A US federal appeals court on Friday tossed out the murder conviction of a Blackwater security guard who was serving a life sentence for a 2007 shooting in Baghdad that left 14 Iraqis dead.

The court also ordered a resentencing for three other members of Blackwater who were involved in the killing of unarmed civilians, including women and children, in a Baghdad traffic circle.

They had each been serving sentences of 30 years in prison.

The four men, members of a Blackwater team named Raven 23 which was providing security to the US State Department, were responding to a security incident in the Iraqi capital on September 16, 2007 when the shooting occurred in Nisur Square.

It was claimed at their 2014 trial that they were acting in self-defense. But no credible evidence emerged that they came under fire and they were accused of opening fire indiscriminately.

The shooting left at least 14 Iraqi civilians dead and another 17 wounded and helped perpetuate the image of US security contractors run amok.

Nicholas Slatten, 33, was determined to have fired the first shots and was convicted of first-degree murder and sentenced to life in prison.

His conviction was tossed out on Friday by the US Court of Appeals for the DC Circuit on the grounds that he should not have been tried separately from the other three defendants.

Slatten is likely to be retried.

The other three Blackwater guards -- Dustin Heard, Evan Liberty and Paul Slough -- were convicted of voluntary manslaughter, attempted manslaughter and using a firearm to commit a violent crime.

The court ruled, however, that their mandatory 30-year sentences because of the firearm violation were "grossly disproportionate" and ordered a resentencing.

"In reaching this conclusion, we by no means intend to minimize the carnage attributable to Slough, Heard and Liberty's actions," the judges said.

"Their poor judgments resulted in the deaths of many innocent people," they said. "What happened in Nisur Square defies civilized description."

Blackwater, founded by Erik Prince, the brother of the current Education Secretary Betsy Devos, was renamed Xe in 2009 and became Academi two years later.

Source: AFP