Image copyright Getty Images

Three former or current Chicago police officers have been charged with allegedly conspiring to cover up the fatal police shooting of a black teen.

Detective David March and officers Joseph Walsh and Thomas Gaffney face charges of conspiracy, obstruction of justice and official misconduct.

Laquan McDonald was shot 16 times by a white officer in 2014, sparking widespread protests across the city.

Prosecutors accuse the three men of lying in the shooting's aftermath.

"The indictment makes clear that these defendants did more than merely obey an unofficial 'code of silence,' rather it alleges that they lied about what occurred to prevent independent criminal investigators from learning the truth," Special Prosecutor Patricia Brown said in a statement on Tuesday.

Officer Jason Van Dyke was charged with first-degree murder in 2015 after dashcam footage appeared to show him fatally shooting Mr McDonald as he moved away from officers, contradicting police accounts. He has pleaded not guilty.

According to the indictment, the three officers allegedly falsified reports and tried to conceal the events surrounding Mr McDonald's death "to shield their fellow officer from criminal investigation".

"The defendants allegedly lied about what occurred and mischaracterised the video recordings so that independent criminal investigators would not learn the truth about the killing and the public would not see the video recordings," Ms Holmes' office said.

Ms Holmes was appointed last July to investigate whether several officers at the scene attempted to cover up the circumstances surrounding the teenager's death.

Image copyright Getty Images Image caption Protesters march in Chicago after the city released dashcam footage showing Laquan McDonald's death.

Mr March, the lead detective, left the department after a damning report by the city's Inspector General Joseph Ferguson he made false statements about the shooting.

The Chicago Police Department has also moved to fire Mr Walsh, who was Mr Van Dyke's partner at the time of the incident.

Police released the dashcam footage in November 2015 after Mayor Rahm Emanuel's administration fought to withhold the video for a year before a judge ordered its release.

The long-delayed footage prompted public backlash and mass protests, culminating with the dismissal of the police chief and a Justice Department investigation into the Chicago Police Department's use of force and practices.