Image copyright AP Image caption Tamir Rice was shot and killed by police in Cleveland, Ohio, last November

A white police officer was justified in shooting and killing last year a black 12-year-old boy who was carrying a toy gun in Cleveland, Ohio, two outside experts have concluded.

The conclusions come ahead of an expected decision by a grand jury on whether criminal charges are warranted.

In June, a judge ruled the policeman should be charged with murder.

Rice family lawyer Subodh Chandra accused the experts of assisting in a "whitewash" of the incident.

Tamir Rice was shown on CCTV waving a pellet gun outside a recreation centre last November, before being shot twice.

He later died in hospital.

Retired FBI agent Kimberly Crawford, in a review of the shooting, wrote that "not only was Officer [Timothy] Loehmann required to make a split-second decision, but also that his response was a reasonable one".

He "had no information to suggest the weapon was anything but a real handgun, and the speed with which the confrontation progressed would not give the officer time to focus on the weapon", she wrote.

In another report, Colorado prosecutor Lamar Sims also concluded that "Officer Loehmann's belief that Rice posed a threat of serious physical harm or death was objectively reasonable, as was his response to that perceived threat".

Cuyahoga County Prosecutor Timothy McGinty said in a statement his office - which commissioned the expert reports - was not reaching any conclusions based on them.

In June, Judge Ron Adrine said there were sufficient grounds to prosecute Officer Loehmann with murder, manslaughter and reckless homicide.

Police have maintained that Rice's pellet gun looked real and that they asked him to raise his hands three times.

But his family said video footage shows the police acted too quickly after arriving at the scene.

Rice's death sparked protests in Cleveland, at a time when the deaths of black men at the hands of police had sparked a national debate.