WASHINGTON - The US Justice Department said Wednesday it will not prosecute the white policeman who shot dead unarmed black teenager Michael Brown in Ferguson, but in a damning report found the local force systematically targeted African Americans.
The fatal shooting in August in the St Louis suburb ignited nationwide outrage and shone a critical spotlight on relations between law enforcement and black Americans, with police tactics also coming in for strong criticism.
The white officer, Darren Wilson, was also cleared in November by a grand jury which opted not to indict him for the death of the 18-year-old Brown, meaning the policeman is no longer facing legal action of any kind.
"Because Wilson did not act with the requisite criminal intent, it cannot be proven beyond reasonable doubt to a jury that he violated (Brown's civil rights) when he fired his weapon at Brown," the official report said.
"For the reasons set forth above, this matter lacks prosecutive merit and should be closed." The teenager's death - on a residential street in a black-majority town with an overwhelmingly white police force - prompted weeks of sometimes violent protests in Ferguson and beyond.
Wilson told the St Louis County grand jury that he had shot Brown in self-defence on August 9 after the youth allegedly tried to get hold of his handgun.
But others contended that Brown had his hands up in the air when the officer, who has since left the Ferguson police force, fatally opened fire.
In a statement, Brown's family called Wednesday's decision "disappointing." But it added that it looked forward to seeing "true change" as a result of the Justice Department's expose of "racial bias and profiling" among Ferguson police.
"If that change happens, our son's death will not have been in vain," the Browns said.
In what Attorney General Eric Holder called a "searing report" into Ferguson's police department, the Justice Department said it found a widespread pattern of racial discrimination and multiple violations of citizens' constitutional rights.
Police officers in the town of 21,000 regularly pulled over motorists without reasonable suspicion, carried out arrests without probable cause and used excessive force, it reported.
While African Americans make up two-thirds of Ferguson's overall population, they accounted for 93 per cent of arrests in 2012 through 2014.
African Americans also accounted for 85 per cent of people stopped by Ferguson police, 90 per cent of citations issued and 88 per cent of instances in which force was used.
Ferguson's local judicial system also came under a harsh light, with the report finding that African Americans were 68 per cent less likely than others to have their cases dismissed by a municipal judge.
And the town itself was accused by Holder of using law enforcement as a means to boost revenues, rather than ensure public order.
"Once the system is primed for maximizing revenue - starting with fines and fine enforcement - the city relies on the police force to serve, essentially, as a collection agency for the municipal court," he said.
While the Justice Department findings dwell on Ferguson, Holder said the concerns they raise "are not confined to any one city, state or geographic region."
He said the federal government would continue to "engage" with the authorities in Ferguson and its neighbouring communities to effect genuine reforms.
Missouri Governor Jay Nixon called the report "deeply disturbing." And Ferguson's white mayor, James Knowles, said a police officer who had written racially charged emails had been dismissed.
"This type of behaviour won't be tolerated," he said, adding: "We must do better not only in the city but in the state and the country. We must all work to address issues of racial disparity in all aspect of society."
In a statement on Tuesday, human rights watchdog Amnesty International said the findings should prompt US President Barack Obama to set up a task force to come up with recommendations for criminal justice reform.
"The United States still has a long way to go before it has truly accountable policing," its US director Steven Hawkins said.
"This country's long history of racial profiling and other police abuses is only matched by its equally long history of inadequate accountability for those responsible."