"An investigation into whether there are patterns and practices of civil rights violations by CPD is vital to bringing about the systemic change that is necessary here," Madigan wrote Tuesday in a letter to US Attorney General Loretta Lynch.
Madigan wrote that Chicago could not move forward without an external independent investigation into its police department that legislates improvement of policing practices. She added that the local community no longer trusts the police.
McDonald's murder prompted widespread public protest in Chicago, as it followed the increasingly common case of a white police officer in the United States killing an African-American. Many of those killed were later shown to have been unarmed and, in some case, restrained.
In August 2014, off-duty white Chicago policeman Dante Servin shot an unarmed black woman named Rekia Boyd, and was found not guilty of the murder.
In July 2014, another unarmed African-American man, Eric Garner, was killed after a white police officer used an illegal choke-hold on him. The officer was not charged with the well-documented murder.
