An inquiry by the US Justice Department is expected to find that police in Ferguson, Missouri routinely engaged in racially biased practices.

Leaked details suggest officers used excessive force against black residents and too often charged them with petty offenses. 

The investigation was launched after the shooting of unarmed black teenager Michael Brown by a police officer.

Last year, the white officer who shot dead unarmed black teenager Mr Brown in Ferguson, Missouri, resigned from the police force.

Mr Wilson had been on administrative leave since the shooting on August 9th.

According to the St Louis Post-Dispatch newspaper, Mr Wilson (28) sent a resignation letter to the Ferguson force which read: "It was my hope to continue in police work, but the safety of other police officers and the community are of paramount importance to me."

"I have been told that my continued employment may put the residents and police officers of the City of Ferguson at risk, which is a circumstance that I cannot allow."

"It is my hope that my resignation will allow the community to heal."

A grand jury spent more than three months reviewing evidence in the case before deciding not to issue any charges against him.

He had told jurors that he feared for his life when Mr Brown (18) hit him and grabbed for his gun.