The "patterns and practices" investigation will determine whether the department systematically violates constitutional rights.
The U.S. Justice Department will open an investigation into the Chicago Police Department after protests over how it handled the case of a black teenager shot by a white police officer.
This follows murder charges filed against the police officer in the October 2014 killing. The shooting was caught on videotape.
Officer Jason Van Dyke was charged with first-degree murder in the death of 17-year-old Laquan McDonald, who was shot 16 times. When the charges were filed, the city released a video of the shooting. Van Dyke fired all the shots.
Protests erupted afterward, culminating in the firing of Police Superintendent Garry McCarthy. Critics have complained it took too long for the McDonald tape to be released and for charges to be filed.
The release of the video comes at a time of heightened debate over police use of lethal force, especially against black people. Over the past year, protests over the issue have rocked a number of U.S. cities.
The Justice Department launched an investigation into the Baltimore Police Department’s use of force and whether there were patterns of discriminatory policing after the death of Freddie Gray, a 25-year-old black man, who suffered fatal injuries while in police custody.
A Justice Department investigation of police in Ferguson, Missouri, where a white officer fatally shot an unarmed black teenager last year, concluded that the department routinely engaged in racially biased practices.