalists to fill the job of police superintendent. The previous superintendent, Garry F. McCarthy, was fired in December as part of the fallout from the McDonald case.

Since early last week, three Chicago police officers were shot and a suspect was killed in an exchange of gunfire, an off-duty officer shot a man who he said had attacked him with a baseball bat and another off-duty officer was shot during an attempted robbery. The review board is investigating all of those cases.

The review of past investigations is expected to start as soon as next week and take about six months, Ms. Fairley said. George J. Terwilliger III, a former United States deputy attorney general who is helping lead the audit, said it was too soon to know how many cases would be examined and whether specific shootings would be detailed in the final report.