Daniel Prude, 41, died last March, several days after his arrest by police in Rochester, New York. Police initially described his death as a drug overdose.

The March 23 video of the fatal encounter was initially withheld by police in part because of concerns it would inflame street demonstrations occurring nationwide over George Floyd's death.

Ultimately released September 4, it showed officers placing a mesh bag over Prude's head to stop him from spitting after they detained him for running naked through the streets. Prude had been evaluated at a hospital for odd behaviour a day earlier, but he wasn't admitted.

One officer pushed Prude's face against the ground, while another officer pressed a knee to his back. The officers held him down for about two minutes until he fell unconscious. He was taken off life support a week later.

Attorney General Letitia James, whose office took over the investigation, said her office had "presented the strongest case possible" to the grand jury, but couldn't persuade it that the officers had committed a crime.

"I know that the Prude family, the Rochester community and communities across the country will rightfully be disappointed by this outcome," James said.

She said she was bound to respect the grand jury's decision, but she also condemned a system that she said had "frustrated efforts to hold law enforcement officers accountable for the unjustified killing of African Americans."

"What binds these cases is a tragic loss of life in circumstances in which the death could have been avoided," said James, who, like the mayor of Rochester and the city's current and former police chiefs, is black.

"One recognises the influences of race, from the slave codes to Jim Crow, to lynching, to the war on crime, to the overincarceration of people of colour: Eric Garner, Tamir Rice, Breonna Taylor, George Floyd. And now Daniel Prude," she said.

Lawyers for the seven police officers suspended over Prude's death have said the officers were strictly following their training that night, employing a restraining technique known as "segmenting." They claimed Prude's use of PCP, which caused irrational behaviour, was "the root cause" of his death.

The US Justice Department planned to review the attorney general's findings, according to a joint statement from its Civil Rights Division, the US attorney in western New York and the FBI.

James also issued a report recommending, among other things, that officers be trained to recognise the symptoms of excited delirium syndrome, which can make people vulnerable to cardiac arrest.

The attorney general also called for communities to minimise or eliminate police responses to mental health calls and to find alternatives to the type of "spit sock" officers placed over Prude's head. She said the mesh hood clearly added to Prude's stress and agitation.

The county medical examiner listed the manner of death as homicide caused by "complications of asphyxia in the setting of physical restraint" and cited PCP as a contributing factor.

Australian Associated Press