The city and several of its officials have been engulfed in controversy since a video of McDonald's shooting was released last month following a court order.
"We can either be defined by what we have failed to do or what we need to do," the mayor said, telling the alderman that "nothing can excuse" what happened to McDonald. "We need a painful but honest reckoning of what went wrong ... over decades."
Emanuel addressed the City Council at the same time a federal judge weighed whether to release yet another video purportedly showing the deadly shooting of a teenager at the hands of police. The video is connected to the death of 17-year-old Cedrick LaMont Chatman, who court documents say was gunned down in 2013 by police. The city has fought to keep the video under wraps, much like in the McDonald case.
Police did not comment on the case.
The Chatman family submitted the motion to release the video as part of an on-going federal wrongful death lawsuit against the city, the family's lawyer, Brian Coffman, told ABC News.
The city did not respond to ABC News' request for comment, but in its U.S. District Court response to the wrongful death lawsuit, the city said that although Chatman did die at the hand of police, the officer shot the teen "in fear of his and/or his partner's life."
The Independent Police Review Authority, which investigated the case, found the shooting had been "justified."
U.S. District Court Judge Robert Gettleman put off the decision on whether to release the video until Jan. 14, a clerk in his office told ABC News. The video has not been presented to the court, the clerk said. Gettleman gave the city two weeks to respond to the motion filed by the Chatman family. He said the city should argue why the video shouldn't be released. The judge also gave plaintiffs two weeks to file a reply to the city's response.
"This has turned into changing the culture of the city of Chicago," Coffman said, adding the city's current push for transparency is "tongue in cheek."
Data on police misconduct complaints show that one of the officers purportedly involved in Chatman's shooting had 30 civilian complaints of misconduct against him. Of those complaints, 12 are for alleged use of excessive force, according to the data collected from police reports by the Invisible Institute, a Chicago-based journalistic production company and watchdog group.
The data shows two of those complaints are still pending a verdict or waiting for the complainant to file an affidavit validating the complaint, six were not sustained and two were unfounded. The officer was exonerated on two of the complaints.
The Invisible Institute is an independent organization whose collaborators include the University of Chicago Law School’s Mandel Legal Aid Clinic.
Its database does not indicate specific dates for many of the complaints. Invisible Institute notes that the City of Chicago’s release of this data was “accompanied by a disclaimer that not all of the information contained in the City’s database may be completely accurate. No independent verification of the City’s records has taken place and this public database does not purport to be an accurate reflection of either the City’s internal database or of its truthfulness.”
"Every police officer is sworn to protect life and in the most extreme circumstances, to take life," Emanuel said. "It may be too much to expect that every officer will always get it right, but it is not too much to expect that we can put the safeguards to ensure police accountability when they get it wrong."
The mayor also mentioned the police department's "code of silence," saying permitting and protecting even the smallest acts of abuse lead to a culture where extreme acts of abuse are more likely.
"We cannot have effective policing if we turn a blind eye to police misconduct," he said. "Respect must be earned. Respect is a two-way street."
Hundreds of protesters took to the streets today, halting traffic in some of the main streets in the city’s downtown area. They mostly called for Emanuel's resignation.
Editor’s note: This story has been updated with additional information about the Cedrick Chatman case.