WASHINGTON, DC - A Blackwater security guard who was tried three times before being convicted of murder charges, relating to a massacre of civilians in Baghdad, has been jailed for life.

Nicholas Slatten was convicted of murder in the first-degree by a federal jury in December, at the end of his third trial in the U.S. District Court in Washington.

Slatten was convicted for his role in the slaying of at least fourteen unarmed civilians, and the injuring of many more, in an unprovoked attack on members of the Iraqi public in Baghdad's Nisour Square while escorting a convoy of diplomats on 16 September 2007.

In the square, which was packed with people going about their business, the Blackwater guards without provocation turned their machine guns on the crowd, snipers supporting the convoy opened fire, and grenades were thrown. In the end at least seventeen people were dead, and more than 20 injured.

Iraqi police and government departments concluded the attack was unprovoked. The U.S., State Department confirmed the innocent people had been killed. An FBI investigation later comncluded that fourteen people killed were unarmed civilians. the Iraqi government hotly disputed the findings, saying the death toll was much higher.

During the occupation of Iraq, the Bush administration on the orders of Vice President Dick Cheney outsourced security for its officials, including diplomats, to Blackwater's Raven 23 security team, which comprised mainly ex-U.S. military personnel. The force was also deployed by the State Department in Afghanistan.

Numerous incidents occurred alleging heavy-handed conduct by the guards resulting eventually in the termination of Blackwater's contract, but not before the Iraqi government banned the group from operating in that country.

Blackwater, unlike the U.S. military did not have immunity from prosecution and several guards faced charges over the incident which caused massive anger in Iraq, adding to rising resentment over the U.S. occupation.

Slatten on Wednesday described his conviction and sentecning as "a miscarriage of justice," and said it would not stand.

Families and supporters of the four former Blackwater guards, including Slatten, who have faced charges over the incident operate a website displaying their version of events.

(Pictured: Nicholas Slatten with his father, Darrell, at Ft. Brag after the then-soldier's return from his second tour of Iraq. Photo supplied).