St Paul, Minnesota: A jury on Friday found the Minnesota police officer who fatally shot a black motorist during a traffic stop last year not guilty of second-degree manslaughter.

St Anthony Police Department officer Jeronimo Yanez fatally shot Philando Castile, 32, last July in an incident that drew international attention and local protests when the driver's girlfriend, who was sitting in the passenger seat, streamed it on social media.

Yanez had testified that he was afraid for his life and that Castile did not follow his orders.

The shooting, like similar incidents across the United States, fuelled debate about the appropriate use of force by law enforcement against minorities.

Castile's mother, Valerie Castile, speaking to reporters outside the court after the verdict, said: "I'm mad as hell right now. Yes, I am. My first born son died. ... Just because he was a police officer, that makes it OK."

She abruptly left the courtroom after the verdict was read, as cursing and sobbing from spectators could be heard.

She said the verdict shows "the system continues to fail black people," adding, "My son loved this city and this city killed my son and the murderer gets away ... Are you kidding me right now? We are not evolving as a civilisation, we are devolving."

A rally "to demand justice (and) accountability" was planned for Friday night at the state capitol by several groups including the local chapter of Black Lives Matter.

St Paul Mayor Chris Coleman said the city would open two community centres and a college for community discussion on Friday, Saturday and Monday.

Castile's sister, Allysza Castile, who spoke after her mother, said, "I will never have faith in the system".

The jury of seven men and five women, 10 of whom were white and the other two black, deliberated for four days before acquitting Yanez on all charges.

Earl Gray, an attorney for Yanez, welcomed the decision.

"Justice was done," Gray said by telephone. "We're very happy. Yanez was innocent. He was just doing his job."

Shortly after the verdict, the City of St Anthony said Yanez will not return to active duty and that it is negotiating a "voluntary separation agreement" with him.

"I extend again my deepest condolences to Philando Castile's family, to his friends, and to his community," Governor Mark Dayton said in a statement.

"Minnesotans continue to grieve with them, for their horrible loss. Mr Castile's death was a terrible tragedy, with devastating consequences for everyone involved."

During his testimony, Yanez said he feared for his life after Castile disregarded his commands and began reaching for a firearm that Castile had disclosed he had in his possession.

Prosecutors said Yanez was not justified in firing his gun, saying Castile was courteous and non-threatening.

Reuters