The shooting death of Laquan McDonald, 17, which was caught on video from a police car dashboard camera, sparked a wave of protests and calls for Chicago Mayor Rahm Emanuel's resignation.
Twenty-three officers, including the case's lead detective and four officers whose accounts of the incident conflicted with video footage, began appearing before the grand jury in June and have appeared as recently as three weeks ago, records obtained by the Chicago Tribune through a Freedom of Information Act request show.
McDonald's death is one in a series of police killings of black teens and men in US cities that have sparked a national debate on race and justice and fueled the rise of the Black Lives Matter movement.
Several of the Chicago officers have been called to testify more than once, and all of the officers remain on active duty. Being called to testify before a grand jury does not indicate wrongdoing.
In November, the city released video footage that shows officer Jason Van Dyke shooting McDonald 16 times while other officers stood nearby. McDonald, who carried a pocket knife, appeared to be walking away from police when he was shot.
The incident has launched several law enforcement probes.
Van Dyke has pleaded not guilty to six counts of first-degree murder and one count of official misconduct for killing McDonald. Police have said McDonald had threatened them with a knife and slashed at the tires and windshield of a patrol car.
Emanuel, a Democrat with strong ties to the White House, and State's Attorney Anita Alvarez have been the target of protests because of the year-long delay in bringing charges against Van Dyke.
Chicago officials on Thursday released the video of another controversial police shooting, that of 17-year-old Cedrick Chatman in 2013, after a judge lifted the order sealing the video.